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Revision 1.160 by root, Thu May 22 03:06:58 2008 UTC vs.
Revision 1.355 by root, Tue Jan 11 01:41:56 2011 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.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
126		150
127	When libev catches an operating system error it cannot handle (for example	151	When libev catches an operating system error it cannot handle (for example
128	a syscall indicating a condition libev cannot fix), it calls the callback	152	a system call indicating a condition libev cannot fix), it calls the callback
129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or	153	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
130	abort. The default is to print a diagnostic message and to call C<abort	154	abort. The default is to print a diagnostic message and to call C<abort
131	()>.	155	()>.
132		156
133	When libev detects a usage error such as a negative timer interval, then	157	When libev detects a usage error such as a negative timer interval, then
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	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
153	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
154	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>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	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
159	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
160	this is a subsecond-resolution C<sleep ()>.	185	this is a sub-second-resolution C<sleep ()>.
161		186
162	=item int ev_version_major ()	187	=item int ev_version_major ()
163		188
164	=item int ev_version_minor ()	189	=item int ev_version_minor ()
165		190
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	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
178	not a problem.	203	not a problem.
179		204
180	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
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
187	=item unsigned int ev_supported_backends ()	213	=item unsigned int ev_supported_backends ()
188		214
189	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_*>
190	value) compiled into this binary of libev (independent of their	216	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	218	a description of the set values.
193		219
194	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
195	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
196		222
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	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
203	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
204	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
205	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
206	(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
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	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
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	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
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	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
258	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
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	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
261	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
262	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
263	(such as abort).	290	(such as abort).
264		291
265	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.
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *>. The library knows two	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	323	libev 3 had an C<ev_loop> function colliding with the struct name).
		324
		325	The library knows two types of such loops, the I<default> loop, which
		326	supports child process events, and dynamically created event loops which
		327	do not.
284		328
285	=over 4	329	=over 4
286		330
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		332
289	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
293		343
294	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
295	function.	345	function (or via the C<EV_DEFAULT> macro).
296		346
297	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
300		351
301	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your app you can either	354	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
307		376
308	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		379
311	The following flags are supported:	380	The following flags are supported:
…		…
317	The default flags value. Use this if you have no clue (it's the right	386	The default flags value. Use this if you have no clue (it's the right
318	thing, believe me).	387	thing, believe me).
319		388
320	=item C<EVFLAG_NOENV>	389	=item C<EVFLAG_NOENV>
321		390
322	If this flag bit is ored into the flag value (or the program runs setuid	391	If this flag bit is or'ed into the flag value (or the program runs setuid
323	or setgid) then libev will I<not> look at the environment variable	392	or setgid) then libev will I<not> look at the environment variable
324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	393	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
325	override the flags completely if it is found in the environment. This is	394	override the flags completely if it is found in the environment. This is
326	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
327	around bugs.	396	around bugs.
328		397
329	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
330		399
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		402
335	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
339	without a syscall and thus I<very> fast, but my GNU/Linux system also has	407	without a system call and thus I<very> fast, but my GNU/Linux system also has
340	C<pthread_atfork> which is even faster).	408	C<pthread_atfork> which is even faster).
341		409
342	The big advantage of this flag is that you can forget about fork (and	410	The big advantage of this flag is that you can forget about fork (and
343	forget about forgetting to tell libev about forking) when you use this	411	forget about forgetting to tell libev about forking) when you use this
344	flag.	412	flag.
345		413
346	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	415	environment variable.
		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
348		448
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		450
351	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
354	using this backend. It doesn't scale too well (O(highest_fd)), but its	454	using this backend. It doesn't scale too well (O(highest_fd)), but its
355	usually the fastest backend for a low number of (low-numbered :) fds.	455	usually the fastest backend for a low number of (low-numbered :) fds.
356		456
357	To get good performance out of this backend you need a high amount of	457	To get good performance out of this backend you need a high amount of
358	parallelity (most of the file descriptors should be busy). If you are	458	parallelism (most of the file descriptors should be busy). If you are
359	writing a server, you should C<accept ()> in a loop to accept as many	459	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	460	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	461	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	462	readiness notifications you get per iteration.
		463
		464	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		465	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		466	C<exceptfds> set on that platform).
363		467
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	468	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		469
366	And this is your standard poll(2) backend. It's more complicated	470	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	471	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	472	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	473	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	474	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	475	performance tips.
372		476
		477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		479
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
374		484
375	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	488	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	489
380	cases and requiring a syscall per fd change, no fork support and bad	490	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
		493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
		496	0.1ms) and so on. The biggest issue is fork races, however - if a program
		497	forks then I<both> parent and child process have to recreate the epoll
		498	set, which can take considerable time (one syscall per file descriptor)
		499	and is of course hard to detect.
		500
		501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		502	of course I<doesn't>, and epoll just loves to report events for totally
		503	I<different> file descriptors (even already closed ones, so one cannot
		504	even remove them from the set) than registered in the set (especially
		505	on SMP systems). Libev tries to counter these spurious notifications by
		506	employing an additional generation counter and comparing that against the
		507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
382		514
383	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a syscall per such incident	516	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	517	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	519	file descriptors might not work very well if you register events for both
388		520	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		521
393	Best performance from this backend is achieved by not unregistering all	522	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	523	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	524	i.e. keep at least one watcher active per fd at all times. Stopping and
		525	starting a watcher (without re-setting it) also usually doesn't cause
		526	extra overhead. A fork can both result in spurious notifications as well
		527	as in libev having to destroy and recreate the epoll object, which can
		528	take considerable time and thus should be avoided.
396		529
		530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		531	faster than epoll for maybe up to a hundred file descriptors, depending on
		532	the usage. So sad.
		533
397	While nominally embeddeble in other event loops, this feature is broken in	534	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	535	all kernel versions tested so far.
		536
		537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		538	C<EVBACKEND_POLL>.
399		539
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		541
402	Kqueue deserves special mention, as at the time of this writing, it	542	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	543	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	544	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "autodetected"	545	it's completely useless). Unlike epoll, however, whose brokenness
		546	is by design, these kqueue bugs can (and eventually will) be fixed
		547	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	548	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	550	system like NetBSD.
409		551
410	You still can embed kqueue into a normal poll or select backend and use it	552	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	553	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	554	the target platform). See C<ev_embed> watchers for more info.
413		555
414	It scales in the same way as the epoll backend, but the interface to the	556	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	557	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	558	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	560	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		562	cases
420		563
421	This backend usually performs well under most conditions.	564	This backend usually performs well under most conditions.
422		565
423	While nominally embeddable in other event loops, this doesn't work	566	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	567	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	568	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	569	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	570	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	571	also broken on OS X)) and, did I mention it, using it only for sockets.
		572
		573	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		574	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		575	C<NOTE_EOF>.
429		576
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	577	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		578
432	This is not implemented yet (and might never be, unless you send me an	579	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	580	implementation). According to reports, C</dev/poll> only supports sockets
…		…
437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
438		585
439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
440	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
441		588
442	Please note that solaris event ports can deliver a lot of spurious
443	notifications, so you need to use non-blocking I/O or other means to avoid
444	blocking when no data (or space) is available.
445
446	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	592	might perform better.
450		593
451	On the positive side, ignoring the spurious readiness notifications, this	594	On the positive side, this backend actually performed fully to
452	backend actually performed to specification in all tests and is fully	595	specification in all tests and is fully embeddable, which is a rare feat
453	embeddable, which is a rare feat among the OS-specific backends.	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
		608
		609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		610	C<EVBACKEND_POLL>.
454		611
455	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
456		613
457	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
460		617
461	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
462		627
463	=back	628	=back
464		629
465	If one or more of these are ored into the flags value, then only these	630	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	631	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	632	here). If none are specified, all backends in C<ev_recommended_backends
468		633	()> will be tried.
469	The most typical usage is like this:
470
471	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473
474	Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:
476
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478
479	Use whatever libev has to offer, but make sure that kqueue is used if
480	available (warning, breaks stuff, best use only with your own private
481	event loop and only if you know the OS supports your types of fds):
482
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484
485	=item struct ev_loop *ev_loop_new (unsigned int flags)
486
487	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491
492	Note that this function I<is> thread-safe, and the recommended way to use
493	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.
495		634
496	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
497		636
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	638	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
501		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
502	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
503		647
504	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
506	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
507	responsibility to either stop all watchers cleanly yoursef I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	654	for example).
511		655
512	Note that certain global state, such as signal state, will not be freed by	656	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	657	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
515		659
516	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
517	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
518	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
519	C<ev_loop_new> and C<ev_loop_destroy>).	667	and C<ev_loop_destroy>.
520		668
521	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
522		670
523	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.
525
526	=item ev_default_fork ()
527
528	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
529	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
530	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
531	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
532	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
533	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
534		681
535	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
536	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
537	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
538		688
539	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
540	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
541	quite nicely into a call to C<pthread_atfork>:
542		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
543	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
544
545	=item ev_loop_fork (loop)
546
547	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.
550		703
551	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
552		705
553	Returns true when the given loop actually is the default loop, false otherwise.	706	Returns true when the given loop is, in fact, the default loop, and false
		707	otherwise.
554		708
555	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
556		710
557	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
558	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
560		714
561	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
564		733
565	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
566		735
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	737	use.
…		…
573	received events and started processing them. This timestamp does not	742	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	743	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	744	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	745	event occurring (or more correctly, libev finding out about it).
577		746
		747	=item ev_now_update (loop)
		748
		749	Establishes the current time by querying the kernel, updating the time
		750	returned by C<ev_now ()> in the progress. This is a costly operation and
		751	is usually done automatically within C<ev_run ()>.
		752
		753	This function is rarely useful, but when some event callback runs for a
		754	very long time without entering the event loop, updating libev's idea of
		755	the current time is a good idea.
		756
		757	See also L<The special problem of time updates> in the C<ev_timer> section.
		758
		759	=item ev_suspend (loop)
		760
		761	=item ev_resume (loop)
		762
		763	These two functions suspend and resume an event loop, for use when the
		764	loop is not used for a while and timeouts should not be processed.
		765
		766	A typical use case would be an interactive program such as a game: When
		767	the user presses C<^Z> to suspend the game and resumes it an hour later it
		768	would be best to handle timeouts as if no time had actually passed while
		769	the program was suspended. This can be achieved by calling C<ev_suspend>
		770	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		771	C<ev_resume> directly afterwards to resume timer processing.
		772
		773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		775	will be rescheduled (that is, they will lose any events that would have
		776	occurred while suspended).
		777
		778	After calling C<ev_suspend> you B<must not> call I<any> function on the
		779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		780	without a previous call to C<ev_suspend>.
		781
		782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		783	event loop time (see C<ev_now_update>).
		784
578	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
579		786
580	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
582	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
583		792
584	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
585	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
586		796
587	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	799	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	800	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	801	of relying on its watchers stopping correctly, that is truly a thing of
		802	beauty.
592		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	810	those events and any already outstanding ones, but will not wait and
595	case there are no events and will return after one iteration of the loop.	811	block your process in case there are no events and will return after one
		812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
596		814
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
598	neccessary) and will handle those and any outstanding ones. It will block	816	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	817	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	818	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	819	user-registered callback will be called), and will return after one
		820	iteration of the loop.
		821
		822	This is useful if you are waiting for some external event in conjunction
		823	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
604		826
605	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
606		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
607	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
608	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
611	- If we have been forked, recreate the kernel state.	837	- If we have been forked, detach and recreate the kernel state
		838	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	840	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
616	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
618	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	849	- Queue all expired timers.
622	- Queue all outstanding periodics.	850	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
624	- Queue all check watchers.	852	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
629	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
630	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
631		863
632	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
633	anymore.	865	anymore.
634		866
635	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
638	... jobs done. yeah!	870	... jobs done or somebody called unloop. yeah!
639		871
640	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
641		873
642	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
646		878
647	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
		880
		881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
648		883
649	=item ev_ref (loop)	884	=item ev_ref (loop)
650		885
651	=item ev_unref (loop)	886	=item ev_unref (loop)
652		887
653	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	890	count is nonzero, C<ev_run> will not return on its own.
656	a watcher you never unregister that should not keep C<ev_loop> from	891
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	892	This is useful when you have a watcher that you never intend to
		893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		895	before stopping it.
		896
658	example, libev itself uses this for its internal signal pipe: It is not	897	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	898	is not visible to the libev user and should not keep C<ev_run> from
660	no event watchers registered by it are active. It is also an excellent	899	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	900	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	901	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	902	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	903	before, respectively. Note also that libev might stop watchers itself
		904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		905	in the callback).
665		906
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
667	running when nothing else is active.	908	running when nothing else is active.
668		909
669	struct ev_signal exitsig;	910	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	913	ev_unref (loop);
673		914
674	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
675		916
676	ev_ref (loop);	917	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
678		919
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	920	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		921
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	922	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		923
683	These advanced functions influence the time that libev will spend waiting	924	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	925	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	926	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		927	latency.
686		928
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	929	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	930	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	931	to increase efficiency of loop iterations (or to increase power-saving
		932	opportunities).
690		933
691	The background is that sometimes your program runs just fast enough to	934	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	935	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	936	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	937	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	938	overhead for the actual polling but can deliver many events at once.
696		939
697	By setting a higher I<io collect interval> you allow libev to spend more	940	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	941	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	943	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
702		947
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	950	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	952	value will not introduce any overhead in libev.
708		953
709	Many (busy) programs can usually benefit by setting the io collect	954	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	955	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	956	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approsaches the timing granularity of most systems.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
714		963
		964	Setting the I<timeout collect interval> can improve the opportunity for
		965	saving power, as the program will "bundle" timer callback invocations that
		966	are "near" in time together, by delaying some, thus reducing the number of
		967	times the process sleeps and wakes up again. Another useful technique to
		968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		969	they fire on, say, one-second boundaries only.
		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
715	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
716		1047
717	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	1049	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	1050	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	1051	is found to be inconsistent, it will print an error message to standard
		1052	error and call C<abort ()>.
721		1053
722	This can be used to catch bugs inside libev itself: under normal	1054	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	1055	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	1056	data structures consistent.
725		1057
726	=back	1058	=back
727		1059
728		1060
729	=head1 ANATOMY OF A WATCHER	1061	=head1 ANATOMY OF A WATCHER
730		1062
		1063	In the following description, uppercase C<TYPE> in names stands for the
		1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1065	watchers and C<ev_io_start> for I/O watchers.
		1066
731	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
732	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
733	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
734		1071
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	1073	{
737	ev_io_stop (w);	1074	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
739	}	1076	}
740		1077
741	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
		1079
742	struct ev_io stdin_watcher;	1080	ev_io stdin_watcher;
		1081
743	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
		1085
746	ev_loop (loop, 0);	1086	ev_run (loop, 0);
747		1087
748	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	1089	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	1090	stack).
751		1091
		1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1094
752	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
753	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
754	callback gets invoked each time the event occurs (or, in the case of io	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
755	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
756	is readable and/or writable).	1099	and/or writable).
757		1100
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1102	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1103	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
762		1105
763	To make the watcher actually watch out for events, you have to start it	1106	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1107	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1108	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1109	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1110
768	As long as your watcher is active (has been started but not stopped) you	1111	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1112	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1113	reinitialise it or call its C<ev_TYPE_set> macro.
771		1114
772	Each and every callback receives the event loop pointer as first, the	1115	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1116	registered watcher structure as second, and a bitset of received events as
774	third argument.	1117	third argument.
775		1118
…		…
784	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
785		1128
786	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
787	writable.	1130	writable.
788		1131
789	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
790		1133
791	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
792		1135
793	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
794		1137
…		…
812		1155
813	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
814		1157
815	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
816		1159
817	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
818	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
819	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
820	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
821	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
822	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
823	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
824		1167
825	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
826		1169
827	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
828		1171
829	=item C<EV_FORK>	1172	=item C<EV_FORK>
830		1173
831	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
832	C<ev_fork>).	1175	C<ev_fork>).
833		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
834	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
835		1182
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1184
		1185	=item C<EV_CUSTOM>
		1186
		1187	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1188	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1189
838	=item C<EV_ERROR>	1190	=item C<EV_ERROR>
839		1191
840	An unspecified error has occured, the watcher has been stopped. This might	1192	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1193	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1194	ran out of memory, a file descriptor was found to be closed or any other
		1195	problem. Libev considers these application bugs.
		1196
843	problem. You best act on it by reporting the problem and somehow coping	1197	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1198	watcher being stopped. Note that well-written programs should not receive
		1199	an error ever, so when your watcher receives it, this usually indicates a
		1200	bug in your program.
845		1201
846	Libev will usually signal a few "dummy" events together with an error,	1202	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1203	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1204	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multithreaded	1205	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1206	programs, though, as the fd could already be closed and reused for another
		1207	thing, so beware.
851		1208
852	=back	1209	=back
853		1210
854	=head2 GENERIC WATCHER FUNCTIONS	1211	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1212
859	=over 4	1213	=over 4
860		1214
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1215	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1216
…		…
868	which rolls both calls into one.	1222	which rolls both calls into one.
869		1223
870	You can reinitialise a watcher at any time as long as it has been stopped	1224	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1225	(or never started) and there are no pending events outstanding.
872		1226
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1227	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1228	int revents)>.
875		1229
		1230	Example: Initialise an C<ev_io> watcher in two steps.
		1231
		1232	ev_io w;
		1233	ev_init (&w, my_cb);
		1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1235
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
877		1237
878	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
881	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
882	difference to the C<ev_init> macro).	1242	difference to the C<ev_init> macro).
883		1243
884	Although some watcher types do not have type-specific arguments	1244	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1245	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1246
		1247	See C<ev_init>, above, for an example.
		1248
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1249	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1250
889	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1251	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convinient method to initialise	1252	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1253	a watcher. The same limitations apply, of course.
892		1254
		1255	Example: Initialise and set an C<ev_io> watcher in one step.
		1256
		1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1258
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
894		1260
895	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
897		1263
		1264	Example: Start the C<ev_io> watcher that is being abused as example in this
		1265	whole section.
		1266
		1267	ev_io_start (EV_DEFAULT_UC, &w);
		1268
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
899		1270
900	Stops the given watcher again (if active) and clears the pending	1271	Stops the given watcher if active, and clears the pending status (whether
		1272	the watcher was active or not).
		1273
901	status. It is possible that stopped watchers are pending (for example,	1274	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1275	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1276	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1277	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1278	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1279
907	=item bool ev_is_active (ev_TYPE *watcher)	1280	=item bool ev_is_active (ev_TYPE *watcher)
908		1281
909	Returns a true value iff the watcher is active (i.e. it has been started	1282	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1283	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
927		1300
928	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
929	(modulo threads).	1302	(modulo threads).
930		1303
931	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
932		1305
933	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
934		1307
935	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
940		1313
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1314	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1316
949	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1318	pending.
951		1319
		1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1321	fine, as long as you do not mind that the priority value you query might
		1322	or might not have been clamped to the valid range.
		1323
952	The default priority used by watchers when no priority has been set is	1324	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1325	always C<0>, which is supposed to not be too high and not be too low :).
954		1326
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1328	priorities.
957	or might not have been adjusted to be within valid range.
958		1329
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1331
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1334	can deal with that fact, as both are simply passed through to the
		1335	callback.
964		1336
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1337	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1338
967	If the watcher is pending, this function returns clears its pending status	1339	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1340	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
970		1342
		1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1344	callback to be invoked, which can be accomplished with this function.
		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
971	=back	1360	=back
972		1361
973
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1363
976	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1366	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1367	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1368	member, you can also "subclass" the watcher type and provide your own
981	data:	1369	data:
982		1370
983	struct my_io	1371	struct my_io
984	{	1372	{
985	struct ev_io io;	1373	ev_io io;
986	int otherfd;	1374	int otherfd;
987	void *somedata;	1375	void *somedata;
988	struct whatever *mostinteresting;	1376	struct whatever *mostinteresting;
989	}	1377	};
		1378
		1379	...
		1380	struct my_io w;
		1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1382
991	And since your callback will be called with a pointer to the watcher, you	1383	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1384	can cast it back to your own type:
993		1385
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1387	{
996	struct my_io *w = (struct my_io *)w_;	1388	struct my_io *w = (struct my_io *)w_;
997	...	1389	...
998	}	1390	}
999		1391
1000	More interesting and less C-conformant ways of casting your callback type	1392	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1393	instead have been omitted.
1002		1394
1003	Another common scenario is having some data structure with multiple	1395	Another common scenario is to use some data structure with multiple
1004	watchers:	1396	embedded watchers:
1005		1397
1006	struct my_biggy	1398	struct my_biggy
1007	{	1399	{
1008	int some_data;	1400	int some_data;
1009	ev_timer t1;	1401	ev_timer t1;
1010	ev_timer t2;	1402	ev_timer t2;
1011	}	1403	}
1012		1404
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1405	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1406	complicated: Either you store the address of your C<my_biggy> struct
		1407	in the C<data> member of the watcher (for woozies), or you need to use
		1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1409	programmers):
1015		1410
1016	#include <stddef.h>	1411	#include <stddef.h>
1017		1412
1018	static void	1413	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1415	{
1021	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1418	}
1024		1419
1025	static void	1420	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1422	{
1028	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
		1485
		1486	=head2 WATCHER PRIORITY MODELS
		1487
		1488	Many event loops support I<watcher priorities>, which are usually small
		1489	integers that influence the ordering of event callback invocation
		1490	between watchers in some way, all else being equal.
		1491
		1492	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1493	description for the more technical details such as the actual priority
		1494	range.
		1495
		1496	There are two common ways how these these priorities are being interpreted
		1497	by event loops:
		1498
		1499	In the more common lock-out model, higher priorities "lock out" invocation
		1500	of lower priority watchers, which means as long as higher priority
		1501	watchers receive events, lower priority watchers are not being invoked.
		1502
		1503	The less common only-for-ordering model uses priorities solely to order
		1504	callback invocation within a single event loop iteration: Higher priority
		1505	watchers are invoked before lower priority ones, but they all get invoked
		1506	before polling for new events.
		1507
		1508	Libev uses the second (only-for-ordering) model for all its watchers
		1509	except for idle watchers (which use the lock-out model).
		1510
		1511	The rationale behind this is that implementing the lock-out model for
		1512	watchers is not well supported by most kernel interfaces, and most event
		1513	libraries will just poll for the same events again and again as long as
		1514	their callbacks have not been executed, which is very inefficient in the
		1515	common case of one high-priority watcher locking out a mass of lower
		1516	priority ones.
		1517
		1518	Static (ordering) priorities are most useful when you have two or more
		1519	watchers handling the same resource: a typical usage example is having an
		1520	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1521	timeouts. Under load, data might be received while the program handles
		1522	other jobs, but since timers normally get invoked first, the timeout
		1523	handler will be executed before checking for data. In that case, giving
		1524	the timer a lower priority than the I/O watcher ensures that I/O will be
		1525	handled first even under adverse conditions (which is usually, but not
		1526	always, what you want).
		1527
		1528	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1529	will only be executed when no same or higher priority watchers have
		1530	received events, they can be used to implement the "lock-out" model when
		1531	required.
		1532
		1533	For example, to emulate how many other event libraries handle priorities,
		1534	you can associate an C<ev_idle> watcher to each such watcher, and in
		1535	the normal watcher callback, you just start the idle watcher. The real
		1536	processing is done in the idle watcher callback. This causes libev to
		1537	continuously poll and process kernel event data for the watcher, but when
		1538	the lock-out case is known to be rare (which in turn is rare :), this is
		1539	workable.
		1540
		1541	Usually, however, the lock-out model implemented that way will perform
		1542	miserably under the type of load it was designed to handle. In that case,
		1543	it might be preferable to stop the real watcher before starting the
		1544	idle watcher, so the kernel will not have to process the event in case
		1545	the actual processing will be delayed for considerable time.
		1546
		1547	Here is an example of an I/O watcher that should run at a strictly lower
		1548	priority than the default, and which should only process data when no
		1549	other events are pending:
		1550
		1551	ev_idle idle; // actual processing watcher
		1552	ev_io io; // actual event watcher
		1553
		1554	static void
		1555	io_cb (EV_P_ ev_io *w, int revents)
		1556	{
		1557	// stop the I/O watcher, we received the event, but
		1558	// are not yet ready to handle it.
		1559	ev_io_stop (EV_A_ w);
		1560
		1561	// start the idle watcher to handle the actual event.
		1562	// it will not be executed as long as other watchers
		1563	// with the default priority are receiving events.
		1564	ev_idle_start (EV_A_ &idle);
		1565	}
		1566
		1567	static void
		1568	idle_cb (EV_P_ ev_idle *w, int revents)
		1569	{
		1570	// actual processing
		1571	read (STDIN_FILENO, ...);
		1572
		1573	// have to start the I/O watcher again, as
		1574	// we have handled the event
		1575	ev_io_start (EV_P_ &io);
		1576	}
		1577
		1578	// initialisation
		1579	ev_idle_init (&idle, idle_cb);
		1580	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1581	ev_io_start (EV_DEFAULT_ &io);
		1582
		1583	In the "real" world, it might also be beneficial to start a timer, so that
		1584	low-priority connections can not be locked out forever under load. This
		1585	enables your program to keep a lower latency for important connections
		1586	during short periods of high load, while not completely locking out less
		1587	important ones.
1031		1588
1032		1589
1033	=head1 WATCHER TYPES	1590	=head1 WATCHER TYPES
1034		1591
1035	This section describes each watcher in detail, but will not repeat	1592	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1619	required if you know what you are doing).
1063		1620
1064	If you must do this, then force the use of a known-to-be-good backend
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1066	C<EVBACKEND_POLL>).
1067
1068	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1072	lot of those (for example solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1073	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1076		1628
1077	If you cannot run the fd in non-blocking mode (for example you should not	1629	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to seperately re-test	1630	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1631	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1632	interface such as poll (fortunately in the case of Xlib, it already does
1081	its own, so its quite safe to use).	1633	this on its own, so its quite safe to use). Some people additionally
		1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1635	indefinitely.
		1636
		1637	But really, best use non-blocking mode.
1082		1638
1083	=head3 The special problem of disappearing file descriptors	1639	=head3 The special problem of disappearing file descriptors
1084		1640
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1641	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1642	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1643	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1644	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1645	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1646	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1647	fact, a different file descriptor.
1092		1648
…		…
1110		1666
1111	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1112	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1114		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1115	=head3 The special problem of fork	1704	=head3 The special problem of fork
1116		1705
1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1118	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1119	it in the child.	1708	it in the child if you want to continue to use it in the child.
1120		1709
1121	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1124	C<EVBACKEND_POLL>.
1125		1713
1126	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1127		1715
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1717	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1718	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1719	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1720
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1721	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1722	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1723	somewhere, as that would have given you a big clue).
1137		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1138		1763
1139	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1140		1765
1141	=over 4	1766	=over 4
1142		1767
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1768	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1769
1145	=item ev_io_set (ev_io *, int fd, int events)	1770	=item ev_io_set (ev_io *, int fd, int events)
1146		1771
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1772	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1773	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1774	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1775
1151	=item int fd [read-only]	1776	=item int fd [read-only]
1152		1777
1153	The file descriptor being watched.	1778	The file descriptor being watched.
1154		1779
…		…
1162		1787
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1788	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1789	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1790	attempt to read a whole line in the callback.
1166		1791
1167	static void	1792	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1793	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1794	{
1170	ev_io_stop (loop, w);	1795	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1796	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1797	}
1173		1798
1174	...	1799	...
1175	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1801	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1180		1805
1181		1806
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1808
1184	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1810	given time, and optionally repeating in regular intervals after that.
1186		1811
1187	The timers are based on real time, that is, if you register an event that	1812	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to january last	1813	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1814	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1816	monotonic clock option helps a lot here).
		1817
		1818	The callback is guaranteed to be invoked only I<after> its timeout has
		1819	passed (not I<at>, so on systems with very low-resolution clocks this
		1820	might introduce a small delay). If multiple timers become ready during the
		1821	same loop iteration then the ones with earlier time-out values are invoked
		1822	before ones of the same priority with later time-out values (but this is
		1823	no longer true when a callback calls C<ev_run> recursively).
		1824
		1825	=head3 Be smart about timeouts
		1826
		1827	Many real-world problems involve some kind of timeout, usually for error
		1828	recovery. A typical example is an HTTP request - if the other side hangs,
		1829	you want to raise some error after a while.
		1830
		1831	What follows are some ways to handle this problem, from obvious and
		1832	inefficient to smart and efficient.
		1833
		1834	In the following, a 60 second activity timeout is assumed - a timeout that
		1835	gets reset to 60 seconds each time there is activity (e.g. each time some
		1836	data or other life sign was received).
		1837
		1838	=over 4
		1839
		1840	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1841
		1842	This is the most obvious, but not the most simple way: In the beginning,
		1843	start the watcher:
		1844
		1845	ev_timer_init (timer, callback, 60., 0.);
		1846	ev_timer_start (loop, timer);
		1847
		1848	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1849	and start it again:
		1850
		1851	ev_timer_stop (loop, timer);
		1852	ev_timer_set (timer, 60., 0.);
		1853	ev_timer_start (loop, timer);
		1854
		1855	This is relatively simple to implement, but means that each time there is
		1856	some activity, libev will first have to remove the timer from its internal
		1857	data structure and then add it again. Libev tries to be fast, but it's
		1858	still not a constant-time operation.
		1859
		1860	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1861
		1862	This is the easiest way, and involves using C<ev_timer_again> instead of
		1863	C<ev_timer_start>.
		1864
		1865	To implement this, configure an C<ev_timer> with a C<repeat> value
		1866	of C<60> and then call C<ev_timer_again> at start and each time you
		1867	successfully read or write some data. If you go into an idle state where
		1868	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1869	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1870
		1871	That means you can ignore both the C<ev_timer_start> function and the
		1872	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1873	member and C<ev_timer_again>.
		1874
		1875	At start:
		1876
		1877	ev_init (timer, callback);
		1878	timer->repeat = 60.;
		1879	ev_timer_again (loop, timer);
		1880
		1881	Each time there is some activity:
		1882
		1883	ev_timer_again (loop, timer);
		1884
		1885	It is even possible to change the time-out on the fly, regardless of
		1886	whether the watcher is active or not:
		1887
		1888	timer->repeat = 30.;
		1889	ev_timer_again (loop, timer);
		1890
		1891	This is slightly more efficient then stopping/starting the timer each time
		1892	you want to modify its timeout value, as libev does not have to completely
		1893	remove and re-insert the timer from/into its internal data structure.
		1894
		1895	It is, however, even simpler than the "obvious" way to do it.
		1896
		1897	=item 3. Let the timer time out, but then re-arm it as required.
		1898
		1899	This method is more tricky, but usually most efficient: Most timeouts are
		1900	relatively long compared to the intervals between other activity - in
		1901	our example, within 60 seconds, there are usually many I/O events with
		1902	associated activity resets.
		1903
		1904	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1905	but remember the time of last activity, and check for a real timeout only
		1906	within the callback:
		1907
		1908	ev_tstamp last_activity; // time of last activity
		1909
		1910	static void
		1911	callback (EV_P_ ev_timer *w, int revents)
		1912	{
		1913	ev_tstamp now = ev_now (EV_A);
		1914	ev_tstamp timeout = last_activity + 60.;
		1915
		1916	// if last_activity + 60. is older than now, we did time out
		1917	if (timeout < now)
		1918	{
		1919	// timeout occurred, take action
		1920	}
		1921	else
		1922	{
		1923	// callback was invoked, but there was some activity, re-arm
		1924	// the watcher to fire in last_activity + 60, which is
		1925	// guaranteed to be in the future, so "again" is positive:
		1926	w->repeat = timeout - now;
		1927	ev_timer_again (EV_A_ w);
		1928	}
		1929	}
		1930
		1931	To summarise the callback: first calculate the real timeout (defined
		1932	as "60 seconds after the last activity"), then check if that time has
		1933	been reached, which means something I<did>, in fact, time out. Otherwise
		1934	the callback was invoked too early (C<timeout> is in the future), so
		1935	re-schedule the timer to fire at that future time, to see if maybe we have
		1936	a timeout then.
		1937
		1938	Note how C<ev_timer_again> is used, taking advantage of the
		1939	C<ev_timer_again> optimisation when the timer is already running.
		1940
		1941	This scheme causes more callback invocations (about one every 60 seconds
		1942	minus half the average time between activity), but virtually no calls to
		1943	libev to change the timeout.
		1944
		1945	To start the timer, simply initialise the watcher and set C<last_activity>
		1946	to the current time (meaning we just have some activity :), then call the
		1947	callback, which will "do the right thing" and start the timer:
		1948
		1949	ev_init (timer, callback);
		1950	last_activity = ev_now (loop);
		1951	callback (loop, timer, EV_TIMER);
		1952
		1953	And when there is some activity, simply store the current time in
		1954	C<last_activity>, no libev calls at all:
		1955
		1956	last_activity = ev_now (loop);
		1957
		1958	This technique is slightly more complex, but in most cases where the
		1959	time-out is unlikely to be triggered, much more efficient.
		1960
		1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1962	callback :) - just change the timeout and invoke the callback, which will
		1963	fix things for you.
		1964
		1965	=item 4. Wee, just use a double-linked list for your timeouts.
		1966
		1967	If there is not one request, but many thousands (millions...), all
		1968	employing some kind of timeout with the same timeout value, then one can
		1969	do even better:
		1970
		1971	When starting the timeout, calculate the timeout value and put the timeout
		1972	at the I<end> of the list.
		1973
		1974	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1975	the list is expected to fire (for example, using the technique #3).
		1976
		1977	When there is some activity, remove the timer from the list, recalculate
		1978	the timeout, append it to the end of the list again, and make sure to
		1979	update the C<ev_timer> if it was taken from the beginning of the list.
		1980
		1981	This way, one can manage an unlimited number of timeouts in O(1) time for
		1982	starting, stopping and updating the timers, at the expense of a major
		1983	complication, and having to use a constant timeout. The constant timeout
		1984	ensures that the list stays sorted.
		1985
		1986	=back
		1987
		1988	So which method the best?
		1989
		1990	Method #2 is a simple no-brain-required solution that is adequate in most
		1991	situations. Method #3 requires a bit more thinking, but handles many cases
		1992	better, and isn't very complicated either. In most case, choosing either
		1993	one is fine, with #3 being better in typical situations.
		1994
		1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1996	rather complicated, but extremely efficient, something that really pays
		1997	off after the first million or so of active timers, i.e. it's usually
		1998	overkill :)
		1999
		2000	=head3 The special problem of time updates
		2001
		2002	Establishing the current time is a costly operation (it usually takes at
		2003	least two system calls): EV therefore updates its idea of the current
		2004	time only before and after C<ev_run> collects new events, which causes a
		2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		2006	lots of events in one iteration.
1192		2007
1193	The relative timeouts are calculated relative to the C<ev_now ()>	2008	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	2009	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	2010	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	2011	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	2012	timeout on the current time, use something like this to adjust for this:
1198		2013
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		2015
1201	The callback is guarenteed to be invoked only after its timeout has passed,	2016	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	2018	()>.
		2019
		2020	=head3 The special problems of suspended animation
		2021
		2022	When you leave the server world it is quite customary to hit machines that
		2023	can suspend/hibernate - what happens to the clocks during such a suspend?
		2024
		2025	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2026	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2027	to run until the system is suspended, but they will not advance while the
		2028	system is suspended. That means, on resume, it will be as if the program
		2029	was frozen for a few seconds, but the suspend time will not be counted
		2030	towards C<ev_timer> when a monotonic clock source is used. The real time
		2031	clock advanced as expected, but if it is used as sole clocksource, then a
		2032	long suspend would be detected as a time jump by libev, and timers would
		2033	be adjusted accordingly.
		2034
		2035	I would not be surprised to see different behaviour in different between
		2036	operating systems, OS versions or even different hardware.
		2037
		2038	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2039	time jump in the monotonic clocks and the realtime clock. If the program
		2040	is suspended for a very long time, and monotonic clock sources are in use,
		2041	then you can expect C<ev_timer>s to expire as the full suspension time
		2042	will be counted towards the timers. When no monotonic clock source is in
		2043	use, then libev will again assume a timejump and adjust accordingly.
		2044
		2045	It might be beneficial for this latter case to call C<ev_suspend>
		2046	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2047	deterministic behaviour in this case (you can do nothing against
		2048	C<SIGSTOP>).
1204		2049
1205	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1206		2051
1207	=over 4	2052	=over 4
1208		2053
…		…
1227	This will act as if the timer timed out and restart it again if it is	2072	This will act as if the timer timed out and restart it again if it is
1228	repeating. The exact semantics are:	2073	repeating. The exact semantics are:
1229		2074
1230	If the timer is pending, its pending status is cleared.	2075	If the timer is pending, its pending status is cleared.
1231		2076
1232	If the timer is started but nonrepeating, stop it (as if it timed out).	2077	If the timer is started but non-repeating, stop it (as if it timed out).
1233		2078
1234	If the timer is repeating, either start it if necessary (with the	2079	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	2080	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		2081
1237	This sounds a bit complicated, but here is a useful and typical	2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a tcp connection and you want a so-called idle	2083	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		2084
1247	That means you can ignore the C<after> value and C<ev_timer_start>	2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		2086
1250	ev_timer_init (timer, callback, 0., 5.);	2087	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	2088	then this time is relative to the current event loop time, otherwise it's
1252	...	2089	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		2090
1259	This is more slightly efficient then stopping/starting the timer each time	2091	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	2092	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2093	will return C<4>. When the timer expires and is restarted, it will return
		2094	roughly C<7> (likely slightly less as callback invocation takes some time,
		2095	too), and so on.
1261		2096
1262	=item ev_tstamp repeat [read-write]	2097	=item ev_tstamp repeat [read-write]
1263		2098
1264	The current C<repeat> value. Will be used each time the watcher times out	2099	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	2100	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	2101	which is also when any modifications are taken into account.
1267		2102
1268	=back	2103	=back
1269		2104
1270	=head3 Examples	2105	=head3 Examples
1271		2106
1272	Example: Create a timer that fires after 60 seconds.	2107	Example: Create a timer that fires after 60 seconds.
1273		2108
1274	static void	2109	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2110	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	2111	{
1277	.. one minute over, w is actually stopped right here	2112	.. one minute over, w is actually stopped right here
1278	}	2113	}
1279		2114
1280	struct ev_timer mytimer;	2115	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2116	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	2117	ev_timer_start (loop, &mytimer);
1283		2118
1284	Example: Create a timeout timer that times out after 10 seconds of	2119	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	2120	inactivity.
1286		2121
1287	static void	2122	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2123	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	2124	{
1290	.. ten seconds without any activity	2125	.. ten seconds without any activity
1291	}	2126	}
1292		2127
1293	struct ev_timer mytimer;	2128	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1297		2132
1298	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1301		2136
1302		2137
1303	=head2 C<ev_periodic> - to cron or not to cron?	2138	=head2 C<ev_periodic> - to cron or not to cron?
1304		2139
1305	Periodic watchers are also timers of a kind, but they are very versatile	2140	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	2141	(and unfortunately a bit complex).
1307		2142
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wallclock time (absolute time). You can tell a periodic watcher	2144	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	2145	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	2146	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	2147	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to january of the previous year, then it will take more than year	2148	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		2149
		2150	You can tell a periodic watcher to trigger after some specific point
		2151	in time: for example, if you tell a periodic watcher to trigger "in 10
		2152	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2153	not a delay) and then reset your system clock to January of the previous
		2154	year, then it will take a year or more to trigger the event (unlike an
		2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2156	it, as it uses a relative timeout).
		2157
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	2158	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	2159	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2161	those cannot react to time jumps.
1320		2162
1321	As with timers, the callback is guarenteed to be invoked only when the	2163	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	2164	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	2165	timers become ready during the same loop iteration then the ones with
		2166	earlier time-out values are invoked before ones with later time-out values
		2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1324		2168
1325	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1326		2170
1327	=over 4	2171	=over 4
1328		2172
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2173	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		2174
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2175	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		2176
1333	Lots of arguments, lets sort it out... There are basically three modes of	2177	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	2178	operation, and we will explain them from simplest to most complex:
1335		2179
1336	=over 4	2180	=over 4
1337		2181
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2182	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		2183
1340	In this configuration the watcher triggers an event after the wallclock	2184	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	2185	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2186	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	2187	will be stopped and invoked when the system clock reaches or surpasses
		2188	this point in time.
1344		2189
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2190	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		2191
1347	In this mode the watcher will always be scheduled to time out at the next	2192	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	2193	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	2194	negative) and then repeat, regardless of any time jumps. The C<offset>
		2195	argument is merely an offset into the C<interval> periods.
1350		2196
1351	This can be used to create timers that do not drift with respect to system	2197	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	2198	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	2199	hour, on the hour (with respect to UTC):
1354		2200
1355	ev_periodic_set (&periodic, 0., 3600., 0);	2201	ev_periodic_set (&periodic, 0., 3600., 0);
1356		2202
1357	This doesn't mean there will always be 3600 seconds in between triggers,	2203	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the the callback will be called when the system time shows a	2204	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	2205	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	2206	by 3600.
1361		2207
1362	Another way to think about it (for the mathematically inclined) is that	2208	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	2209	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	2210	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		2211
1366	For numerical stability it is preferable that the C<at> value is near	2212	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	2213	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	2214	this value, and in fact is often specified as zero.
1369		2215
1370	Note also that there is an upper limit to how often a timer can fire (cpu	2216	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	2217	speed for example), so if C<interval> is very small then timing stability
1372	will of course detoriate. Libev itself tries to be exact to be about one	2218	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	2219	millisecond (if the OS supports it and the machine is fast enough).
1374		2220
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2221	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		2222
1377	In this mode the values for C<interval> and C<at> are both being	2223	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	2224	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	2225	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2226	current time as second argument.
1381		2227
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2228	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2229	or make ANY other event loop modifications whatsoever, unless explicitly
		2230	allowed by documentation here>.
1384		2231
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2232	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2233	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2234	only event loop modification you are allowed to do).
1388		2235
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2236	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2237	*w, ev_tstamp now)>, e.g.:
1391		2238
		2239	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2240	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2241	{
1394	return now + 60.;	2242	return now + 60.;
1395	}	2243	}
1396		2244
1397	It must return the next time to trigger, based on the passed time value	2245	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2265	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2266	program when the crontabs have changed).
1419		2267
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2268	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2269
1422	When active, returns the absolute time that the watcher is supposed to	2270	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2271	to trigger next. This is not the same as the C<offset> argument to
		2272	C<ev_periodic_set>, but indeed works even in interval and manual
		2273	rescheduling modes.
1424		2274
1425	=item ev_tstamp offset [read-write]	2275	=item ev_tstamp offset [read-write]
1426		2276
1427	When repeating, this contains the offset value, otherwise this is the	2277	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2278	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2279	although libev might modify this value for better numerical stability).
1429		2280
1430	Can be modified any time, but changes only take effect when the periodic	2281	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2282	timer fires or C<ev_periodic_again> is being called.
1432		2283
1433	=item ev_tstamp interval [read-write]	2284	=item ev_tstamp interval [read-write]
1434		2285
1435	The current interval value. Can be modified any time, but changes only	2286	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2287	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2288	called.
1438		2289
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2290	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2291
1441	The current reschedule callback, or C<0>, if this functionality is	2292	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2293	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2294	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2295
1445	=back	2296	=back
1446		2297
1447	=head3 Examples	2298	=head3 Examples
1448		2299
1449	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jittering, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
1452		2303
1453	static void	2304	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1455	{	2306	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2308	}
1458		2309
1459	struct ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2311	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2312	ev_periodic_start (loop, &hourly_tick);
1462		2313
1463	Example: The same as above, but use a reschedule callback to do it:	2314	Example: The same as above, but use a reschedule callback to do it:
1464		2315
1465	#include <math.h>	2316	#include <math.h>
1466		2317
1467	static ev_tstamp	2318	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2319	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2320	{
1470	return fmod (now, 3600.) + 3600.;	2321	return now + (3600. - fmod (now, 3600.));
1471	}	2322	}
1472		2323
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2324	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2325
1475	Example: Call a callback every hour, starting now:	2326	Example: Call a callback every hour, starting now:
1476		2327
1477	struct ev_periodic hourly_tick;	2328	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2329	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2330	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2331	ev_periodic_start (loop, &hourly_tick);
1481		2332
1482		2333
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		2335
1485	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2339	normal event processing, like any other event.
1489		2340
		2341	If you want signals to be delivered truly asynchronously, just use
		2342	C<sigaction> as you would do without libev and forget about sharing
		2343	the signal. You can even use C<ev_async> from a signal handler to
		2344	synchronously wake up an event loop.
		2345
1490	You can configure as many watchers as you like per signal. Only when the	2346	You can configure as many watchers as you like for the same signal, but
		2347	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2348	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2349	C<SIGINT> in both the default loop and another loop at the same time. At
		2350	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2351
1491	first watcher gets started will libev actually register a signal watcher	2352	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2353	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2354	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2355
1497	If possible and supported, libev will install its handlers with	2356	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with syscalls getting interrupted by	2358	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2359	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2360	and unblock them in an C<ev_prepare> watcher.
		2361
		2362	=head3 The special problem of inheritance over fork/execve/pthread_create
		2363
		2364	Both the signal mask (C<sigprocmask>) and the signal disposition
		2365	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2366	stopping it again), that is, libev might or might not block the signal,
		2367	and might or might not set or restore the installed signal handler.
		2368
		2369	While this does not matter for the signal disposition (libev never
		2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2371	C<execve>), this matters for the signal mask: many programs do not expect
		2372	certain signals to be blocked.
		2373
		2374	This means that before calling C<exec> (from the child) you should reset
		2375	the signal mask to whatever "default" you expect (all clear is a good
		2376	choice usually).
		2377
		2378	The simplest way to ensure that the signal mask is reset in the child is
		2379	to install a fork handler with C<pthread_atfork> that resets it. That will
		2380	catch fork calls done by libraries (such as the libc) as well.
		2381
		2382	In current versions of libev, the signal will not be blocked indefinitely
		2383	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2384	the window of opportunity for problems, it will not go away, as libev
		2385	I<has> to modify the signal mask, at least temporarily.
		2386
		2387	So I can't stress this enough: I<If you do not reset your signal mask when
		2388	you expect it to be empty, you have a race condition in your code>. This
		2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
1502		2404
1503	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
1504		2406
1505	=over 4	2407	=over 4
1506		2408
…		…
1517		2419
1518	=back	2420	=back
1519		2421
1520	=head3 Examples	2422	=head3 Examples
1521		2423
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2424	Example: Try to exit cleanly on SIGINT.
1523		2425
1524	static void	2426	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2428	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
1528	}	2430	}
1529		2431
1530	struct ev_signal signal_watcher;	2432	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2434	ev_signal_start (loop, &signal_watcher);
1533		2435
1534		2436
1535	=head2 C<ev_child> - watch out for process status changes	2437	=head2 C<ev_child> - watch out for process status changes
1536		2438
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2439	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2440	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2441	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2442	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2443	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2444	forking and then immediately registering a watcher for the child is fine,
		2445	but forking and registering a watcher a few event loop iterations later or
		2446	in the next callback invocation is not.
1542		2447
1543	Only the default event loop is capable of handling signals, and therefore	2448	Only the default event loop is capable of handling signals, and therefore
1544	you can only rgeister child watchers in the default event loop.	2449	you can only register child watchers in the default event loop.
		2450
		2451	Due to some design glitches inside libev, child watchers will always be
		2452	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2453	libev)
1545		2454
1546	=head3 Process Interaction	2455	=head3 Process Interaction
1547		2456
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2457	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2458	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurance	2459	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2460	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2461	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2462	children, even ones not watched.
1554		2463
1555	=head3 Overriding the Built-In Processing	2464	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2468	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2469	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2470	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2471	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2472	that, so other libev users can use C<ev_child> watchers freely.
		2473
		2474	=head3 Stopping the Child Watcher
		2475
		2476	Currently, the child watcher never gets stopped, even when the
		2477	child terminates, so normally one needs to stop the watcher in the
		2478	callback. Future versions of libev might stop the watcher automatically
		2479	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2480	problem).
1564		2481
1565	=head3 Watcher-Specific Functions and Data Members	2482	=head3 Watcher-Specific Functions and Data Members
1566		2483
1567	=over 4	2484	=over 4
1568		2485
…		…
1597	=head3 Examples	2514	=head3 Examples
1598		2515
1599	Example: C<fork()> a new process and install a child handler to wait for	2516	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	2517	its completion.
1601		2518
1602	ev_child cw;	2519	ev_child cw;
1603		2520
1604	static void	2521	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2522	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2523	{
1607	ev_child_stop (EV_A_ w);	2524	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2525	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2526	}
1610		2527
1611	pid_t pid = fork ();	2528	pid_t pid = fork ();
1612		2529
1613	if (pid < 0)	2530	if (pid < 0)
1614	// error	2531	// error
1615	else if (pid == 0)	2532	else if (pid == 0)
1616	{	2533	{
1617	// the forked child executes here	2534	// the forked child executes here
1618	exit (1);	2535	exit (1);
1619	}	2536	}
1620	else	2537	else
1621	{	2538	{
1622	ev_child_init (&cw, child_cb, pid, 0);	2539	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	2540	ev_child_start (EV_DEFAULT_ &cw);
1624	}	2541	}
1625		2542
1626		2543
1627	=head2 C<ev_stat> - did the file attributes just change?	2544	=head2 C<ev_stat> - did the file attributes just change?
1628		2545
1629	This watches a filesystem path for attribute changes. That is, it calls	2546	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2547	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2548	and sees if it changed compared to the last time, invoking the callback if
		2549	it did.
1632		2550
1633	The path does not need to exist: changing from "path exists" to "path does	2551	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2552	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2553	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2554	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2555	least one) and all the other fields of the stat buffer having unspecified
		2556	contents.
1638		2557
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2558	The path I<must not> end in a slash or contain special components such as
		2559	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2560	your working directory changes, then the behaviour is undefined.
1641		2561
1642	Since there is no standard to do this, the portable implementation simply	2562	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2563	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2564	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2565	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2566	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2567	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2568	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2569	currently around C<0.1>, but that's usually overkill.
1650		2570
1651	This watcher type is not meant for massive numbers of stat watchers,	2571	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2572	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2573	resource-intensive.
1654		2574
1655	At the time of this writing, only the Linux inotify interface is	2575	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2576	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2577	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2578	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2579
1664	=head3 ABI Issues (Largefile Support)	2580	=head3 ABI Issues (Largefile Support)
1665		2581
1666	Libev by default (unless the user overrides this) uses the default	2582	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2583	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2584	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2585	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2586	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2587	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2588	obviously the case with any flags that change the ABI, but the problem is
1673	most noticably with ev_stat and largefile support.	2589	most noticeably displayed with ev_stat and large file support.
1674		2590
1675	=head3 Inotify	2591	The solution for this is to lobby your distribution maker to make large
		2592	file interfaces available by default (as e.g. FreeBSD does) and not
		2593	optional. Libev cannot simply switch on large file support because it has
		2594	to exchange stat structures with application programs compiled using the
		2595	default compilation environment.
1676		2596
		2597	=head3 Inotify and Kqueue
		2598
1677	When C<inotify (7)> support has been compiled into libev (generally only	2599	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2600	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2601	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2602	watcher is being started.
1681		2603
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2604	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2605	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2606	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2607	there are many cases where libev has to resort to regular C<stat> polling,
		2608	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2609	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2610	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2611	xfs are fully working) libev usually gets away without polling.
1686		2612
1687	(There is no support for kqueue, as apparently it cannot be used to	2613	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2614	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2615	descriptor open on the object at all times, and detecting renames, unlinks
		2616	etc. is difficult.
		2617
		2618	=head3 C<stat ()> is a synchronous operation
		2619
		2620	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2621	the process. The exception are C<ev_stat> watchers - those call C<stat
		2622	()>, which is a synchronous operation.
		2623
		2624	For local paths, this usually doesn't matter: unless the system is very
		2625	busy or the intervals between stat's are large, a stat call will be fast,
		2626	as the path data is usually in memory already (except when starting the
		2627	watcher).
		2628
		2629	For networked file systems, calling C<stat ()> can block an indefinite
		2630	time due to network issues, and even under good conditions, a stat call
		2631	often takes multiple milliseconds.
		2632
		2633	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2634	paths, although this is fully supported by libev.
1690		2635
1691	=head3 The special problem of stat time resolution	2636	=head3 The special problem of stat time resolution
1692		2637
1693	The C<stat ()> syscall only supports full-second resolution portably, and	2638	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many filesystems still	2639	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2640	still only support whole seconds.
1696		2641
1697	That means that, if the time is the only thing that changes, you can	2642	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2643	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2644	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2645	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2646	stat data does change in other ways (e.g. file size).
1702		2647
1703	The solution to this is to delay acting on a change for slightly more	2648	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2649	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2650	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2651	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2671	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2672	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2673	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2674	path for as long as the watcher is active.
1730		2675
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2676	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2677	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2678	last change was detected).
1734		2679
1735	=item ev_stat_stat (loop, ev_stat *)	2680	=item ev_stat_stat (loop, ev_stat *)
1736		2681
1737	Updates the stat buffer immediately with new values. If you change the	2682	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2683	watched path in your callback, you could call this function to avoid
…		…
1759		2704
1760	The specified interval.	2705	The specified interval.
1761		2706
1762	=item const char *path [read-only]	2707	=item const char *path [read-only]
1763		2708
1764	The filesystem path that is being watched.	2709	The file system path that is being watched.
1765		2710
1766	=back	2711	=back
1767		2712
1768	=head3 Examples	2713	=head3 Examples
1769		2714
1770	Example: Watch C</etc/passwd> for attribute changes.	2715	Example: Watch C</etc/passwd> for attribute changes.
1771		2716
1772	static void	2717	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2718	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2719	{
1775	/* /etc/passwd changed in some way */	2720	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2721	if (w->attr.st_nlink)
1777	{	2722	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2723	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2724	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2725	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2726	}
1782	else	2727	else
1783	/* you shalt not abuse printf for puts */	2728	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2729	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2730	"if this is windows, they already arrived\n");
1786	}	2731	}
1787		2732
1788	...	2733	...
1789	ev_stat passwd;	2734	ev_stat passwd;
1790		2735
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2736	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2737	ev_stat_start (loop, &passwd);
1793		2738
1794	Example: Like above, but additionally use a one-second delay so we do not	2739	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2740	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2741	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2742	C<ev_timer> callback invocation).
1798		2743
1799	static ev_stat passwd;	2744	static ev_stat passwd;
1800	static ev_timer timer;	2745	static ev_timer timer;
1801		2746
1802	static void	2747	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2748	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2749	{
1805	ev_timer_stop (EV_A_ w);	2750	ev_timer_stop (EV_A_ w);
1806		2751
1807	/* now it's one second after the most recent passwd change */	2752	/* now it's one second after the most recent passwd change */
1808	}	2753	}
1809		2754
1810	static void	2755	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2756	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2757	{
1813	/* reset the one-second timer */	2758	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2759	ev_timer_again (EV_A_ &timer);
1815	}	2760	}
1816		2761
1817	...	2762	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2763	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2764	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2765	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2766
1822		2767
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2768	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2769
1825	Idle watchers trigger events when no other events of the same or higher	2770	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2771	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2772	as receiving "events").
1828		2773
1829	That is, as long as your process is busy handling sockets or timeouts	2774	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2775	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2776	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2777	are pending), the idle watchers are being called once per event loop
…		…
1843		2788
1844	=head3 Watcher-Specific Functions and Data Members	2789	=head3 Watcher-Specific Functions and Data Members
1845		2790
1846	=over 4	2791	=over 4
1847		2792
1848	=item ev_idle_init (ev_signal *, callback)	2793	=item ev_idle_init (ev_idle *, callback)
1849		2794
1850	Initialises and configures the idle watcher - it has no parameters of any	2795	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2796	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2797	believe me.
1853		2798
…		…
1856	=head3 Examples	2801	=head3 Examples
1857		2802
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2803	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2804	callback, free it. Also, use no error checking, as usual.
1860		2805
1861	static void	2806	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2807	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2808	{
1864	free (w);	2809	free (w);
1865	// now do something you wanted to do when the program has	2810	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2811	// no longer anything immediate to do.
1867	}	2812	}
1868		2813
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2815	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2816	ev_idle_start (loop, idle_watcher);
1872		2817
1873		2818
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2820
1876	Prepare and check watchers are usually (but not always) used in tandem:	2821	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2823	afterwards.
1879		2824
1880	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
1882	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
1883	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2831	called in pairs bracketing the blocking call.
1887		2832
1888	Their main purpose is to integrate other event mechanisms into libev and	2833	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2834	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2835	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2836	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2837	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2838	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2839	watcher).
1895		2840
1896	This is done by examining in each prepare call which file descriptors need	2841	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2842	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2843	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2844	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occured (by checking the pending status of all watchers	2845	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2846	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2847	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2848	nevertheless, because you never know, you know?).
1904		2849
1905	As another example, the Perl Coro module uses these hooks to integrate	2850	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2851	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2852	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2853	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2856	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2857	low-priority coroutines to idle/background tasks).
1913		2858
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2860	priority, to ensure that they are being run before any other watchers
		2861	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2862
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2864	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2865	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2866	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2867	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2869	others).
1923		2870
1924	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
1925		2872
1926	=over 4	2873	=over 4
1927		2874
…		…
1929		2876
1930	=item ev_check_init (ev_check *, callback)	2877	=item ev_check_init (ev_check *, callback)
1931		2878
1932	Initialises and configures the prepare or check watcher - they have no	2879	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2880	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2881	macros, but using them is utterly, utterly, utterly and completely
		2882	pointless.
1935		2883
1936	=back	2884	=back
1937		2885
1938	=head3 Examples	2886	=head3 Examples
1939		2887
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2896	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2897	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2899	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2900
1953	static ev_io iow [nfd];	2901	static ev_io iow [nfd];
1954	static ev_timer tw;	2902	static ev_timer tw;
1955		2903
1956	static void	2904	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2905	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2906	{
1959	}	2907	}
1960		2908
1961	// create io watchers for each fd and a timer before blocking	2909	// create io watchers for each fd and a timer before blocking
1962	static void	2910	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2911	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2912	{
1965	int timeout = 3600000;	2913	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2914	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2915	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2917
1970	/* the callback is illegal, but won't be called as we stop during check */	2918	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2919	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2920	ev_timer_start (loop, &tw);
1973		2921
1974	// create one ev_io per pollfd	2922	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2923	for (int i = 0; i < nfd; ++i)
1976	{	2924	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2925	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2926	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2928
1981	fds [i].revents = 0;	2929	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2930	ev_io_start (loop, iow + i);
1983	}	2931	}
1984	}	2932	}
1985		2933
1986	// stop all watchers after blocking	2934	// stop all watchers after blocking
1987	static void	2935	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2936	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2937	{
1990	ev_timer_stop (loop, &tw);	2938	ev_timer_stop (loop, &tw);
1991		2939
1992	for (int i = 0; i < nfd; ++i)	2940	for (int i = 0; i < nfd; ++i)
1993	{	2941	{
1994	// set the relevant poll flags	2942	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2943	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2944	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2945	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2948
2001	// now stop the watcher	2949	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2950	ev_io_stop (loop, iow + i);
2003	}	2951	}
2004		2952
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2954	}
2007		2955
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2957	in the prepare watcher and would dispose of the check watcher.
2010		2958
2011	Method 3: If the module to be embedded supports explicit event	2959	Method 3: If the module to be embedded supports explicit event
2012	notification (adns does), you can also make use of the actual watcher	2960	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2961	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2962
2015	static void	2963	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2964	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2965	{
2018	adns_state ads = (adns_state)w->data;	2966	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2967	update_now (EV_A);
2020		2968
2021	adns_processtimeouts (ads, &tv_now);	2969	adns_processtimeouts (ads, &tv_now);
2022	}	2970	}
2023		2971
2024	static void	2972	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2973	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2974	{
2027	adns_state ads = (adns_state)w->data;	2975	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2976	update_now (EV_A);
2029		2977
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2980	}
2033		2981
2034	// do not ever call adns_afterpoll	2982	// do not ever call adns_afterpoll
2035		2983
2036	Method 4: Do not use a prepare or check watcher because the module you	2984	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, youc na override	2985	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2986	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2987	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2988	this approach, effectively embedding EV as a client into the horrible
		2989	libglib event loop.
2041		2990
2042	static gint	2991	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2992	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2993	{
2045	int got_events = 0;	2994	int got_events = 0;
2046		2995
2047	for (n = 0; n < nfds; ++n)	2996	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2997	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2998
2050	if (timeout >= 0)	2999	if (timeout >= 0)
2051	// create/start timer	3000	// create/start timer
2052		3001
2053	// poll	3002	// poll
2054	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
2055		3004
2056	// stop timer again	3005	// stop timer again
2057	if (timeout >= 0)	3006	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2059		3008
2060	// stop io watchers again - their callbacks should have set	3009	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	3010	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	3011	ev_io_stop (EV_A_ iow [n]);
2063		3012
2064	return got_events;	3013	return got_events;
2065	}	3014	}
2066		3015
2067		3016
2068	=head2 C<ev_embed> - when one backend isn't enough...	3017	=head2 C<ev_embed> - when one backend isn't enough...
2069		3018
2070	This is a rather advanced watcher type that lets you embed one event loop	3019	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	3025	prioritise I/O.
2077		3026
2078	As an example for a bug workaround, the kqueue backend might only support	3027	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	3028	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	3029	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	3030	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	3031	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	3032	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	3033	C<kevent>, but at least you can use both mechanisms for what they are
		3034	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		3035
2086	As for prioritising I/O: rarely you have the case where some fds have	3036	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	3037	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	3038	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	3039	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	3040	the rest in a second one, and embed the second one in the first.
2091		3041
2092	As long as the watcher is active, the callback will be invoked every time	3042	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	3043	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3044	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	3045	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	3046	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	3047	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		3048
2100	As long as the watcher is started it will automatically handle events. The	3049	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	3050	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		3051
2105	Also, there have not currently been made special provisions for forking:	3052	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3053	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	3054	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	3055	C<ev_loop_fork> on the embedded loop.
2109		3056
2110	Unfortunately, not all backends are embeddable, only the ones returned by	3057	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3058	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	3059	portable one.
2113		3060
2114	So when you want to use this feature you will always have to be prepared	3061	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	3062	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	3063	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	3064	create it, and if that fails, use the normal loop for everything.
2118		3065
		3066	=head3 C<ev_embed> and fork
		3067
		3068	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3069	automatically be applied to the embedded loop as well, so no special
		3070	fork handling is required in that case. When the watcher is not running,
		3071	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3072	as applicable.
		3073
2119	=head3 Watcher-Specific Functions and Data Members	3074	=head3 Watcher-Specific Functions and Data Members
2120		3075
2121	=over 4	3076	=over 4
2122		3077
2123	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3078	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2126		3081
2127	Configures the watcher to embed the given loop, which must be	3082	Configures the watcher to embed the given loop, which must be
2128	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3083	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2129	invoked automatically, otherwise it is the responsibility of the callback	3084	invoked automatically, otherwise it is the responsibility of the callback
2130	to invoke it (it will continue to be called until the sweep has been done,	3085	to invoke it (it will continue to be called until the sweep has been done,
2131	if you do not want thta, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2132		3087
2133	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2134		3089
2135	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2137	apropriate way for embedded loops.	3092	appropriate way for embedded loops.
2138		3093
2139	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2140		3095
2141	The embedded event loop.	3096	The embedded event loop.
2142		3097
…		…
2144		3099
2145	=head3 Examples	3100	=head3 Examples
2146		3101
2147	Example: Try to get an embeddable event loop and embed it into the default	3102	Example: Try to get an embeddable event loop and embed it into the default
2148	event loop. If that is not possible, use the default loop. The default	3103	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	3104	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	3105	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	3106	used).
2152		3107
2153	struct ev_loop *loop_hi = ev_default_init (0);	3108	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	3109	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	3110	ev_embed embed;
2156		3111
2157	// see if there is a chance of getting one that works	3112	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	3113	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	3116	: 0;
2162		3117
2163	// if we got one, then embed it, otherwise default to loop_hi	3118	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	3119	if (loop_lo)
2165	{	3120	{
2166	ev_embed_init (&embed, 0, loop_lo);	3121	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	3122	ev_embed_start (loop_hi, &embed);
2168	}	3123	}
2169	else	3124	else
2170	loop_lo = loop_hi;	3125	loop_lo = loop_hi;
2171		3126
2172	Example: Check if kqueue is available but not recommended and create	3127	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	3128	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	3129	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		3131
2177	struct ev_loop *loop = ev_default_init (0);	3132	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	3133	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	3134	ev_embed embed;
2180		3135
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	3138	{
2184	ev_embed_init (&embed, 0, loop_socket);	3139	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	3140	ev_embed_start (loop, &embed);
2186	}	3141	}
2187		3142
2188	if (!loop_socket)	3143	if (!loop_socket)
2189	loop_socket = loop;	3144	loop_socket = loop;
2190		3145
2191	// now use loop_socket for all sockets, and loop for everything else	3146	// now use loop_socket for all sockets, and loop for everything else
2192		3147
2193		3148
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		3150
2196	Fork watchers are called when a C<fork ()> was detected (usually because	3151	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	3154	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	3155	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2203		3158
		3159	=head3 The special problem of life after fork - how is it possible?
		3160
		3161	Most uses of C<fork()> consist of forking, then some simple calls to set
		3162	up/change the process environment, followed by a call to C<exec()>. This
		3163	sequence should be handled by libev without any problems.
		3164
		3165	This changes when the application actually wants to do event handling
		3166	in the child, or both parent in child, in effect "continuing" after the
		3167	fork.
		3168
		3169	The default mode of operation (for libev, with application help to detect
		3170	forks) is to duplicate all the state in the child, as would be expected
		3171	when I<either> the parent I<or> the child process continues.
		3172
		3173	When both processes want to continue using libev, then this is usually the
		3174	wrong result. In that case, usually one process (typically the parent) is
		3175	supposed to continue with all watchers in place as before, while the other
		3176	process typically wants to start fresh, i.e. without any active watchers.
		3177
		3178	The cleanest and most efficient way to achieve that with libev is to
		3179	simply create a new event loop, which of course will be "empty", and
		3180	use that for new watchers. This has the advantage of not touching more
		3181	memory than necessary, and thus avoiding the copy-on-write, and the
		3182	disadvantage of having to use multiple event loops (which do not support
		3183	signal watchers).
		3184
		3185	When this is not possible, or you want to use the default loop for
		3186	other reasons, then in the process that wants to start "fresh", call
		3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3188	Destroying the default loop will "orphan" (not stop) all registered
		3189	watchers, so you have to be careful not to execute code that modifies
		3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
		3192
2204	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2205		3194
2206	=over 4	3195	=over 4
2207		3196
2208	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2209		3198
2210	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2211	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2212	believe me.	3201	really.
2213		3202
2214	=back	3203	=back
2215		3204
2216		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2217	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2218		3247
2219	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2220	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2221	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2222		3251
2223	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2224	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2226	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2227	safe.
2228		3256
2229	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2230	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2231	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2232	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2233		3264
2234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2235	just the default loop.	3266	just the default loop.
2236		3267
2237	=head3 Queueing	3268	=head3 Queueing
2238		3269
2239	C<ev_async> does not support queueing of data in any way. The reason	3270	C<ev_async> does not support queueing of data in any way. The reason
2240	is that the author does not know of a simple (or any) algorithm for a	3271	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	3272	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	3273	need elaborate support such as pthreads or unportable memory access
		3274	semantics.
2243		3275
2244	That means that if you want to queue data, you have to provide your own	3276	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	3277	queue. But at least I can tell you how to implement locking around your
2246	queue:	3278	queue:
2247		3279
2248	=over 4	3280	=over 4
2249		3281
2250	=item queueing from a signal handler context	3282	=item queueing from a signal handler context
2251		3283
2252	To implement race-free queueing, you simply add to the queue in the signal	3284	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3285	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitiuous SIGUSR1 handler:	3286	an example that does that for some fictitious SIGUSR1 handler:
2255		3287
2256	static ev_async mysig;	3288	static ev_async mysig;
2257		3289
2258	static void	3290	static void
2259	sigusr1_handler (void)	3291	sigusr1_handler (void)
…		…
2325	=over 4	3357	=over 4
2326		3358
2327	=item ev_async_init (ev_async *, callback)	3359	=item ev_async_init (ev_async *, callback)
2328		3360
2329	Initialises and configures the async watcher - it has no parameters of any	3361	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3362	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3363	trust me.
2332		3364
2333	=item ev_async_send (loop, ev_async *)	3365	=item ev_async_send (loop, ev_async *)
2334		3366
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3369	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3371	section below on what exactly this means).
2340		3372
		3373	Note that, as with other watchers in libev, multiple events might get
		3374	compressed into a single callback invocation (another way to look at this
		3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3376	reset when the event loop detects that).
		3377
2341	This call incurs the overhead of a syscall only once per loop iteration,	3378	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticable, it doesn't apply to repeated	3379	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3380	repeated calls to C<ev_async_send> for the same event loop.
2344		3381
2345	=item bool = ev_async_pending (ev_async *)	3382	=item bool = ev_async_pending (ev_async *)
2346		3383
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3384	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3385	watcher but the event has not yet been processed (or even noted) by the
2349	event loop.	3386	event loop.
2350		3387
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3388	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3389	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3390	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check wether invoking the loop might be a good idea.	3391	quickly check whether invoking the loop might be a good idea.
2355		3392
2356	Not that this does I<not> check wether the watcher itself is pending, only	3393	Not that this does I<not> check whether the watcher itself is pending,
2357	wether it has been requested to make this watcher pending.	3394	only whether it has been requested to make this watcher pending: there
		3395	is a time window between the event loop checking and resetting the async
		3396	notification, and the callback being invoked.
2358		3397
2359	=back	3398	=back
2360		3399
2361		3400
2362	=head1 OTHER FUNCTIONS	3401	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3405	=over 4
2367		3406
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3407	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3408
2370	This function combines a simple timer and an I/O watcher, calls your	3409	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3410	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3411	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3412	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3413	more watchers yourself.
2375		3414
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3415	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3416	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be craeted and started.	3417	the given C<fd> and C<events> set will be created and started.
2379		3418
2380	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3421	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3422
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2386	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2388	value passed to C<ev_once>:	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3427	a timeout and an io event at the same time - you probably should give io
		3428	events precedence.
2389		3429
		3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3431
2390	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
2391	{	3433	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	3434	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
		3436	else if (revents & EV_TIMER)
		3437	/* doh, nothing entered */;
2396	}	3438	}
2397		3439
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3441
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3442	=item ev_feed_fd_event (loop, int fd, int revents)
2407		3443
2408	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3445	the given events it.
2410		3446
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
2412		3448
2413	Feed an event as if the given signal occured (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2414	loop!).	3450	which is async-safe.
		3451
		3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
2415		3637
2416	=back	3638	=back
2417		3639
2418		3640
2419	=head1 LIBEVENT EMULATION	3641	=head1 LIBEVENT EMULATION
2420		3642
2421	Libev offers a compatibility emulation layer for libevent. It cannot	3643	Libev offers a compatibility emulation layer for libevent. It cannot
2422	emulate the internals of libevent, so here are some usage hints:	3644	emulate the internals of libevent, so here are some usage hints:
2423		3645
2424	=over 4	3646	=over 4
		3647
		3648	=item * Only the libevent-1.4.1-beta API is being emulated.
		3649
		3650	This was the newest libevent version available when libev was implemented,
		3651	and is still mostly unchanged in 2010.
2425		3652
2426	=item * Use it by including <event.h>, as usual.	3653	=item * Use it by including <event.h>, as usual.
2427		3654
2428	=item * The following members are fully supported: ev_base, ev_callback,	3655	=item * The following members are fully supported: ev_base, ev_callback,
2429	ev_arg, ev_fd, ev_res, ev_events.	3656	ev_arg, ev_fd, ev_res, ev_events.
…		…
2435	=item * Priorities are not currently supported. Initialising priorities	3662	=item * Priorities are not currently supported. Initialising priorities
2436	will fail and all watchers will have the same priority, even though there	3663	will fail and all watchers will have the same priority, even though there
2437	is an ev_pri field.	3664	is an ev_pri field.
2438		3665
2439	=item * In libevent, the last base created gets the signals, in libev, the	3666	=item * In libevent, the last base created gets the signals, in libev, the
2440	first base created (== the default loop) gets the signals.	3667	base that registered the signal gets the signals.
2441		3668
2442	=item * Other members are not supported.	3669	=item * Other members are not supported.
2443		3670
2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3671	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2445	to use the libev header file and library.	3672	to use the libev header file and library.
…		…
2447	=back	3674	=back
2448		3675
2449	=head1 C++ SUPPORT	3676	=head1 C++ SUPPORT
2450		3677
2451	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3678	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2452	you to use some convinience methods to start/stop watchers and also change	3679	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	3680	the callback model to a model using method callbacks on objects.
2454		3681
2455	To use it,	3682	To use it,
2456		3683
2457	#include <ev++.h>	3684	#include <ev++.h>
2458		3685
2459	This automatically includes F<ev.h> and puts all of its definitions (many	3686	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	3687	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	3688	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3689	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2464	Care has been taken to keep the overhead low. The only data member the C++	3691	Care has been taken to keep the overhead low. The only data member the C++
2465	classes add (compared to plain C-style watchers) is the event loop pointer	3692	classes add (compared to plain C-style watchers) is the event loop pointer
2466	that the watcher is associated with (or no additional members at all if	3693	that the watcher is associated with (or no additional members at all if
2467	you disable C<EV_MULTIPLICITY> when embedding libev).	3694	you disable C<EV_MULTIPLICITY> when embedding libev).
2468		3695
2469	Currently, functions, and static and non-static member functions can be	3696	Currently, functions, static and non-static member functions and classes
2470	used as callbacks. Other types should be easy to add as long as they only	3697	with C<operator ()> can be used as callbacks. Other types should be easy
2471	need one additional pointer for context. If you need support for other	3698	to add as long as they only need one additional pointer for context. If
2472	types of functors please contact the author (preferably after implementing	3699	you need support for other types of functors please contact the author
2473	it).	3700	(preferably after implementing it).
2474		3701
2475	Here is a list of things available in the C<ev> namespace:	3702	Here is a list of things available in the C<ev> namespace:
2476		3703
2477	=over 4	3704	=over 4
2478		3705
…		…
2496		3723
2497	=over 4	3724	=over 4
2498		3725
2499	=item ev::TYPE::TYPE ()	3726	=item ev::TYPE::TYPE ()
2500		3727
2501	=item ev::TYPE::TYPE (struct ev_loop *)	3728	=item ev::TYPE::TYPE (loop)
2502		3729
2503	=item ev::TYPE::~TYPE	3730	=item ev::TYPE::~TYPE
2504		3731
2505	The constructor (optionally) takes an event loop to associate the watcher	3732	The constructor (optionally) takes an event loop to associate the watcher
2506	with. If it is omitted, it will use C<EV_DEFAULT>.	3733	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	3756	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	3757	thunking function, making it as fast as a direct C callback.
2531		3758
2532	Example: simple class declaration and watcher initialisation	3759	Example: simple class declaration and watcher initialisation
2533		3760
2534	struct myclass	3761	struct myclass
2535	{	3762	{
2536	void io_cb (ev::io &w, int revents) { }	3763	void io_cb (ev::io &w, int revents) { }
2537	}	3764	}
2538		3765
2539	myclass obj;	3766	myclass obj;
2540	ev::io iow;	3767	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3768	iow.set <myclass, &myclass::io_cb> (&obj);
		3769
		3770	=item w->set (object *)
		3771
		3772	This is a variation of a method callback - leaving out the method to call
		3773	will default the method to C<operator ()>, which makes it possible to use
		3774	functor objects without having to manually specify the C<operator ()> all
		3775	the time. Incidentally, you can then also leave out the template argument
		3776	list.
		3777
		3778	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3779	int revents)>.
		3780
		3781	See the method-C<set> above for more details.
		3782
		3783	Example: use a functor object as callback.
		3784
		3785	struct myfunctor
		3786	{
		3787	void operator() (ev::io &w, int revents)
		3788	{
		3789	...
		3790	}
		3791	}
		3792
		3793	myfunctor f;
		3794
		3795	ev::io w;
		3796	w.set (&f);
2542		3797
2543	=item w->set<function> (void *data = 0)	3798	=item w->set<function> (void *data = 0)
2544		3799
2545	Also sets a callback, but uses a static method or plain function as	3800	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3801	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		3803
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3804	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3805
2551	See the method-C<set> above for more details.	3806	See the method-C<set> above for more details.
2552		3807
2553	Example:	3808	Example: Use a plain function as callback.
2554		3809
2555	static void io_cb (ev::io &w, int revents) { }	3810	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3811	iow.set <io_cb> ();
2557		3812
2558	=item w->set (struct ev_loop *)	3813	=item w->set (loop)
2559		3814
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3815	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3816	do this when the watcher is inactive (and not pending either).
2562		3817
2563	=item w->set ([args])	3818	=item w->set ([arguments])
2564		3819
2565	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3820	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2566	called at least once. Unlike the C counterpart, an active watcher gets	3821	method or a suitable start method must be called at least once. Unlike the
2567	automatically stopped and restarted when reconfiguring it with this	3822	C counterpart, an active watcher gets automatically stopped and restarted
2568	method.	3823	when reconfiguring it with this method.
2569		3824
2570	=item w->start ()	3825	=item w->start ()
2571		3826
2572	Starts the watcher. Note that there is no C<loop> argument, as the	3827	Starts the watcher. Note that there is no C<loop> argument, as the
2573	constructor already stores the event loop.	3828	constructor already stores the event loop.
2574		3829
		3830	=item w->start ([arguments])
		3831
		3832	Instead of calling C<set> and C<start> methods separately, it is often
		3833	convenient to wrap them in one call. Uses the same type of arguments as
		3834	the configure C<set> method of the watcher.
		3835
2575	=item w->stop ()	3836	=item w->stop ()
2576		3837
2577	Stops the watcher if it is active. Again, no C<loop> argument.	3838	Stops the watcher if it is active. Again, no C<loop> argument.
2578		3839
2579	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3840	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2591		3852
2592	=back	3853	=back
2593		3854
2594	=back	3855	=back
2595		3856
2596	Example: Define a class with an IO and idle watcher, start one of them in	3857	Example: Define a class with two I/O and idle watchers, start the I/O
2597	the constructor.	3858	watchers in the constructor.
2598		3859
2599	class myclass	3860	class myclass
2600	{	3861	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3862	ev::io io ; void io_cb (ev::io &w, int revents);
		3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3865
2604	myclass (int fd)	3866	myclass (int fd)
2605	{	3867	{
2606	io .set <myclass, &myclass::io_cb > (this);	3868	io .set <myclass, &myclass::io_cb > (this);
		3869	io2 .set <myclass, &myclass::io2_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3870	idle.set <myclass, &myclass::idle_cb> (this);
2608		3871
2609	io.start (fd, ev::READ);	3872	io.set (fd, ev::WRITE); // configure the watcher
		3873	io.start (); // start it whenever convenient
		3874
		3875	io2.start (fd, ev::READ); // set + start in one call
2610	}	3876	}
2611	};	3877	};
2612		3878
2613		3879
2614	=head1 OTHER LANGUAGE BINDINGS	3880	=head1 OTHER LANGUAGE BINDINGS
2615		3881
2616	Libev does not offer other language bindings itself, but bindings for a	3882	Libev does not offer other language bindings itself, but bindings for a
2617	numbe rof languages exist in the form of third-party packages. If you know	3883	number of languages exist in the form of third-party packages. If you know
2618	any interesting language binding in addition to the ones listed here, drop	3884	any interesting language binding in addition to the ones listed here, drop
2619	me a note.	3885	me a note.
2620		3886
2621	=over 4	3887	=over 4
2622		3888
2623	=item Perl	3889	=item Perl
2624		3890
2625	The EV module implements the full libev API and is actually used to test	3891	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3892	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3893	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3894	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3895	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3896	and C<EV::Glib>).
2630		3897
2631	It can be found and installed via CPAN, its homepage is found at	3898	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3899	L<http://software.schmorp.de/pkg/EV>.
2633		3900
		3901	=item Python
		3902
		3903	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3904	seems to be quite complete and well-documented.
		3905
2634	=item Ruby	3906	=item Ruby
2635		3907
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3908	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds filehandle abstractions, asynchronous DNS and	3909	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3910	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3911	L<http://rev.rubyforge.org/>.
2640		3912
		3913	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3914	makes rev work even on mingw.
		3915
		3916	=item Haskell
		3917
		3918	A haskell binding to libev is available at
		3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3920
2641	=item D	3921	=item D
2642		3922
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3925
		3926	=item Ocaml
		3927
		3928	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3930
		3931	=item Lua
		3932
		3933	Brian Maher has written a partial interface to libev for lua (at the
		3934	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3935	L<http://github.com/brimworks/lua-ev>.
2645		3936
2646	=back	3937	=back
2647		3938
2648		3939
2649	=head1 MACRO MAGIC	3940	=head1 MACRO MAGIC
2650		3941
2651	Libev can be compiled with a variety of options, the most fundamantal	3942	Libev can be compiled with a variety of options, the most fundamental
2652	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3943	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2653	functions and callbacks have an initial C<struct ev_loop *> argument.	3944	functions and callbacks have an initial C<struct ev_loop *> argument.
2654		3945
2655	To make it easier to write programs that cope with either variant, the	3946	To make it easier to write programs that cope with either variant, the
2656	following macros are defined:	3947	following macros are defined:
…		…
2661		3952
2662	This provides the loop I<argument> for functions, if one is required ("ev	3953	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3954	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3955	C<EV_A_> is used when other arguments are following. Example:
2665		3956
2666	ev_unref (EV_A);	3957	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3958	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3959	ev_run (EV_A_ 0);
2669		3960
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3961	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3962	which is often provided by the following macro.
2672		3963
2673	=item C<EV_P>, C<EV_P_>	3964	=item C<EV_P>, C<EV_P_>
2674		3965
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3966	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3967	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	3968	C<EV_P_> is used when other parameters are following. Example:
2678		3969
2679	// this is how ev_unref is being declared	3970	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3971	static void ev_unref (EV_P);
2681		3972
2682	// this is how you can declare your typical callback	3973	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3974	static void cb (EV_P_ ev_timer *w, int revents)
2684		3975
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3976	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3977	suitable for use with C<EV_A>.
2687		3978
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3979	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3995
2705	Example: Declare and initialise a check watcher, utilising the above	3996	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3997	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3998	or not.
2708		3999
2709	static void	4000	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	4001	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	4002	{
2712	ev_check_stop (EV_A_ w);	4003	ev_check_stop (EV_A_ w);
2713	}	4004	}
2714		4005
2715	ev_check check;	4006	ev_check check;
2716	ev_check_init (&check, check_cb);	4007	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	4008	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	4009	ev_run (EV_DEFAULT_ 0);
2719		4010
2720	=head1 EMBEDDING	4011	=head1 EMBEDDING
2721		4012
2722	Libev can (and often is) directly embedded into host	4013	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	4014	applications. Examples of applications that embed it include the Deliantra
…		…
2730	libev somewhere in your source tree).	4021	libev somewhere in your source tree).
2731		4022
2732	=head2 FILESETS	4023	=head2 FILESETS
2733		4024
2734	Depending on what features you need you need to include one or more sets of files	4025	Depending on what features you need you need to include one or more sets of files
2735	in your app.	4026	in your application.
2736		4027
2737	=head3 CORE EVENT LOOP	4028	=head3 CORE EVENT LOOP
2738		4029
2739	To include only the libev core (all the C<ev_*> functions), with manual	4030	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	4031	configuration (no autoconf):
2741		4032
2742	#define EV_STANDALONE 1	4033	#define EV_STANDALONE 1
2743	#include "ev.c"	4034	#include "ev.c"
2744		4035
2745	This will automatically include F<ev.h>, too, and should be done in a	4036	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	4037	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	4038	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	4039	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	4040	where you can put other configuration options):
2750		4041
2751	#define EV_STANDALONE 1	4042	#define EV_STANDALONE 1
2752	#include "ev.h"	4043	#include "ev.h"
2753		4044
2754	Both header files and implementation files can be compiled with a C++	4045	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	4046	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	4047	as a bug).
2757		4048
2758	You need the following files in your source tree, or in a directory	4049	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	4050	in your include path (e.g. in libev/ when using -Ilibev):
2760		4051
2761	ev.h	4052	ev.h
2762	ev.c	4053	ev.c
2763	ev_vars.h	4054	ev_vars.h
2764	ev_wrap.h	4055	ev_wrap.h
2765		4056
2766	ev_win32.c required on win32 platforms only	4057	ev_win32.c required on win32 platforms only
2767		4058
2768	ev_select.c only when select backend is enabled (which is enabled by default)	4059	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	4060	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4061	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4062	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	4063	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		4064
2774	F<ev.c> includes the backend files directly when enabled, so you only need	4065	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	4066	to compile this single file.
2776		4067
2777	=head3 LIBEVENT COMPATIBILITY API	4068	=head3 LIBEVENT COMPATIBILITY API
2778		4069
2779	To include the libevent compatibility API, also include:	4070	To include the libevent compatibility API, also include:
2780		4071
2781	#include "event.c"	4072	#include "event.c"
2782		4073
2783	in the file including F<ev.c>, and:	4074	in the file including F<ev.c>, and:
2784		4075
2785	#include "event.h"	4076	#include "event.h"
2786		4077
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	4078	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		4079
2789	You need the following additional files for this:	4080	You need the following additional files for this:
2790		4081
2791	event.h	4082	event.h
2792	event.c	4083	event.c
2793		4084
2794	=head3 AUTOCONF SUPPORT	4085	=head3 AUTOCONF SUPPORT
2795		4086
2796	Instead of using C<EV_STANDALONE=1> and providing your config in	4087	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	4088	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	4089	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	4090	include F<config.h> and configure itself accordingly.
2800		4091
2801	For this of course you need the m4 file:	4092	For this of course you need the m4 file:
2802		4093
2803	libev.m4	4094	libev.m4
2804		4095
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	4096	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		4097
2807	Libev can be configured via a variety of preprocessor symbols you have to	4098	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absense of	4099	define before including (or compiling) any of its files. The default in
2809	autoconf is noted for every option.	4100	the absence of autoconf is documented for every option.
		4101
		4102	Symbols marked with "(h)" do not change the ABI, and can have different
		4103	values when compiling libev vs. including F<ev.h>, so it is permissible
		4104	to redefine them before including F<ev.h> without breaking compatibility
		4105	to a compiled library. All other symbols change the ABI, which means all
		4106	users of libev and the libev code itself must be compiled with compatible
		4107	settings.
2810		4108
2811	=over 4	4109	=over 4
2812		4110
		4111	=item EV_COMPAT3 (h)
		4112
		4113	Backwards compatibility is a major concern for libev. This is why this
		4114	release of libev comes with wrappers for the functions and symbols that
		4115	have been renamed between libev version 3 and 4.
		4116
		4117	You can disable these wrappers (to test compatibility with future
		4118	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4119	sources. This has the additional advantage that you can drop the C<struct>
		4120	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4121	typedef in that case.
		4122
		4123	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4124	and in some even more future version the compatibility code will be
		4125	removed completely.
		4126
2813	=item EV_STANDALONE	4127	=item EV_STANDALONE (h)
2814		4128
2815	Must always be C<1> if you do not use autoconf configuration, which	4129	Must always be C<1> if you do not use autoconf configuration, which
2816	keeps libev from including F<config.h>, and it also defines dummy	4130	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	4131	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	4132	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	4133	F<event.h> that are not directly supported by the libev core alone.
2820		4134
		4135	In standalone mode, libev will still try to automatically deduce the
		4136	configuration, but has to be more conservative.
		4137
2821	=item EV_USE_MONOTONIC	4138	=item EV_USE_MONOTONIC
2822		4139
2823	If defined to be C<1>, libev will try to detect the availability of the	4140	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compiletime and runtime. Otherwise no use	4141	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	4142	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	4143	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	4144	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	4145	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	4146	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		4147
2831	=item EV_USE_REALTIME	4148	=item EV_USE_REALTIME
2832		4149
2833	If defined to be C<1>, libev will try to detect the availability of the	4150	If defined to be C<1>, libev will try to detect the availability of the
2834	realtime clock option at compiletime (and assume its availability at	4151	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the realtime clock option will	4152	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4153	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4154	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4155	correctness. See the note about libraries in the description of
		4156	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4157	C<EV_USE_CLOCK_SYSCALL>.
		4158
		4159	=item EV_USE_CLOCK_SYSCALL
		4160
		4161	If defined to be C<1>, libev will try to use a direct syscall instead
		4162	of calling the system-provided C<clock_gettime> function. This option
		4163	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4164	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4165	programs needlessly. Using a direct syscall is slightly slower (in
		4166	theory), because no optimised vdso implementation can be used, but avoids
		4167	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4168	higher, as it simplifies linking (no need for C<-lrt>).
2839		4169
2840	=item EV_USE_NANOSLEEP	4170	=item EV_USE_NANOSLEEP
2841		4171
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4172	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	4173	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2851	2.7 or newer, otherwise disabled.	4181	2.7 or newer, otherwise disabled.
2852		4182
2853	=item EV_USE_SELECT	4183	=item EV_USE_SELECT
2854		4184
2855	If undefined or defined to be C<1>, libev will compile in support for the	4185	If undefined or defined to be C<1>, libev will compile in support for the
2856	C<select>(2) backend. No attempt at autodetection will be done: if no	4186	C<select>(2) backend. No attempt at auto-detection will be done: if no
2857	other method takes over, select will be it. Otherwise the select backend	4187	other method takes over, select will be it. Otherwise the select backend
2858	will not be compiled in.	4188	will not be compiled in.
2859		4189
2860	=item EV_SELECT_USE_FD_SET	4190	=item EV_SELECT_USE_FD_SET
2861		4191
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	4192	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	4193	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	4194	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	4195	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	4196	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4197	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	4198	configures the maximum size of the C<fd_set>.
2869		4199
2870	=item EV_SELECT_IS_WINSOCKET	4200	=item EV_SELECT_IS_WINSOCKET
2871		4201
2872	When defined to C<1>, the select backend will assume that	4202	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	4203	select/socket/connect etc. don't understand file descriptors but
…		…
2875	be used is the winsock select). This means that it will call	4205	be used is the winsock select). This means that it will call
2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4206	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2877	it is assumed that all these functions actually work on fds, even	4207	it is assumed that all these functions actually work on fds, even
2878	on win32. Should not be defined on non-win32 platforms.	4208	on win32. Should not be defined on non-win32 platforms.
2879		4209
2880	=item EV_FD_TO_WIN32_HANDLE	4210	=item EV_FD_TO_WIN32_HANDLE(fd)
2881		4211
2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4212	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2883	file descriptors to socket handles. When not defining this symbol (the	4213	file descriptors to socket handles. When not defining this symbol (the
2884	default), then libev will call C<_get_osfhandle>, which is usually	4214	default), then libev will call C<_get_osfhandle>, which is usually
2885	correct. In some cases, programs use their own file descriptor management,	4215	correct. In some cases, programs use their own file descriptor management,
2886	in which case they can provide this function to map fds to socket handles.	4216	in which case they can provide this function to map fds to socket handles.
		4217
		4218	=item EV_WIN32_HANDLE_TO_FD(handle)
		4219
		4220	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4221	using the standard C<_open_osfhandle> function. For programs implementing
		4222	their own fd to handle mapping, overwriting this function makes it easier
		4223	to do so. This can be done by defining this macro to an appropriate value.
		4224
		4225	=item EV_WIN32_CLOSE_FD(fd)
		4226
		4227	If programs implement their own fd to handle mapping on win32, then this
		4228	macro can be used to override the C<close> function, useful to unregister
		4229	file descriptors again. Note that the replacement function has to close
		4230	the underlying OS handle.
2887		4231
2888	=item EV_USE_POLL	4232	=item EV_USE_POLL
2889		4233
2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4234	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2891	backend. Otherwise it will be enabled on non-win32 platforms. It	4235	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2918	otherwise another method will be used as fallback. This is the preferred	4262	otherwise another method will be used as fallback. This is the preferred
2919	backend for Solaris 10 systems.	4263	backend for Solaris 10 systems.
2920		4264
2921	=item EV_USE_DEVPOLL	4265	=item EV_USE_DEVPOLL
2922		4266
2923	reserved for future expansion, works like the USE symbols above.	4267	Reserved for future expansion, works like the USE symbols above.
2924		4268
2925	=item EV_USE_INOTIFY	4269	=item EV_USE_INOTIFY
2926		4270
2927	If defined to be C<1>, libev will compile in support for the Linux inotify	4271	If defined to be C<1>, libev will compile in support for the Linux inotify
2928	interface to speed up C<ev_stat> watchers. Its actual availability will	4272	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2935	access is atomic with respect to other threads or signal contexts. No such	4279	access is atomic with respect to other threads or signal contexts. No such
2936	type is easily found in the C language, so you can provide your own type	4280	type is easily found in the C language, so you can provide your own type
2937	that you know is safe for your purposes. It is used both for signal handler "locking"	4281	that you know is safe for your purposes. It is used both for signal handler "locking"
2938	as well as for signal and thread safety in C<ev_async> watchers.	4282	as well as for signal and thread safety in C<ev_async> watchers.
2939		4283
2940	In the absense of this define, libev will use C<sig_atomic_t volatile>	4284	In the absence of this define, libev will use C<sig_atomic_t volatile>
2941	(from F<signal.h>), which is usually good enough on most platforms.	4285	(from F<signal.h>), which is usually good enough on most platforms.
2942		4286
2943	=item EV_H	4287	=item EV_H (h)
2944		4288
2945	The name of the F<ev.h> header file used to include it. The default if	4289	The name of the F<ev.h> header file used to include it. The default if
2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2947	used to virtually rename the F<ev.h> header file in case of conflicts.	4291	used to virtually rename the F<ev.h> header file in case of conflicts.
2948		4292
2949	=item EV_CONFIG_H	4293	=item EV_CONFIG_H (h)
2950		4294
2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2953	C<EV_H>, above.	4297	C<EV_H>, above.
2954		4298
2955	=item EV_EVENT_H	4299	=item EV_EVENT_H (h)
2956		4300
2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2958	of how the F<event.h> header can be found, the default is C<"event.h">.	4302	of how the F<event.h> header can be found, the default is C<"event.h">.
2959		4303
2960	=item EV_PROTOTYPES	4304	=item EV_PROTOTYPES (h)
2961		4305
2962	If defined to be C<0>, then F<ev.h> will not define any function	4306	If defined to be C<0>, then F<ev.h> will not define any function
2963	prototypes, but still define all the structs and other symbols. This is	4307	prototypes, but still define all the structs and other symbols. This is
2964	occasionally useful if you want to provide your own wrapper functions	4308	occasionally useful if you want to provide your own wrapper functions
2965	around libev functions.	4309	around libev functions.
…		…
2984	When doing priority-based operations, libev usually has to linearly search	4328	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	4329	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	4330	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	4331	fine.
2988		4332
2989	If your embedding app does not need any priorities, defining these both to	4333	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and cpu.	4334	both to C<0> will save some memory and CPU.
2991		4335
2992	=item EV_PERIODIC_ENABLE	4336	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4337	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4338	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2993		4339
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	4340	If undefined or defined to be C<1> (and the platform supports it), then
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	4341	the respective watcher type is supported. If defined to be C<0>, then it
2996	code.	4342	is not. Disabling watcher types mainly saves code size.
2997		4343
2998	=item EV_IDLE_ENABLE	4344	=item EV_FEATURES
2999
3000	If undefined or defined to be C<1>, then idle watchers are supported. If
3001	defined to be C<0>, then they are not. Disabling them saves a few kB of
3002	code.
3003
3004	=item EV_EMBED_ENABLE
3005
3006	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.
3008
3009	=item EV_STAT_ENABLE
3010
3011	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.
3013
3014	=item EV_FORK_ENABLE
3015
3016	If undefined or defined to be C<1>, then fork watchers are supported. If
3017	defined to be C<0>, then they are not.
3018
3019	=item EV_ASYNC_ENABLE
3020
3021	If undefined or defined to be C<1>, then async watchers are supported. If
3022	defined to be C<0>, then they are not.
3023
3024	=item EV_MINIMAL
3025		4345
3026	If you need to shave off some kilobytes of code at the expense of some	4346	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	4347	speed (but with the full API), you can define this symbol to request
3028	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	4348	certain subsets of functionality. The default is to enable all features
3029	much smaller 2-heap for timer management over the default 4-heap.	4349	that can be enabled on the platform.
		4350
		4351	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4352	with some broad features you want) and then selectively re-enable
		4353	additional parts you want, for example if you want everything minimal,
		4354	but multiple event loop support, async and child watchers and the poll
		4355	backend, use this:
		4356
		4357	#define EV_FEATURES 0
		4358	#define EV_MULTIPLICITY 1
		4359	#define EV_USE_POLL 1
		4360	#define EV_CHILD_ENABLE 1
		4361	#define EV_ASYNC_ENABLE 1
		4362
		4363	The actual value is a bitset, it can be a combination of the following
		4364	values:
		4365
		4366	=over 4
		4367
		4368	=item C<1> - faster/larger code
		4369
		4370	Use larger code to speed up some operations.
		4371
		4372	Currently this is used to override some inlining decisions (enlarging the
		4373	code size by roughly 30% on amd64).
		4374
		4375	When optimising for size, use of compiler flags such as C<-Os> with
		4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4377	assertions.
		4378
		4379	=item C<2> - faster/larger data structures
		4380
		4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4382	hash table sizes and so on. This will usually further increase code size
		4383	and can additionally have an effect on the size of data structures at
		4384	runtime.
		4385
		4386	=item C<4> - full API configuration
		4387
		4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4389	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4390
		4391	=item C<8> - full API
		4392
		4393	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4394	details on which parts of the API are still available without this
		4395	feature, and do not complain if this subset changes over time.
		4396
		4397	=item C<16> - enable all optional watcher types
		4398
		4399	Enables all optional watcher types. If you want to selectively enable
		4400	only some watcher types other than I/O and timers (e.g. prepare,
		4401	embed, async, child...) you can enable them manually by defining
		4402	C<EV_watchertype_ENABLE> to C<1> instead.
		4403
		4404	=item C<32> - enable all backends
		4405
		4406	This enables all backends - without this feature, you need to enable at
		4407	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4408
		4409	=item C<64> - enable OS-specific "helper" APIs
		4410
		4411	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4412	default.
		4413
		4414	=back
		4415
		4416	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4417	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4418	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4419	watchers, timers and monotonic clock support.
		4420
		4421	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4423	your program might be left out as well - a binary starting a timer and an
		4424	I/O watcher then might come out at only 5Kb.
		4425
		4426	=item EV_AVOID_STDIO
		4427
		4428	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4429	functions (printf, scanf, perror etc.). This will increase the code size
		4430	somewhat, but if your program doesn't otherwise depend on stdio and your
		4431	libc allows it, this avoids linking in the stdio library which is quite
		4432	big.
		4433
		4434	Note that error messages might become less precise when this option is
		4435	enabled.
		4436
		4437	=item EV_NSIG
		4438
		4439	The highest supported signal number, +1 (or, the number of
		4440	signals): Normally, libev tries to deduce the maximum number of signals
		4441	automatically, but sometimes this fails, in which case it can be
		4442	specified. Also, using a lower number than detected (C<32> should be
		4443	good for about any system in existence) can save some memory, as libev
		4444	statically allocates some 12-24 bytes per signal number.
3030		4445
3031	=item EV_PID_HASHSIZE	4446	=item EV_PID_HASHSIZE
3032		4447
3033	C<ev_child> watchers use a small hash table to distribute workload by	4448	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4449	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3035	than enough. If you need to manage thousands of children you might want to	4450	usually more than enough. If you need to manage thousands of children you
3036	increase this value (I<must> be a power of two).	4451	might want to increase this value (I<must> be a power of two).
3037		4452
3038	=item EV_INOTIFY_HASHSIZE	4453	=item EV_INOTIFY_HASHSIZE
3039		4454
3040	C<ev_stat> watchers use a small hash table to distribute workload by	4455	C<ev_stat> watchers use a small hash table to distribute workload by
3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4456	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3042	usually more than enough. If you need to manage thousands of C<ev_stat>	4457	disabled), usually more than enough. If you need to manage thousands of
3043	watchers you might want to increase this value (I<must> be a power of	4458	C<ev_stat> watchers you might want to increase this value (I<must> be a
3044	two).	4459	power of two).
3045		4460
3046	=item EV_USE_4HEAP	4461	=item EV_USE_4HEAP
3047		4462
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4463	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4464	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	4465	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticably faster performance with many (thousands) of watchers.	4466	faster performance with many (thousands) of watchers.
3052		4467
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4468	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3054	(disabled).	4469	will be C<0>.
3055		4470
3056	=item EV_HEAP_CACHE_AT	4471	=item EV_HEAP_CACHE_AT
3057		4472
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4473	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	4474	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4475	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4476	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	4477	but avoids random read accesses on heap changes. This improves performance
3063	noticably with with many (hundreds) of watchers.	4478	noticeably with many (hundreds) of watchers.
3064		4479
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4480	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3066	(disabled).	4481	will be C<0>.
3067		4482
3068	=item EV_VERIFY	4483	=item EV_VERIFY
3069		4484
3070	Controls how much internal verification (see C<ev_loop_verify ()>) will	4485	Controls how much internal verification (see C<ev_verify ()>) will
3071	be done: If set to C<0>, no internal verification code will be compiled	4486	be done: If set to C<0>, no internal verification code will be compiled
3072	in. If set to C<1>, then verification code will be compiled in, but not	4487	in. If set to C<1>, then verification code will be compiled in, but not
3073	called. If set to C<2>, then the internal verification code will be	4488	called. If set to C<2>, then the internal verification code will be
3074	called once per loop, which can slow down libev. If set to C<3>, then the	4489	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	4490	verification code will be called very frequently, which will slow down
3076	libev considerably.	4491	libev considerably.
3077		4492
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4493	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3079	C<0.>	4494	will be C<0>.
3080		4495
3081	=item EV_COMMON	4496	=item EV_COMMON
3082		4497
3083	By default, all watchers have a C<void *data> member. By redefining	4498	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	4499	this macro to something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	4500	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	4501	though, and it must be identical each time.
3087		4502
3088	For example, the perl EV module uses something like this:	4503	For example, the perl EV module uses something like this:
3089		4504
3090	#define EV_COMMON \	4505	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	4506	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	4507	SV *cb_sv, *fh /* note no trailing ";" */
3093		4508
3094	=item EV_CB_DECLARE (type)	4509	=item EV_CB_DECLARE (type)
3095		4510
3096	=item EV_CB_INVOKE (watcher, revents)	4511	=item EV_CB_INVOKE (watcher, revents)
3097		4512
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	4517	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	4518	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4519	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	4520	method calls instead of plain function calls in C++.
3106		4521
		4522	=back
		4523
3107	=head2 EXPORTED API SYMBOLS	4524	=head2 EXPORTED API SYMBOLS
3108		4525
3109	If you need to re-export the API (e.g. via a dll) and you need a list of	4526	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	4527	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	4528	all public symbols, one per line:
3112		4529
3113	Symbols.ev for libev proper	4530	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	4531	Symbols.event for the libevent emulation
3115		4532
3116	This can also be used to rename all public symbols to avoid clashes with	4533	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	4534	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvinient to avoid this).	4535	itself, but sometimes it is inconvenient to avoid this).
3119		4536
3120	A sed command like this will create wrapper C<#define>'s that you need to	4537	A sed command like this will create wrapper C<#define>'s that you need to
3121	include before including F<ev.h>:	4538	include before including F<ev.h>:
3122		4539
3123	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4540	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3140	file.	4557	file.
3141		4558
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4559	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	4560	that everybody includes and which overrides some configure choices:
3144		4561
3145	#define EV_MINIMAL 1	4562	#define EV_FEATURES 8
3146	#define EV_USE_POLL 0	4563	#define EV_USE_SELECT 1
3147	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	4564	#define EV_PREPARE_ENABLE 1
		4565	#define EV_IDLE_ENABLE 1
3149	#define EV_STAT_ENABLE 0	4566	#define EV_SIGNAL_ENABLE 1
3150	#define EV_FORK_ENABLE 0	4567	#define EV_CHILD_ENABLE 1
		4568	#define EV_USE_STDEXCEPT 0
3151	#define EV_CONFIG_H <config.h>	4569	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0
3154		4570
3155	#include "ev++.h"	4571	#include "ev++.h"
3156		4572
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		4574
3159	#include "ev_cpp.h"	4575	#include "ev_cpp.h"
3160	#include "ev.c"	4576	#include "ev.c"
3161		4577
		4578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		4579
3163	=head1 THREADS AND COROUTINES	4580	=head2 THREADS AND COROUTINES
3164		4581
3165	=head2 THREADS	4582	=head3 THREADS
3166		4583
3167	Libev itself is completely threadsafe, but it uses no locking. This	4584	All libev functions are reentrant and thread-safe unless explicitly
		4585	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	4586	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	4587	are no concurrent calls into any libev function with the same loop
3170	parameter.	4588	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4589	of course): libev guarantees that different event loops share no data
		4590	structures that need any locking.
3171		4591
3172	Or put differently: calls with different loop parameters can be done in	4592	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	4593	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	4594	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	4595	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	4596	a mutex per loop).
3177		4597
3178	If you want to know which design is best for your problem, then I cannot	4598	Specifically to support threads (and signal handlers), libev implements
		4599	so-called C<ev_async> watchers, which allow some limited form of
		4600	concurrency on the same event loop, namely waking it up "from the
		4601	outside".
		4602
		4603	If you want to know which design (one loop, locking, or multiple loops
		4604	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	4605	help you, but here is some generic advice:
3180		4606
3181	=over 4	4607	=over 4
3182		4608
3183	=item * most applications have a main thread: use the default libev loop	4609	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a seperate thread running only the default loop.	4610	in that thread, or create a separate thread running only the default loop.
3185		4611
3186	This helps integrating other libraries or software modules that use libev	4612	This helps integrating other libraries or software modules that use libev
3187	themselves and don't care/know about threading.	4613	themselves and don't care/know about threading.
3188		4614
3189	=item * one loop per thread is usually a good model.	4615	=item * one loop per thread is usually a good model.
3190		4616
3191	Doing this is almost never wrong, sometimes a better-performance model	4617	Doing this is almost never wrong, sometimes a better-performance model
3192	exists, but it is always a good start.	4618	exists, but it is always a good start.
3193		4619
3194	=item * other models exist, such as the leader/follower pattern, where one	4620	=item * other models exist, such as the leader/follower pattern, where one
3195	loop is handed through multiple threads in a kind of round-robbin fashion.	4621	loop is handed through multiple threads in a kind of round-robin fashion.
3196		4622
3197	Chosing a model is hard - look around, learn, know that usually you cna do	4623	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	4624	better than you currently do :-)
3199		4625
3200	=item * often you need to talk to some other thread which blocks in the	4626	=item * often you need to talk to some other thread which blocks in the
		4627	event loop.
		4628
3201	event loop - C<ev_async> watchers can be used to wake them up from other	4629	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	4630	(or from signal contexts...).
		4631
		4632	An example use would be to communicate signals or other events that only
		4633	work in the default loop by registering the signal watcher with the
		4634	default loop and triggering an C<ev_async> watcher from the default loop
		4635	watcher callback into the event loop interested in the signal.
3203		4636
3204	=back	4637	=back
3205		4638
		4639	See also L<THREAD LOCKING EXAMPLE>.
		4640
3206	=head2 COROUTINES	4641	=head3 COROUTINES
3207		4642
3208	Libev is much more accomodating to coroutines ("cooperative threads"):	4643	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4644	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4645	coroutines (e.g. you can call C<ev_run> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4646	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4647	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4648	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4649
3215	Care has been invested into making sure that libev does not keep local	4650	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4651	C<ev_run>, and other calls do not usually allow for coroutine switches as
3217	switches.	4652	they do not call any callbacks.
3218		4653
		4654	=head2 COMPILER WARNINGS
3219		4655
3220	=head1 COMPLEXITIES	4656	Depending on your compiler and compiler settings, you might get no or a
		4657	lot of warnings when compiling libev code. Some people are apparently
		4658	scared by this.
3221		4659
3222	In this section the complexities of (many of) the algorithms used inside	4660	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4661	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4662	warning options. "Warn-free" code therefore cannot be a goal except when
		4663	targeting a specific compiler and compiler-version.
3225		4664
3226	All of the following are about amortised time: If an array needs to be	4665	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4666	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4667	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4668
3232	=over 4	4669	And of course, some compiler warnings are just plain stupid, or simply
		4670	wrong (because they don't actually warn about the condition their message
		4671	seems to warn about). For example, certain older gcc versions had some
		4672	warnings that resulted in an extreme number of false positives. These have
		4673	been fixed, but some people still insist on making code warn-free with
		4674	such buggy versions.
3233		4675
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4676	While libev is written to generate as few warnings as possible,
		4677	"warn-free" code is not a goal, and it is recommended not to build libev
		4678	with any compiler warnings enabled unless you are prepared to cope with
		4679	them (e.g. by ignoring them). Remember that warnings are just that:
		4680	warnings, not errors, or proof of bugs.
3235		4681
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4682
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4683	=head2 VALGRIND
3241		4684
3242	That means that changing a timer costs less than removing/adding them	4685	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4686	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4687
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4688	If you think you found a bug (memory leak, uninitialised data access etc.)
		4689	in libev, then check twice: If valgrind reports something like:
3246		4690
3247	These just add the watcher into an array or at the head of a list.	4691	==2274== definitely lost: 0 bytes in 0 blocks.
		4692	==2274== possibly lost: 0 bytes in 0 blocks.
		4693	==2274== still reachable: 256 bytes in 1 blocks.
3248		4694
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4695	Then there is no memory leak, just as memory accounted to global variables
		4696	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4697
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4698	Similarly, under some circumstances, valgrind might report kernel bugs
		4699	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4700	although an acceptable workaround has been found here), or it might be
		4701	confused.
3252		4702
3253	These watchers are stored in lists then need to be walked to find the	4703	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4704	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4705
3257	=item Finding the next timer in each loop iteration: O(1)	4706	If you are unsure about something, feel free to contact the mailing list
		4707	with the full valgrind report and an explanation on why you think this
		4708	is a bug in libev (best check the archives, too :). However, don't be
		4709	annoyed when you get a brisk "this is no bug" answer and take the chance
		4710	of learning how to interpret valgrind properly.
3258		4711
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4712	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4713	I suggest using suppression lists.
3261		4714
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4715
3264	A change means an I/O watcher gets started or stopped, which requires	4716	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and wether C<ev_io_set> was used).
3267		4717
3268	=item Activating one watcher (putting it into the pending state): O(1)	4718	=head2 GNU/LINUX 32 BIT LIMITATIONS
3269		4719
3270	=item Priority handling: O(number_of_priorities)	4720	GNU/Linux is the only common platform that supports 64 bit file/large file
		4721	interfaces but I<disables> them by default.
3271		4722
3272	Priorities are implemented by allocating some space for each	4723	That means that libev compiled in the default environment doesn't support
3273	priority. When doing priority-based operations, libev usually has to	4724	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276		4725
3277	=item Sending an ev_async: O(1)	4726	Unfortunately, many programs try to work around this GNU/Linux issue
		4727	by enabling the large file API, which makes them incompatible with the
		4728	standard libev compiled for their system.
3278		4729
3279	=item Processing ev_async_send: O(number_of_async_watchers)	4730	Likewise, libev cannot enable the large file API itself as this would
		4731	suddenly make it incompatible to the default compile time environment,
		4732	i.e. all programs not using special compile switches.
3280		4733
3281	=item Processing signals: O(max_signal_number)	4734	=head2 OS/X AND DARWIN BUGS
3282		4735
3283	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4736	The whole thing is a bug if you ask me - basically any system interface
3284	calls in the current loop iteration. Checking for async and signal events	4737	you touch is broken, whether it is locales, poll, kqueue or even the
3285	involves iterating over all running async watchers or all signal numbers.	4738	OpenGL drivers.
3286		4739
3287	=back	4740	=head3 C<kqueue> is buggy
3288		4741
		4742	The kqueue syscall is broken in all known versions - most versions support
		4743	only sockets, many support pipes.
3289		4744
3290	=head1 Win32 platform limitations and workarounds	4745	Libev tries to work around this by not using C<kqueue> by default on this
		4746	rotten platform, but of course you can still ask for it when creating a
		4747	loop - embedding a socket-only kqueue loop into a select-based one is
		4748	probably going to work well.
		4749
		4750	=head3 C<poll> is buggy
		4751
		4752	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4753	implementation by something calling C<kqueue> internally around the 10.5.6
		4754	release, so now C<kqueue> I<and> C<poll> are broken.
		4755
		4756	Libev tries to work around this by not using C<poll> by default on
		4757	this rotten platform, but of course you can still ask for it when creating
		4758	a loop.
		4759
		4760	=head3 C<select> is buggy
		4761
		4762	All that's left is C<select>, and of course Apple found a way to fuck this
		4763	one up as well: On OS/X, C<select> actively limits the number of file
		4764	descriptors you can pass in to 1024 - your program suddenly crashes when
		4765	you use more.
		4766
		4767	There is an undocumented "workaround" for this - defining
		4768	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4769	work on OS/X.
		4770
		4771	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4772
		4773	=head3 C<errno> reentrancy
		4774
		4775	The default compile environment on Solaris is unfortunately so
		4776	thread-unsafe that you can't even use components/libraries compiled
		4777	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4778	defined by default. A valid, if stupid, implementation choice.
		4779
		4780	If you want to use libev in threaded environments you have to make sure
		4781	it's compiled with C<_REENTRANT> defined.
		4782
		4783	=head3 Event port backend
		4784
		4785	The scalable event interface for Solaris is called "event
		4786	ports". Unfortunately, this mechanism is very buggy in all major
		4787	releases. If you run into high CPU usage, your program freezes or you get
		4788	a large number of spurious wakeups, make sure you have all the relevant
		4789	and latest kernel patches applied. No, I don't know which ones, but there
		4790	are multiple ones to apply, and afterwards, event ports actually work
		4791	great.
		4792
		4793	If you can't get it to work, you can try running the program by setting
		4794	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4795	C<select> backends.
		4796
		4797	=head2 AIX POLL BUG
		4798
		4799	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4800	this by trying to avoid the poll backend altogether (i.e. it's not even
		4801	compiled in), which normally isn't a big problem as C<select> works fine
		4802	with large bitsets on AIX, and AIX is dead anyway.
		4803
		4804	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4805
		4806	=head3 General issues
3291		4807
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4808	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4809	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4810	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3296	descriptors. This only applies when using Win32 natively, not when using	4812	descriptors. This only applies when using Win32 natively, not when using
3297	e.g. cygwin.	4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4814	as every compielr comes with a slightly differently broken/incompatible
		4815	environment.
3298		4816
3299	Lifting these limitations would basically require the full	4817	Lifting these limitations would basically require the full
3300	re-implementation of the I/O system. If you are into these kinds of	4818	re-implementation of the I/O system. If you are into this kind of thing,
3301	things, then note that glib does exactly that for you in a very portable	4819	then note that glib does exactly that for you in a very portable way (note
3302	way (note also that glib is the slowest event library known to man).	4820	also that glib is the slowest event library known to man).
3303		4821
3304	There is no supported compilation method available on windows except	4822	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4823	embedding it into other applications.
		4824
		4825	Sensible signal handling is officially unsupported by Microsoft - libev
		4826	tries its best, but under most conditions, signals will simply not work.
		4827
		4828	Not a libev limitation but worth mentioning: windows apparently doesn't
		4829	accept large writes: instead of resulting in a partial write, windows will
		4830	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4831	so make sure you only write small amounts into your sockets (less than a
		4832	megabyte seems safe, but this apparently depends on the amount of memory
		4833	available).
3306		4834
3307	Due to the many, low, and arbitrary limits on the win32 platform and	4835	Due to the many, low, and arbitrary limits on the win32 platform and
3308	the abysmal performance of winsockets, using a large number of sockets	4836	the abysmal performance of winsockets, using a large number of sockets
3309	is not recommended (and not reasonable). If your program needs to use	4837	is not recommended (and not reasonable). If your program needs to use
3310	more than a hundred or so sockets, then likely it needs to use a totally	4838	more than a hundred or so sockets, then likely it needs to use a totally
3311	different implementation for windows, as libev offers the POSIX readiness	4839	different implementation for windows, as libev offers the POSIX readiness
3312	notification model, which cannot be implemented efficiently on windows	4840	notification model, which cannot be implemented efficiently on windows
3313	(microsoft monopoly games).	4841	(due to Microsoft monopoly games).
3314		4842
3315	=over 4	4843	A typical way to use libev under windows is to embed it (see the embedding
		4844	section for details) and use the following F<evwrap.h> header file instead
		4845	of F<ev.h>:
3316		4846
		4847	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4848	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4849
		4850	#include "ev.h"
		4851
		4852	And compile the following F<evwrap.c> file into your project (make sure
		4853	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4854
		4855	#include "evwrap.h"
		4856	#include "ev.c"
		4857
3317	=item The winsocket select function	4858	=head3 The winsocket C<select> function
3318		4859
3319	The winsocket C<select> function doesn't follow POSIX in that it	4860	The winsocket C<select> function doesn't follow POSIX in that it
3320	requires socket I<handles> and not socket I<file descriptors> (it is	4861	requires socket I<handles> and not socket I<file descriptors> (it is
3321	also extremely buggy). This makes select very inefficient, and also	4862	also extremely buggy). This makes select very inefficient, and also
3322	requires a mapping from file descriptors to socket handles. See the	4863	requires a mapping from file descriptors to socket handles (the Microsoft
		4864	C runtime provides the function C<_open_osfhandle> for this). See the
3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4865	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4866	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3325		4867
3326	The configuration for a "naked" win32 using the microsoft runtime	4868	The configuration for a "naked" win32 using the Microsoft runtime
3327	libraries and raw winsocket select is:	4869	libraries and raw winsocket select is:
3328		4870
3329	#define EV_USE_SELECT 1	4871	#define EV_USE_SELECT 1
3330	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4872	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3331		4873
3332	Note that winsockets handling of fd sets is O(n), so you can easily get a	4874	Note that winsockets handling of fd sets is O(n), so you can easily get a
3333	complexity in the O(n²) range when using win32.	4875	complexity in the O(n²) range when using win32.
3334		4876
3335	=item Limited number of file descriptors	4877	=head3 Limited number of file descriptors
3336		4878
3337	Windows has numerous arbitrary (and low) limits on things.	4879	Windows has numerous arbitrary (and low) limits on things.
3338		4880
3339	Early versions of winsocket's select only supported waiting for a maximum	4881	Early versions of winsocket's select only supported waiting for a maximum
3340	of C<64> handles (probably owning to the fact that all windows kernels	4882	of C<64> handles (probably owning to the fact that all windows kernels
3341	can only wait for C<64> things at the same time internally; microsoft	4883	can only wait for C<64> things at the same time internally; Microsoft
3342	recommends spawning a chain of threads and wait for 63 handles and the	4884	recommends spawning a chain of threads and wait for 63 handles and the
3343	previous thread in each. Great).	4885	previous thread in each. Sounds great!).
3344		4886
3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4887	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3346	to some high number (e.g. C<2048>) before compiling the winsocket select	4888	to some high number (e.g. C<2048>) before compiling the winsocket select
3347	call (which might be in libev or elsewhere, for example, perl does its own	4889	call (which might be in libev or elsewhere, for example, perl and many
3348	select emulation on windows).	4890	other interpreters do their own select emulation on windows).
3349		4891
3350	Another limit is the number of file descriptors in the microsoft runtime	4892	Another limit is the number of file descriptors in the Microsoft runtime
3351	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4893	libraries, which by default is C<64> (there must be a hidden I<64>
3352	or something like this inside microsoft). You can increase this by calling	4894	fetish or something like this inside Microsoft). You can increase this
3353	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4895	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3354	arbitrary limit), but is broken in many versions of the microsoft runtime	4896	(another arbitrary limit), but is broken in many versions of the Microsoft
3355	libraries.
3356
3357	This might get you to about C<512> or C<2048> sockets (depending on	4897	runtime libraries. This might get you to about C<512> or C<2048> sockets
3358	windows version and/or the phase of the moon). To get more, you need to	4898	(depending on windows version and/or the phase of the moon). To get more,
3359	wrap all I/O functions and provide your own fd management, but the cost of	4899	you need to wrap all I/O functions and provide your own fd management, but
3360	calling select (O(n²)) will likely make this unworkable.	4900	the cost of calling select (O(n²)) will likely make this unworkable.
3361		4901
3362	=back
3363
3364
3365	=head1 PORTABILITY REQUIREMENTS	4902	=head2 PORTABILITY REQUIREMENTS
3366		4903
3367	In addition to a working ISO-C implementation, libev relies on a few	4904	In addition to a working ISO-C implementation and of course the
3368	additional extensions:	4905	backend-specific APIs, libev relies on a few additional extensions:
3369		4906
3370	=over 4	4907	=over 4
3371		4908
		4909	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4910	calling conventions regardless of C<ev_watcher_type *>.
		4911
		4912	Libev assumes not only that all watcher pointers have the same internal
		4913	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4914	assumes that the same (machine) code can be used to call any watcher
		4915	callback: The watcher callbacks have different type signatures, but libev
		4916	calls them using an C<ev_watcher *> internally.
		4917
		4918	=item pointer accesses must be thread-atomic
		4919
		4920	Accessing a pointer value must be atomic, it must both be readable and
		4921	writable in one piece - this is the case on all current architectures.
		4922
3372	=item C<sig_atomic_t volatile> must be thread-atomic as well	4923	=item C<sig_atomic_t volatile> must be thread-atomic as well
3373		4924
3374	The type C<sig_atomic_t volatile> (or whatever is defined as	4925	The type C<sig_atomic_t volatile> (or whatever is defined as
3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4926	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3376	threads. This is not part of the specification for C<sig_atomic_t>, but is	4927	threads. This is not part of the specification for C<sig_atomic_t>, but is
3377	believed to be sufficiently portable.	4928	believed to be sufficiently portable.
3378		4929
3379	=item C<sigprocmask> must work in a threaded environment	4930	=item C<sigprocmask> must work in a threaded environment
3380		4931
…		…
3389	except the initial one, and run the default loop in the initial thread as	4940	except the initial one, and run the default loop in the initial thread as
3390	well.	4941	well.
3391		4942
3392	=item C<long> must be large enough for common memory allocation sizes	4943	=item C<long> must be large enough for common memory allocation sizes
3393		4944
3394	To improve portability and simplify using libev, libev uses C<long>	4945	To improve portability and simplify its API, libev uses C<long> internally
3395	internally instead of C<size_t> when allocating its data structures. On	4946	instead of C<size_t> when allocating its data structures. On non-POSIX
3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4947	systems (Microsoft...) this might be unexpectedly low, but is still at
3397	is still at least 31 bits everywhere, which is enough for hundreds of	4948	least 31 bits everywhere, which is enough for hundreds of millions of
3398	millions of watchers.	4949	watchers.
3399		4950
3400	=item C<double> must hold a time value in seconds with enough accuracy	4951	=item C<double> must hold a time value in seconds with enough accuracy
3401		4952
3402	The type C<double> is used to represent timestamps. It is required to	4953	The type C<double> is used to represent timestamps. It is required to
3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3404	enough for at least into the year 4000. This requirement is fulfilled by	4955	good enough for at least into the year 4000 with millisecond accuracy
		4956	(the design goal for libev). This requirement is overfulfilled by
3405	implementations implementing IEEE 754 (basically all existing ones).	4957	implementations using IEEE 754, which is basically all existing ones. With
		4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3406		4959
3407	=back	4960	=back
3408		4961
3409	If you know of other additional requirements drop me a note.	4962	If you know of other additional requirements drop me a note.
3410		4963
3411		4964
3412	=head1 COMPILER WARNINGS	4965	=head1 ALGORITHMIC COMPLEXITIES
3413		4966
3414	Depending on your compiler and compiler settings, you might get no or a	4967	In this section the complexities of (many of) the algorithms used inside
3415	lot of warnings when compiling libev code. Some people are apparently	4968	libev will be documented. For complexity discussions about backends see
3416	scared by this.	4969	the documentation for C<ev_default_init>.
3417		4970
3418	However, these are unavoidable for many reasons. For one, each compiler	4971	All of the following are about amortised time: If an array needs to be
3419	has different warnings, and each user has different tastes regarding	4972	extended, libev needs to realloc and move the whole array, but this
3420	warning options. "Warn-free" code therefore cannot be a goal except when	4973	happens asymptotically rarer with higher number of elements, so O(1) might
3421	targetting a specific compiler and compiler-version.	4974	mean that libev does a lengthy realloc operation in rare cases, but on
		4975	average it is much faster and asymptotically approaches constant time.
3422		4976
3423	Another reason is that some compiler warnings require elaborate	4977	=over 4
3424	workarounds, or other changes to the code that make it less clear and less
3425	maintainable.
3426		4978
3427	And of course, some compiler warnings are just plain stupid, or simply	4979	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3428	wrong (because they don't actually warn about the cindition their message
3429	seems to warn about).
3430		4980
3431	While libev is written to generate as few warnings as possible,	4981	This means that, when you have a watcher that triggers in one hour and
3432	"warn-free" code is not a goal, and it is recommended not to build libev	4982	there are 100 watchers that would trigger before that, then inserting will
3433	with any compiler warnings enabled unless you are prepared to cope with	4983	have to skip roughly seven (C<ld 100>) of these watchers.
3434	them (e.g. by ignoring them). Remember that warnings are just that:
3435	warnings, not errors, or proof of bugs.
3436		4984
		4985	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3437		4986
3438	=head1 VALGRIND	4987	That means that changing a timer costs less than removing/adding them,
		4988	as only the relative motion in the event queue has to be paid for.
3439		4989
3440	Valgrind has a special section here because it is a popular tool that is	4990	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3441	highly useful, but valgrind reports are very hard to interpret.
3442		4991
3443	If you think you found a bug (memory leak, uninitialised data access etc.)	4992	These just add the watcher into an array or at the head of a list.
3444	in libev, then check twice: If valgrind reports something like:
3445		4993
3446	==2274== definitely lost: 0 bytes in 0 blocks.	4994	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3447	==2274== possibly lost: 0 bytes in 0 blocks.
3448	==2274== still reachable: 256 bytes in 1 blocks.
3449		4995
3450	then there is no memory leak. Similarly, under some circumstances,	4996	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3451	valgrind might report kernel bugs as if it were a bug in libev, or it
3452	might be confused (it is a very good tool, but only a tool).
3453		4997
3454	If you are unsure about something, feel free to contact the mailing list	4998	These watchers are stored in lists, so they need to be walked to find the
3455	with the full valgrind report and an explanation on why you think this is	4999	correct watcher to remove. The lists are usually short (you don't usually
3456	a bug in libev. However, don't be annoyed when you get a brisk "this is	5000	have many watchers waiting for the same fd or signal: one is typical, two
3457	no bug" answer and take the chance of learning how to interpret valgrind	5001	is rare).
3458	properly.
3459		5002
3460	If you need, for some reason, empty reports from valgrind for your project	5003	=item Finding the next timer in each loop iteration: O(1)
3461	I suggest using suppression lists.
3462		5004
		5005	By virtue of using a binary or 4-heap, the next timer is always found at a
		5006	fixed position in the storage array.
		5007
		5008	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		5009
		5010	A change means an I/O watcher gets started or stopped, which requires
		5011	libev to recalculate its status (and possibly tell the kernel, depending
		5012	on backend and whether C<ev_io_set> was used).
		5013
		5014	=item Activating one watcher (putting it into the pending state): O(1)
		5015
		5016	=item Priority handling: O(number_of_priorities)
		5017
		5018	Priorities are implemented by allocating some space for each
		5019	priority. When doing priority-based operations, libev usually has to
		5020	linearly search all the priorities, but starting/stopping and activating
		5021	watchers becomes O(1) with respect to priority handling.
		5022
		5023	=item Sending an ev_async: O(1)
		5024
		5025	=item Processing ev_async_send: O(number_of_async_watchers)
		5026
		5027	=item Processing signals: O(max_signal_number)
		5028
		5029	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5030	calls in the current loop iteration. Checking for async and signal events
		5031	involves iterating over all running async watchers or all signal numbers.
		5032
		5033	=back
		5034
		5035
		5036	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5037
		5038	The major version 4 introduced some incompatible changes to the API.
		5039
		5040	At the moment, the C<ev.h> header file provides compatibility definitions
		5041	for all changes, so most programs should still compile. The compatibility
		5042	layer might be removed in later versions of libev, so better update to the
		5043	new API early than late.
		5044
		5045	=over 4
		5046
		5047	=item C<EV_COMPAT3> backwards compatibility mechanism
		5048
		5049	The backward compatibility mechanism can be controlled by
		5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5051	section.
		5052
		5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5054
		5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5056
		5057	ev_loop_destroy (EV_DEFAULT_UC);
		5058	ev_loop_fork (EV_DEFAULT);
		5059
		5060	=item function/symbol renames
		5061
		5062	A number of functions and symbols have been renamed:
		5063
		5064	ev_loop => ev_run
		5065	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5066	EVLOOP_ONESHOT => EVRUN_ONCE
		5067
		5068	ev_unloop => ev_break
		5069	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5070	EVUNLOOP_ONE => EVBREAK_ONE
		5071	EVUNLOOP_ALL => EVBREAK_ALL
		5072
		5073	EV_TIMEOUT => EV_TIMER
		5074
		5075	ev_loop_count => ev_iteration
		5076	ev_loop_depth => ev_depth
		5077	ev_loop_verify => ev_verify
		5078
		5079	Most functions working on C<struct ev_loop> objects don't have an
		5080	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5081	associated constants have been renamed to not collide with the C<struct
		5082	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5083	as all other watcher types. Note that C<ev_loop_fork> is still called
		5084	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5085	typedef.
		5086
		5087	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5088
		5089	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5090	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5091	and work, but the library code will of course be larger.
		5092
		5093	=back
		5094
		5095
		5096	=head1 GLOSSARY
		5097
		5098	=over 4
		5099
		5100	=item active
		5101
		5102	A watcher is active as long as it has been started and not yet stopped.
		5103	See L<WATCHER STATES> for details.
		5104
		5105	=item application
		5106
		5107	In this document, an application is whatever is using libev.
		5108
		5109	=item backend
		5110
		5111	The part of the code dealing with the operating system interfaces.
		5112
		5113	=item callback
		5114
		5115	The address of a function that is called when some event has been
		5116	detected. Callbacks are being passed the event loop, the watcher that
		5117	received the event, and the actual event bitset.
		5118
		5119	=item callback/watcher invocation
		5120
		5121	The act of calling the callback associated with a watcher.
		5122
		5123	=item event
		5124
		5125	A change of state of some external event, such as data now being available
		5126	for reading on a file descriptor, time having passed or simply not having
		5127	any other events happening anymore.
		5128
		5129	In libev, events are represented as single bits (such as C<EV_READ> or
		5130	C<EV_TIMER>).
		5131
		5132	=item event library
		5133
		5134	A software package implementing an event model and loop.
		5135
		5136	=item event loop
		5137
		5138	An entity that handles and processes external events and converts them
		5139	into callback invocations.
		5140
		5141	=item event model
		5142
		5143	The model used to describe how an event loop handles and processes
		5144	watchers and events.
		5145
		5146	=item pending
		5147
		5148	A watcher is pending as soon as the corresponding event has been
		5149	detected. See L<WATCHER STATES> for details.
		5150
		5151	=item real time
		5152
		5153	The physical time that is observed. It is apparently strictly monotonic :)
		5154
		5155	=item wall-clock time
		5156
		5157	The time and date as shown on clocks. Unlike real time, it can actually
		5158	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5159	clock.
		5160
		5161	=item watcher
		5162
		5163	A data structure that describes interest in certain events. Watchers need
		5164	to be started (attached to an event loop) before they can receive events.
		5165
		5166	=back
3463		5167
3464	=head1 AUTHOR	5168	=head1 AUTHOR
3465		5169
3466	Marc Lehmann <libev@schmorp.de>.	5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5171	Magnusson and Emanuele Giaquinta.
3467		5172

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