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…		…
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);
…		…
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 floating point 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).
…		…
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
…		…
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
…		…
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 auto-detected 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 system call 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 situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
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 application 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:
…		…
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
…		…
344	flag.	412	flag.
345		413
346	This flag setting cannot be overridden 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.
348		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.
		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
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		479
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
382	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,
383	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
384	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),
385	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).
386	of shortcomings, such as silently dropping events in some hard-to-detect	489
387	cases and requiring a system call per fd change, no fork support and bad	490	The epoll mechanism deserves honorable mention as the most misdesigned
388	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.
389		512
390	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	514	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	515	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	517	file descriptors might not work very well if you register events for both
395		518	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		519
400	Best performance from this backend is achieved by not unregistering all	520	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	521	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	522	i.e. keep at least one watcher active per fd at all times. Stopping and
		523	starting a watcher (without re-setting it) also usually doesn't cause
		524	extra overhead. A fork can both result in spurious notifications as well
		525	as in libev having to destroy and recreate the epoll object, which can
		526	take considerable time and thus should be avoided.
		527
		528	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		529	faster than epoll for maybe up to a hundred file descriptors, depending on
		530	the usage. So sad.
403		531
404	While nominally embeddable in other event loops, this feature is broken in	532	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	533	all kernel versions tested so far.
406		534
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	535	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	538	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		539
412	Kqueue deserves special mention, as at the time of this writing, it	540	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	541	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	542	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	543	it's completely useless). Unlike epoll, however, whose brokenness
		544	is by design, these kqueue bugs can (and eventually will) be fixed
		545	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	546	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	547	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	548	system like NetBSD.
419		549
420	You still can embed kqueue into a normal poll or select backend and use it	550	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	551	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		553
424	It scales in the same way as the epoll backend, but the interface to the	554	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	555	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	556	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	557	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	558	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	559	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		560	cases
430		561
431	This backend usually performs well under most conditions.	562	This backend usually performs well under most conditions.
432		563
433	While nominally embeddable in other event loops, this doesn't work	564	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	565	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	566	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	567	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	568	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	569	also broken on OS X)) and, did I mention it, using it only for sockets.
439		570
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	571	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	572	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	573	C<NOTE_EOF>.
443		574
…		…
451	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	582	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
452		583
453	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	584	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
454	it's really slow, but it still scales very well (O(active_fds)).	585	it's really slow, but it still scales very well (O(active_fds)).
455		586
456	Please note that Solaris event ports can deliver a lot of spurious
457	notifications, so you need to use non-blocking I/O or other means to avoid
458	blocking when no data (or space) is available.
459
460	While this backend scales well, it requires one system call per active	587	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	588	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	589	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	590	might perform better.
464		591
465	On the positive side, ignoring the spurious readiness notifications, this	592	On the positive side, this backend actually performed fully to
466	backend actually performed to specification in all tests and is fully	593	specification in all tests and is fully embeddable, which is a rare feat
467	embeddable, which is a rare feat among the OS-specific backends.	594	among the OS-specific backends (I vastly prefer correctness over speed
		595	hacks).
		596
		597	On the negative side, the interface is I<bizarre> - so bizarre that
		598	even sun itself gets it wrong in their code examples: The event polling
		599	function sometimes returning events to the caller even though an error
		600	occured, but with no indication whether it has done so or not (yes, it's
		601	even documented that way) - deadly for edge-triggered interfaces where
		602	you absolutely have to know whether an event occured or not because you
		603	have to re-arm the watcher.
		604
		605	Fortunately libev seems to be able to work around these idiocies.
468		606
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
471		609
472	=item C<EVBACKEND_ALL>	610	=item C<EVBACKEND_ALL>
473		611
474	Try all backends (even potentially broken ones that wouldn't be tried	612	Try all backends (even potentially broken ones that wouldn't be tried
475	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	613	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
476	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	614	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
477		615
478	It is definitely not recommended to use this flag.	616	It is definitely not recommended to use this flag, use whatever
		617	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		618	at all.
		619
		620	=item C<EVBACKEND_MASK>
		621
		622	Not a backend at all, but a mask to select all backend bits from a
		623	C<flags> value, in case you want to mask out any backends from a flags
		624	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
479		625
480	=back	626	=back
481		627
482	If one or more of these are or'ed into the flags value, then only these	628	If one or more of the backend flags are or'ed into the flags value,
483	backends will be tried (in the reverse order as listed here). If none are	629	then only these backends will be tried (in the reverse order as listed
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	630	here). If none are specified, all backends in C<ev_recommended_backends
485		631	()> will be tried.
486	The most typical usage is like this:
487
488	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490
491	Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:
493
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495
496	Use whatever libev has to offer, but make sure that kqueue is used if
497	available (warning, breaks stuff, best use only with your own private
498	event loop and only if you know the OS supports your types of fds):
499
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501
502	=item struct ev_loop *ev_loop_new (unsigned int flags)
503
504	Similar to C<ev_default_loop>, but always creates a new event loop that is
505	always distinct from the default loop. Unlike the default loop, it cannot
506	handle signal and child watchers, and attempts to do so will be greeted by
507	undefined behaviour (or a failed assertion if assertions are enabled).
508
509	Note that this function I<is> thread-safe, and the recommended way to use
510	libev with threads is indeed to create one loop per thread, and using the
511	default loop in the "main" or "initial" thread.
512		632
513	Example: Try to create a event loop that uses epoll and nothing else.	633	Example: Try to create a event loop that uses epoll and nothing else.
514		634
515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	635	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
516	if (!epoller)	636	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	637	fatal ("no epoll found here, maybe it hides under your chair");
518		638
		639	Example: Use whatever libev has to offer, but make sure that kqueue is
		640	used if available.
		641
		642	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		643
519	=item ev_default_destroy ()	644	=item ev_loop_destroy (loop)
520		645
521	Destroys the default loop again (frees all memory and kernel state	646	Destroys an event loop object (frees all memory and kernel state
522	etc.). None of the active event watchers will be stopped in the normal	647	etc.). None of the active event watchers will be stopped in the normal
523	sense, so e.g. C<ev_is_active> might still return true. It is your	648	sense, so e.g. C<ev_is_active> might still return true. It is your
524	responsibility to either stop all watchers cleanly yourself I<before>	649	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	650	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	651	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	652	for example).
528		653
529	Note that certain global state, such as signal state, will not be freed by	654	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	655	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	656	as signal and child watchers) would need to be stopped manually.
532		657
533	In general it is not advisable to call this function except in the	658	This function is normally used on loop objects allocated by
534	rare occasion where you really need to free e.g. the signal handling	659	C<ev_loop_new>, but it can also be used on the default loop returned by
		660	C<ev_default_loop>, in which case it is not thread-safe.
		661
		662	Note that it is not advisable to call this function on the default loop
		663	except in the rare occasion where you really need to free its resources.
535	pipe fds. If you need dynamically allocated loops it is better to use	664	If you need dynamically allocated loops it is better to use C<ev_loop_new>
536	C<ev_loop_new> and C<ev_loop_destroy>).	665	and C<ev_loop_destroy>.
537		666
538	=item ev_loop_destroy (loop)	667	=item ev_loop_fork (loop)
539		668
540	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.
542
543	=item ev_default_fork ()
544
545	This function sets a flag that causes subsequent C<ev_loop> iterations	669	This function sets a flag that causes subsequent C<ev_run> iterations to
546	to reinitialise the kernel state for backends that have one. Despite the	670	reinitialise the kernel state for backends that have one. Despite the
547	name, you can call it anytime, but it makes most sense after forking, in	671	name, you can call it anytime, but it makes most sense after forking, in
548	the child process (or both child and parent, but that again makes little	672	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
549	sense). You I<must> call it in the child before using any of the libev	673	child before resuming or calling C<ev_run>.
550	functions, and it will only take effect at the next C<ev_loop> iteration.	674
		675	Again, you I<have> to call it on I<any> loop that you want to re-use after
		676	a fork, I<even if you do not plan to use the loop in the parent>. This is
		677	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		678	during fork.
551		679
552	On the other hand, you only need to call this function in the child	680	On the other hand, you only need to call this function in the child
553	process if and only if you want to use the event library in the child. If	681	process if and only if you want to use the event loop in the child. If
554	you just fork+exec, you don't have to call it at all.	682	you just fork+exec or create a new loop in the child, you don't have to
		683	call it at all (in fact, C<epoll> is so badly broken that it makes a
		684	difference, but libev will usually detect this case on its own and do a
		685	costly reset of the backend).
555		686
556	The function itself is quite fast and it's usually not a problem to call	687	The function itself is quite fast and it's usually not a problem to call
557	it just in case after a fork. To make this easy, the function will fit in	688	it just in case after a fork.
558	quite nicely into a call to C<pthread_atfork>:
559		689
		690	Example: Automate calling C<ev_loop_fork> on the default loop when
		691	using pthreads.
		692
		693	static void
		694	post_fork_child (void)
		695	{
		696	ev_loop_fork (EV_DEFAULT);
		697	}
		698
		699	...
560	pthread_atfork (0, 0, ev_default_fork);	700	pthread_atfork (0, 0, post_fork_child);
561
562	=item ev_loop_fork (loop)
563
564	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.
567		701
568	=item int ev_is_default_loop (loop)	702	=item int ev_is_default_loop (loop)
569		703
570	Returns true when the given loop actually is the default loop, false otherwise.	704	Returns true when the given loop is, in fact, the default loop, and false
		705	otherwise.
571		706
572	=item unsigned int ev_loop_count (loop)	707	=item unsigned int ev_iteration (loop)
573		708
574	Returns the count of loop iterations for the loop, which is identical to	709	Returns the current iteration count for the event loop, which is identical
575	the number of times libev did poll for new events. It starts at C<0> and	710	to the number of times libev did poll for new events. It starts at C<0>
576	happily wraps around with enough iterations.	711	and happily wraps around with enough iterations.
577		712
578	This value can sometimes be useful as a generation counter of sorts (it	713	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	714	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	715	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		716	prepare and check phases.
		717
		718	=item unsigned int ev_depth (loop)
		719
		720	Returns the number of times C<ev_run> was entered minus the number of
		721	times C<ev_run> was exited normally, in other words, the recursion depth.
		722
		723	Outside C<ev_run>, this number is zero. In a callback, this number is
		724	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		725	in which case it is higher.
		726
		727	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		728	throwing an exception etc.), doesn't count as "exit" - consider this
		729	as a hint to avoid such ungentleman-like behaviour unless it's really
		730	convenient, in which case it is fully supported.
581		731
582	=item unsigned int ev_backend (loop)	732	=item unsigned int ev_backend (loop)
583		733
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	734	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	735	use.
…		…
594		744
595	=item ev_now_update (loop)	745	=item ev_now_update (loop)
596		746
597	Establishes the current time by querying the kernel, updating the time	747	Establishes the current time by querying the kernel, updating the time
598	returned by C<ev_now ()> in the progress. This is a costly operation and	748	returned by C<ev_now ()> in the progress. This is a costly operation and
599	is usually done automatically within C<ev_loop ()>.	749	is usually done automatically within C<ev_run ()>.
600		750
601	This function is rarely useful, but when some event callback runs for a	751	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	752	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	753	the current time is a good idea.
604		754
605	See also "The special problem of time updates" in the C<ev_timer> section.	755	See also L<The special problem of time updates> in the C<ev_timer> section.
606		756
		757	=item ev_suspend (loop)
		758
		759	=item ev_resume (loop)
		760
		761	These two functions suspend and resume an event loop, for use when the
		762	loop is not used for a while and timeouts should not be processed.
		763
		764	A typical use case would be an interactive program such as a game: When
		765	the user presses C<^Z> to suspend the game and resumes it an hour later it
		766	would be best to handle timeouts as if no time had actually passed while
		767	the program was suspended. This can be achieved by calling C<ev_suspend>
		768	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		769	C<ev_resume> directly afterwards to resume timer processing.
		770
		771	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		772	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		773	will be rescheduled (that is, they will lose any events that would have
		774	occurred while suspended).
		775
		776	After calling C<ev_suspend> you B<must not> call I<any> function on the
		777	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		778	without a previous call to C<ev_suspend>.
		779
		780	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		781	event loop time (see C<ev_now_update>).
		782
607	=item ev_loop (loop, int flags)	783	=item ev_run (loop, int flags)
608		784
609	Finally, this is it, the event handler. This function usually is called	785	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	786	after you have initialised all your watchers and you want to start
611	events.	787	handling events. It will ask the operating system for any new events, call
		788	the watcher callbacks, an then repeat the whole process indefinitely: This
		789	is why event loops are called I<loops>.
612		790
613	If the flags argument is specified as C<0>, it will not return until	791	If the flags argument is specified as C<0>, it will keep handling events
614	either no event watchers are active anymore or C<ev_unloop> was called.	792	until either no event watchers are active anymore or C<ev_break> was
		793	called.
615		794
616	Please note that an explicit C<ev_unloop> is usually better than	795	Please note that an explicit C<ev_break> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	796	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	797	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	798	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	799	of relying on its watchers stopping correctly, that is truly a thing of
		800	beauty.
621		801
		802	This function is also I<mostly> exception-safe - you can break out of
		803	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		804	exception and so on. This does not decrement the C<ev_depth> value, nor
		805	will it clear any outstanding C<EVBREAK_ONE> breaks.
		806
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	807	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	808	those events and any already outstanding ones, but will not wait and
624	case there are no events and will return after one iteration of the loop.	809	block your process in case there are no events and will return after one
		810	iteration of the loop. This is sometimes useful to poll and handle new
		811	events while doing lengthy calculations, to keep the program responsive.
625		812
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	813	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	814	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	815	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	816	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	817	user-registered callback will be called), and will return after one
		818	iteration of the loop.
		819
		820	This is useful if you are waiting for some external event in conjunction
		821	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	822	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	823	usually a better approach for this kind of thing.
633		824
634	Here are the gory details of what C<ev_loop> does:	825	Here are the gory details of what C<ev_run> does:
635		826
		827	- Increment loop depth.
		828	- Reset the ev_break status.
636	- Before the first iteration, call any pending watchers.	829	- Before the first iteration, call any pending watchers.
		830	LOOP:
637	* If EVFLAG_FORKCHECK was used, check for a fork.	831	- If EVFLAG_FORKCHECK was used, check for a fork.
638	- If a fork was detected (by any means), queue and call all fork watchers.	832	- If a fork was detected (by any means), queue and call all fork watchers.
639	- Queue and call all prepare watchers.	833	- Queue and call all prepare watchers.
		834	- If ev_break was called, goto FINISH.
640	- If we have been forked, detach and recreate the kernel state	835	- If we have been forked, detach and recreate the kernel state
641	as to not disturb the other process.	836	as to not disturb the other process.
642	- Update the kernel state with all outstanding changes.	837	- Update the kernel state with all outstanding changes.
643	- Update the "event loop time" (ev_now ()).	838	- Update the "event loop time" (ev_now ()).
644	- Calculate for how long to sleep or block, if at all	839	- Calculate for how long to sleep or block, if at all
645	(active idle watchers, EVLOOP_NONBLOCK or not having	840	(active idle watchers, EVRUN_NOWAIT or not having
646	any active watchers at all will result in not sleeping).	841	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	842	- Sleep if the I/O and timer collect interval say so.
		843	- Increment loop iteration counter.
648	- Block the process, waiting for any events.	844	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	845	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	846	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	847	- Queue all expired timers.
652	- Queue all outstanding periodics.	848	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	849	- Queue all idle watchers with priority higher than that of pending events.
654	- Queue all check watchers.	850	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	851	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	852	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	853	be handled here by queueing them when their watcher gets executed.
658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	854	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
659	were used, or there are no active watchers, return, otherwise	855	were used, or there are no active watchers, goto FINISH, otherwise
660	continue with step *.	856	continue with step LOOP.
		857	FINISH:
		858	- Reset the ev_break status iff it was EVBREAK_ONE.
		859	- Decrement the loop depth.
		860	- Return.
661		861
662	Example: Queue some jobs and then loop until no events are outstanding	862	Example: Queue some jobs and then loop until no events are outstanding
663	anymore.	863	anymore.
664		864
665	... queue jobs here, make sure they register event watchers as long	865	... queue jobs here, make sure they register event watchers as long
666	... as they still have work to do (even an idle watcher will do..)	866	... as they still have work to do (even an idle watcher will do..)
667	ev_loop (my_loop, 0);	867	ev_run (my_loop, 0);
668	... jobs done or somebody called unloop. yeah!	868	... jobs done or somebody called unloop. yeah!
669		869
670	=item ev_unloop (loop, how)	870	=item ev_break (loop, how)
671		871
672	Can be used to make a call to C<ev_loop> return early (but only after it	872	Can be used to make a call to C<ev_run> return early (but only after it
673	has processed all outstanding events). The C<how> argument must be either	873	has processed all outstanding events). The C<how> argument must be either
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	874	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	875	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
676		876
677	This "unloop state" will be cleared when entering C<ev_loop> again.	877	This "break state" will be cleared on the next call to C<ev_run>.
		878
		879	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		880	which case it will have no effect.
678		881
679	=item ev_ref (loop)	882	=item ev_ref (loop)
680		883
681	=item ev_unref (loop)	884	=item ev_unref (loop)
682		885
683	Ref/unref can be used to add or remove a reference count on the event	886	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	887	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	888	count is nonzero, C<ev_run> will not return on its own.
686	a watcher you never unregister that should not keep C<ev_loop> from	889
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	890	This is useful when you have a watcher that you never intend to
		891	unregister, but that nevertheless should not keep C<ev_run> from
		892	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		893	before stopping it.
		894
688	example, libev itself uses this for its internal signal pipe: It is not	895	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	896	is not visible to the libev user and should not keep C<ev_run> from
690	no event watchers registered by it are active. It is also an excellent	897	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	898	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	899	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	900	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	901	before, respectively. Note also that libev might stop watchers itself
		902	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		903	in the callback).
695		904
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	905	Example: Create a signal watcher, but keep it from keeping C<ev_run>
697	running when nothing else is active.	906	running when nothing else is active.
698		907
699	struct ev_signal exitsig;	908	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	909	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	910	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	911	ev_unref (loop);
703		912
704	Example: For some weird reason, unregister the above signal handler again.	913	Example: For some weird reason, unregister the above signal handler again.
705		914
706	ev_ref (loop);	915	ev_ref (loop);
707	ev_signal_stop (loop, &exitsig);	916	ev_signal_stop (loop, &exitsig);
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	927	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	928	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	929	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	930	opportunities).
722		931
723	The background is that sometimes your program runs just fast enough to	932	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	933	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	934	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	935	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	936	overhead for the actual polling but can deliver many events at once.
728		937
729	By setting a higher I<io collect interval> you allow libev to spend more	938	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	939	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	940	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	941	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	942	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		943	sleep time ensures that libev will not poll for I/O events more often then
		944	once per this interval, on average.
734		945
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	946	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	947	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	948	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	949	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	950	value will not introduce any overhead in libev.
740		951
741	Many (busy) programs can usually benefit by setting the I/O collect	952	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	953	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	954	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	955	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	956	as this approaches the timing granularity of most systems. Note that if
		957	you do transactions with the outside world and you can't increase the
		958	parallelity, then this setting will limit your transaction rate (if you
		959	need to poll once per transaction and the I/O collect interval is 0.01,
		960	then you can't do more than 100 transactions per second).
746		961
747	Setting the I<timeout collect interval> can improve the opportunity for	962	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	963	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	964	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	965	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	966	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	967	they fire on, say, one-second boundaries only.
753		968
		969	Example: we only need 0.1s timeout granularity, and we wish not to poll
		970	more often than 100 times per second:
		971
		972	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		973	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		974
		975	=item ev_invoke_pending (loop)
		976
		977	This call will simply invoke all pending watchers while resetting their
		978	pending state. Normally, C<ev_run> does this automatically when required,
		979	but when overriding the invoke callback this call comes handy. This
		980	function can be invoked from a watcher - this can be useful for example
		981	when you want to do some lengthy calculation and want to pass further
		982	event handling to another thread (you still have to make sure only one
		983	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		984
		985	=item int ev_pending_count (loop)
		986
		987	Returns the number of pending watchers - zero indicates that no watchers
		988	are pending.
		989
		990	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		991
		992	This overrides the invoke pending functionality of the loop: Instead of
		993	invoking all pending watchers when there are any, C<ev_run> will call
		994	this callback instead. This is useful, for example, when you want to
		995	invoke the actual watchers inside another context (another thread etc.).
		996
		997	If you want to reset the callback, use C<ev_invoke_pending> as new
		998	callback.
		999
		1000	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1001
		1002	Sometimes you want to share the same loop between multiple threads. This
		1003	can be done relatively simply by putting mutex_lock/unlock calls around
		1004	each call to a libev function.
		1005
		1006	However, C<ev_run> can run an indefinite time, so it is not feasible
		1007	to wait for it to return. One way around this is to wake up the event
		1008	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1009	I<release> and I<acquire> callbacks on the loop.
		1010
		1011	When set, then C<release> will be called just before the thread is
		1012	suspended waiting for new events, and C<acquire> is called just
		1013	afterwards.
		1014
		1015	Ideally, C<release> will just call your mutex_unlock function, and
		1016	C<acquire> will just call the mutex_lock function again.
		1017
		1018	While event loop modifications are allowed between invocations of
		1019	C<release> and C<acquire> (that's their only purpose after all), no
		1020	modifications done will affect the event loop, i.e. adding watchers will
		1021	have no effect on the set of file descriptors being watched, or the time
		1022	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1023	to take note of any changes you made.
		1024
		1025	In theory, threads executing C<ev_run> will be async-cancel safe between
		1026	invocations of C<release> and C<acquire>.
		1027
		1028	See also the locking example in the C<THREADS> section later in this
		1029	document.
		1030
		1031	=item ev_set_userdata (loop, void *data)
		1032
		1033	=item void *ev_userdata (loop)
		1034
		1035	Set and retrieve a single C<void *> associated with a loop. When
		1036	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1037	C<0>.
		1038
		1039	These two functions can be used to associate arbitrary data with a loop,
		1040	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1041	C<acquire> callbacks described above, but of course can be (ab-)used for
		1042	any other purpose as well.
		1043
754	=item ev_loop_verify (loop)	1044	=item ev_verify (loop)
755		1045
756	This function only does something when C<EV_VERIFY> support has been	1046	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	1047	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	1048	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	1049	is found to be inconsistent, it will print an error message to standard
		1050	error and call C<abort ()>.
760		1051
761	This can be used to catch bugs inside libev itself: under normal	1052	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	1053	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	1054	data structures consistent.
764		1055
765	=back	1056	=back
766		1057
767		1058
768	=head1 ANATOMY OF A WATCHER	1059	=head1 ANATOMY OF A WATCHER
769		1060
		1061	In the following description, uppercase C<TYPE> in names stands for the
		1062	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1063	watchers and C<ev_io_start> for I/O watchers.
		1064
770	A watcher is a structure that you create and register to record your	1065	A watcher is an opaque structure that you allocate and register to record
771	interest in some event. For instance, if you want to wait for STDIN to	1066	your interest in some event. To make a concrete example, imagine you want
772	become readable, you would create an C<ev_io> watcher for that:	1067	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1068	for that:
773		1069
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1070	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	1071	{
776	ev_io_stop (w);	1072	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	1073	ev_break (loop, EVBREAK_ALL);
778	}	1074	}
779		1075
780	struct ev_loop *loop = ev_default_loop (0);	1076	struct ev_loop *loop = ev_default_loop (0);
		1077
781	struct ev_io stdin_watcher;	1078	ev_io stdin_watcher;
		1079
782	ev_init (&stdin_watcher, my_cb);	1080	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1081	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	1082	ev_io_start (loop, &stdin_watcher);
		1083
785	ev_loop (loop, 0);	1084	ev_run (loop, 0);
786		1085
787	As you can see, you are responsible for allocating the memory for your	1086	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	1087	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1088	stack).
790		1089
		1090	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1091	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1092
791	Each watcher structure must be initialised by a call to C<ev_init	1093	Each watcher structure must be initialised by a call to C<ev_init (watcher
792	(watcher *, callback)>, which expects a callback to be provided. This	1094	*, callback)>, which expects a callback to be provided. This callback is
793	callback gets invoked each time the event occurs (or, in the case of I/O	1095	invoked each time the event occurs (or, in the case of I/O watchers, each
794	watchers, each time the event loop detects that the file descriptor given	1096	time the event loop detects that the file descriptor given is readable
795	is readable and/or writable).	1097	and/or writable).
796		1098
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1099	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1100	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1101	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1102	ev_TYPE_init (watcher *, callback, ...) >>.
801		1103
802	To make the watcher actually watch out for events, you have to start it	1104	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1105	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1106	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1107	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1108
807	As long as your watcher is active (has been started but not stopped) you	1109	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1110	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1111	reinitialise it or call its C<ev_TYPE_set> macro.
810		1112
811	Each and every callback receives the event loop pointer as first, the	1113	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1114	registered watcher structure as second, and a bitset of received events as
813	third argument.	1115	third argument.
814		1116
…		…
823	=item C<EV_WRITE>	1125	=item C<EV_WRITE>
824		1126
825	The file descriptor in the C<ev_io> watcher has become readable and/or	1127	The file descriptor in the C<ev_io> watcher has become readable and/or
826	writable.	1128	writable.
827		1129
828	=item C<EV_TIMEOUT>	1130	=item C<EV_TIMER>
829		1131
830	The C<ev_timer> watcher has timed out.	1132	The C<ev_timer> watcher has timed out.
831		1133
832	=item C<EV_PERIODIC>	1134	=item C<EV_PERIODIC>
833		1135
…		…
851		1153
852	=item C<EV_PREPARE>	1154	=item C<EV_PREPARE>
853		1155
854	=item C<EV_CHECK>	1156	=item C<EV_CHECK>
855		1157
856	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1158	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
857	to gather new events, and all C<ev_check> watchers are invoked just after	1159	to gather new events, and all C<ev_check> watchers are invoked just after
858	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1160	C<ev_run> has gathered them, but before it invokes any callbacks for any
859	received events. Callbacks of both watcher types can start and stop as	1161	received events. Callbacks of both watcher types can start and stop as
860	many watchers as they want, and all of them will be taken into account	1162	many watchers as they want, and all of them will be taken into account
861	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1163	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
862	C<ev_loop> from blocking).	1164	C<ev_run> from blocking).
863		1165
864	=item C<EV_EMBED>	1166	=item C<EV_EMBED>
865		1167
866	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1168	The embedded event loop specified in the C<ev_embed> watcher needs attention.
867		1169
868	=item C<EV_FORK>	1170	=item C<EV_FORK>
869		1171
870	The event loop has been resumed in the child process after fork (see	1172	The event loop has been resumed in the child process after fork (see
871	C<ev_fork>).	1173	C<ev_fork>).
872		1174
		1175	=item C<EV_CLEANUP>
		1176
		1177	The event loop is about to be destroyed (see C<ev_cleanup>).
		1178
873	=item C<EV_ASYNC>	1179	=item C<EV_ASYNC>
874		1180
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1181	The given async watcher has been asynchronously notified (see C<ev_async>).
		1182
		1183	=item C<EV_CUSTOM>
		1184
		1185	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1186	by libev users to signal watchers (e.g. via C<ev_feed_event>).
876		1187
877	=item C<EV_ERROR>	1188	=item C<EV_ERROR>
878		1189
879	An unspecified error has occurred, the watcher has been stopped. This might	1190	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1191	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1192	ran out of memory, a file descriptor was found to be closed or any other
		1193	problem. Libev considers these application bugs.
		1194
882	problem. You best act on it by reporting the problem and somehow coping	1195	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1196	watcher being stopped. Note that well-written programs should not receive
		1197	an error ever, so when your watcher receives it, this usually indicates a
		1198	bug in your program.
884		1199
885	Libev will usually signal a few "dummy" events together with an error,	1200	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1201	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1202	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1203	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1204	programs, though, as the fd could already be closed and reused for another
		1205	thing, so beware.
890		1206
891	=back	1207	=back
892		1208
893	=head2 GENERIC WATCHER FUNCTIONS	1209	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1210
898	=over 4	1211	=over 4
899		1212
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1213	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1214
…		…
907	which rolls both calls into one.	1220	which rolls both calls into one.
908		1221
909	You can reinitialise a watcher at any time as long as it has been stopped	1222	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1223	(or never started) and there are no pending events outstanding.
911		1224
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1225	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1226	int revents)>.
914		1227
		1228	Example: Initialise an C<ev_io> watcher in two steps.
		1229
		1230	ev_io w;
		1231	ev_init (&w, my_cb);
		1232	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1233
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1234	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1235
917	This macro initialises the type-specific parts of a watcher. You need to	1236	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	1237	call C<ev_init> at least once before you call this macro, but you can
919	call C<ev_TYPE_set> any number of times. You must not, however, call this	1238	call C<ev_TYPE_set> any number of times. You must not, however, call this
920	macro on a watcher that is active (it can be pending, however, which is a	1239	macro on a watcher that is active (it can be pending, however, which is a
921	difference to the C<ev_init> macro).	1240	difference to the C<ev_init> macro).
922		1241
923	Although some watcher types do not have type-specific arguments	1242	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1243	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1244
		1245	See C<ev_init>, above, for an example.
		1246
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1247	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1248
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1249	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1250	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1251	a watcher. The same limitations apply, of course.
931		1252
		1253	Example: Initialise and set an C<ev_io> watcher in one step.
		1254
		1255	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1256
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1257	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1258
934	Starts (activates) the given watcher. Only active watchers will receive	1259	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1260	events. If the watcher is already active nothing will happen.
936		1261
		1262	Example: Start the C<ev_io> watcher that is being abused as example in this
		1263	whole section.
		1264
		1265	ev_io_start (EV_DEFAULT_UC, &w);
		1266
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1267	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1268
939	Stops the given watcher again (if active) and clears the pending	1269	Stops the given watcher if active, and clears the pending status (whether
		1270	the watcher was active or not).
		1271
940	status. It is possible that stopped watchers are pending (for example,	1272	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1273	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1274	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1275	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1276	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1277
946	=item bool ev_is_active (ev_TYPE *watcher)	1278	=item bool ev_is_active (ev_TYPE *watcher)
947		1279
948	Returns a true value iff the watcher is active (i.e. it has been started	1280	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1281	and not yet been stopped). As long as a watcher is active you must not modify
…		…
965	=item ev_cb_set (ev_TYPE *watcher, callback)	1297	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1298
967	Change the callback. You can change the callback at virtually any time	1299	Change the callback. You can change the callback at virtually any time
968	(modulo threads).	1300	(modulo threads).
969		1301
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1302	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1303
972	=item int ev_priority (ev_TYPE *watcher)	1304	=item int ev_priority (ev_TYPE *watcher)
973		1305
974	Set and query the priority of the watcher. The priority is a small	1306	Set and query the priority of the watcher. The priority is a small
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1307	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1308	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1309	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1310	from being executed (except for C<ev_idle> watchers).
979		1311
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	If you need to suppress invocation when higher priority events are pending	1312	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1313	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1314
988	You I<must not> change the priority of a watcher as long as it is active or	1315	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1316	pending.
990		1317
		1318	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1319	fine, as long as you do not mind that the priority value you query might
		1320	or might not have been clamped to the valid range.
		1321
991	The default priority used by watchers when no priority has been set is	1322	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1323	always C<0>, which is supposed to not be too high and not be too low :).
993		1324
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1325	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1326	priorities.
996	or might not have been adjusted to be within valid range.
997		1327
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1328	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1329
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1330	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1331	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1332	can deal with that fact, as both are simply passed through to the
		1333	callback.
1003		1334
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1335	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1336
1006	If the watcher is pending, this function returns clears its pending status	1337	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1338	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1339	watcher isn't pending it does nothing and returns C<0>.
1009		1340
		1341	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1342	callback to be invoked, which can be accomplished with this function.
		1343
		1344	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1345
		1346	Feeds the given event set into the event loop, as if the specified event
		1347	had happened for the specified watcher (which must be a pointer to an
		1348	initialised but not necessarily started event watcher). Obviously you must
		1349	not free the watcher as long as it has pending events.
		1350
		1351	Stopping the watcher, letting libev invoke it, or calling
		1352	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1353	not started in the first place.
		1354
		1355	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1356	functions that do not need a watcher.
		1357
1010	=back	1358	=back
1011		1359
1012
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1361
1015	Each watcher has, by default, a member C<void *data> that you can change	1362	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1363	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1364	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1365	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1366	member, you can also "subclass" the watcher type and provide your own
1020	data:	1367	data:
1021		1368
1022	struct my_io	1369	struct my_io
1023	{	1370	{
1024	struct ev_io io;	1371	ev_io io;
1025	int otherfd;	1372	int otherfd;
1026	void *somedata;	1373	void *somedata;
1027	struct whatever *mostinteresting;	1374	struct whatever *mostinteresting;
1028	};	1375	};
1029		1376
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1380
1034	And since your callback will be called with a pointer to the watcher, you	1381	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1382	can cast it back to your own type:
1036		1383
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1385	{
1039	struct my_io *w = (struct my_io *)w_;	1386	struct my_io *w = (struct my_io *)w_;
1040	...	1387	...
1041	}	1388	}
1042		1389
…		…
1053	ev_timer t2;	1400	ev_timer t2;
1054	}	1401	}
1055		1402
1056	In this case getting the pointer to C<my_biggy> is a bit more	1403	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1404	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1405	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1407	programmers):
1060		1408
1061	#include <stddef.h>	1409	#include <stddef.h>
1062		1410
1063	static void	1411	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1412	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1413	{
1066	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1415	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1416	}
1069		1417
1070	static void	1418	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1420	{
1073	struct my_biggy big = (struct my_biggy *	1421	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1423	}
		1424
		1425	=head2 WATCHER STATES
		1426
		1427	There are various watcher states mentioned throughout this manual -
		1428	active, pending and so on. In this section these states and the rules to
		1429	transition between them will be described in more detail - and while these
		1430	rules might look complicated, they usually do "the right thing".
		1431
		1432	=over 4
		1433
		1434	=item initialiased
		1435
		1436	Before a watcher can be registered with the event looop it has to be
		1437	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1438	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1439
		1440	In this state it is simply some block of memory that is suitable for use
		1441	in an event loop. It can be moved around, freed, reused etc. at will.
		1442
		1443	=item started/running/active
		1444
		1445	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1446	property of the event loop, and is actively waiting for events. While in
		1447	this state it cannot be accessed (except in a few documented ways), moved,
		1448	freed or anything else - the only legal thing is to keep a pointer to it,
		1449	and call libev functions on it that are documented to work on active watchers.
		1450
		1451	=item pending
		1452
		1453	If a watcher is active and libev determines that an event it is interested
		1454	in has occurred (such as a timer expiring), it will become pending. It will
		1455	stay in this pending state until either it is stopped or its callback is
		1456	about to be invoked, so it is not normally pending inside the watcher
		1457	callback.
		1458
		1459	The watcher might or might not be active while it is pending (for example,
		1460	an expired non-repeating timer can be pending but no longer active). If it
		1461	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1462	but it is still property of the event loop at this time, so cannot be
		1463	moved, freed or reused. And if it is active the rules described in the
		1464	previous item still apply.
		1465
		1466	It is also possible to feed an event on a watcher that is not active (e.g.
		1467	via C<ev_feed_event>), in which case it becomes pending without being
		1468	active.
		1469
		1470	=item stopped
		1471
		1472	A watcher can be stopped implicitly by libev (in which case it might still
		1473	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1474	latter will clear any pending state the watcher might be in, regardless
		1475	of whether it was active or not, so stopping a watcher explicitly before
		1476	freeing it is often a good idea.
		1477
		1478	While stopped (and not pending) the watcher is essentially in the
		1479	initialised state, that is it can be reused, moved, modified in any way
		1480	you wish.
		1481
		1482	=back
		1483
		1484	=head2 WATCHER PRIORITY MODELS
		1485
		1486	Many event loops support I<watcher priorities>, which are usually small
		1487	integers that influence the ordering of event callback invocation
		1488	between watchers in some way, all else being equal.
		1489
		1490	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1491	description for the more technical details such as the actual priority
		1492	range.
		1493
		1494	There are two common ways how these these priorities are being interpreted
		1495	by event loops:
		1496
		1497	In the more common lock-out model, higher priorities "lock out" invocation
		1498	of lower priority watchers, which means as long as higher priority
		1499	watchers receive events, lower priority watchers are not being invoked.
		1500
		1501	The less common only-for-ordering model uses priorities solely to order
		1502	callback invocation within a single event loop iteration: Higher priority
		1503	watchers are invoked before lower priority ones, but they all get invoked
		1504	before polling for new events.
		1505
		1506	Libev uses the second (only-for-ordering) model for all its watchers
		1507	except for idle watchers (which use the lock-out model).
		1508
		1509	The rationale behind this is that implementing the lock-out model for
		1510	watchers is not well supported by most kernel interfaces, and most event
		1511	libraries will just poll for the same events again and again as long as
		1512	their callbacks have not been executed, which is very inefficient in the
		1513	common case of one high-priority watcher locking out a mass of lower
		1514	priority ones.
		1515
		1516	Static (ordering) priorities are most useful when you have two or more
		1517	watchers handling the same resource: a typical usage example is having an
		1518	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1519	timeouts. Under load, data might be received while the program handles
		1520	other jobs, but since timers normally get invoked first, the timeout
		1521	handler will be executed before checking for data. In that case, giving
		1522	the timer a lower priority than the I/O watcher ensures that I/O will be
		1523	handled first even under adverse conditions (which is usually, but not
		1524	always, what you want).
		1525
		1526	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1527	will only be executed when no same or higher priority watchers have
		1528	received events, they can be used to implement the "lock-out" model when
		1529	required.
		1530
		1531	For example, to emulate how many other event libraries handle priorities,
		1532	you can associate an C<ev_idle> watcher to each such watcher, and in
		1533	the normal watcher callback, you just start the idle watcher. The real
		1534	processing is done in the idle watcher callback. This causes libev to
		1535	continuously poll and process kernel event data for the watcher, but when
		1536	the lock-out case is known to be rare (which in turn is rare :), this is
		1537	workable.
		1538
		1539	Usually, however, the lock-out model implemented that way will perform
		1540	miserably under the type of load it was designed to handle. In that case,
		1541	it might be preferable to stop the real watcher before starting the
		1542	idle watcher, so the kernel will not have to process the event in case
		1543	the actual processing will be delayed for considerable time.
		1544
		1545	Here is an example of an I/O watcher that should run at a strictly lower
		1546	priority than the default, and which should only process data when no
		1547	other events are pending:
		1548
		1549	ev_idle idle; // actual processing watcher
		1550	ev_io io; // actual event watcher
		1551
		1552	static void
		1553	io_cb (EV_P_ ev_io *w, int revents)
		1554	{
		1555	// stop the I/O watcher, we received the event, but
		1556	// are not yet ready to handle it.
		1557	ev_io_stop (EV_A_ w);
		1558
		1559	// start the idle watcher to handle the actual event.
		1560	// it will not be executed as long as other watchers
		1561	// with the default priority are receiving events.
		1562	ev_idle_start (EV_A_ &idle);
		1563	}
		1564
		1565	static void
		1566	idle_cb (EV_P_ ev_idle *w, int revents)
		1567	{
		1568	// actual processing
		1569	read (STDIN_FILENO, ...);
		1570
		1571	// have to start the I/O watcher again, as
		1572	// we have handled the event
		1573	ev_io_start (EV_P_ &io);
		1574	}
		1575
		1576	// initialisation
		1577	ev_idle_init (&idle, idle_cb);
		1578	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1579	ev_io_start (EV_DEFAULT_ &io);
		1580
		1581	In the "real" world, it might also be beneficial to start a timer, so that
		1582	low-priority connections can not be locked out forever under load. This
		1583	enables your program to keep a lower latency for important connections
		1584	during short periods of high load, while not completely locking out less
		1585	important ones.
1076		1586
1077		1587
1078	=head1 WATCHER TYPES	1588	=head1 WATCHER TYPES
1079		1589
1080	This section describes each watcher in detail, but will not repeat	1590	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1614	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1615	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1616	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1617	required if you know what you are doing).
1108		1618
1109	If you must do this, then force the use of a known-to-be-good backend	1619	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1620	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1621	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1622	descriptors for which non-blocking operation makes no sense (such as
		1623	files) - libev doesn't guarantee any specific behaviour in that case.
1112		1624
1113	Another thing you have to watch out for is that it is quite easy to	1625	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1626	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1627	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1628	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1629	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1630	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1631	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1632	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1633
1122	If you cannot run the fd in non-blocking mode (for example you should not	1634	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1635	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1636	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1637	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1638	does this on its own, so its quite safe to use). Some people additionally
		1639	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1640	indefinitely.
		1641
		1642	But really, best use non-blocking mode.
1127		1643
1128	=head3 The special problem of disappearing file descriptors	1644	=head3 The special problem of disappearing file descriptors
1129		1645
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1646	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1647	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1648	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1649	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1650	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1651	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1652	fact, a different file descriptor.
1137		1653
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1684	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1685	C<EVBACKEND_POLL>.
1170		1686
1171	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1172		1688
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1689	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1690	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1691	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1692	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1693
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1694	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1695	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1696	somewhere, as that would have given you a big clue).
1181		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1182		1736
1183	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1184		1738
1185	=over 4	1739	=over 4
1186		1740
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1741	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1742
1189	=item ev_io_set (ev_io *, int fd, int events)	1743	=item ev_io_set (ev_io *, int fd, int events)
1190		1744
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1745	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1746	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1747	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1748
1195	=item int fd [read-only]	1749	=item int fd [read-only]
1196		1750
1197	The file descriptor being watched.	1751	The file descriptor being watched.
1198		1752
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1761	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1762	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1763	attempt to read a whole line in the callback.
1210		1764
1211	static void	1765	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1766	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1767	{
1214	ev_io_stop (loop, w);	1768	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1769	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1770	}
1217		1771
1218	...	1772	...
1219	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1774	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1224		1778
1225		1779
1226	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1227		1781
1228	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1783	given time, and optionally repeating in regular intervals after that.
1230		1784
1231	The timers are based on real time, that is, if you register an event that	1785	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1786	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1787	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1236		1790
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1793	might introduce a small delay). If multiple timers become ready during the
		1794	same loop iteration then the ones with earlier time-out values are invoked
		1795	before ones of the same priority with later time-out values (but this is
		1796	no longer true when a callback calls C<ev_run> recursively).
		1797
		1798	=head3 Be smart about timeouts
		1799
		1800	Many real-world problems involve some kind of timeout, usually for error
		1801	recovery. A typical example is an HTTP request - if the other side hangs,
		1802	you want to raise some error after a while.
		1803
		1804	What follows are some ways to handle this problem, from obvious and
		1805	inefficient to smart and efficient.
		1806
		1807	In the following, a 60 second activity timeout is assumed - a timeout that
		1808	gets reset to 60 seconds each time there is activity (e.g. each time some
		1809	data or other life sign was received).
		1810
		1811	=over 4
		1812
		1813	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1814
		1815	This is the most obvious, but not the most simple way: In the beginning,
		1816	start the watcher:
		1817
		1818	ev_timer_init (timer, callback, 60., 0.);
		1819	ev_timer_start (loop, timer);
		1820
		1821	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1822	and start it again:
		1823
		1824	ev_timer_stop (loop, timer);
		1825	ev_timer_set (timer, 60., 0.);
		1826	ev_timer_start (loop, timer);
		1827
		1828	This is relatively simple to implement, but means that each time there is
		1829	some activity, libev will first have to remove the timer from its internal
		1830	data structure and then add it again. Libev tries to be fast, but it's
		1831	still not a constant-time operation.
		1832
		1833	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1834
		1835	This is the easiest way, and involves using C<ev_timer_again> instead of
		1836	C<ev_timer_start>.
		1837
		1838	To implement this, configure an C<ev_timer> with a C<repeat> value
		1839	of C<60> and then call C<ev_timer_again> at start and each time you
		1840	successfully read or write some data. If you go into an idle state where
		1841	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1842	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1843
		1844	That means you can ignore both the C<ev_timer_start> function and the
		1845	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1846	member and C<ev_timer_again>.
		1847
		1848	At start:
		1849
		1850	ev_init (timer, callback);
		1851	timer->repeat = 60.;
		1852	ev_timer_again (loop, timer);
		1853
		1854	Each time there is some activity:
		1855
		1856	ev_timer_again (loop, timer);
		1857
		1858	It is even possible to change the time-out on the fly, regardless of
		1859	whether the watcher is active or not:
		1860
		1861	timer->repeat = 30.;
		1862	ev_timer_again (loop, timer);
		1863
		1864	This is slightly more efficient then stopping/starting the timer each time
		1865	you want to modify its timeout value, as libev does not have to completely
		1866	remove and re-insert the timer from/into its internal data structure.
		1867
		1868	It is, however, even simpler than the "obvious" way to do it.
		1869
		1870	=item 3. Let the timer time out, but then re-arm it as required.
		1871
		1872	This method is more tricky, but usually most efficient: Most timeouts are
		1873	relatively long compared to the intervals between other activity - in
		1874	our example, within 60 seconds, there are usually many I/O events with
		1875	associated activity resets.
		1876
		1877	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1878	but remember the time of last activity, and check for a real timeout only
		1879	within the callback:
		1880
		1881	ev_tstamp last_activity; // time of last activity
		1882
		1883	static void
		1884	callback (EV_P_ ev_timer *w, int revents)
		1885	{
		1886	ev_tstamp now = ev_now (EV_A);
		1887	ev_tstamp timeout = last_activity + 60.;
		1888
		1889	// if last_activity + 60. is older than now, we did time out
		1890	if (timeout < now)
		1891	{
		1892	// timeout occurred, take action
		1893	}
		1894	else
		1895	{
		1896	// callback was invoked, but there was some activity, re-arm
		1897	// the watcher to fire in last_activity + 60, which is
		1898	// guaranteed to be in the future, so "again" is positive:
		1899	w->repeat = timeout - now;
		1900	ev_timer_again (EV_A_ w);
		1901	}
		1902	}
		1903
		1904	To summarise the callback: first calculate the real timeout (defined
		1905	as "60 seconds after the last activity"), then check if that time has
		1906	been reached, which means something I<did>, in fact, time out. Otherwise
		1907	the callback was invoked too early (C<timeout> is in the future), so
		1908	re-schedule the timer to fire at that future time, to see if maybe we have
		1909	a timeout then.
		1910
		1911	Note how C<ev_timer_again> is used, taking advantage of the
		1912	C<ev_timer_again> optimisation when the timer is already running.
		1913
		1914	This scheme causes more callback invocations (about one every 60 seconds
		1915	minus half the average time between activity), but virtually no calls to
		1916	libev to change the timeout.
		1917
		1918	To start the timer, simply initialise the watcher and set C<last_activity>
		1919	to the current time (meaning we just have some activity :), then call the
		1920	callback, which will "do the right thing" and start the timer:
		1921
		1922	ev_init (timer, callback);
		1923	last_activity = ev_now (loop);
		1924	callback (loop, timer, EV_TIMER);
		1925
		1926	And when there is some activity, simply store the current time in
		1927	C<last_activity>, no libev calls at all:
		1928
		1929	last_activity = ev_now (loop);
		1930
		1931	This technique is slightly more complex, but in most cases where the
		1932	time-out is unlikely to be triggered, much more efficient.
		1933
		1934	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1935	callback :) - just change the timeout and invoke the callback, which will
		1936	fix things for you.
		1937
		1938	=item 4. Wee, just use a double-linked list for your timeouts.
		1939
		1940	If there is not one request, but many thousands (millions...), all
		1941	employing some kind of timeout with the same timeout value, then one can
		1942	do even better:
		1943
		1944	When starting the timeout, calculate the timeout value and put the timeout
		1945	at the I<end> of the list.
		1946
		1947	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1948	the list is expected to fire (for example, using the technique #3).
		1949
		1950	When there is some activity, remove the timer from the list, recalculate
		1951	the timeout, append it to the end of the list again, and make sure to
		1952	update the C<ev_timer> if it was taken from the beginning of the list.
		1953
		1954	This way, one can manage an unlimited number of timeouts in O(1) time for
		1955	starting, stopping and updating the timers, at the expense of a major
		1956	complication, and having to use a constant timeout. The constant timeout
		1957	ensures that the list stays sorted.
		1958
		1959	=back
		1960
		1961	So which method the best?
		1962
		1963	Method #2 is a simple no-brain-required solution that is adequate in most
		1964	situations. Method #3 requires a bit more thinking, but handles many cases
		1965	better, and isn't very complicated either. In most case, choosing either
		1966	one is fine, with #3 being better in typical situations.
		1967
		1968	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1969	rather complicated, but extremely efficient, something that really pays
		1970	off after the first million or so of active timers, i.e. it's usually
		1971	overkill :)
1240		1972
1241	=head3 The special problem of time updates	1973	=head3 The special problem of time updates
1242		1974
1243	Establishing the current time is a costly operation (it usually takes at	1975	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1976	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1977	time only before and after C<ev_run> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1978	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1979	lots of events in one iteration.
1248		1980
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1981	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1982	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1983	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1984	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1988
1257	If the event loop is suspended for a long time, you can also force an	1989	If the event loop is suspended for a long time, you can also force an
1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1990	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1991	()>.
1260		1992
		1993	=head3 The special problems of suspended animation
		1994
		1995	When you leave the server world it is quite customary to hit machines that
		1996	can suspend/hibernate - what happens to the clocks during such a suspend?
		1997
		1998	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1999	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2000	to run until the system is suspended, but they will not advance while the
		2001	system is suspended. That means, on resume, it will be as if the program
		2002	was frozen for a few seconds, but the suspend time will not be counted
		2003	towards C<ev_timer> when a monotonic clock source is used. The real time
		2004	clock advanced as expected, but if it is used as sole clocksource, then a
		2005	long suspend would be detected as a time jump by libev, and timers would
		2006	be adjusted accordingly.
		2007
		2008	I would not be surprised to see different behaviour in different between
		2009	operating systems, OS versions or even different hardware.
		2010
		2011	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2012	time jump in the monotonic clocks and the realtime clock. If the program
		2013	is suspended for a very long time, and monotonic clock sources are in use,
		2014	then you can expect C<ev_timer>s to expire as the full suspension time
		2015	will be counted towards the timers. When no monotonic clock source is in
		2016	use, then libev will again assume a timejump and adjust accordingly.
		2017
		2018	It might be beneficial for this latter case to call C<ev_suspend>
		2019	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2020	deterministic behaviour in this case (you can do nothing against
		2021	C<SIGSTOP>).
		2022
1261	=head3 Watcher-Specific Functions and Data Members	2023	=head3 Watcher-Specific Functions and Data Members
1262		2024
1263	=over 4	2025	=over 4
1264		2026
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2027	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	2050	If the timer is started but non-repeating, stop it (as if it timed out).
1289		2051
1290	If the timer is repeating, either start it if necessary (with the	2052	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	2053	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		2054
1293	This sounds a bit complicated, but here is a useful and typical	2055	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	2056	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		2057
1303	That means you can ignore the C<after> value and C<ev_timer_start>	2058	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		2059
1306	ev_timer_init (timer, callback, 0., 5.);	2060	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	2061	then this time is relative to the current event loop time, otherwise it's
1308	...	2062	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		2063
1315	This is more slightly efficient then stopping/starting the timer each time	2064	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	2065	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2066	will return C<4>. When the timer expires and is restarted, it will return
		2067	roughly C<7> (likely slightly less as callback invocation takes some time,
		2068	too), and so on.
1317		2069
1318	=item ev_tstamp repeat [read-write]	2070	=item ev_tstamp repeat [read-write]
1319		2071
1320	The current C<repeat> value. Will be used each time the watcher times out	2072	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	2073	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	2074	which is also when any modifications are taken into account.
1323		2075
1324	=back	2076	=back
1325		2077
1326	=head3 Examples	2078	=head3 Examples
1327		2079
1328	Example: Create a timer that fires after 60 seconds.	2080	Example: Create a timer that fires after 60 seconds.
1329		2081
1330	static void	2082	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2083	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	2084	{
1333	.. one minute over, w is actually stopped right here	2085	.. one minute over, w is actually stopped right here
1334	}	2086	}
1335		2087
1336	struct ev_timer mytimer;	2088	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2089	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	2090	ev_timer_start (loop, &mytimer);
1339		2091
1340	Example: Create a timeout timer that times out after 10 seconds of	2092	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	2093	inactivity.
1342		2094
1343	static void	2095	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2096	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	2097	{
1346	.. ten seconds without any activity	2098	.. ten seconds without any activity
1347	}	2099	}
1348		2100
1349	struct ev_timer mytimer;	2101	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2102	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	2103	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	2104	ev_run (loop, 0);
1353		2105
1354	// and in some piece of code that gets executed on any "activity":	2106	// and in some piece of code that gets executed on any "activity":
1355	// reset the timeout to start ticking again at 10 seconds	2107	// reset the timeout to start ticking again at 10 seconds
1356	ev_timer_again (&mytimer);	2108	ev_timer_again (&mytimer);
1357		2109
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	2111	=head2 C<ev_periodic> - to cron or not to cron?
1360		2112
1361	Periodic watchers are also timers of a kind, but they are very versatile	2113	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	2114	(and unfortunately a bit complex).
1363		2115
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2116	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	2117	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	2118	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2119	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	2120	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	2121	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		2122
		2123	You can tell a periodic watcher to trigger after some specific point
		2124	in time: for example, if you tell a periodic watcher to trigger "in 10
		2125	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2126	not a delay) and then reset your system clock to January of the previous
		2127	year, then it will take a year or more to trigger the event (unlike an
		2128	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2129	it, as it uses a relative timeout).
		2130
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	2131	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	2132	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	2133	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2134	those cannot react to time jumps.
1376		2135
1377	As with timers, the callback is guaranteed to be invoked only when the	2136	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	2137	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	2138	timers become ready during the same loop iteration then the ones with
		2139	earlier time-out values are invoked before ones with later time-out values
		2140	(but this is no longer true when a callback calls C<ev_run> recursively).
1380		2141
1381	=head3 Watcher-Specific Functions and Data Members	2142	=head3 Watcher-Specific Functions and Data Members
1382		2143
1383	=over 4	2144	=over 4
1384		2145
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2146	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		2147
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2148	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2149
1389	Lots of arguments, lets sort it out... There are basically three modes of	2150	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	2151	operation, and we will explain them from simplest to most complex:
1391		2152
1392	=over 4	2153	=over 4
1393		2154
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2155	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2156
1396	In this configuration the watcher triggers an event after the wall clock	2157	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	2158	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2159	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	2160	will be stopped and invoked when the system clock reaches or surpasses
		2161	this point in time.
1400		2162
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2163	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2164
1403	In this mode the watcher will always be scheduled to time out at the next	2165	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	2166	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2167	negative) and then repeat, regardless of any time jumps. The C<offset>
		2168	argument is merely an offset into the C<interval> periods.
1406		2169
1407	This can be used to create timers that do not drift with respect to system	2170	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	2171	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2172	hour, on the hour (with respect to UTC):
1410		2173
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2174	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2175
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2176	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	2177	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	2178	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2179	by 3600.
1417		2180
1418	Another way to think about it (for the mathematically inclined) is that	2181	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	2182	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	2183	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2184
1422	For numerical stability it is preferable that the C<at> value is near	2185	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	2186	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2187	this value, and in fact is often specified as zero.
1425		2188
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2189	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	2190	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	2191	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	2192	millisecond (if the OS supports it and the machine is fast enough).
1430		2193
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2194	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2195
1433	In this mode the values for C<interval> and C<at> are both being	2196	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	2197	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2198	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2199	current time as second argument.
1437		2200
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2201	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2202	or make ANY other event loop modifications whatsoever, unless explicitly
		2203	allowed by documentation here>.
1440		2204
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2205	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2206	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2207	only event loop modification you are allowed to do).
1444		2208
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2209	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2210	*w, ev_tstamp now)>, e.g.:
1447		2211
		2212	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2213	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2214	{
1450	return now + 60.;	2215	return now + 60.;
1451	}	2216	}
1452		2217
1453	It must return the next time to trigger, based on the passed time value	2218	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2238	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2239	program when the crontabs have changed).
1475		2240
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2241	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2242
1478	When active, returns the absolute time that the watcher is supposed to	2243	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2244	to trigger next. This is not the same as the C<offset> argument to
		2245	C<ev_periodic_set>, but indeed works even in interval and manual
		2246	rescheduling modes.
1480		2247
1481	=item ev_tstamp offset [read-write]	2248	=item ev_tstamp offset [read-write]
1482		2249
1483	When repeating, this contains the offset value, otherwise this is the	2250	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2251	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2252	although libev might modify this value for better numerical stability).
1485		2253
1486	Can be modified any time, but changes only take effect when the periodic	2254	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2255	timer fires or C<ev_periodic_again> is being called.
1488		2256
1489	=item ev_tstamp interval [read-write]	2257	=item ev_tstamp interval [read-write]
1490		2258
1491	The current interval value. Can be modified any time, but changes only	2259	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2260	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2261	called.
1494		2262
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2263	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2264
1497	The current reschedule callback, or C<0>, if this functionality is	2265	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2266	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2267	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2268
1501	=back	2269	=back
1502		2270
1503	=head3 Examples	2271	=head3 Examples
1504		2272
1505	Example: Call a callback every hour, or, more precisely, whenever the	2273	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2274	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2275	potentially a lot of jitter, but good long-term stability.
1508		2276
1509	static void	2277	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2278	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2279	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2280	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2281	}
1514		2282
1515	struct ev_periodic hourly_tick;	2283	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2284	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2285	ev_periodic_start (loop, &hourly_tick);
1518		2286
1519	Example: The same as above, but use a reschedule callback to do it:	2287	Example: The same as above, but use a reschedule callback to do it:
1520		2288
1521	#include <math.h>	2289	#include <math.h>
1522		2290
1523	static ev_tstamp	2291	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2292	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2293	{
1526	return fmod (now, 3600.) + 3600.;	2294	return now + (3600. - fmod (now, 3600.));
1527	}	2295	}
1528		2296
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2297	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2298
1531	Example: Call a callback every hour, starting now:	2299	Example: Call a callback every hour, starting now:
1532		2300
1533	struct ev_periodic hourly_tick;	2301	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2302	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2303	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2304	ev_periodic_start (loop, &hourly_tick);
1537		2305
1538		2306
1539	=head2 C<ev_signal> - signal me when a signal gets signalled!	2307	=head2 C<ev_signal> - signal me when a signal gets signalled!
1540		2308
1541	Signal watchers will trigger an event when the process receives a specific	2309	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	2310	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2311	will try its best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2312	normal event processing, like any other event.
1545		2313
		2314	If you want signals to be delivered truly asynchronously, just use
		2315	C<sigaction> as you would do without libev and forget about sharing
		2316	the signal. You can even use C<ev_async> from a signal handler to
		2317	synchronously wake up an event loop.
		2318
1546	You can configure as many watchers as you like per signal. Only when the	2319	You can configure as many watchers as you like for the same signal, but
		2320	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2321	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2322	C<SIGINT> in both the default loop and another loop at the same time. At
		2323	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2324
1547	first watcher gets started will libev actually register a signal watcher	2325	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2326	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2327	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2328
1553	If possible and supported, libev will install its handlers with	2329	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2330	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2331	not be unduly interrupted. If you have a problem with system calls getting
1556	signals you can block all signals in an C<ev_check> watcher and unblock	2332	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2333	and unblock them in an C<ev_prepare> watcher.
		2334
		2335	=head3 The special problem of inheritance over fork/execve/pthread_create
		2336
		2337	Both the signal mask (C<sigprocmask>) and the signal disposition
		2338	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2339	stopping it again), that is, libev might or might not block the signal,
		2340	and might or might not set or restore the installed signal handler.
		2341
		2342	While this does not matter for the signal disposition (libev never
		2343	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2344	C<execve>), this matters for the signal mask: many programs do not expect
		2345	certain signals to be blocked.
		2346
		2347	This means that before calling C<exec> (from the child) you should reset
		2348	the signal mask to whatever "default" you expect (all clear is a good
		2349	choice usually).
		2350
		2351	The simplest way to ensure that the signal mask is reset in the child is
		2352	to install a fork handler with C<pthread_atfork> that resets it. That will
		2353	catch fork calls done by libraries (such as the libc) as well.
		2354
		2355	In current versions of libev, the signal will not be blocked indefinitely
		2356	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2357	the window of opportunity for problems, it will not go away, as libev
		2358	I<has> to modify the signal mask, at least temporarily.
		2359
		2360	So I can't stress this enough: I<If you do not reset your signal mask when
		2361	you expect it to be empty, you have a race condition in your code>. This
		2362	is not a libev-specific thing, this is true for most event libraries.
		2363
		2364	=head3 The special problem of threads signal handling
		2365
		2366	POSIX threads has problematic signal handling semantics, specifically,
		2367	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2368	threads in a process block signals, which is hard to achieve.
		2369
		2370	When you want to use sigwait (or mix libev signal handling with your own
		2371	for the same signals), you can tackle this problem by globally blocking
		2372	all signals before creating any threads (or creating them with a fully set
		2373	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2374	loops. Then designate one thread as "signal receiver thread" which handles
		2375	these signals. You can pass on any signals that libev might be interested
		2376	in by calling C<ev_feed_signal>.
1558		2377
1559	=head3 Watcher-Specific Functions and Data Members	2378	=head3 Watcher-Specific Functions and Data Members
1560		2379
1561	=over 4	2380	=over 4
1562		2381
…		…
1573		2392
1574	=back	2393	=back
1575		2394
1576	=head3 Examples	2395	=head3 Examples
1577		2396
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2397	Example: Try to exit cleanly on SIGINT.
1579		2398
1580	static void	2399	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2400	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2401	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2402	ev_break (loop, EVBREAK_ALL);
1584	}	2403	}
1585		2404
1586	struct ev_signal signal_watcher;	2405	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2406	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2407	ev_signal_start (loop, &signal_watcher);
1589		2408
1590		2409
1591	=head2 C<ev_child> - watch out for process status changes	2410	=head2 C<ev_child> - watch out for process status changes
1592		2411
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2412	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2413	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2414	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2415	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2416	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2417	forking and then immediately registering a watcher for the child is fine,
		2418	but forking and registering a watcher a few event loop iterations later or
		2419	in the next callback invocation is not.
1598		2420
1599	Only the default event loop is capable of handling signals, and therefore	2421	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2422	you can only register child watchers in the default event loop.
1601		2423
		2424	Due to some design glitches inside libev, child watchers will always be
		2425	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2426	libev)
		2427
1602	=head3 Process Interaction	2428	=head3 Process Interaction
1603		2429
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2430	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2431	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2432	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2433	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2434	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2435	children, even ones not watched.
1610		2436
1611	=head3 Overriding the Built-In Processing	2437	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2447	=head3 Stopping the Child Watcher
1622		2448
1623	Currently, the child watcher never gets stopped, even when the	2449	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2450	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2451	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2452	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2453	problem).
1627		2454
1628	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
1629		2456
1630	=over 4	2457	=over 4
1631		2458
…		…
1663	its completion.	2490	its completion.
1664		2491
1665	ev_child cw;	2492	ev_child cw;
1666		2493
1667	static void	2494	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2495	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2496	{
1670	ev_child_stop (EV_A_ w);	2497	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2498	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2499	}
1673		2500
…		…
1688		2515
1689		2516
1690	=head2 C<ev_stat> - did the file attributes just change?	2517	=head2 C<ev_stat> - did the file attributes just change?
1691		2518
1692	This watches a file system path for attribute changes. That is, it calls	2519	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2520	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2521	and sees if it changed compared to the last time, invoking the callback if
		2522	it did.
1695		2523
1696	The path does not need to exist: changing from "path exists" to "path does	2524	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2525	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2526	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2527	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2528	least one) and all the other fields of the stat buffer having unspecified
		2529	contents.
1701		2530
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2531	The path I<must not> end in a slash or contain special components such as
		2532	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2533	your working directory changes, then the behaviour is undefined.
1704		2534
1705	Since there is no standard to do this, the portable implementation simply	2535	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2536	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2537	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2538	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2539	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2540	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2541	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2542	currently around C<0.1>, but that's usually overkill.
1713		2543
1714	This watcher type is not meant for massive numbers of stat watchers,	2544	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2545	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2546	resource-intensive.
1717		2547
1718	At the time of this writing, only the Linux inotify interface is	2548	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2549	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2550	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2551	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2552
1727	=head3 ABI Issues (Largefile Support)	2553	=head3 ABI Issues (Largefile Support)
1728		2554
1729	Libev by default (unless the user overrides this) uses the default	2555	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2556	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2557	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2558	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2559	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2560	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2561	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2562	most noticeably displayed with ev_stat and large file support.
1737		2563
1738	The solution for this is to lobby your distribution maker to make large	2564	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2565	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2566	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2567	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2568	default compilation environment.
1743		2569
1744	=head3 Inotify	2570	=head3 Inotify and Kqueue
1745		2571
1746	When C<inotify (7)> support has been compiled into libev (generally only	2572	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2573	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2574	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2575	watcher is being started.
1750		2576
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2577	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2578	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2579	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2580	there are many cases where libev has to resort to regular C<stat> polling,
		2581	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2582	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2583	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2584	xfs are fully working) libev usually gets away without polling.
1755		2585
1756	(There is no support for kqueue, as apparently it cannot be used to	2586	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2587	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2588	descriptor open on the object at all times, and detecting renames, unlinks
		2589	etc. is difficult.
		2590
		2591	=head3 C<stat ()> is a synchronous operation
		2592
		2593	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2594	the process. The exception are C<ev_stat> watchers - those call C<stat
		2595	()>, which is a synchronous operation.
		2596
		2597	For local paths, this usually doesn't matter: unless the system is very
		2598	busy or the intervals between stat's are large, a stat call will be fast,
		2599	as the path data is usually in memory already (except when starting the
		2600	watcher).
		2601
		2602	For networked file systems, calling C<stat ()> can block an indefinite
		2603	time due to network issues, and even under good conditions, a stat call
		2604	often takes multiple milliseconds.
		2605
		2606	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2607	paths, although this is fully supported by libev.
1759		2608
1760	=head3 The special problem of stat time resolution	2609	=head3 The special problem of stat time resolution
1761		2610
1762	The C<stat ()> system call only supports full-second resolution portably, and	2611	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2612	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2613	still only support whole seconds.
1765		2614
1766	That means that, if the time is the only thing that changes, you can	2615	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2616	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2617	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2618	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2619	stat data does change in other ways (e.g. file size).
1771		2620
1772	The solution to this is to delay acting on a change for slightly more	2621	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2622	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2623	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2624	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2644	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2645	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2646	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2647	path for as long as the watcher is active.
1799		2648
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2649	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2650	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2651	last change was detected).
1803		2652
1804	=item ev_stat_stat (loop, ev_stat *)	2653	=item ev_stat_stat (loop, ev_stat *)
1805		2654
1806	Updates the stat buffer immediately with new values. If you change the	2655	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2656	watched path in your callback, you could call this function to avoid
…		…
1890		2739
1891		2740
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2741	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2742
1894	Idle watchers trigger events when no other events of the same or higher	2743	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2744	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2745	as receiving "events").
1897		2746
1898	That is, as long as your process is busy handling sockets or timeouts	2747	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2748	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2749	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2750	are pending), the idle watchers are being called once per event loop
…		…
1912		2761
1913	=head3 Watcher-Specific Functions and Data Members	2762	=head3 Watcher-Specific Functions and Data Members
1914		2763
1915	=over 4	2764	=over 4
1916		2765
1917	=item ev_idle_init (ev_signal *, callback)	2766	=item ev_idle_init (ev_idle *, callback)
1918		2767
1919	Initialises and configures the idle watcher - it has no parameters of any	2768	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2769	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2770	believe me.
1922		2771
…		…
1926		2775
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2776	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2777	callback, free it. Also, use no error checking, as usual.
1929		2778
1930	static void	2779	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2780	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2781	{
1933	free (w);	2782	free (w);
1934	// now do something you wanted to do when the program has	2783	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2784	// no longer anything immediate to do.
1936	}	2785	}
1937		2786
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2787	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2788	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2789	ev_idle_start (loop, idle_watcher);
1941		2790
1942		2791
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2792	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2793
1945	Prepare and check watchers are usually (but not always) used in tandem:	2794	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2795	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2796	afterwards.
1948		2797
1949	You I<must not> call C<ev_loop> or similar functions that enter	2798	You I<must not> call C<ev_run> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2799	the current event loop from either C<ev_prepare> or C<ev_check>
1951	watchers. Other loops than the current one are fine, however. The	2800	watchers. Other loops than the current one are fine, however. The
1952	rationale behind this is that you do not need to check for recursion in	2801	rationale behind this is that you do not need to check for recursion in
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2802	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2803	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2804	called in pairs bracketing the blocking call.
1956		2805
1957	Their main purpose is to integrate other event mechanisms into libev and	2806	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2807	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2808	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2809	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2810	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2811	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2812	watcher).
1964		2813
1965	This is done by examining in each prepare call which file descriptors need	2814	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2815	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2816	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2817	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2818	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2819	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2820	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2821	nevertheless, because you never know, you know?).
1973		2822
1974	As another example, the Perl Coro module uses these hooks to integrate	2823	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2824	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2825	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2826	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2829	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2830	low-priority coroutines to idle/background tasks).
1982		2831
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2832	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2833	priority, to ensure that they are being run before any other watchers
		2834	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2835
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2836	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2837	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2838	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2839	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2840	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2841	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2842	others).
1992		2843
1993	=head3 Watcher-Specific Functions and Data Members	2844	=head3 Watcher-Specific Functions and Data Members
1994		2845
1995	=over 4	2846	=over 4
1996		2847
…		…
1998		2849
1999	=item ev_check_init (ev_check *, callback)	2850	=item ev_check_init (ev_check *, callback)
2000		2851
2001	Initialises and configures the prepare or check watcher - they have no	2852	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2853	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2854	macros, but using them is utterly, utterly, utterly and completely
		2855	pointless.
2004		2856
2005	=back	2857	=back
2006		2858
2007	=head3 Examples	2859	=head3 Examples
2008		2860
…		…
2021		2873
2022	static ev_io iow [nfd];	2874	static ev_io iow [nfd];
2023	static ev_timer tw;	2875	static ev_timer tw;
2024		2876
2025	static void	2877	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2878	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2879	{
2028	}	2880	}
2029		2881
2030	// create io watchers for each fd and a timer before blocking	2882	// create io watchers for each fd and a timer before blocking
2031	static void	2883	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2884	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2885	{
2034	int timeout = 3600000;	2886	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2887	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2888	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2889	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2890
2039	/* the callback is illegal, but won't be called as we stop during check */	2891	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2892	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2893	ev_timer_start (loop, &tw);
2042		2894
2043	// create one ev_io per pollfd	2895	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2896	for (int i = 0; i < nfd; ++i)
2045	{	2897	{
…		…
2052	}	2904	}
2053	}	2905	}
2054		2906
2055	// stop all watchers after blocking	2907	// stop all watchers after blocking
2056	static void	2908	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2909	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2910	{
2059	ev_timer_stop (loop, &tw);	2911	ev_timer_stop (loop, &tw);
2060		2912
2061	for (int i = 0; i < nfd; ++i)	2913	for (int i = 0; i < nfd; ++i)
2062	{	2914	{
…		…
2101	}	2953	}
2102		2954
2103	// do not ever call adns_afterpoll	2955	// do not ever call adns_afterpoll
2104		2956
2105	Method 4: Do not use a prepare or check watcher because the module you	2957	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2958	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2959	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2960	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2961	this approach, effectively embedding EV as a client into the horrible
		2962	libglib event loop.
2110		2963
2111	static gint	2964	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2965	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2966	{
2114	int got_events = 0;	2967	int got_events = 0;
…		…
2118		2971
2119	if (timeout >= 0)	2972	if (timeout >= 0)
2120	// create/start timer	2973	// create/start timer
2121		2974
2122	// poll	2975	// poll
2123	ev_loop (EV_A_ 0);	2976	ev_run (EV_A_ 0);
2124		2977
2125	// stop timer again	2978	// stop timer again
2126	if (timeout >= 0)	2979	if (timeout >= 0)
2127	ev_timer_stop (EV_A_ &to);	2980	ev_timer_stop (EV_A_ &to);
2128		2981
…		…
2145	prioritise I/O.	2998	prioritise I/O.
2146		2999
2147	As an example for a bug workaround, the kqueue backend might only support	3000	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	3001	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	3002	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	3003	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	3004	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	3005	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	3006	C<kevent>, but at least you can use both mechanisms for what they are
		3007	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		3008
2155	As for prioritising I/O: rarely you have the case where some fds have	3009	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	3010	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	3011	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	3012	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	3013	the rest in a second one, and embed the second one in the first.
2160		3014
2161	As long as the watcher is active, the callback will be invoked every time	3015	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	3016	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3017	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	3018	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	3019	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	3020	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		3021
2169	As long as the watcher is started it will automatically handle events. The	3022	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	3023	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		3024
2174	Also, there have not currently been made special provisions for forking:	3025	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3026	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	3027	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	3028	C<ev_loop_fork> on the embedded loop.
2178		3029
2179	Unfortunately, not all backends are embeddable, only the ones returned by	3030	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3031	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	3032	portable one.
2182		3033
2183	So when you want to use this feature you will always have to be prepared	3034	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	3035	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	3036	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	3037	create it, and if that fails, use the normal loop for everything.
		3038
		3039	=head3 C<ev_embed> and fork
		3040
		3041	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3042	automatically be applied to the embedded loop as well, so no special
		3043	fork handling is required in that case. When the watcher is not running,
		3044	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3045	as applicable.
2187		3046
2188	=head3 Watcher-Specific Functions and Data Members	3047	=head3 Watcher-Specific Functions and Data Members
2189		3048
2190	=over 4	3049	=over 4
2191		3050
…		…
2200	if you do not want that, you need to temporarily stop the embed watcher).	3059	if you do not want that, you need to temporarily stop the embed watcher).
2201		3060
2202	=item ev_embed_sweep (loop, ev_embed *)	3061	=item ev_embed_sweep (loop, ev_embed *)
2203		3062
2204	Make a single, non-blocking sweep over the embedded loop. This works	3063	Make a single, non-blocking sweep over the embedded loop. This works
2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3064	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2206	appropriate way for embedded loops.	3065	appropriate way for embedded loops.
2207		3066
2208	=item struct ev_loop *other [read-only]	3067	=item struct ev_loop *other [read-only]
2209		3068
2210	The embedded event loop.	3069	The embedded event loop.
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3078	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	3079	used).
2221		3080
2222	struct ev_loop *loop_hi = ev_default_init (0);	3081	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	3082	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	3083	ev_embed embed;
2225		3084
2226	// see if there is a chance of getting one that works	3085	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	3086	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3087	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3088	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	3102	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3103	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		3104
2246	struct ev_loop *loop = ev_default_init (0);	3105	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	3106	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	3107	ev_embed embed;
2249		3108
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3109	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3110	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	3111	{
2253	ev_embed_init (&embed, 0, loop_socket);	3112	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	3127	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	3128	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3129	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	3130	handlers will be invoked, too, of course.
2272		3131
		3132	=head3 The special problem of life after fork - how is it possible?
		3133
		3134	Most uses of C<fork()> consist of forking, then some simple calls to set
		3135	up/change the process environment, followed by a call to C<exec()>. This
		3136	sequence should be handled by libev without any problems.
		3137
		3138	This changes when the application actually wants to do event handling
		3139	in the child, or both parent in child, in effect "continuing" after the
		3140	fork.
		3141
		3142	The default mode of operation (for libev, with application help to detect
		3143	forks) is to duplicate all the state in the child, as would be expected
		3144	when I<either> the parent I<or> the child process continues.
		3145
		3146	When both processes want to continue using libev, then this is usually the
		3147	wrong result. In that case, usually one process (typically the parent) is
		3148	supposed to continue with all watchers in place as before, while the other
		3149	process typically wants to start fresh, i.e. without any active watchers.
		3150
		3151	The cleanest and most efficient way to achieve that with libev is to
		3152	simply create a new event loop, which of course will be "empty", and
		3153	use that for new watchers. This has the advantage of not touching more
		3154	memory than necessary, and thus avoiding the copy-on-write, and the
		3155	disadvantage of having to use multiple event loops (which do not support
		3156	signal watchers).
		3157
		3158	When this is not possible, or you want to use the default loop for
		3159	other reasons, then in the process that wants to start "fresh", call
		3160	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3161	Destroying the default loop will "orphan" (not stop) all registered
		3162	watchers, so you have to be careful not to execute code that modifies
		3163	those watchers. Note also that in that case, you have to re-register any
		3164	signal watchers.
		3165
2273	=head3 Watcher-Specific Functions and Data Members	3166	=head3 Watcher-Specific Functions and Data Members
2274		3167
2275	=over 4	3168	=over 4
2276		3169
2277	=item ev_fork_init (ev_signal *, callback)	3170	=item ev_fork_init (ev_fork *, callback)
2278		3171
2279	Initialises and configures the fork watcher - it has no parameters of any	3172	Initialises and configures the fork watcher - it has no parameters of any
2280	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3173	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2281	believe me.	3174	really.
2282		3175
2283	=back	3176	=back
2284		3177
2285		3178
		3179	=head2 C<ev_cleanup> - even the best things end
		3180
		3181	Cleanup watchers are called just before the event loop is being destroyed
		3182	by a call to C<ev_loop_destroy>.
		3183
		3184	While there is no guarantee that the event loop gets destroyed, cleanup
		3185	watchers provide a convenient method to install cleanup hooks for your
		3186	program, worker threads and so on - you just to make sure to destroy the
		3187	loop when you want them to be invoked.
		3188
		3189	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3190	all other watchers, they do not keep a reference to the event loop (which
		3191	makes a lot of sense if you think about it). Like all other watchers, you
		3192	can call libev functions in the callback, except C<ev_cleanup_start>.
		3193
		3194	=head3 Watcher-Specific Functions and Data Members
		3195
		3196	=over 4
		3197
		3198	=item ev_cleanup_init (ev_cleanup *, callback)
		3199
		3200	Initialises and configures the cleanup watcher - it has no parameters of
		3201	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3202	pointless, I assure you.
		3203
		3204	=back
		3205
		3206	Example: Register an atexit handler to destroy the default loop, so any
		3207	cleanup functions are called.
		3208
		3209	static void
		3210	program_exits (void)
		3211	{
		3212	ev_loop_destroy (EV_DEFAULT_UC);
		3213	}
		3214
		3215	...
		3216	atexit (program_exits);
		3217
		3218
2286	=head2 C<ev_async> - how to wake up another event loop	3219	=head2 C<ev_async> - how to wake up an event loop
2287		3220
2288	In general, you cannot use an C<ev_loop> from multiple threads or other	3221	In general, you cannot use an C<ev_run> from multiple threads or other
2289	asynchronous sources such as signal handlers (as opposed to multiple event	3222	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3223	loops - those are of course safe to use in different threads).
2291		3224
2292	Sometimes, however, you need to wake up another event loop you do not	3225	Sometimes, however, you need to wake up an event loop you do not control,
2293	control, for example because it belongs to another thread. This is what	3226	for example because it belongs to another thread. This is what C<ev_async>
2294	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3227	watchers do: as long as the C<ev_async> watcher is active, you can signal
2295	can signal it by calling C<ev_async_send>, which is thread- and signal	3228	it by calling C<ev_async_send>, which is thread- and signal safe.
2296	safe.
2297		3229
2298	This functionality is very similar to C<ev_signal> watchers, as signals,	3230	This functionality is very similar to C<ev_signal> watchers, as signals,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3231	too, are asynchronous in nature, and signals, too, will be compressed
2300	(i.e. the number of callback invocations may be less than the number of	3232	(i.e. the number of callback invocations may be less than the number of
2301	C<ev_async_sent> calls).	3233	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3234	of "global async watchers" by using a watcher on an otherwise unused
		3235	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3236	even without knowing which loop owns the signal.
2302		3237
2303	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3238	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2304	just the default loop.	3239	just the default loop.
2305		3240
2306	=head3 Queueing	3241	=head3 Queueing
2307		3242
2308	C<ev_async> does not support queueing of data in any way. The reason	3243	C<ev_async> does not support queueing of data in any way. The reason
2309	is that the author does not know of a simple (or any) algorithm for a	3244	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	3245	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	3246	need elaborate support such as pthreads or unportable memory access
		3247	semantics.
2312		3248
2313	That means that if you want to queue data, you have to provide your own	3249	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	3250	queue. But at least I can tell you how to implement locking around your
2315	queue:	3251	queue:
2316		3252
2317	=over 4	3253	=over 4
2318		3254
2319	=item queueing from a signal handler context	3255	=item queueing from a signal handler context
2320		3256
2321	To implement race-free queueing, you simply add to the queue in the signal	3257	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3258	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3259	an example that does that for some fictitious SIGUSR1 handler:
2324		3260
2325	static ev_async mysig;	3261	static ev_async mysig;
2326		3262
2327	static void	3263	static void
2328	sigusr1_handler (void)	3264	sigusr1_handler (void)
…		…
2394	=over 4	3330	=over 4
2395		3331
2396	=item ev_async_init (ev_async *, callback)	3332	=item ev_async_init (ev_async *, callback)
2397		3333
2398	Initialises and configures the async watcher - it has no parameters of any	3334	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3335	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3336	trust me.
2401		3337
2402	=item ev_async_send (loop, ev_async *)	3338	=item ev_async_send (loop, ev_async *)
2403		3339
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3340	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3341	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3342	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3343	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3344	section below on what exactly this means).
2409		3345
		3346	Note that, as with other watchers in libev, multiple events might get
		3347	compressed into a single callback invocation (another way to look at this
		3348	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3349	reset when the event loop detects that).
		3350
2410	This call incurs the overhead of a system call only once per loop iteration,	3351	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3352	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3353	repeated calls to C<ev_async_send> for the same event loop.
2413		3354
2414	=item bool = ev_async_pending (ev_async *)	3355	=item bool = ev_async_pending (ev_async *)
2415		3356
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3357	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3358	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3361	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3362	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3363	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3364	quickly check whether invoking the loop might be a good idea.
2424		3365
2425	Not that this does I<not> check whether the watcher itself is pending, only	3366	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3367	only whether it has been requested to make this watcher pending: there
		3368	is a time window between the event loop checking and resetting the async
		3369	notification, and the callback being invoked.
2427		3370
2428	=back	3371	=back
2429		3372
2430		3373
2431	=head1 OTHER FUNCTIONS	3374	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3378	=over 4
2436		3379
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3380	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3381
2439	This function combines a simple timer and an I/O watcher, calls your	3382	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3383	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3384	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3385	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3386	more watchers yourself.
2444		3387
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3388	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3389	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3390	the given C<fd> and C<events> set will be created and started.
2448		3391
2449	If C<timeout> is less than 0, then no timeout watcher will be	3392	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3393	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3394	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3395
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3396	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2455	passed an C<revents> set like normal event callbacks (a combination of	3397	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3398	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2457	value passed to C<ev_once>:	3399	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3400	a timeout and an io event at the same time - you probably should give io
		3401	events precedence.
		3402
		3403	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3404
2459	static void stdin_ready (int revents, void *arg)	3405	static void stdin_ready (int revents, void *arg)
2460	{	3406	{
		3407	if (revents & EV_READ)
		3408	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3409	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3410	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3411	}
2466		3412
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3413	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3414
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3415	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3416
2477	Feed an event on the given fd, as if a file descriptor backend detected	3417	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3418	the given events it.
2479		3419
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3420	=item ev_feed_signal_event (loop, int signum)
2481		3421
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3422	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2483	loop!).	3423	which is async-safe.
		3424
		3425	=back
		3426
		3427
		3428	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3429
		3430	This section explains some common idioms that are not immediately
		3431	obvious. Note that examples are sprinkled over the whole manual, and this
		3432	section only contains stuff that wouldn't fit anywhere else.
		3433
		3434	=over 4
		3435
		3436	=item Model/nested event loop invocations and exit conditions.
		3437
		3438	Often (especially in GUI toolkits) there are places where you have
		3439	I<modal> interaction, which is most easily implemented by recursively
		3440	invoking C<ev_run>.
		3441
		3442	This brings the problem of exiting - a callback might want to finish the
		3443	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3444	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3445	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3446	other combination: In these cases, C<ev_break> will not work alone.
		3447
		3448	The solution is to maintain "break this loop" variable for each C<ev_run>
		3449	invocation, and use a loop around C<ev_run> until the condition is
		3450	triggered, using C<EVRUN_ONCE>:
		3451
		3452	// main loop
		3453	int exit_main_loop = 0;
		3454
		3455	while (!exit_main_loop)
		3456	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3457
		3458	// in a model watcher
		3459	int exit_nested_loop = 0;
		3460
		3461	while (!exit_nested_loop)
		3462	ev_run (EV_A_ EVRUN_ONCE);
		3463
		3464	To exit from any of these loops, just set the corresponding exit variable:
		3465
		3466	// exit modal loop
		3467	exit_nested_loop = 1;
		3468
		3469	// exit main program, after modal loop is finished
		3470	exit_main_loop = 1;
		3471
		3472	// exit both
		3473	exit_main_loop = exit_nested_loop = 1;
2484		3474
2485	=back	3475	=back
2486		3476
2487		3477
2488	=head1 LIBEVENT EMULATION	3478	=head1 LIBEVENT EMULATION
2489		3479
2490	Libev offers a compatibility emulation layer for libevent. It cannot	3480	Libev offers a compatibility emulation layer for libevent. It cannot
2491	emulate the internals of libevent, so here are some usage hints:	3481	emulate the internals of libevent, so here are some usage hints:
2492		3482
2493	=over 4	3483	=over 4
		3484
		3485	=item * Only the libevent-1.4.1-beta API is being emulated.
		3486
		3487	This was the newest libevent version available when libev was implemented,
		3488	and is still mostly unchanged in 2010.
2494		3489
2495	=item * Use it by including <event.h>, as usual.	3490	=item * Use it by including <event.h>, as usual.
2496		3491
2497	=item * The following members are fully supported: ev_base, ev_callback,	3492	=item * The following members are fully supported: ev_base, ev_callback,
2498	ev_arg, ev_fd, ev_res, ev_events.	3493	ev_arg, ev_fd, ev_res, ev_events.
…		…
2504	=item * Priorities are not currently supported. Initialising priorities	3499	=item * Priorities are not currently supported. Initialising priorities
2505	will fail and all watchers will have the same priority, even though there	3500	will fail and all watchers will have the same priority, even though there
2506	is an ev_pri field.	3501	is an ev_pri field.
2507		3502
2508	=item * In libevent, the last base created gets the signals, in libev, the	3503	=item * In libevent, the last base created gets the signals, in libev, the
2509	first base created (== the default loop) gets the signals.	3504	base that registered the signal gets the signals.
2510		3505
2511	=item * Other members are not supported.	3506	=item * Other members are not supported.
2512		3507
2513	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3508	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2514	to use the libev header file and library.	3509	to use the libev header file and library.
…		…
2533	Care has been taken to keep the overhead low. The only data member the C++	3528	Care has been taken to keep the overhead low. The only data member the C++
2534	classes add (compared to plain C-style watchers) is the event loop pointer	3529	classes add (compared to plain C-style watchers) is the event loop pointer
2535	that the watcher is associated with (or no additional members at all if	3530	that the watcher is associated with (or no additional members at all if
2536	you disable C<EV_MULTIPLICITY> when embedding libev).	3531	you disable C<EV_MULTIPLICITY> when embedding libev).
2537		3532
2538	Currently, functions, and static and non-static member functions can be	3533	Currently, functions, static and non-static member functions and classes
2539	used as callbacks. Other types should be easy to add as long as they only	3534	with C<operator ()> can be used as callbacks. Other types should be easy
2540	need one additional pointer for context. If you need support for other	3535	to add as long as they only need one additional pointer for context. If
2541	types of functors please contact the author (preferably after implementing	3536	you need support for other types of functors please contact the author
2542	it).	3537	(preferably after implementing it).
2543		3538
2544	Here is a list of things available in the C<ev> namespace:	3539	Here is a list of things available in the C<ev> namespace:
2545		3540
2546	=over 4	3541	=over 4
2547		3542
…		…
2565		3560
2566	=over 4	3561	=over 4
2567		3562
2568	=item ev::TYPE::TYPE ()	3563	=item ev::TYPE::TYPE ()
2569		3564
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3565	=item ev::TYPE::TYPE (loop)
2571		3566
2572	=item ev::TYPE::~TYPE	3567	=item ev::TYPE::~TYPE
2573		3568
2574	The constructor (optionally) takes an event loop to associate the watcher	3569	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3570	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3602
2608	myclass obj;	3603	myclass obj;
2609	ev::io iow;	3604	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3605	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3606
		3607	=item w->set (object *)
		3608
		3609	This is a variation of a method callback - leaving out the method to call
		3610	will default the method to C<operator ()>, which makes it possible to use
		3611	functor objects without having to manually specify the C<operator ()> all
		3612	the time. Incidentally, you can then also leave out the template argument
		3613	list.
		3614
		3615	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3616	int revents)>.
		3617
		3618	See the method-C<set> above for more details.
		3619
		3620	Example: use a functor object as callback.
		3621
		3622	struct myfunctor
		3623	{
		3624	void operator() (ev::io &w, int revents)
		3625	{
		3626	...
		3627	}
		3628	}
		3629
		3630	myfunctor f;
		3631
		3632	ev::io w;
		3633	w.set (&f);
		3634
2612	=item w->set<function> (void *data = 0)	3635	=item w->set<function> (void *data = 0)
2613		3636
2614	Also sets a callback, but uses a static method or plain function as	3637	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3638	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3639	C<data> member and is free for you to use.
2617		3640
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3641	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3642
2620	See the method-C<set> above for more details.	3643	See the method-C<set> above for more details.
2621		3644
2622	Example:	3645	Example: Use a plain function as callback.
2623		3646
2624	static void io_cb (ev::io &w, int revents) { }	3647	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3648	iow.set <io_cb> ();
2626		3649
2627	=item w->set (struct ev_loop *)	3650	=item w->set (loop)
2628		3651
2629	Associates a different C<struct ev_loop> with this watcher. You can only	3652	Associates a different C<struct ev_loop> with this watcher. You can only
2630	do this when the watcher is inactive (and not pending either).	3653	do this when the watcher is inactive (and not pending either).
2631		3654
2632	=item w->set ([arguments])	3655	=item w->set ([arguments])
2633		3656
2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3657	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2635	called at least once. Unlike the C counterpart, an active watcher gets	3658	method or a suitable start method must be called at least once. Unlike the
2636	automatically stopped and restarted when reconfiguring it with this	3659	C counterpart, an active watcher gets automatically stopped and restarted
2637	method.	3660	when reconfiguring it with this method.
2638		3661
2639	=item w->start ()	3662	=item w->start ()
2640		3663
2641	Starts the watcher. Note that there is no C<loop> argument, as the	3664	Starts the watcher. Note that there is no C<loop> argument, as the
2642	constructor already stores the event loop.	3665	constructor already stores the event loop.
2643		3666
		3667	=item w->start ([arguments])
		3668
		3669	Instead of calling C<set> and C<start> methods separately, it is often
		3670	convenient to wrap them in one call. Uses the same type of arguments as
		3671	the configure C<set> method of the watcher.
		3672
2644	=item w->stop ()	3673	=item w->stop ()
2645		3674
2646	Stops the watcher if it is active. Again, no C<loop> argument.	3675	Stops the watcher if it is active. Again, no C<loop> argument.
2647		3676
2648	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3677	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2660		3689
2661	=back	3690	=back
2662		3691
2663	=back	3692	=back
2664		3693
2665	Example: Define a class with an IO and idle watcher, start one of them in	3694	Example: Define a class with two I/O and idle watchers, start the I/O
2666	the constructor.	3695	watchers in the constructor.
2667		3696
2668	class myclass	3697	class myclass
2669	{	3698	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3699	ev::io io ; void io_cb (ev::io &w, int revents);
		3700	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3701	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3702
2673	myclass (int fd)	3703	myclass (int fd)
2674	{	3704	{
2675	io .set <myclass, &myclass::io_cb > (this);	3705	io .set <myclass, &myclass::io_cb > (this);
		3706	io2 .set <myclass, &myclass::io2_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3707	idle.set <myclass, &myclass::idle_cb> (this);
2677		3708
2678	io.start (fd, ev::READ);	3709	io.set (fd, ev::WRITE); // configure the watcher
		3710	io.start (); // start it whenever convenient
		3711
		3712	io2.start (fd, ev::READ); // set + start in one call
2679	}	3713	}
2680	};	3714	};
2681		3715
2682		3716
2683	=head1 OTHER LANGUAGE BINDINGS	3717	=head1 OTHER LANGUAGE BINDINGS
…		…
2692	=item Perl	3726	=item Perl
2693		3727
2694	The EV module implements the full libev API and is actually used to test	3728	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3729	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3730	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3731	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3732	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3733	and C<EV::Glib>).
2699		3734
2700	It can be found and installed via CPAN, its homepage is at	3735	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3736	L<http://software.schmorp.de/pkg/EV>.
2702		3737
2703	=item Python	3738	=item Python
2704		3739
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3740	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3741	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3742
2712	=item Ruby	3743	=item Ruby
2713		3744
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3745	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3746	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3747	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3748	L<http://rev.rubyforge.org/>.
2718		3749
		3750	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3751	makes rev work even on mingw.
		3752
		3753	=item Haskell
		3754
		3755	A haskell binding to libev is available at
		3756	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3757
2719	=item D	3758	=item D
2720		3759
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3760	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3761	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3762
		3763	=item Ocaml
		3764
		3765	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3766	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3767
		3768	=item Lua
		3769
		3770	Brian Maher has written a partial interface to libev for lua (at the
		3771	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3772	L<http://github.com/brimworks/lua-ev>.
2723		3773
2724	=back	3774	=back
2725		3775
2726		3776
2727	=head1 MACRO MAGIC	3777	=head1 MACRO MAGIC
…		…
2741	loop argument"). The C<EV_A> form is used when this is the sole argument,	3791	loop argument"). The C<EV_A> form is used when this is the sole argument,
2742	C<EV_A_> is used when other arguments are following. Example:	3792	C<EV_A_> is used when other arguments are following. Example:
2743		3793
2744	ev_unref (EV_A);	3794	ev_unref (EV_A);
2745	ev_timer_add (EV_A_ watcher);	3795	ev_timer_add (EV_A_ watcher);
2746	ev_loop (EV_A_ 0);	3796	ev_run (EV_A_ 0);
2747		3797
2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3798	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2749	which is often provided by the following macro.	3799	which is often provided by the following macro.
2750		3800
2751	=item C<EV_P>, C<EV_P_>	3801	=item C<EV_P>, C<EV_P_>
…		…
2791	}	3841	}
2792		3842
2793	ev_check check;	3843	ev_check check;
2794	ev_check_init (&check, check_cb);	3844	ev_check_init (&check, check_cb);
2795	ev_check_start (EV_DEFAULT_ &check);	3845	ev_check_start (EV_DEFAULT_ &check);
2796	ev_loop (EV_DEFAULT_ 0);	3846	ev_run (EV_DEFAULT_ 0);
2797		3847
2798	=head1 EMBEDDING	3848	=head1 EMBEDDING
2799		3849
2800	Libev can (and often is) directly embedded into host	3850	Libev can (and often is) directly embedded into host
2801	applications. Examples of applications that embed it include the Deliantra	3851	applications. Examples of applications that embed it include the Deliantra
…		…
2828		3878
2829	#define EV_STANDALONE 1	3879	#define EV_STANDALONE 1
2830	#include "ev.h"	3880	#include "ev.h"
2831		3881
2832	Both header files and implementation files can be compiled with a C++	3882	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3883	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3884	as a bug).
2835		3885
2836	You need the following files in your source tree, or in a directory	3886	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3887	in your include path (e.g. in libev/ when using -Ilibev):
2838		3888
…		…
2881	libev.m4	3931	libev.m4
2882		3932
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3933	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3934
2885	Libev can be configured via a variety of preprocessor symbols you have to	3935	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3936	define before including (or compiling) any of its files. The default in
2887	autoconf is noted for every option.	3937	the absence of autoconf is documented for every option.
		3938
		3939	Symbols marked with "(h)" do not change the ABI, and can have different
		3940	values when compiling libev vs. including F<ev.h>, so it is permissible
		3941	to redefine them before including F<ev.h> without breaking compatibility
		3942	to a compiled library. All other symbols change the ABI, which means all
		3943	users of libev and the libev code itself must be compiled with compatible
		3944	settings.
2888		3945
2889	=over 4	3946	=over 4
2890		3947
		3948	=item EV_COMPAT3 (h)
		3949
		3950	Backwards compatibility is a major concern for libev. This is why this
		3951	release of libev comes with wrappers for the functions and symbols that
		3952	have been renamed between libev version 3 and 4.
		3953
		3954	You can disable these wrappers (to test compatibility with future
		3955	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3956	sources. This has the additional advantage that you can drop the C<struct>
		3957	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3958	typedef in that case.
		3959
		3960	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3961	and in some even more future version the compatibility code will be
		3962	removed completely.
		3963
2891	=item EV_STANDALONE	3964	=item EV_STANDALONE (h)
2892		3965
2893	Must always be C<1> if you do not use autoconf configuration, which	3966	Must always be C<1> if you do not use autoconf configuration, which
2894	keeps libev from including F<config.h>, and it also defines dummy	3967	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3968	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3969	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3970	F<event.h> that are not directly supported by the libev core alone.
2898		3971
		3972	In standalone mode, libev will still try to automatically deduce the
		3973	configuration, but has to be more conservative.
		3974
2899	=item EV_USE_MONOTONIC	3975	=item EV_USE_MONOTONIC
2900		3976
2901	If defined to be C<1>, libev will try to detect the availability of the	3977	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3978	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3979	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3980	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3981	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3982	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3983	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3984
2909	=item EV_USE_REALTIME	3985	=item EV_USE_REALTIME
2910		3986
2911	If defined to be C<1>, libev will try to detect the availability of the	3987	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3988	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3989	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3990	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3991	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3992	correctness. See the note about libraries in the description of
		3993	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3994	C<EV_USE_CLOCK_SYSCALL>.
		3995
		3996	=item EV_USE_CLOCK_SYSCALL
		3997
		3998	If defined to be C<1>, libev will try to use a direct syscall instead
		3999	of calling the system-provided C<clock_gettime> function. This option
		4000	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4001	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4002	programs needlessly. Using a direct syscall is slightly slower (in
		4003	theory), because no optimised vdso implementation can be used, but avoids
		4004	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4005	higher, as it simplifies linking (no need for C<-lrt>).
2917		4006
2918	=item EV_USE_NANOSLEEP	4007	=item EV_USE_NANOSLEEP
2919		4008
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4009	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	4010	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		4026
2938	=item EV_SELECT_USE_FD_SET	4027	=item EV_SELECT_USE_FD_SET
2939		4028
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	4029	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	4030	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4031	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	4032	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	4033	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4034	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	4035	configures the maximum size of the C<fd_set>.
2947		4036
2948	=item EV_SELECT_IS_WINSOCKET	4037	=item EV_SELECT_IS_WINSOCKET
2949		4038
2950	When defined to C<1>, the select backend will assume that	4039	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	4040	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	4042	be used is the winsock select). This means that it will call
2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4043	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2955	it is assumed that all these functions actually work on fds, even	4044	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	4045	on win32. Should not be defined on non-win32 platforms.
2957		4046
2958	=item EV_FD_TO_WIN32_HANDLE	4047	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		4048
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4049	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2961	file descriptors to socket handles. When not defining this symbol (the	4050	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	4051	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	4052	correct. In some cases, programs use their own file descriptor management,
2964	in which case they can provide this function to map fds to socket handles.	4053	in which case they can provide this function to map fds to socket handles.
		4054
		4055	=item EV_WIN32_HANDLE_TO_FD(handle)
		4056
		4057	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4058	using the standard C<_open_osfhandle> function. For programs implementing
		4059	their own fd to handle mapping, overwriting this function makes it easier
		4060	to do so. This can be done by defining this macro to an appropriate value.
		4061
		4062	=item EV_WIN32_CLOSE_FD(fd)
		4063
		4064	If programs implement their own fd to handle mapping on win32, then this
		4065	macro can be used to override the C<close> function, useful to unregister
		4066	file descriptors again. Note that the replacement function has to close
		4067	the underlying OS handle.
2965		4068
2966	=item EV_USE_POLL	4069	=item EV_USE_POLL
2967		4070
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4071	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	4072	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3016	as well as for signal and thread safety in C<ev_async> watchers.	4119	as well as for signal and thread safety in C<ev_async> watchers.
3017		4120
3018	In the absence of this define, libev will use C<sig_atomic_t volatile>	4121	In the absence of this define, libev will use C<sig_atomic_t volatile>
3019	(from F<signal.h>), which is usually good enough on most platforms.	4122	(from F<signal.h>), which is usually good enough on most platforms.
3020		4123
3021	=item EV_H	4124	=item EV_H (h)
3022		4125
3023	The name of the F<ev.h> header file used to include it. The default if	4126	The name of the F<ev.h> header file used to include it. The default if
3024	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4127	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3025	used to virtually rename the F<ev.h> header file in case of conflicts.	4128	used to virtually rename the F<ev.h> header file in case of conflicts.
3026		4129
3027	=item EV_CONFIG_H	4130	=item EV_CONFIG_H (h)
3028		4131
3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4132	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3030	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4133	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3031	C<EV_H>, above.	4134	C<EV_H>, above.
3032		4135
3033	=item EV_EVENT_H	4136	=item EV_EVENT_H (h)
3034		4137
3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4138	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3036	of how the F<event.h> header can be found, the default is C<"event.h">.	4139	of how the F<event.h> header can be found, the default is C<"event.h">.
3037		4140
3038	=item EV_PROTOTYPES	4141	=item EV_PROTOTYPES (h)
3039		4142
3040	If defined to be C<0>, then F<ev.h> will not define any function	4143	If defined to be C<0>, then F<ev.h> will not define any function
3041	prototypes, but still define all the structs and other symbols. This is	4144	prototypes, but still define all the structs and other symbols. This is
3042	occasionally useful if you want to provide your own wrapper functions	4145	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	4146	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	4165	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	4166	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	4167	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	4168	fine.
3066		4169
3067	If your embedding application does not need any priorities, defining these both to	4170	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	4171	both to C<0> will save some memory and CPU.
3069		4172
3070	=item EV_PERIODIC_ENABLE	4173	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4174	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4175	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3071		4176
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	4177	If undefined or defined to be C<1> (and the platform supports it), then
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	4178	the respective watcher type is supported. If defined to be C<0>, then it
3074	code.	4179	is not. Disabling watcher types mainly saves code size.
3075		4180
3076	=item EV_IDLE_ENABLE	4181	=item EV_FEATURES
3077
3078	If undefined or defined to be C<1>, then idle watchers are supported. If
3079	defined to be C<0>, then they are not. Disabling them saves a few kB of
3080	code.
3081
3082	=item EV_EMBED_ENABLE
3083
3084	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.
3086
3087	=item EV_STAT_ENABLE
3088
3089	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.
3091
3092	=item EV_FORK_ENABLE
3093
3094	If undefined or defined to be C<1>, then fork watchers are supported. If
3095	defined to be C<0>, then they are not.
3096
3097	=item EV_ASYNC_ENABLE
3098
3099	If undefined or defined to be C<1>, then async watchers are supported. If
3100	defined to be C<0>, then they are not.
3101
3102	=item EV_MINIMAL
3103		4182
3104	If you need to shave off some kilobytes of code at the expense of some	4183	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	4184	speed (but with the full API), you can define this symbol to request
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4185	certain subsets of functionality. The default is to enable all features
3107	much smaller 2-heap for timer management over the default 4-heap.	4186	that can be enabled on the platform.
		4187
		4188	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4189	with some broad features you want) and then selectively re-enable
		4190	additional parts you want, for example if you want everything minimal,
		4191	but multiple event loop support, async and child watchers and the poll
		4192	backend, use this:
		4193
		4194	#define EV_FEATURES 0
		4195	#define EV_MULTIPLICITY 1
		4196	#define EV_USE_POLL 1
		4197	#define EV_CHILD_ENABLE 1
		4198	#define EV_ASYNC_ENABLE 1
		4199
		4200	The actual value is a bitset, it can be a combination of the following
		4201	values:
		4202
		4203	=over 4
		4204
		4205	=item C<1> - faster/larger code
		4206
		4207	Use larger code to speed up some operations.
		4208
		4209	Currently this is used to override some inlining decisions (enlarging the
		4210	code size by roughly 30% on amd64).
		4211
		4212	When optimising for size, use of compiler flags such as C<-Os> with
		4213	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4214	assertions.
		4215
		4216	=item C<2> - faster/larger data structures
		4217
		4218	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4219	hash table sizes and so on. This will usually further increase code size
		4220	and can additionally have an effect on the size of data structures at
		4221	runtime.
		4222
		4223	=item C<4> - full API configuration
		4224
		4225	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4226	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4227
		4228	=item C<8> - full API
		4229
		4230	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4231	details on which parts of the API are still available without this
		4232	feature, and do not complain if this subset changes over time.
		4233
		4234	=item C<16> - enable all optional watcher types
		4235
		4236	Enables all optional watcher types. If you want to selectively enable
		4237	only some watcher types other than I/O and timers (e.g. prepare,
		4238	embed, async, child...) you can enable them manually by defining
		4239	C<EV_watchertype_ENABLE> to C<1> instead.
		4240
		4241	=item C<32> - enable all backends
		4242
		4243	This enables all backends - without this feature, you need to enable at
		4244	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4245
		4246	=item C<64> - enable OS-specific "helper" APIs
		4247
		4248	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4249	default.
		4250
		4251	=back
		4252
		4253	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4254	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4255	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4256	watchers, timers and monotonic clock support.
		4257
		4258	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4259	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4260	your program might be left out as well - a binary starting a timer and an
		4261	I/O watcher then might come out at only 5Kb.
		4262
		4263	=item EV_AVOID_STDIO
		4264
		4265	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4266	functions (printf, scanf, perror etc.). This will increase the code size
		4267	somewhat, but if your program doesn't otherwise depend on stdio and your
		4268	libc allows it, this avoids linking in the stdio library which is quite
		4269	big.
		4270
		4271	Note that error messages might become less precise when this option is
		4272	enabled.
		4273
		4274	=item EV_NSIG
		4275
		4276	The highest supported signal number, +1 (or, the number of
		4277	signals): Normally, libev tries to deduce the maximum number of signals
		4278	automatically, but sometimes this fails, in which case it can be
		4279	specified. Also, using a lower number than detected (C<32> should be
		4280	good for about any system in existence) can save some memory, as libev
		4281	statically allocates some 12-24 bytes per signal number.
3108		4282
3109	=item EV_PID_HASHSIZE	4283	=item EV_PID_HASHSIZE
3110		4284
3111	C<ev_child> watchers use a small hash table to distribute workload by	4285	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4286	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3113	than enough. If you need to manage thousands of children you might want to	4287	usually more than enough. If you need to manage thousands of children you
3114	increase this value (I<must> be a power of two).	4288	might want to increase this value (I<must> be a power of two).
3115		4289
3116	=item EV_INOTIFY_HASHSIZE	4290	=item EV_INOTIFY_HASHSIZE
3117		4291
3118	C<ev_stat> watchers use a small hash table to distribute workload by	4292	C<ev_stat> watchers use a small hash table to distribute workload by
3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4293	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3120	usually more than enough. If you need to manage thousands of C<ev_stat>	4294	disabled), usually more than enough. If you need to manage thousands of
3121	watchers you might want to increase this value (I<must> be a power of	4295	C<ev_stat> watchers you might want to increase this value (I<must> be a
3122	two).	4296	power of two).
3123		4297
3124	=item EV_USE_4HEAP	4298	=item EV_USE_4HEAP
3125		4299
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4300	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4301	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	4302	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4303	faster performance with many (thousands) of watchers.
3130		4304
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4305	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3132	(disabled).	4306	will be C<0>.
3133		4307
3134	=item EV_HEAP_CACHE_AT	4308	=item EV_HEAP_CACHE_AT
3135		4309
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4310	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	4311	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4312	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4313	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	4314	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4315	noticeably with many (hundreds) of watchers.
3142		4316
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4317	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3144	(disabled).	4318	will be C<0>.
3145		4319
3146	=item EV_VERIFY	4320	=item EV_VERIFY
3147		4321
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4322	Controls how much internal verification (see C<ev_verify ()>) will
3149	be done: If set to C<0>, no internal verification code will be compiled	4323	be done: If set to C<0>, no internal verification code will be compiled
3150	in. If set to C<1>, then verification code will be compiled in, but not	4324	in. If set to C<1>, then verification code will be compiled in, but not
3151	called. If set to C<2>, then the internal verification code will be	4325	called. If set to C<2>, then the internal verification code will be
3152	called once per loop, which can slow down libev. If set to C<3>, then the	4326	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	4327	verification code will be called very frequently, which will slow down
3154	libev considerably.	4328	libev considerably.
3155		4329
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4330	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3157	C<0.>	4331	will be C<0>.
3158		4332
3159	=item EV_COMMON	4333	=item EV_COMMON
3160		4334
3161	By default, all watchers have a C<void *data> member. By redefining	4335	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	4336	this macro to something else you can include more and other types of
3163	members. You have to define it each time you include one of the files,	4337	members. You have to define it each time you include one of the files,
3164	though, and it must be identical each time.	4338	though, and it must be identical each time.
3165		4339
3166	For example, the perl EV module uses something like this:	4340	For example, the perl EV module uses something like this:
3167		4341
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4353	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	4354	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	4355	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4356	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	4357	method calls instead of plain function calls in C++.
		4358
		4359	=back
3184		4360
3185	=head2 EXPORTED API SYMBOLS	4361	=head2 EXPORTED API SYMBOLS
3186		4362
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4363	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	4364	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4394	file.
3219		4395
3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4396	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3221	that everybody includes and which overrides some configure choices:	4397	that everybody includes and which overrides some configure choices:
3222		4398
3223	#define EV_MINIMAL 1	4399	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4400	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4401	#define EV_PREPARE_ENABLE 1
		4402	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4403	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4404	#define EV_CHILD_ENABLE 1
		4405	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4406	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4407
3233	#include "ev++.h"	4408	#include "ev++.h"
3234		4409
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4410	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4411
3237	#include "ev_cpp.h"	4412	#include "ev_cpp.h"
3238	#include "ev.c"	4413	#include "ev.c"
3239		4414
		4415	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4416
3241	=head1 THREADS AND COROUTINES	4417	=head2 THREADS AND COROUTINES
3242		4418
3243	=head2 THREADS	4419	=head3 THREADS
3244		4420
3245	Libev itself is thread-safe (unless the opposite is specifically	4421	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4422	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	4423	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	4424	are no concurrent calls into any libev function with the same loop
		4425	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4426	of course): libev guarantees that different event loops share no data
3250	need locking.	4427	structures that need any locking.
3251		4428
3252	Or to put it differently: calls with different loop parameters can be done	4429	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4430	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	4431	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	4432	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4433	a mutex per loop).
3257		4434
3258	Specifically to support threads (and signal handlers), libev implements	4435	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4436	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4437	concurrency on the same event loop, namely waking it up "from the
		4438	outside".
3261		4439
3262	If you want to know which design (one loop, locking, or multiple loops	4440	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	4441	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4442	help you, but here is some generic advice:
3265		4443
3266	=over 4	4444	=over 4
3267		4445
3268	=item * most applications have a main thread: use the default libev loop	4446	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	4447	in that thread, or create a separate thread running only the default loop.
…		…
3281		4459
3282	Choosing a model is hard - look around, learn, know that usually you can do	4460	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	4461	better than you currently do :-)
3284		4462
3285	=item * often you need to talk to some other thread which blocks in the	4463	=item * often you need to talk to some other thread which blocks in the
		4464	event loop.
		4465
3286	event loop - C<ev_async> watchers can be used to wake them up from other	4466	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	4467	(or from signal contexts...).
3288		4468
3289	=item * some watcher types are only supported in the default loop - use	4469	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	4470	work in the default loop by registering the signal watcher with the
		4471	default loop and triggering an C<ev_async> watcher from the default loop
		4472	watcher callback into the event loop interested in the signal.
3291		4473
3292	=back	4474	=back
3293		4475
		4476	=head4 THREAD LOCKING EXAMPLE
		4477
		4478	Here is a fictitious example of how to run an event loop in a different
		4479	thread than where callbacks are being invoked and watchers are
		4480	created/added/removed.
		4481
		4482	For a real-world example, see the C<EV::Loop::Async> perl module,
		4483	which uses exactly this technique (which is suited for many high-level
		4484	languages).
		4485
		4486	The example uses a pthread mutex to protect the loop data, a condition
		4487	variable to wait for callback invocations, an async watcher to notify the
		4488	event loop thread and an unspecified mechanism to wake up the main thread.
		4489
		4490	First, you need to associate some data with the event loop:
		4491
		4492	typedef struct {
		4493	mutex_t lock; /* global loop lock */
		4494	ev_async async_w;
		4495	thread_t tid;
		4496	cond_t invoke_cv;
		4497	} userdata;
		4498
		4499	void prepare_loop (EV_P)
		4500	{
		4501	// for simplicity, we use a static userdata struct.
		4502	static userdata u;
		4503
		4504	ev_async_init (&u->async_w, async_cb);
		4505	ev_async_start (EV_A_ &u->async_w);
		4506
		4507	pthread_mutex_init (&u->lock, 0);
		4508	pthread_cond_init (&u->invoke_cv, 0);
		4509
		4510	// now associate this with the loop
		4511	ev_set_userdata (EV_A_ u);
		4512	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4513	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4514
		4515	// then create the thread running ev_loop
		4516	pthread_create (&u->tid, 0, l_run, EV_A);
		4517	}
		4518
		4519	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4520	solely to wake up the event loop so it takes notice of any new watchers
		4521	that might have been added:
		4522
		4523	static void
		4524	async_cb (EV_P_ ev_async *w, int revents)
		4525	{
		4526	// just used for the side effects
		4527	}
		4528
		4529	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4530	protecting the loop data, respectively.
		4531
		4532	static void
		4533	l_release (EV_P)
		4534	{
		4535	userdata *u = ev_userdata (EV_A);
		4536	pthread_mutex_unlock (&u->lock);
		4537	}
		4538
		4539	static void
		4540	l_acquire (EV_P)
		4541	{
		4542	userdata *u = ev_userdata (EV_A);
		4543	pthread_mutex_lock (&u->lock);
		4544	}
		4545
		4546	The event loop thread first acquires the mutex, and then jumps straight
		4547	into C<ev_run>:
		4548
		4549	void *
		4550	l_run (void *thr_arg)
		4551	{
		4552	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4553
		4554	l_acquire (EV_A);
		4555	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4556	ev_run (EV_A_ 0);
		4557	l_release (EV_A);
		4558
		4559	return 0;
		4560	}
		4561
		4562	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4563	signal the main thread via some unspecified mechanism (signals? pipe
		4564	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4565	have been called (in a while loop because a) spurious wakeups are possible
		4566	and b) skipping inter-thread-communication when there are no pending
		4567	watchers is very beneficial):
		4568
		4569	static void
		4570	l_invoke (EV_P)
		4571	{
		4572	userdata *u = ev_userdata (EV_A);
		4573
		4574	while (ev_pending_count (EV_A))
		4575	{
		4576	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4577	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4578	}
		4579	}
		4580
		4581	Now, whenever the main thread gets told to invoke pending watchers, it
		4582	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4583	thread to continue:
		4584
		4585	static void
		4586	real_invoke_pending (EV_P)
		4587	{
		4588	userdata *u = ev_userdata (EV_A);
		4589
		4590	pthread_mutex_lock (&u->lock);
		4591	ev_invoke_pending (EV_A);
		4592	pthread_cond_signal (&u->invoke_cv);
		4593	pthread_mutex_unlock (&u->lock);
		4594	}
		4595
		4596	Whenever you want to start/stop a watcher or do other modifications to an
		4597	event loop, you will now have to lock:
		4598
		4599	ev_timer timeout_watcher;
		4600	userdata *u = ev_userdata (EV_A);
		4601
		4602	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4603
		4604	pthread_mutex_lock (&u->lock);
		4605	ev_timer_start (EV_A_ &timeout_watcher);
		4606	ev_async_send (EV_A_ &u->async_w);
		4607	pthread_mutex_unlock (&u->lock);
		4608
		4609	Note that sending the C<ev_async> watcher is required because otherwise
		4610	an event loop currently blocking in the kernel will have no knowledge
		4611	about the newly added timer. By waking up the loop it will pick up any new
		4612	watchers in the next event loop iteration.
		4613
3294	=head2 COROUTINES	4614	=head3 COROUTINES
3295		4615
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	4616	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	4617	libev fully supports nesting calls to its functions from different
3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4618	coroutines (e.g. you can call C<ev_run> on the same loop from two
3299	different coroutines and switch freely between both coroutines running the	4619	different coroutines, and switch freely between both coroutines running
3300	loop, as long as you don't confuse yourself). The only exception is that	4620	the loop, as long as you don't confuse yourself). The only exception is
3301	you must not do this from C<ev_periodic> reschedule callbacks.	4621	that you must not do this from C<ev_periodic> reschedule callbacks.
3302		4622
3303	Care has been invested into making sure that libev does not keep local	4623	Care has been taken to ensure that libev does not keep local state inside
3304	state inside C<ev_loop>, and other calls do not usually allow coroutine	4624	C<ev_run>, and other calls do not usually allow for coroutine switches as
3305	switches.	4625	they do not call any callbacks.
3306		4626
		4627	=head2 COMPILER WARNINGS
3307		4628
3308	=head1 COMPLEXITIES	4629	Depending on your compiler and compiler settings, you might get no or a
		4630	lot of warnings when compiling libev code. Some people are apparently
		4631	scared by this.
3309		4632
3310	In this section the complexities of (many of) the algorithms used inside	4633	However, these are unavoidable for many reasons. For one, each compiler
3311	libev will be explained. For complexity discussions about backends see the	4634	has different warnings, and each user has different tastes regarding
3312	documentation for C<ev_default_init>.	4635	warning options. "Warn-free" code therefore cannot be a goal except when
		4636	targeting a specific compiler and compiler-version.
3313		4637
3314	All of the following are about amortised time: If an array needs to be	4638	Another reason is that some compiler warnings require elaborate
3315	extended, libev needs to realloc and move the whole array, but this	4639	workarounds, or other changes to the code that make it less clear and less
3316	happens asymptotically never with higher number of elements, so O(1) might	4640	maintainable.
3317	mean it might do a lengthy realloc operation in rare cases, but on average
3318	it is much faster and asymptotically approaches constant time.
3319		4641
3320	=over 4	4642	And of course, some compiler warnings are just plain stupid, or simply
		4643	wrong (because they don't actually warn about the condition their message
		4644	seems to warn about). For example, certain older gcc versions had some
		4645	warnings that resulted in an extreme number of false positives. These have
		4646	been fixed, but some people still insist on making code warn-free with
		4647	such buggy versions.
3321		4648
3322	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4649	While libev is written to generate as few warnings as possible,
		4650	"warn-free" code is not a goal, and it is recommended not to build libev
		4651	with any compiler warnings enabled unless you are prepared to cope with
		4652	them (e.g. by ignoring them). Remember that warnings are just that:
		4653	warnings, not errors, or proof of bugs.
3323		4654
3324	This means that, when you have a watcher that triggers in one hour and
3325	there are 100 watchers that would trigger before that then inserting will
3326	have to skip roughly seven (C<ld 100>) of these watchers.
3327		4655
3328	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4656	=head2 VALGRIND
3329		4657
3330	That means that changing a timer costs less than removing/adding them	4658	Valgrind has a special section here because it is a popular tool that is
3331	as only the relative motion in the event queue has to be paid for.	4659	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3332		4660
3333	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4661	If you think you found a bug (memory leak, uninitialised data access etc.)
		4662	in libev, then check twice: If valgrind reports something like:
3334		4663
3335	These just add the watcher into an array or at the head of a list.	4664	==2274== definitely lost: 0 bytes in 0 blocks.
		4665	==2274== possibly lost: 0 bytes in 0 blocks.
		4666	==2274== still reachable: 256 bytes in 1 blocks.
3336		4667
3337	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4668	Then there is no memory leak, just as memory accounted to global variables
		4669	is not a memleak - the memory is still being referenced, and didn't leak.
3338		4670
3339	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4671	Similarly, under some circumstances, valgrind might report kernel bugs
		4672	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4673	although an acceptable workaround has been found here), or it might be
		4674	confused.
3340		4675
3341	These watchers are stored in lists then need to be walked to find the	4676	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3342	correct watcher to remove. The lists are usually short (you don't usually	4677	make it into some kind of religion.
3343	have many watchers waiting for the same fd or signal).
3344		4678
3345	=item Finding the next timer in each loop iteration: O(1)	4679	If you are unsure about something, feel free to contact the mailing list
		4680	with the full valgrind report and an explanation on why you think this
		4681	is a bug in libev (best check the archives, too :). However, don't be
		4682	annoyed when you get a brisk "this is no bug" answer and take the chance
		4683	of learning how to interpret valgrind properly.
3346		4684
3347	By virtue of using a binary or 4-heap, the next timer is always found at a	4685	If you need, for some reason, empty reports from valgrind for your project
3348	fixed position in the storage array.	4686	I suggest using suppression lists.
3349		4687
3350	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3351		4688
3352	A change means an I/O watcher gets started or stopped, which requires	4689	=head1 PORTABILITY NOTES
3353	libev to recalculate its status (and possibly tell the kernel, depending
3354	on backend and whether C<ev_io_set> was used).
3355		4690
3356	=item Activating one watcher (putting it into the pending state): O(1)	4691	=head2 GNU/LINUX 32 BIT LIMITATIONS
3357		4692
3358	=item Priority handling: O(number_of_priorities)	4693	GNU/Linux is the only common platform that supports 64 bit file/large file
		4694	interfaces but I<disables> them by default.
3359		4695
3360	Priorities are implemented by allocating some space for each	4696	That means that libev compiled in the default environment doesn't support
3361	priority. When doing priority-based operations, libev usually has to	4697	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3362	linearly search all the priorities, but starting/stopping and activating
3363	watchers becomes O(1) w.r.t. priority handling.
3364		4698
3365	=item Sending an ev_async: O(1)	4699	Unfortunately, many programs try to work around this GNU/Linux issue
		4700	by enabling the large file API, which makes them incompatible with the
		4701	standard libev compiled for their system.
3366		4702
3367	=item Processing ev_async_send: O(number_of_async_watchers)	4703	Likewise, libev cannot enable the large file API itself as this would
		4704	suddenly make it incompatible to the default compile time environment,
		4705	i.e. all programs not using special compile switches.
3368		4706
3369	=item Processing signals: O(max_signal_number)	4707	=head2 OS/X AND DARWIN BUGS
3370		4708
3371	Sending involves a system call I<iff> there were no other C<ev_async_send>	4709	The whole thing is a bug if you ask me - basically any system interface
3372	calls in the current loop iteration. Checking for async and signal events	4710	you touch is broken, whether it is locales, poll, kqueue or even the
3373	involves iterating over all running async watchers or all signal numbers.	4711	OpenGL drivers.
3374		4712
3375	=back	4713	=head3 C<kqueue> is buggy
3376		4714
		4715	The kqueue syscall is broken in all known versions - most versions support
		4716	only sockets, many support pipes.
3377		4717
		4718	Libev tries to work around this by not using C<kqueue> by default on this
		4719	rotten platform, but of course you can still ask for it when creating a
		4720	loop - embedding a socket-only kqueue loop into a select-based one is
		4721	probably going to work well.
		4722
		4723	=head3 C<poll> is buggy
		4724
		4725	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4726	implementation by something calling C<kqueue> internally around the 10.5.6
		4727	release, so now C<kqueue> I<and> C<poll> are broken.
		4728
		4729	Libev tries to work around this by not using C<poll> by default on
		4730	this rotten platform, but of course you can still ask for it when creating
		4731	a loop.
		4732
		4733	=head3 C<select> is buggy
		4734
		4735	All that's left is C<select>, and of course Apple found a way to fuck this
		4736	one up as well: On OS/X, C<select> actively limits the number of file
		4737	descriptors you can pass in to 1024 - your program suddenly crashes when
		4738	you use more.
		4739
		4740	There is an undocumented "workaround" for this - defining
		4741	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4742	work on OS/X.
		4743
		4744	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4745
		4746	=head3 C<errno> reentrancy
		4747
		4748	The default compile environment on Solaris is unfortunately so
		4749	thread-unsafe that you can't even use components/libraries compiled
		4750	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4751	defined by default. A valid, if stupid, implementation choice.
		4752
		4753	If you want to use libev in threaded environments you have to make sure
		4754	it's compiled with C<_REENTRANT> defined.
		4755
		4756	=head3 Event port backend
		4757
		4758	The scalable event interface for Solaris is called "event
		4759	ports". Unfortunately, this mechanism is very buggy in all major
		4760	releases. If you run into high CPU usage, your program freezes or you get
		4761	a large number of spurious wakeups, make sure you have all the relevant
		4762	and latest kernel patches applied. No, I don't know which ones, but there
		4763	are multiple ones to apply, and afterwards, event ports actually work
		4764	great.
		4765
		4766	If you can't get it to work, you can try running the program by setting
		4767	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4768	C<select> backends.
		4769
		4770	=head2 AIX POLL BUG
		4771
		4772	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4773	this by trying to avoid the poll backend altogether (i.e. it's not even
		4774	compiled in), which normally isn't a big problem as C<select> works fine
		4775	with large bitsets on AIX, and AIX is dead anyway.
		4776
3378	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4777	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4778
		4779	=head3 General issues
3379		4780
3380	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4781	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3381	requires, and its I/O model is fundamentally incompatible with the POSIX	4782	requires, and its I/O model is fundamentally incompatible with the POSIX
3382	model. Libev still offers limited functionality on this platform in	4783	model. Libev still offers limited functionality on this platform in
3383	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4784	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3384	descriptors. This only applies when using Win32 natively, not when using	4785	descriptors. This only applies when using Win32 natively, not when using
3385	e.g. cygwin.	4786	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4787	as every compielr comes with a slightly differently broken/incompatible
		4788	environment.
3386		4789
3387	Lifting these limitations would basically require the full	4790	Lifting these limitations would basically require the full
3388	re-implementation of the I/O system. If you are into these kinds of	4791	re-implementation of the I/O system. If you are into this kind of thing,
3389	things, then note that glib does exactly that for you in a very portable	4792	then note that glib does exactly that for you in a very portable way (note
3390	way (note also that glib is the slowest event library known to man).	4793	also that glib is the slowest event library known to man).
3391		4794
3392	There is no supported compilation method available on windows except	4795	There is no supported compilation method available on windows except
3393	embedding it into other applications.	4796	embedding it into other applications.
		4797
		4798	Sensible signal handling is officially unsupported by Microsoft - libev
		4799	tries its best, but under most conditions, signals will simply not work.
3394		4800
3395	Not a libev limitation but worth mentioning: windows apparently doesn't	4801	Not a libev limitation but worth mentioning: windows apparently doesn't
3396	accept large writes: instead of resulting in a partial write, windows will	4802	accept large writes: instead of resulting in a partial write, windows will
3397	either accept everything or return C<ENOBUFS> if the buffer is too large,	4803	either accept everything or return C<ENOBUFS> if the buffer is too large,
3398	so make sure you only write small amounts into your sockets (less than a	4804	so make sure you only write small amounts into your sockets (less than a
3399	megabyte seems safe, but thsi apparently depends on the amount of memory	4805	megabyte seems safe, but this apparently depends on the amount of memory
3400	available).	4806	available).
3401		4807
3402	Due to the many, low, and arbitrary limits on the win32 platform and	4808	Due to the many, low, and arbitrary limits on the win32 platform and
3403	the abysmal performance of winsockets, using a large number of sockets	4809	the abysmal performance of winsockets, using a large number of sockets
3404	is not recommended (and not reasonable). If your program needs to use	4810	is not recommended (and not reasonable). If your program needs to use
3405	more than a hundred or so sockets, then likely it needs to use a totally	4811	more than a hundred or so sockets, then likely it needs to use a totally
3406	different implementation for windows, as libev offers the POSIX readiness	4812	different implementation for windows, as libev offers the POSIX readiness
3407	notification model, which cannot be implemented efficiently on windows	4813	notification model, which cannot be implemented efficiently on windows
3408	(Microsoft monopoly games).	4814	(due to Microsoft monopoly games).
3409		4815
3410	A typical way to use libev under windows is to embed it (see the embedding	4816	A typical way to use libev under windows is to embed it (see the embedding
3411	section for details) and use the following F<evwrap.h> header file instead	4817	section for details) and use the following F<evwrap.h> header file instead
3412	of F<ev.h>:	4818	of F<ev.h>:
3413		4819
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4821	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3416		4822
3417	#include "ev.h"	4823	#include "ev.h"
3418		4824
3419	And compile the following F<evwrap.c> file into your project (make sure	4825	And compile the following F<evwrap.c> file into your project (make sure
3420	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4826	you do I<not> compile the F<ev.c> or any other embedded source files!):
3421		4827
3422	#include "evwrap.h"	4828	#include "evwrap.h"
3423	#include "ev.c"	4829	#include "ev.c"
3424		4830
3425	=over 4
3426
3427	=item The winsocket select function	4831	=head3 The winsocket C<select> function
3428		4832
3429	The winsocket C<select> function doesn't follow POSIX in that it	4833	The winsocket C<select> function doesn't follow POSIX in that it
3430	requires socket I<handles> and not socket I<file descriptors> (it is	4834	requires socket I<handles> and not socket I<file descriptors> (it is
3431	also extremely buggy). This makes select very inefficient, and also	4835	also extremely buggy). This makes select very inefficient, and also
3432	requires a mapping from file descriptors to socket handles (the Microsoft	4836	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3441	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4845	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3442		4846
3443	Note that winsockets handling of fd sets is O(n), so you can easily get a	4847	Note that winsockets handling of fd sets is O(n), so you can easily get a
3444	complexity in the O(n²) range when using win32.	4848	complexity in the O(n²) range when using win32.
3445		4849
3446	=item Limited number of file descriptors	4850	=head3 Limited number of file descriptors
3447		4851
3448	Windows has numerous arbitrary (and low) limits on things.	4852	Windows has numerous arbitrary (and low) limits on things.
3449		4853
3450	Early versions of winsocket's select only supported waiting for a maximum	4854	Early versions of winsocket's select only supported waiting for a maximum
3451	of C<64> handles (probably owning to the fact that all windows kernels	4855	of C<64> handles (probably owning to the fact that all windows kernels
3452	can only wait for C<64> things at the same time internally; Microsoft	4856	can only wait for C<64> things at the same time internally; Microsoft
3453	recommends spawning a chain of threads and wait for 63 handles and the	4857	recommends spawning a chain of threads and wait for 63 handles and the
3454	previous thread in each. Great).	4858	previous thread in each. Sounds great!).
3455		4859
3456	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4860	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3457	to some high number (e.g. C<2048>) before compiling the winsocket select	4861	to some high number (e.g. C<2048>) before compiling the winsocket select
3458	call (which might be in libev or elsewhere, for example, perl does its own	4862	call (which might be in libev or elsewhere, for example, perl and many
3459	select emulation on windows).	4863	other interpreters do their own select emulation on windows).
3460		4864
3461	Another limit is the number of file descriptors in the Microsoft runtime	4865	Another limit is the number of file descriptors in the Microsoft runtime
3462	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4866	libraries, which by default is C<64> (there must be a hidden I<64>
3463	or something like this inside Microsoft). You can increase this by calling	4867	fetish or something like this inside Microsoft). You can increase this
3464	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4868	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3465	arbitrary limit), but is broken in many versions of the Microsoft runtime	4869	(another arbitrary limit), but is broken in many versions of the Microsoft
3466	libraries.
3467
3468	This might get you to about C<512> or C<2048> sockets (depending on	4870	runtime libraries. This might get you to about C<512> or C<2048> sockets
3469	windows version and/or the phase of the moon). To get more, you need to	4871	(depending on windows version and/or the phase of the moon). To get more,
3470	wrap all I/O functions and provide your own fd management, but the cost of	4872	you need to wrap all I/O functions and provide your own fd management, but
3471	calling select (O(n²)) will likely make this unworkable.	4873	the cost of calling select (O(n²)) will likely make this unworkable.
3472		4874
3473	=back
3474
3475
3476	=head1 PORTABILITY REQUIREMENTS	4875	=head2 PORTABILITY REQUIREMENTS
3477		4876
3478	In addition to a working ISO-C implementation, libev relies on a few	4877	In addition to a working ISO-C implementation and of course the
3479	additional extensions:	4878	backend-specific APIs, libev relies on a few additional extensions:
3480		4879
3481	=over 4	4880	=over 4
3482		4881
3483	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4882	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3484	calling conventions regardless of C<ev_watcher_type *>.	4883	calling conventions regardless of C<ev_watcher_type *>.
…		…
3487	structure (guaranteed by POSIX but not by ISO C for example), but it also	4886	structure (guaranteed by POSIX but not by ISO C for example), but it also
3488	assumes that the same (machine) code can be used to call any watcher	4887	assumes that the same (machine) code can be used to call any watcher
3489	callback: The watcher callbacks have different type signatures, but libev	4888	callback: The watcher callbacks have different type signatures, but libev
3490	calls them using an C<ev_watcher *> internally.	4889	calls them using an C<ev_watcher *> internally.
3491		4890
		4891	=item pointer accesses must be thread-atomic
		4892
		4893	Accessing a pointer value must be atomic, it must both be readable and
		4894	writable in one piece - this is the case on all current architectures.
		4895
3492	=item C<sig_atomic_t volatile> must be thread-atomic as well	4896	=item C<sig_atomic_t volatile> must be thread-atomic as well
3493		4897
3494	The type C<sig_atomic_t volatile> (or whatever is defined as	4898	The type C<sig_atomic_t volatile> (or whatever is defined as
3495	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4899	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3496	threads. This is not part of the specification for C<sig_atomic_t>, but is	4900	threads. This is not part of the specification for C<sig_atomic_t>, but is
3497	believed to be sufficiently portable.	4901	believed to be sufficiently portable.
3498		4902
3499	=item C<sigprocmask> must work in a threaded environment	4903	=item C<sigprocmask> must work in a threaded environment
3500		4904
…		…
3509	except the initial one, and run the default loop in the initial thread as	4913	except the initial one, and run the default loop in the initial thread as
3510	well.	4914	well.
3511		4915
3512	=item C<long> must be large enough for common memory allocation sizes	4916	=item C<long> must be large enough for common memory allocation sizes
3513		4917
3514	To improve portability and simplify using libev, libev uses C<long>	4918	To improve portability and simplify its API, libev uses C<long> internally
3515	internally instead of C<size_t> when allocating its data structures. On	4919	instead of C<size_t> when allocating its data structures. On non-POSIX
3516	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4920	systems (Microsoft...) this might be unexpectedly low, but is still at
3517	is still at least 31 bits everywhere, which is enough for hundreds of	4921	least 31 bits everywhere, which is enough for hundreds of millions of
3518	millions of watchers.	4922	watchers.
3519		4923
3520	=item C<double> must hold a time value in seconds with enough accuracy	4924	=item C<double> must hold a time value in seconds with enough accuracy
3521		4925
3522	The type C<double> is used to represent timestamps. It is required to	4926	The type C<double> is used to represent timestamps. It is required to
3523	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4927	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3524	enough for at least into the year 4000. This requirement is fulfilled by	4928	good enough for at least into the year 4000 with millisecond accuracy
		4929	(the design goal for libev). This requirement is overfulfilled by
3525	implementations implementing IEEE 754 (basically all existing ones).	4930	implementations using IEEE 754, which is basically all existing ones. With
		4931	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3526		4932
3527	=back	4933	=back
3528		4934
3529	If you know of other additional requirements drop me a note.	4935	If you know of other additional requirements drop me a note.
3530		4936
3531		4937
3532	=head1 COMPILER WARNINGS	4938	=head1 ALGORITHMIC COMPLEXITIES
3533		4939
3534	Depending on your compiler and compiler settings, you might get no or a	4940	In this section the complexities of (many of) the algorithms used inside
3535	lot of warnings when compiling libev code. Some people are apparently	4941	libev will be documented. For complexity discussions about backends see
3536	scared by this.	4942	the documentation for C<ev_default_init>.
3537		4943
3538	However, these are unavoidable for many reasons. For one, each compiler	4944	All of the following are about amortised time: If an array needs to be
3539	has different warnings, and each user has different tastes regarding	4945	extended, libev needs to realloc and move the whole array, but this
3540	warning options. "Warn-free" code therefore cannot be a goal except when	4946	happens asymptotically rarer with higher number of elements, so O(1) might
3541	targeting a specific compiler and compiler-version.	4947	mean that libev does a lengthy realloc operation in rare cases, but on
		4948	average it is much faster and asymptotically approaches constant time.
3542		4949
3543	Another reason is that some compiler warnings require elaborate	4950	=over 4
3544	workarounds, or other changes to the code that make it less clear and less
3545	maintainable.
3546		4951
3547	And of course, some compiler warnings are just plain stupid, or simply	4952	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3548	wrong (because they don't actually warn about the condition their message
3549	seems to warn about).
3550		4953
3551	While libev is written to generate as few warnings as possible,	4954	This means that, when you have a watcher that triggers in one hour and
3552	"warn-free" code is not a goal, and it is recommended not to build libev	4955	there are 100 watchers that would trigger before that, then inserting will
3553	with any compiler warnings enabled unless you are prepared to cope with	4956	have to skip roughly seven (C<ld 100>) of these watchers.
3554	them (e.g. by ignoring them). Remember that warnings are just that:
3555	warnings, not errors, or proof of bugs.
3556		4957
		4958	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3557		4959
3558	=head1 VALGRIND	4960	That means that changing a timer costs less than removing/adding them,
		4961	as only the relative motion in the event queue has to be paid for.
3559		4962
3560	Valgrind has a special section here because it is a popular tool that is	4963	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3561	highly useful, but valgrind reports are very hard to interpret.
3562		4964
3563	If you think you found a bug (memory leak, uninitialised data access etc.)	4965	These just add the watcher into an array or at the head of a list.
3564	in libev, then check twice: If valgrind reports something like:
3565		4966
3566	==2274== definitely lost: 0 bytes in 0 blocks.	4967	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3567	==2274== possibly lost: 0 bytes in 0 blocks.
3568	==2274== still reachable: 256 bytes in 1 blocks.
3569		4968
3570	Then there is no memory leak. Similarly, under some circumstances,	4969	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3571	valgrind might report kernel bugs as if it were a bug in libev, or it
3572	might be confused (it is a very good tool, but only a tool).
3573		4970
3574	If you are unsure about something, feel free to contact the mailing list	4971	These watchers are stored in lists, so they need to be walked to find the
3575	with the full valgrind report and an explanation on why you think this is	4972	correct watcher to remove. The lists are usually short (you don't usually
3576	a bug in libev. However, don't be annoyed when you get a brisk "this is	4973	have many watchers waiting for the same fd or signal: one is typical, two
3577	no bug" answer and take the chance of learning how to interpret valgrind	4974	is rare).
3578	properly.
3579		4975
3580	If you need, for some reason, empty reports from valgrind for your project	4976	=item Finding the next timer in each loop iteration: O(1)
3581	I suggest using suppression lists.
3582		4977
		4978	By virtue of using a binary or 4-heap, the next timer is always found at a
		4979	fixed position in the storage array.
		4980
		4981	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4982
		4983	A change means an I/O watcher gets started or stopped, which requires
		4984	libev to recalculate its status (and possibly tell the kernel, depending
		4985	on backend and whether C<ev_io_set> was used).
		4986
		4987	=item Activating one watcher (putting it into the pending state): O(1)
		4988
		4989	=item Priority handling: O(number_of_priorities)
		4990
		4991	Priorities are implemented by allocating some space for each
		4992	priority. When doing priority-based operations, libev usually has to
		4993	linearly search all the priorities, but starting/stopping and activating
		4994	watchers becomes O(1) with respect to priority handling.
		4995
		4996	=item Sending an ev_async: O(1)
		4997
		4998	=item Processing ev_async_send: O(number_of_async_watchers)
		4999
		5000	=item Processing signals: O(max_signal_number)
		5001
		5002	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5003	calls in the current loop iteration. Checking for async and signal events
		5004	involves iterating over all running async watchers or all signal numbers.
		5005
		5006	=back
		5007
		5008
		5009	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5010
		5011	The major version 4 introduced some incompatible changes to the API.
		5012
		5013	At the moment, the C<ev.h> header file provides compatibility definitions
		5014	for all changes, so most programs should still compile. The compatibility
		5015	layer might be removed in later versions of libev, so better update to the
		5016	new API early than late.
		5017
		5018	=over 4
		5019
		5020	=item C<EV_COMPAT3> backwards compatibility mechanism
		5021
		5022	The backward compatibility mechanism can be controlled by
		5023	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5024	section.
		5025
		5026	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5027
		5028	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5029
		5030	ev_loop_destroy (EV_DEFAULT_UC);
		5031	ev_loop_fork (EV_DEFAULT);
		5032
		5033	=item function/symbol renames
		5034
		5035	A number of functions and symbols have been renamed:
		5036
		5037	ev_loop => ev_run
		5038	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5039	EVLOOP_ONESHOT => EVRUN_ONCE
		5040
		5041	ev_unloop => ev_break
		5042	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5043	EVUNLOOP_ONE => EVBREAK_ONE
		5044	EVUNLOOP_ALL => EVBREAK_ALL
		5045
		5046	EV_TIMEOUT => EV_TIMER
		5047
		5048	ev_loop_count => ev_iteration
		5049	ev_loop_depth => ev_depth
		5050	ev_loop_verify => ev_verify
		5051
		5052	Most functions working on C<struct ev_loop> objects don't have an
		5053	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5054	associated constants have been renamed to not collide with the C<struct
		5055	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5056	as all other watcher types. Note that C<ev_loop_fork> is still called
		5057	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5058	typedef.
		5059
		5060	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5061
		5062	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5063	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5064	and work, but the library code will of course be larger.
		5065
		5066	=back
		5067
		5068
		5069	=head1 GLOSSARY
		5070
		5071	=over 4
		5072
		5073	=item active
		5074
		5075	A watcher is active as long as it has been started and not yet stopped.
		5076	See L<WATCHER STATES> for details.
		5077
		5078	=item application
		5079
		5080	In this document, an application is whatever is using libev.
		5081
		5082	=item backend
		5083
		5084	The part of the code dealing with the operating system interfaces.
		5085
		5086	=item callback
		5087
		5088	The address of a function that is called when some event has been
		5089	detected. Callbacks are being passed the event loop, the watcher that
		5090	received the event, and the actual event bitset.
		5091
		5092	=item callback/watcher invocation
		5093
		5094	The act of calling the callback associated with a watcher.
		5095
		5096	=item event
		5097
		5098	A change of state of some external event, such as data now being available
		5099	for reading on a file descriptor, time having passed or simply not having
		5100	any other events happening anymore.
		5101
		5102	In libev, events are represented as single bits (such as C<EV_READ> or
		5103	C<EV_TIMER>).
		5104
		5105	=item event library
		5106
		5107	A software package implementing an event model and loop.
		5108
		5109	=item event loop
		5110
		5111	An entity that handles and processes external events and converts them
		5112	into callback invocations.
		5113
		5114	=item event model
		5115
		5116	The model used to describe how an event loop handles and processes
		5117	watchers and events.
		5118
		5119	=item pending
		5120
		5121	A watcher is pending as soon as the corresponding event has been
		5122	detected. See L<WATCHER STATES> for details.
		5123
		5124	=item real time
		5125
		5126	The physical time that is observed. It is apparently strictly monotonic :)
		5127
		5128	=item wall-clock time
		5129
		5130	The time and date as shown on clocks. Unlike real time, it can actually
		5131	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5132	clock.
		5133
		5134	=item watcher
		5135
		5136	A data structure that describes interest in certain events. Watchers need
		5137	to be started (attached to an event loop) before they can receive events.
		5138
		5139	=back
3583		5140
3584	=head1 AUTHOR	5141	=head1 AUTHOR
3585		5142
3586	Marc Lehmann <libev@schmorp.de>.	5143	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5144	Magnusson and Emanuele Giaquinta.
3587		5145

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