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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>, with the event polling
		598	function sometimes returning events to the caller even though an error
		599	occured, but with no indication whether it has done so or not (yes, it's
		600	even documented that way) - deadly for edge-triggered interfaces, but
		601	fortunately libev seems to be able to work around it.
468		602
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	603	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	604	C<EVBACKEND_POLL>.
471		605
472	=item C<EVBACKEND_ALL>	606	=item C<EVBACKEND_ALL>
473		607
474	Try all backends (even potentially broken ones that wouldn't be tried	608	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	609	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
476	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	610	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
477		611
478	It is definitely not recommended to use this flag.	612	It is definitely not recommended to use this flag, use whatever
		613	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		614	at all.
		615
		616	=item C<EVBACKEND_MASK>
		617
		618	Not a backend at all, but a mask to select all backend bits from a
		619	C<flags> value, in case you want to mask out any backends from a flags
		620	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
479		621
480	=back	622	=back
481		623
482	If one or more of these are or'ed into the flags value, then only these	624	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	625	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.	626	here). If none are specified, all backends in C<ev_recommended_backends
485		627	()> 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		628
513	Example: Try to create a event loop that uses epoll and nothing else.	629	Example: Try to create a event loop that uses epoll and nothing else.
514		630
515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	631	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
516	if (!epoller)	632	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	633	fatal ("no epoll found here, maybe it hides under your chair");
518		634
		635	Example: Use whatever libev has to offer, but make sure that kqueue is
		636	used if available.
		637
		638	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		639
519	=item ev_default_destroy ()	640	=item ev_loop_destroy (loop)
520		641
521	Destroys the default loop again (frees all memory and kernel state	642	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	643	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	644	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>	645	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	646	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	647	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	648	for example).
528		649
529	Note that certain global state, such as signal state, will not be freed by	650	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	651	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	652	as signal and child watchers) would need to be stopped manually.
532		653
533	In general it is not advisable to call this function except in the	654	This function is normally used on loop objects allocated by
534	rare occasion where you really need to free e.g. the signal handling	655	C<ev_loop_new>, but it can also be used on the default loop returned by
		656	C<ev_default_loop>, in which case it is not thread-safe.
		657
		658	Note that it is not advisable to call this function on the default loop
		659	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	660	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>).	661	and C<ev_loop_destroy>.
537		662
538	=item ev_loop_destroy (loop)	663	=item ev_loop_fork (loop)
539		664
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	665	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	666	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	667	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	668	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	669	child before resuming or calling C<ev_run>.
550	functions, and it will only take effect at the next C<ev_loop> iteration.	670
		671	Again, you I<have> to call it on I<any> loop that you want to re-use after
		672	a fork, I<even if you do not plan to use the loop in the parent>. This is
		673	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		674	during fork.
551		675
552	On the other hand, you only need to call this function in the child	676	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	677	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.	678	you just fork+exec or create a new loop in the child, you don't have to
		679	call it at all (in fact, C<epoll> is so badly broken that it makes a
		680	difference, but libev will usually detect this case on its own and do a
		681	costly reset of the backend).
555		682
556	The function itself is quite fast and it's usually not a problem to call	683	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	684	it just in case after a fork.
558	quite nicely into a call to C<pthread_atfork>:
559		685
		686	Example: Automate calling C<ev_loop_fork> on the default loop when
		687	using pthreads.
		688
		689	static void
		690	post_fork_child (void)
		691	{
		692	ev_loop_fork (EV_DEFAULT);
		693	}
		694
		695	...
560	pthread_atfork (0, 0, ev_default_fork);	696	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		697
568	=item int ev_is_default_loop (loop)	698	=item int ev_is_default_loop (loop)
569		699
570	Returns true when the given loop actually is the default loop, false otherwise.	700	Returns true when the given loop is, in fact, the default loop, and false
		701	otherwise.
571		702
572	=item unsigned int ev_loop_count (loop)	703	=item unsigned int ev_iteration (loop)
573		704
574	Returns the count of loop iterations for the loop, which is identical to	705	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	706	to the number of times libev did poll for new events. It starts at C<0>
576	happily wraps around with enough iterations.	707	and happily wraps around with enough iterations.
577		708
578	This value can sometimes be useful as a generation counter of sorts (it	709	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	710	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	711	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		712	prepare and check phases.
		713
		714	=item unsigned int ev_depth (loop)
		715
		716	Returns the number of times C<ev_run> was entered minus the number of
		717	times C<ev_run> was exited normally, in other words, the recursion depth.
		718
		719	Outside C<ev_run>, this number is zero. In a callback, this number is
		720	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		721	in which case it is higher.
		722
		723	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		724	throwing an exception etc.), doesn't count as "exit" - consider this
		725	as a hint to avoid such ungentleman-like behaviour unless it's really
		726	convenient, in which case it is fully supported.
581		727
582	=item unsigned int ev_backend (loop)	728	=item unsigned int ev_backend (loop)
583		729
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	730	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	731	use.
…		…
594		740
595	=item ev_now_update (loop)	741	=item ev_now_update (loop)
596		742
597	Establishes the current time by querying the kernel, updating the time	743	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	744	returned by C<ev_now ()> in the progress. This is a costly operation and
599	is usually done automatically within C<ev_loop ()>.	745	is usually done automatically within C<ev_run ()>.
600		746
601	This function is rarely useful, but when some event callback runs for a	747	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	748	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	749	the current time is a good idea.
604		750
605	See also "The special problem of time updates" in the C<ev_timer> section.	751	See also L<The special problem of time updates> in the C<ev_timer> section.
606		752
		753	=item ev_suspend (loop)
		754
		755	=item ev_resume (loop)
		756
		757	These two functions suspend and resume an event loop, for use when the
		758	loop is not used for a while and timeouts should not be processed.
		759
		760	A typical use case would be an interactive program such as a game: When
		761	the user presses C<^Z> to suspend the game and resumes it an hour later it
		762	would be best to handle timeouts as if no time had actually passed while
		763	the program was suspended. This can be achieved by calling C<ev_suspend>
		764	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		765	C<ev_resume> directly afterwards to resume timer processing.
		766
		767	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		768	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		769	will be rescheduled (that is, they will lose any events that would have
		770	occurred while suspended).
		771
		772	After calling C<ev_suspend> you B<must not> call I<any> function on the
		773	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		774	without a previous call to C<ev_suspend>.
		775
		776	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		777	event loop time (see C<ev_now_update>).
		778
607	=item ev_loop (loop, int flags)	779	=item ev_run (loop, int flags)
608		780
609	Finally, this is it, the event handler. This function usually is called	781	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	782	after you have initialised all your watchers and you want to start
611	events.	783	handling events. It will ask the operating system for any new events, call
		784	the watcher callbacks, an then repeat the whole process indefinitely: This
		785	is why event loops are called I<loops>.
612		786
613	If the flags argument is specified as C<0>, it will not return until	787	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.	788	until either no event watchers are active anymore or C<ev_break> was
		789	called.
615		790
616	Please note that an explicit C<ev_unloop> is usually better than	791	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	792	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	793	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	794	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.	795	of relying on its watchers stopping correctly, that is truly a thing of
		796	beauty.
621		797
		798	This function is also I<mostly> exception-safe - you can break out of
		799	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		800	exception and so on. This does not decrement the C<ev_depth> value, nor
		801	will it clear any outstanding C<EVBREAK_ONE> breaks.
		802
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	803	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	804	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.	805	block your process in case there are no events and will return after one
		806	iteration of the loop. This is sometimes useful to poll and handle new
		807	events while doing lengthy calculations, to keep the program responsive.
625		808
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	809	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	810	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	811	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	812	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	813	user-registered callback will be called), and will return after one
		814	iteration of the loop.
		815
		816	This is useful if you are waiting for some external event in conjunction
		817	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	818	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.	819	usually a better approach for this kind of thing.
633		820
634	Here are the gory details of what C<ev_loop> does:	821	Here are the gory details of what C<ev_run> does:
635		822
		823	- Increment loop depth.
		824	- Reset the ev_break status.
636	- Before the first iteration, call any pending watchers.	825	- Before the first iteration, call any pending watchers.
		826	LOOP:
637	* If EVFLAG_FORKCHECK was used, check for a fork.	827	- If EVFLAG_FORKCHECK was used, check for a fork.
638	- If a fork was detected (by any means), queue and call all fork watchers.	828	- If a fork was detected (by any means), queue and call all fork watchers.
639	- Queue and call all prepare watchers.	829	- Queue and call all prepare watchers.
		830	- If ev_break was called, goto FINISH.
640	- If we have been forked, detach and recreate the kernel state	831	- If we have been forked, detach and recreate the kernel state
641	as to not disturb the other process.	832	as to not disturb the other process.
642	- Update the kernel state with all outstanding changes.	833	- Update the kernel state with all outstanding changes.
643	- Update the "event loop time" (ev_now ()).	834	- Update the "event loop time" (ev_now ()).
644	- Calculate for how long to sleep or block, if at all	835	- Calculate for how long to sleep or block, if at all
645	(active idle watchers, EVLOOP_NONBLOCK or not having	836	(active idle watchers, EVRUN_NOWAIT or not having
646	any active watchers at all will result in not sleeping).	837	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	838	- Sleep if the I/O and timer collect interval say so.
		839	- Increment loop iteration counter.
648	- Block the process, waiting for any events.	840	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	841	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	842	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	843	- Queue all expired timers.
652	- Queue all outstanding periodics.	844	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	845	- Queue all idle watchers with priority higher than that of pending events.
654	- Queue all check watchers.	846	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	847	- 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	848	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	849	be handled here by queueing them when their watcher gets executed.
658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	850	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
659	were used, or there are no active watchers, return, otherwise	851	were used, or there are no active watchers, goto FINISH, otherwise
660	continue with step *.	852	continue with step LOOP.
		853	FINISH:
		854	- Reset the ev_break status iff it was EVBREAK_ONE.
		855	- Decrement the loop depth.
		856	- Return.
661		857
662	Example: Queue some jobs and then loop until no events are outstanding	858	Example: Queue some jobs and then loop until no events are outstanding
663	anymore.	859	anymore.
664		860
665	... queue jobs here, make sure they register event watchers as long	861	... 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..)	862	... as they still have work to do (even an idle watcher will do..)
667	ev_loop (my_loop, 0);	863	ev_run (my_loop, 0);
668	... jobs done or somebody called unloop. yeah!	864	... jobs done or somebody called unloop. yeah!
669		865
670	=item ev_unloop (loop, how)	866	=item ev_break (loop, how)
671		867
672	Can be used to make a call to C<ev_loop> return early (but only after it	868	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	869	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	870	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.	871	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
676		872
677	This "unloop state" will be cleared when entering C<ev_loop> again.	873	This "break state" will be cleared on the next call to C<ev_run>.
		874
		875	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		876	which case it will have no effect.
678		877
679	=item ev_ref (loop)	878	=item ev_ref (loop)
680		879
681	=item ev_unref (loop)	880	=item ev_unref (loop)
682		881
683	Ref/unref can be used to add or remove a reference count on the event	882	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	883	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	884	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	885
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	886	This is useful when you have a watcher that you never intend to
		887	unregister, but that nevertheless should not keep C<ev_run> from
		888	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		889	before stopping it.
		890
688	example, libev itself uses this for its internal signal pipe: It is not	891	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	892	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	893	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	894	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>	895	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,	896	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	897	before, respectively. Note also that libev might stop watchers itself
		898	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		899	in the callback).
695		900
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	901	Example: Create a signal watcher, but keep it from keeping C<ev_run>
697	running when nothing else is active.	902	running when nothing else is active.
698		903
699	struct ev_signal exitsig;	904	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	905	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	906	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	907	ev_unref (loop);
703		908
704	Example: For some weird reason, unregister the above signal handler again.	909	Example: For some weird reason, unregister the above signal handler again.
705		910
706	ev_ref (loop);	911	ev_ref (loop);
707	ev_signal_stop (loop, &exitsig);	912	ev_signal_stop (loop, &exitsig);
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	923	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	924	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	925	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	926	opportunities).
722		927
723	The background is that sometimes your program runs just fast enough to	928	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	929	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	930	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	931	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	932	overhead for the actual polling but can deliver many events at once.
728		933
729	By setting a higher I<io collect interval> you allow libev to spend more	934	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,	935	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	936	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	937	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.	938	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		939	sleep time ensures that libev will not poll for I/O events more often then
		940	once per this interval, on average.
734		941
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	942	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	943	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	944	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	945	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	946	value will not introduce any overhead in libev.
740		947
741	Many (busy) programs can usually benefit by setting the I/O collect	948	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	949	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	950	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>,	951	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.	952	as this approaches the timing granularity of most systems. Note that if
		953	you do transactions with the outside world and you can't increase the
		954	parallelity, then this setting will limit your transaction rate (if you
		955	need to poll once per transaction and the I/O collect interval is 0.01,
		956	then you can't do more than 100 transactions per second).
746		957
747	Setting the I<timeout collect interval> can improve the opportunity for	958	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	959	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	960	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	961	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	962	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	963	they fire on, say, one-second boundaries only.
753		964
		965	Example: we only need 0.1s timeout granularity, and we wish not to poll
		966	more often than 100 times per second:
		967
		968	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		969	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		970
		971	=item ev_invoke_pending (loop)
		972
		973	This call will simply invoke all pending watchers while resetting their
		974	pending state. Normally, C<ev_run> does this automatically when required,
		975	but when overriding the invoke callback this call comes handy. This
		976	function can be invoked from a watcher - this can be useful for example
		977	when you want to do some lengthy calculation and want to pass further
		978	event handling to another thread (you still have to make sure only one
		979	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		980
		981	=item int ev_pending_count (loop)
		982
		983	Returns the number of pending watchers - zero indicates that no watchers
		984	are pending.
		985
		986	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		987
		988	This overrides the invoke pending functionality of the loop: Instead of
		989	invoking all pending watchers when there are any, C<ev_run> will call
		990	this callback instead. This is useful, for example, when you want to
		991	invoke the actual watchers inside another context (another thread etc.).
		992
		993	If you want to reset the callback, use C<ev_invoke_pending> as new
		994	callback.
		995
		996	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		997
		998	Sometimes you want to share the same loop between multiple threads. This
		999	can be done relatively simply by putting mutex_lock/unlock calls around
		1000	each call to a libev function.
		1001
		1002	However, C<ev_run> can run an indefinite time, so it is not feasible
		1003	to wait for it to return. One way around this is to wake up the event
		1004	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1005	I<release> and I<acquire> callbacks on the loop.
		1006
		1007	When set, then C<release> will be called just before the thread is
		1008	suspended waiting for new events, and C<acquire> is called just
		1009	afterwards.
		1010
		1011	Ideally, C<release> will just call your mutex_unlock function, and
		1012	C<acquire> will just call the mutex_lock function again.
		1013
		1014	While event loop modifications are allowed between invocations of
		1015	C<release> and C<acquire> (that's their only purpose after all), no
		1016	modifications done will affect the event loop, i.e. adding watchers will
		1017	have no effect on the set of file descriptors being watched, or the time
		1018	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1019	to take note of any changes you made.
		1020
		1021	In theory, threads executing C<ev_run> will be async-cancel safe between
		1022	invocations of C<release> and C<acquire>.
		1023
		1024	See also the locking example in the C<THREADS> section later in this
		1025	document.
		1026
		1027	=item ev_set_userdata (loop, void *data)
		1028
		1029	=item void *ev_userdata (loop)
		1030
		1031	Set and retrieve a single C<void *> associated with a loop. When
		1032	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1033	C<0>.
		1034
		1035	These two functions can be used to associate arbitrary data with a loop,
		1036	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1037	C<acquire> callbacks described above, but of course can be (ab-)used for
		1038	any other purpose as well.
		1039
754	=item ev_loop_verify (loop)	1040	=item ev_verify (loop)
755		1041
756	This function only does something when C<EV_VERIFY> support has been	1042	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	1043	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	1044	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	1045	is found to be inconsistent, it will print an error message to standard
		1046	error and call C<abort ()>.
760		1047
761	This can be used to catch bugs inside libev itself: under normal	1048	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	1049	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	1050	data structures consistent.
764		1051
765	=back	1052	=back
766		1053
767		1054
768	=head1 ANATOMY OF A WATCHER	1055	=head1 ANATOMY OF A WATCHER
769		1056
		1057	In the following description, uppercase C<TYPE> in names stands for the
		1058	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1059	watchers and C<ev_io_start> for I/O watchers.
		1060
770	A watcher is a structure that you create and register to record your	1061	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	1062	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:	1063	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1064	for that:
773		1065
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1066	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	1067	{
776	ev_io_stop (w);	1068	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	1069	ev_break (loop, EVBREAK_ALL);
778	}	1070	}
779		1071
780	struct ev_loop *loop = ev_default_loop (0);	1072	struct ev_loop *loop = ev_default_loop (0);
		1073
781	struct ev_io stdin_watcher;	1074	ev_io stdin_watcher;
		1075
782	ev_init (&stdin_watcher, my_cb);	1076	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1077	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	1078	ev_io_start (loop, &stdin_watcher);
		1079
785	ev_loop (loop, 0);	1080	ev_run (loop, 0);
786		1081
787	As you can see, you are responsible for allocating the memory for your	1082	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,	1083	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1084	stack).
790		1085
		1086	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1087	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1088
791	Each watcher structure must be initialised by a call to C<ev_init	1089	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	1090	*, 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	1091	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	1092	time the event loop detects that the file descriptor given is readable
795	is readable and/or writable).	1093	and/or writable).
796		1094
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1095	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	1096	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	1097	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1098	ev_TYPE_init (watcher *, callback, ...) >>.
801		1099
802	To make the watcher actually watch out for events, you have to start it	1100	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	1101	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	1102	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1103	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1104
807	As long as your watcher is active (has been started but not stopped) you	1105	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	1106	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1107	reinitialise it or call its C<ev_TYPE_set> macro.
810		1108
811	Each and every callback receives the event loop pointer as first, the	1109	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	1110	registered watcher structure as second, and a bitset of received events as
813	third argument.	1111	third argument.
814		1112
…		…
823	=item C<EV_WRITE>	1121	=item C<EV_WRITE>
824		1122
825	The file descriptor in the C<ev_io> watcher has become readable and/or	1123	The file descriptor in the C<ev_io> watcher has become readable and/or
826	writable.	1124	writable.
827		1125
828	=item C<EV_TIMEOUT>	1126	=item C<EV_TIMER>
829		1127
830	The C<ev_timer> watcher has timed out.	1128	The C<ev_timer> watcher has timed out.
831		1129
832	=item C<EV_PERIODIC>	1130	=item C<EV_PERIODIC>
833		1131
…		…
851		1149
852	=item C<EV_PREPARE>	1150	=item C<EV_PREPARE>
853		1151
854	=item C<EV_CHECK>	1152	=item C<EV_CHECK>
855		1153
856	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1154	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	1155	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	1156	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	1157	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	1158	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	1159	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
862	C<ev_loop> from blocking).	1160	C<ev_run> from blocking).
863		1161
864	=item C<EV_EMBED>	1162	=item C<EV_EMBED>
865		1163
866	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1164	The embedded event loop specified in the C<ev_embed> watcher needs attention.
867		1165
868	=item C<EV_FORK>	1166	=item C<EV_FORK>
869		1167
870	The event loop has been resumed in the child process after fork (see	1168	The event loop has been resumed in the child process after fork (see
871	C<ev_fork>).	1169	C<ev_fork>).
872		1170
		1171	=item C<EV_CLEANUP>
		1172
		1173	The event loop is about to be destroyed (see C<ev_cleanup>).
		1174
873	=item C<EV_ASYNC>	1175	=item C<EV_ASYNC>
874		1176
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1177	The given async watcher has been asynchronously notified (see C<ev_async>).
		1178
		1179	=item C<EV_CUSTOM>
		1180
		1181	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1182	by libev users to signal watchers (e.g. via C<ev_feed_event>).
876		1183
877	=item C<EV_ERROR>	1184	=item C<EV_ERROR>
878		1185
879	An unspecified error has occurred, the watcher has been stopped. This might	1186	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1187	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	1188	ran out of memory, a file descriptor was found to be closed or any other
		1189	problem. Libev considers these application bugs.
		1190
882	problem. You best act on it by reporting the problem and somehow coping	1191	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1192	watcher being stopped. Note that well-written programs should not receive
		1193	an error ever, so when your watcher receives it, this usually indicates a
		1194	bug in your program.
884		1195
885	Libev will usually signal a few "dummy" events together with an error,	1196	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	1197	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	1198	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	1199	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1200	programs, though, as the fd could already be closed and reused for another
		1201	thing, so beware.
890		1202
891	=back	1203	=back
892		1204
893	=head2 GENERIC WATCHER FUNCTIONS	1205	=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		1206
898	=over 4	1207	=over 4
899		1208
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1209	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1210
…		…
907	which rolls both calls into one.	1216	which rolls both calls into one.
908		1217
909	You can reinitialise a watcher at any time as long as it has been stopped	1218	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.	1219	(or never started) and there are no pending events outstanding.
911		1220
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1221	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1222	int revents)>.
914		1223
		1224	Example: Initialise an C<ev_io> watcher in two steps.
		1225
		1226	ev_io w;
		1227	ev_init (&w, my_cb);
		1228	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1229
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1230	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1231
917	This macro initialises the type-specific parts of a watcher. You need to	1232	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	1233	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	1234	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	1235	macro on a watcher that is active (it can be pending, however, which is a
921	difference to the C<ev_init> macro).	1236	difference to the C<ev_init> macro).
922		1237
923	Although some watcher types do not have type-specific arguments	1238	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.	1239	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1240
		1241	See C<ev_init>, above, for an example.
		1242
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1243	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1244
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1245	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	1246	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1247	a watcher. The same limitations apply, of course.
931		1248
		1249	Example: Initialise and set an C<ev_io> watcher in one step.
		1250
		1251	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1252
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1253	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1254
934	Starts (activates) the given watcher. Only active watchers will receive	1255	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1256	events. If the watcher is already active nothing will happen.
936		1257
		1258	Example: Start the C<ev_io> watcher that is being abused as example in this
		1259	whole section.
		1260
		1261	ev_io_start (EV_DEFAULT_UC, &w);
		1262
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1263	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1264
939	Stops the given watcher again (if active) and clears the pending	1265	Stops the given watcher if active, and clears the pending status (whether
		1266	the watcher was active or not).
		1267
940	status. It is possible that stopped watchers are pending (for example,	1268	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1269	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	1270	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	1271	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.	1272	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1273
946	=item bool ev_is_active (ev_TYPE *watcher)	1274	=item bool ev_is_active (ev_TYPE *watcher)
947		1275
948	Returns a true value iff the watcher is active (i.e. it has been started	1276	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	1277	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)	1293	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1294
967	Change the callback. You can change the callback at virtually any time	1295	Change the callback. You can change the callback at virtually any time
968	(modulo threads).	1296	(modulo threads).
969		1297
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1298	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1299
972	=item int ev_priority (ev_TYPE *watcher)	1300	=item int ev_priority (ev_TYPE *watcher)
973		1301
974	Set and query the priority of the watcher. The priority is a small	1302	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>	1303	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1304	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1305	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1306	from being executed (except for C<ev_idle> watchers).
979		1307
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	1308	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.	1309	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1310
988	You I<must not> change the priority of a watcher as long as it is active or	1311	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1312	pending.
990		1313
		1314	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1315	fine, as long as you do not mind that the priority value you query might
		1316	or might not have been clamped to the valid range.
		1317
991	The default priority used by watchers when no priority has been set is	1318	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 :).	1319	always C<0>, which is supposed to not be too high and not be too low :).
993		1320
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1321	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	1322	priorities.
996	or might not have been adjusted to be within valid range.
997		1323
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1324	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1325
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1326	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	1327	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1328	can deal with that fact, as both are simply passed through to the
		1329	callback.
1003		1330
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1331	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1332
1006	If the watcher is pending, this function returns clears its pending status	1333	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	1334	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>.	1335	watcher isn't pending it does nothing and returns C<0>.
1009		1336
		1337	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1338	callback to be invoked, which can be accomplished with this function.
		1339
		1340	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1341
		1342	Feeds the given event set into the event loop, as if the specified event
		1343	had happened for the specified watcher (which must be a pointer to an
		1344	initialised but not necessarily started event watcher). Obviously you must
		1345	not free the watcher as long as it has pending events.
		1346
		1347	Stopping the watcher, letting libev invoke it, or calling
		1348	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1349	not started in the first place.
		1350
		1351	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1352	functions that do not need a watcher.
		1353
1010	=back	1354	=back
1011		1355
1012
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1356	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1357
1015	Each watcher has, by default, a member C<void *data> that you can change	1358	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	1359	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	1360	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	1361	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	1362	member, you can also "subclass" the watcher type and provide your own
1020	data:	1363	data:
1021		1364
1022	struct my_io	1365	struct my_io
1023	{	1366	{
1024	struct ev_io io;	1367	ev_io io;
1025	int otherfd;	1368	int otherfd;
1026	void *somedata;	1369	void *somedata;
1027	struct whatever *mostinteresting;	1370	struct whatever *mostinteresting;
1028	};	1371	};
1029		1372
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1375	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1376
1034	And since your callback will be called with a pointer to the watcher, you	1377	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1378	can cast it back to your own type:
1036		1379
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1380	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1381	{
1039	struct my_io *w = (struct my_io *)w_;	1382	struct my_io *w = (struct my_io *)w_;
1040	...	1383	...
1041	}	1384	}
1042		1385
…		…
1053	ev_timer t2;	1396	ev_timer t2;
1054	}	1397	}
1055		1398
1056	In this case getting the pointer to C<my_biggy> is a bit more	1399	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	1400	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	1401	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1402	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1403	programmers):
1060		1404
1061	#include <stddef.h>	1405	#include <stddef.h>
1062		1406
1063	static void	1407	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1408	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1409	{
1066	struct my_biggy big = (struct my_biggy *	1410	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1411	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1412	}
1069		1413
1070	static void	1414	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1415	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1416	{
1073	struct my_biggy big = (struct my_biggy *	1417	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1418	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1419	}
		1420
		1421	=head2 WATCHER STATES
		1422
		1423	There are various watcher states mentioned throughout this manual -
		1424	active, pending and so on. In this section these states and the rules to
		1425	transition between them will be described in more detail - and while these
		1426	rules might look complicated, they usually do "the right thing".
		1427
		1428	=over 4
		1429
		1430	=item initialiased
		1431
		1432	Before a watcher can be registered with the event looop it has to be
		1433	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1434	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1435
		1436	In this state it is simply some block of memory that is suitable for use
		1437	in an event loop. It can be moved around, freed, reused etc. at will.
		1438
		1439	=item started/running/active
		1440
		1441	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1442	property of the event loop, and is actively waiting for events. While in
		1443	this state it cannot be accessed (except in a few documented ways), moved,
		1444	freed or anything else - the only legal thing is to keep a pointer to it,
		1445	and call libev functions on it that are documented to work on active watchers.
		1446
		1447	=item pending
		1448
		1449	If a watcher is active and libev determines that an event it is interested
		1450	in has occurred (such as a timer expiring), it will become pending. It will
		1451	stay in this pending state until either it is stopped or its callback is
		1452	about to be invoked, so it is not normally pending inside the watcher
		1453	callback.
		1454
		1455	The watcher might or might not be active while it is pending (for example,
		1456	an expired non-repeating timer can be pending but no longer active). If it
		1457	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1458	but it is still property of the event loop at this time, so cannot be
		1459	moved, freed or reused. And if it is active the rules described in the
		1460	previous item still apply.
		1461
		1462	It is also possible to feed an event on a watcher that is not active (e.g.
		1463	via C<ev_feed_event>), in which case it becomes pending without being
		1464	active.
		1465
		1466	=item stopped
		1467
		1468	A watcher can be stopped implicitly by libev (in which case it might still
		1469	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1470	latter will clear any pending state the watcher might be in, regardless
		1471	of whether it was active or not, so stopping a watcher explicitly before
		1472	freeing it is often a good idea.
		1473
		1474	While stopped (and not pending) the watcher is essentially in the
		1475	initialised state, that is it can be reused, moved, modified in any way
		1476	you wish.
		1477
		1478	=back
		1479
		1480	=head2 WATCHER PRIORITY MODELS
		1481
		1482	Many event loops support I<watcher priorities>, which are usually small
		1483	integers that influence the ordering of event callback invocation
		1484	between watchers in some way, all else being equal.
		1485
		1486	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1487	description for the more technical details such as the actual priority
		1488	range.
		1489
		1490	There are two common ways how these these priorities are being interpreted
		1491	by event loops:
		1492
		1493	In the more common lock-out model, higher priorities "lock out" invocation
		1494	of lower priority watchers, which means as long as higher priority
		1495	watchers receive events, lower priority watchers are not being invoked.
		1496
		1497	The less common only-for-ordering model uses priorities solely to order
		1498	callback invocation within a single event loop iteration: Higher priority
		1499	watchers are invoked before lower priority ones, but they all get invoked
		1500	before polling for new events.
		1501
		1502	Libev uses the second (only-for-ordering) model for all its watchers
		1503	except for idle watchers (which use the lock-out model).
		1504
		1505	The rationale behind this is that implementing the lock-out model for
		1506	watchers is not well supported by most kernel interfaces, and most event
		1507	libraries will just poll for the same events again and again as long as
		1508	their callbacks have not been executed, which is very inefficient in the
		1509	common case of one high-priority watcher locking out a mass of lower
		1510	priority ones.
		1511
		1512	Static (ordering) priorities are most useful when you have two or more
		1513	watchers handling the same resource: a typical usage example is having an
		1514	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1515	timeouts. Under load, data might be received while the program handles
		1516	other jobs, but since timers normally get invoked first, the timeout
		1517	handler will be executed before checking for data. In that case, giving
		1518	the timer a lower priority than the I/O watcher ensures that I/O will be
		1519	handled first even under adverse conditions (which is usually, but not
		1520	always, what you want).
		1521
		1522	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1523	will only be executed when no same or higher priority watchers have
		1524	received events, they can be used to implement the "lock-out" model when
		1525	required.
		1526
		1527	For example, to emulate how many other event libraries handle priorities,
		1528	you can associate an C<ev_idle> watcher to each such watcher, and in
		1529	the normal watcher callback, you just start the idle watcher. The real
		1530	processing is done in the idle watcher callback. This causes libev to
		1531	continuously poll and process kernel event data for the watcher, but when
		1532	the lock-out case is known to be rare (which in turn is rare :), this is
		1533	workable.
		1534
		1535	Usually, however, the lock-out model implemented that way will perform
		1536	miserably under the type of load it was designed to handle. In that case,
		1537	it might be preferable to stop the real watcher before starting the
		1538	idle watcher, so the kernel will not have to process the event in case
		1539	the actual processing will be delayed for considerable time.
		1540
		1541	Here is an example of an I/O watcher that should run at a strictly lower
		1542	priority than the default, and which should only process data when no
		1543	other events are pending:
		1544
		1545	ev_idle idle; // actual processing watcher
		1546	ev_io io; // actual event watcher
		1547
		1548	static void
		1549	io_cb (EV_P_ ev_io *w, int revents)
		1550	{
		1551	// stop the I/O watcher, we received the event, but
		1552	// are not yet ready to handle it.
		1553	ev_io_stop (EV_A_ w);
		1554
		1555	// start the idle watcher to handle the actual event.
		1556	// it will not be executed as long as other watchers
		1557	// with the default priority are receiving events.
		1558	ev_idle_start (EV_A_ &idle);
		1559	}
		1560
		1561	static void
		1562	idle_cb (EV_P_ ev_idle *w, int revents)
		1563	{
		1564	// actual processing
		1565	read (STDIN_FILENO, ...);
		1566
		1567	// have to start the I/O watcher again, as
		1568	// we have handled the event
		1569	ev_io_start (EV_P_ &io);
		1570	}
		1571
		1572	// initialisation
		1573	ev_idle_init (&idle, idle_cb);
		1574	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1575	ev_io_start (EV_DEFAULT_ &io);
		1576
		1577	In the "real" world, it might also be beneficial to start a timer, so that
		1578	low-priority connections can not be locked out forever under load. This
		1579	enables your program to keep a lower latency for important connections
		1580	during short periods of high load, while not completely locking out less
		1581	important ones.
1076		1582
1077		1583
1078	=head1 WATCHER TYPES	1584	=head1 WATCHER TYPES
1079		1585
1080	This section describes each watcher in detail, but will not repeat	1586	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	1610	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	1611	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	1612	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1613	required if you know what you are doing).
1108		1614
1109	If you must do this, then force the use of a known-to-be-good backend	1615	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	1616	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1617	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1618	descriptors for which non-blocking operation makes no sense (such as
		1619	files) - libev doesn't guarantee any specific behaviour in that case.
1112		1620
1113	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1622	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	1623	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	1624	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	1625	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	1626	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	1627	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.	1628	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1629
1122	If you cannot run the fd in non-blocking mode (for example you should not	1630	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	1631	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	1632	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	1633	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1634	does this on its own, so its quite safe to use). Some people additionally
		1635	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1636	indefinitely.
		1637
		1638	But really, best use non-blocking mode.
1127		1639
1128	=head3 The special problem of disappearing file descriptors	1640	=head3 The special problem of disappearing file descriptors
1129		1641
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1642	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,	1643	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	1644	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	1645	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	1646	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	1647	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1648	fact, a different file descriptor.
1137		1649
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1680	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1681	C<EVBACKEND_POLL>.
1170		1682
1171	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1172		1684
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1685	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	1686	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	1687	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1688	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1689
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1690	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	1691	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).	1692	somewhere, as that would have given you a big clue).
1181		1693
		1694	=head3 The special problem of accept()ing when you can't
		1695
		1696	Many implementations of the POSIX C<accept> function (for example,
		1697	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1698	connection from the pending queue in all error cases.
		1699
		1700	For example, larger servers often run out of file descriptors (because
		1701	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1702	rejecting the connection, leading to libev signalling readiness on
		1703	the next iteration again (the connection still exists after all), and
		1704	typically causing the program to loop at 100% CPU usage.
		1705
		1706	Unfortunately, the set of errors that cause this issue differs between
		1707	operating systems, there is usually little the app can do to remedy the
		1708	situation, and no known thread-safe method of removing the connection to
		1709	cope with overload is known (to me).
		1710
		1711	One of the easiest ways to handle this situation is to just ignore it
		1712	- when the program encounters an overload, it will just loop until the
		1713	situation is over. While this is a form of busy waiting, no OS offers an
		1714	event-based way to handle this situation, so it's the best one can do.
		1715
		1716	A better way to handle the situation is to log any errors other than
		1717	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1718	messages, and continue as usual, which at least gives the user an idea of
		1719	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1720	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1721	usage.
		1722
		1723	If your program is single-threaded, then you could also keep a dummy file
		1724	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1725	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1726	close that fd, and create a new dummy fd. This will gracefully refuse
		1727	clients under typical overload conditions.
		1728
		1729	The last way to handle it is to simply log the error and C<exit>, as
		1730	is often done with C<malloc> failures, but this results in an easy
		1731	opportunity for a DoS attack.
1182		1732
1183	=head3 Watcher-Specific Functions	1733	=head3 Watcher-Specific Functions
1184		1734
1185	=over 4	1735	=over 4
1186		1736
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1737	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1738
1189	=item ev_io_set (ev_io *, int fd, int events)	1739	=item ev_io_set (ev_io *, int fd, int events)
1190		1740
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1741	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	1742	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.	1743	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1744
1195	=item int fd [read-only]	1745	=item int fd [read-only]
1196		1746
1197	The file descriptor being watched.	1747	The file descriptor being watched.
1198		1748
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1757	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	1758	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1759	attempt to read a whole line in the callback.
1210		1760
1211	static void	1761	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1762	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1763	{
1214	ev_io_stop (loop, w);	1764	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1765	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1766	}
1217		1767
1218	...	1768	...
1219	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1770	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1224		1774
1225		1775
1226	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1227		1777
1228	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1779	given time, and optionally repeating in regular intervals after that.
1230		1780
1231	The timers are based on real time, that is, if you register an event that	1781	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	1782	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	1783	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1236		1786
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1787	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	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1789	might introduce a small delay). If multiple timers become ready during the
		1790	same loop iteration then the ones with earlier time-out values are invoked
		1791	before ones of the same priority with later time-out values (but this is
		1792	no longer true when a callback calls C<ev_run> recursively).
		1793
		1794	=head3 Be smart about timeouts
		1795
		1796	Many real-world problems involve some kind of timeout, usually for error
		1797	recovery. A typical example is an HTTP request - if the other side hangs,
		1798	you want to raise some error after a while.
		1799
		1800	What follows are some ways to handle this problem, from obvious and
		1801	inefficient to smart and efficient.
		1802
		1803	In the following, a 60 second activity timeout is assumed - a timeout that
		1804	gets reset to 60 seconds each time there is activity (e.g. each time some
		1805	data or other life sign was received).
		1806
		1807	=over 4
		1808
		1809	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1810
		1811	This is the most obvious, but not the most simple way: In the beginning,
		1812	start the watcher:
		1813
		1814	ev_timer_init (timer, callback, 60., 0.);
		1815	ev_timer_start (loop, timer);
		1816
		1817	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1818	and start it again:
		1819
		1820	ev_timer_stop (loop, timer);
		1821	ev_timer_set (timer, 60., 0.);
		1822	ev_timer_start (loop, timer);
		1823
		1824	This is relatively simple to implement, but means that each time there is
		1825	some activity, libev will first have to remove the timer from its internal
		1826	data structure and then add it again. Libev tries to be fast, but it's
		1827	still not a constant-time operation.
		1828
		1829	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1830
		1831	This is the easiest way, and involves using C<ev_timer_again> instead of
		1832	C<ev_timer_start>.
		1833
		1834	To implement this, configure an C<ev_timer> with a C<repeat> value
		1835	of C<60> and then call C<ev_timer_again> at start and each time you
		1836	successfully read or write some data. If you go into an idle state where
		1837	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1838	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1839
		1840	That means you can ignore both the C<ev_timer_start> function and the
		1841	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1842	member and C<ev_timer_again>.
		1843
		1844	At start:
		1845
		1846	ev_init (timer, callback);
		1847	timer->repeat = 60.;
		1848	ev_timer_again (loop, timer);
		1849
		1850	Each time there is some activity:
		1851
		1852	ev_timer_again (loop, timer);
		1853
		1854	It is even possible to change the time-out on the fly, regardless of
		1855	whether the watcher is active or not:
		1856
		1857	timer->repeat = 30.;
		1858	ev_timer_again (loop, timer);
		1859
		1860	This is slightly more efficient then stopping/starting the timer each time
		1861	you want to modify its timeout value, as libev does not have to completely
		1862	remove and re-insert the timer from/into its internal data structure.
		1863
		1864	It is, however, even simpler than the "obvious" way to do it.
		1865
		1866	=item 3. Let the timer time out, but then re-arm it as required.
		1867
		1868	This method is more tricky, but usually most efficient: Most timeouts are
		1869	relatively long compared to the intervals between other activity - in
		1870	our example, within 60 seconds, there are usually many I/O events with
		1871	associated activity resets.
		1872
		1873	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1874	but remember the time of last activity, and check for a real timeout only
		1875	within the callback:
		1876
		1877	ev_tstamp last_activity; // time of last activity
		1878
		1879	static void
		1880	callback (EV_P_ ev_timer *w, int revents)
		1881	{
		1882	ev_tstamp now = ev_now (EV_A);
		1883	ev_tstamp timeout = last_activity + 60.;
		1884
		1885	// if last_activity + 60. is older than now, we did time out
		1886	if (timeout < now)
		1887	{
		1888	// timeout occurred, take action
		1889	}
		1890	else
		1891	{
		1892	// callback was invoked, but there was some activity, re-arm
		1893	// the watcher to fire in last_activity + 60, which is
		1894	// guaranteed to be in the future, so "again" is positive:
		1895	w->repeat = timeout - now;
		1896	ev_timer_again (EV_A_ w);
		1897	}
		1898	}
		1899
		1900	To summarise the callback: first calculate the real timeout (defined
		1901	as "60 seconds after the last activity"), then check if that time has
		1902	been reached, which means something I<did>, in fact, time out. Otherwise
		1903	the callback was invoked too early (C<timeout> is in the future), so
		1904	re-schedule the timer to fire at that future time, to see if maybe we have
		1905	a timeout then.
		1906
		1907	Note how C<ev_timer_again> is used, taking advantage of the
		1908	C<ev_timer_again> optimisation when the timer is already running.
		1909
		1910	This scheme causes more callback invocations (about one every 60 seconds
		1911	minus half the average time between activity), but virtually no calls to
		1912	libev to change the timeout.
		1913
		1914	To start the timer, simply initialise the watcher and set C<last_activity>
		1915	to the current time (meaning we just have some activity :), then call the
		1916	callback, which will "do the right thing" and start the timer:
		1917
		1918	ev_init (timer, callback);
		1919	last_activity = ev_now (loop);
		1920	callback (loop, timer, EV_TIMER);
		1921
		1922	And when there is some activity, simply store the current time in
		1923	C<last_activity>, no libev calls at all:
		1924
		1925	last_activity = ev_now (loop);
		1926
		1927	This technique is slightly more complex, but in most cases where the
		1928	time-out is unlikely to be triggered, much more efficient.
		1929
		1930	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1931	callback :) - just change the timeout and invoke the callback, which will
		1932	fix things for you.
		1933
		1934	=item 4. Wee, just use a double-linked list for your timeouts.
		1935
		1936	If there is not one request, but many thousands (millions...), all
		1937	employing some kind of timeout with the same timeout value, then one can
		1938	do even better:
		1939
		1940	When starting the timeout, calculate the timeout value and put the timeout
		1941	at the I<end> of the list.
		1942
		1943	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1944	the list is expected to fire (for example, using the technique #3).
		1945
		1946	When there is some activity, remove the timer from the list, recalculate
		1947	the timeout, append it to the end of the list again, and make sure to
		1948	update the C<ev_timer> if it was taken from the beginning of the list.
		1949
		1950	This way, one can manage an unlimited number of timeouts in O(1) time for
		1951	starting, stopping and updating the timers, at the expense of a major
		1952	complication, and having to use a constant timeout. The constant timeout
		1953	ensures that the list stays sorted.
		1954
		1955	=back
		1956
		1957	So which method the best?
		1958
		1959	Method #2 is a simple no-brain-required solution that is adequate in most
		1960	situations. Method #3 requires a bit more thinking, but handles many cases
		1961	better, and isn't very complicated either. In most case, choosing either
		1962	one is fine, with #3 being better in typical situations.
		1963
		1964	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1965	rather complicated, but extremely efficient, something that really pays
		1966	off after the first million or so of active timers, i.e. it's usually
		1967	overkill :)
1240		1968
1241	=head3 The special problem of time updates	1969	=head3 The special problem of time updates
1242		1970
1243	Establishing the current time is a costly operation (it usually takes at	1971	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	1972	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	1973	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	1974	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1975	lots of events in one iteration.
1248		1976
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1977	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	1978	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	1979	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	1980	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1984
1257	If the event loop is suspended for a long time, you can also force an	1985	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	1986	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1987	()>.
1260		1988
		1989	=head3 The special problems of suspended animation
		1990
		1991	When you leave the server world it is quite customary to hit machines that
		1992	can suspend/hibernate - what happens to the clocks during such a suspend?
		1993
		1994	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1995	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1996	to run until the system is suspended, but they will not advance while the
		1997	system is suspended. That means, on resume, it will be as if the program
		1998	was frozen for a few seconds, but the suspend time will not be counted
		1999	towards C<ev_timer> when a monotonic clock source is used. The real time
		2000	clock advanced as expected, but if it is used as sole clocksource, then a
		2001	long suspend would be detected as a time jump by libev, and timers would
		2002	be adjusted accordingly.
		2003
		2004	I would not be surprised to see different behaviour in different between
		2005	operating systems, OS versions or even different hardware.
		2006
		2007	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2008	time jump in the monotonic clocks and the realtime clock. If the program
		2009	is suspended for a very long time, and monotonic clock sources are in use,
		2010	then you can expect C<ev_timer>s to expire as the full suspension time
		2011	will be counted towards the timers. When no monotonic clock source is in
		2012	use, then libev will again assume a timejump and adjust accordingly.
		2013
		2014	It might be beneficial for this latter case to call C<ev_suspend>
		2015	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2016	deterministic behaviour in this case (you can do nothing against
		2017	C<SIGSTOP>).
		2018
1261	=head3 Watcher-Specific Functions and Data Members	2019	=head3 Watcher-Specific Functions and Data Members
1262		2020
1263	=over 4	2021	=over 4
1264		2022
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2023	=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).	2046	If the timer is started but non-repeating, stop it (as if it timed out).
1289		2047
1290	If the timer is repeating, either start it if necessary (with the	2048	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.	2049	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		2050
1293	This sounds a bit complicated, but here is a useful and typical	2051	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	2052	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		2053
1303	That means you can ignore the C<after> value and C<ev_timer_start>	2054	=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		2055
1306	ev_timer_init (timer, callback, 0., 5.);	2056	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	2057	then this time is relative to the current event loop time, otherwise it's
1308	...	2058	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		2059
1315	This is more slightly efficient then stopping/starting the timer each time	2060	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	2061	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2062	will return C<4>. When the timer expires and is restarted, it will return
		2063	roughly C<7> (likely slightly less as callback invocation takes some time,
		2064	too), and so on.
1317		2065
1318	=item ev_tstamp repeat [read-write]	2066	=item ev_tstamp repeat [read-write]
1319		2067
1320	The current C<repeat> value. Will be used each time the watcher times out	2068	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),	2069	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.	2070	which is also when any modifications are taken into account.
1323		2071
1324	=back	2072	=back
1325		2073
1326	=head3 Examples	2074	=head3 Examples
1327		2075
1328	Example: Create a timer that fires after 60 seconds.	2076	Example: Create a timer that fires after 60 seconds.
1329		2077
1330	static void	2078	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2079	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	2080	{
1333	.. one minute over, w is actually stopped right here	2081	.. one minute over, w is actually stopped right here
1334	}	2082	}
1335		2083
1336	struct ev_timer mytimer;	2084	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2085	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	2086	ev_timer_start (loop, &mytimer);
1339		2087
1340	Example: Create a timeout timer that times out after 10 seconds of	2088	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	2089	inactivity.
1342		2090
1343	static void	2091	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2092	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	2093	{
1346	.. ten seconds without any activity	2094	.. ten seconds without any activity
1347	}	2095	}
1348		2096
1349	struct ev_timer mytimer;	2097	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2098	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	2099	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	2100	ev_run (loop, 0);
1353		2101
1354	// and in some piece of code that gets executed on any "activity":	2102	// and in some piece of code that gets executed on any "activity":
1355	// reset the timeout to start ticking again at 10 seconds	2103	// reset the timeout to start ticking again at 10 seconds
1356	ev_timer_again (&mytimer);	2104	ev_timer_again (&mytimer);
1357		2105
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	2107	=head2 C<ev_periodic> - to cron or not to cron?
1360		2108
1361	Periodic watchers are also timers of a kind, but they are very versatile	2109	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	2110	(and unfortunately a bit complex).
1363		2111
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2112	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	2113	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	2114	(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 ()	2115	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	2116	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	2117	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		2118
		2119	You can tell a periodic watcher to trigger after some specific point
		2120	in time: for example, if you tell a periodic watcher to trigger "in 10
		2121	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2122	not a delay) and then reset your system clock to January of the previous
		2123	year, then it will take a year or more to trigger the event (unlike an
		2124	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2125	it, as it uses a relative timeout).
		2126
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	2127	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	2128	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	2129	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2130	those cannot react to time jumps.
1376		2131
1377	As with timers, the callback is guaranteed to be invoked only when the	2132	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	2133	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.	2134	timers become ready during the same loop iteration then the ones with
		2135	earlier time-out values are invoked before ones with later time-out values
		2136	(but this is no longer true when a callback calls C<ev_run> recursively).
1380		2137
1381	=head3 Watcher-Specific Functions and Data Members	2138	=head3 Watcher-Specific Functions and Data Members
1382		2139
1383	=over 4	2140	=over 4
1384		2141
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2142	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		2143
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2144	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2145
1389	Lots of arguments, lets sort it out... There are basically three modes of	2146	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:	2147	operation, and we will explain them from simplest to most complex:
1391		2148
1392	=over 4	2149	=over 4
1393		2150
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2151	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2152
1396	In this configuration the watcher triggers an event after the wall clock	2153	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	2154	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	2155	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.	2156	will be stopped and invoked when the system clock reaches or surpasses
		2157	this point in time.
1400		2158
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2159	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2160
1403	In this mode the watcher will always be scheduled to time out at the next	2161	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)	2162	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2163	negative) and then repeat, regardless of any time jumps. The C<offset>
		2164	argument is merely an offset into the C<interval> periods.
1406		2165
1407	This can be used to create timers that do not drift with respect to system	2166	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	2167	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2168	hour, on the hour (with respect to UTC):
1410		2169
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2170	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2171
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2172	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	2173	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	2174	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2175	by 3600.
1417		2176
1418	Another way to think about it (for the mathematically inclined) is that	2177	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	2178	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.	2179	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2180
1422	For numerical stability it is preferable that the C<at> value is near	2181	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	2182	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2183	this value, and in fact is often specified as zero.
1425		2184
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2185	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	2186	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	2187	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).	2188	millisecond (if the OS supports it and the machine is fast enough).
1430		2189
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2190	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2191
1433	In this mode the values for C<interval> and C<at> are both being	2192	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	2193	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2194	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2195	current time as second argument.
1437		2196
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2197	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2198	or make ANY other event loop modifications whatsoever, unless explicitly
		2199	allowed by documentation here>.
1440		2200
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2201	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	2202	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2203	only event loop modification you are allowed to do).
1444		2204
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2205	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2206	*w, ev_tstamp now)>, e.g.:
1447		2207
		2208	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2209	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2210	{
1450	return now + 60.;	2211	return now + 60.;
1451	}	2212	}
1452		2213
1453	It must return the next time to trigger, based on the passed time value	2214	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	2234	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2235	program when the crontabs have changed).
1475		2236
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2237	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2238
1478	When active, returns the absolute time that the watcher is supposed to	2239	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2240	to trigger next. This is not the same as the C<offset> argument to
		2241	C<ev_periodic_set>, but indeed works even in interval and manual
		2242	rescheduling modes.
1480		2243
1481	=item ev_tstamp offset [read-write]	2244	=item ev_tstamp offset [read-write]
1482		2245
1483	When repeating, this contains the offset value, otherwise this is the	2246	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>).	2247	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2248	although libev might modify this value for better numerical stability).
1485		2249
1486	Can be modified any time, but changes only take effect when the periodic	2250	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2251	timer fires or C<ev_periodic_again> is being called.
1488		2252
1489	=item ev_tstamp interval [read-write]	2253	=item ev_tstamp interval [read-write]
1490		2254
1491	The current interval value. Can be modified any time, but changes only	2255	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	2256	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2257	called.
1494		2258
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2259	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2260
1497	The current reschedule callback, or C<0>, if this functionality is	2261	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	2262	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.	2263	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2264
1501	=back	2265	=back
1502		2266
1503	=head3 Examples	2267	=head3 Examples
1504		2268
1505	Example: Call a callback every hour, or, more precisely, whenever the	2269	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2270	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2271	potentially a lot of jitter, but good long-term stability.
1508		2272
1509	static void	2273	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2274	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2275	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2276	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2277	}
1514		2278
1515	struct ev_periodic hourly_tick;	2279	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2280	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2281	ev_periodic_start (loop, &hourly_tick);
1518		2282
1519	Example: The same as above, but use a reschedule callback to do it:	2283	Example: The same as above, but use a reschedule callback to do it:
1520		2284
1521	#include <math.h>	2285	#include <math.h>
1522		2286
1523	static ev_tstamp	2287	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2288	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2289	{
1526	return fmod (now, 3600.) + 3600.;	2290	return now + (3600. - fmod (now, 3600.));
1527	}	2291	}
1528		2292
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2293	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2294
1531	Example: Call a callback every hour, starting now:	2295	Example: Call a callback every hour, starting now:
1532		2296
1533	struct ev_periodic hourly_tick;	2297	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2298	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2299	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2300	ev_periodic_start (loop, &hourly_tick);
1537		2301
1538		2302
1539	=head2 C<ev_signal> - signal me when a signal gets signalled!	2303	=head2 C<ev_signal> - signal me when a signal gets signalled!
1540		2304
1541	Signal watchers will trigger an event when the process receives a specific	2305	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	2306	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	2307	will try its best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2308	normal event processing, like any other event.
1545		2309
		2310	If you want signals to be delivered truly asynchronously, just use
		2311	C<sigaction> as you would do without libev and forget about sharing
		2312	the signal. You can even use C<ev_async> from a signal handler to
		2313	synchronously wake up an event loop.
		2314
1546	You can configure as many watchers as you like per signal. Only when the	2315	You can configure as many watchers as you like for the same signal, but
		2316	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2317	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2318	C<SIGINT> in both the default loop and another loop at the same time. At
		2319	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2320
1547	first watcher gets started will libev actually register a signal watcher	2321	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	2322	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	2323	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		2324
1553	If possible and supported, libev will install its handlers with	2325	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2326	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2327	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	2328	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2329	and unblock them in an C<ev_prepare> watcher.
		2330
		2331	=head3 The special problem of inheritance over fork/execve/pthread_create
		2332
		2333	Both the signal mask (C<sigprocmask>) and the signal disposition
		2334	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2335	stopping it again), that is, libev might or might not block the signal,
		2336	and might or might not set or restore the installed signal handler.
		2337
		2338	While this does not matter for the signal disposition (libev never
		2339	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2340	C<execve>), this matters for the signal mask: many programs do not expect
		2341	certain signals to be blocked.
		2342
		2343	This means that before calling C<exec> (from the child) you should reset
		2344	the signal mask to whatever "default" you expect (all clear is a good
		2345	choice usually).
		2346
		2347	The simplest way to ensure that the signal mask is reset in the child is
		2348	to install a fork handler with C<pthread_atfork> that resets it. That will
		2349	catch fork calls done by libraries (such as the libc) as well.
		2350
		2351	In current versions of libev, the signal will not be blocked indefinitely
		2352	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2353	the window of opportunity for problems, it will not go away, as libev
		2354	I<has> to modify the signal mask, at least temporarily.
		2355
		2356	So I can't stress this enough: I<If you do not reset your signal mask when
		2357	you expect it to be empty, you have a race condition in your code>. This
		2358	is not a libev-specific thing, this is true for most event libraries.
		2359
		2360	=head3 The special problem of threads signal handling
		2361
		2362	POSIX threads has problematic signal handling semantics, specifically,
		2363	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2364	threads in a process block signals, which is hard to achieve.
		2365
		2366	When you want to use sigwait (or mix libev signal handling with your own
		2367	for the same signals), you can tackle this problem by globally blocking
		2368	all signals before creating any threads (or creating them with a fully set
		2369	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2370	loops. Then designate one thread as "signal receiver thread" which handles
		2371	these signals. You can pass on any signals that libev might be interested
		2372	in by calling C<ev_feed_signal>.
1558		2373
1559	=head3 Watcher-Specific Functions and Data Members	2374	=head3 Watcher-Specific Functions and Data Members
1560		2375
1561	=over 4	2376	=over 4
1562		2377
…		…
1573		2388
1574	=back	2389	=back
1575		2390
1576	=head3 Examples	2391	=head3 Examples
1577		2392
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2393	Example: Try to exit cleanly on SIGINT.
1579		2394
1580	static void	2395	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2396	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2397	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2398	ev_break (loop, EVBREAK_ALL);
1584	}	2399	}
1585		2400
1586	struct ev_signal signal_watcher;	2401	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2402	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2403	ev_signal_start (loop, &signal_watcher);
1589		2404
1590		2405
1591	=head2 C<ev_child> - watch out for process status changes	2406	=head2 C<ev_child> - watch out for process status changes
1592		2407
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2408	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	2409	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	2410	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	2411	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2412	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2413	forking and then immediately registering a watcher for the child is fine,
		2414	but forking and registering a watcher a few event loop iterations later or
		2415	in the next callback invocation is not.
1598		2416
1599	Only the default event loop is capable of handling signals, and therefore	2417	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2418	you can only register child watchers in the default event loop.
1601		2419
		2420	Due to some design glitches inside libev, child watchers will always be
		2421	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2422	libev)
		2423
1602	=head3 Process Interaction	2424	=head3 Process Interaction
1603		2425
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2426	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2427	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2428	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2429	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2430	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2431	children, even ones not watched.
1610		2432
1611	=head3 Overriding the Built-In Processing	2433	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2443	=head3 Stopping the Child Watcher
1622		2444
1623	Currently, the child watcher never gets stopped, even when the	2445	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2446	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2447	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2448	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2449	problem).
1627		2450
1628	=head3 Watcher-Specific Functions and Data Members	2451	=head3 Watcher-Specific Functions and Data Members
1629		2452
1630	=over 4	2453	=over 4
1631		2454
…		…
1663	its completion.	2486	its completion.
1664		2487
1665	ev_child cw;	2488	ev_child cw;
1666		2489
1667	static void	2490	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2491	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2492	{
1670	ev_child_stop (EV_A_ w);	2493	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2494	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2495	}
1673		2496
…		…
1688		2511
1689		2512
1690	=head2 C<ev_stat> - did the file attributes just change?	2513	=head2 C<ev_stat> - did the file attributes just change?
1691		2514
1692	This watches a file system path for attribute changes. That is, it calls	2515	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	2516	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.	2517	and sees if it changed compared to the last time, invoking the callback if
		2518	it did.
1695		2519
1696	The path does not need to exist: changing from "path exists" to "path does	2520	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	2521	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	2522	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	2523	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2524	least one) and all the other fields of the stat buffer having unspecified
		2525	contents.
1701		2526
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2527	The path I<must not> end in a slash or contain special components such as
		2528	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.	2529	your working directory changes, then the behaviour is undefined.
1704		2530
1705	Since there is no standard to do this, the portable implementation simply	2531	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	2532	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2533	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,	2534	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	2535	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2536	(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	2537	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2538	currently around C<0.1>, but that's usually overkill.
1713		2539
1714	This watcher type is not meant for massive numbers of stat watchers,	2540	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2541	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2542	resource-intensive.
1717		2543
1718	At the time of this writing, only the Linux inotify interface is	2544	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2545	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	2546	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	2547	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		2548
1727	=head3 ABI Issues (Largefile Support)	2549	=head3 ABI Issues (Largefile Support)
1728		2550
1729	Libev by default (unless the user overrides this) uses the default	2551	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2552	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2553	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	2554	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	2555	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	2556	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	2557	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.	2558	most noticeably displayed with ev_stat and large file support.
1737		2559
1738	The solution for this is to lobby your distribution maker to make large	2560	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	2561	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	2562	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2563	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2564	default compilation environment.
1743		2565
1744	=head3 Inotify	2566	=head3 Inotify and Kqueue
1745		2567
1746	When C<inotify (7)> support has been compiled into libev (generally only	2568	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	2569	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	2570	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2571	watcher is being started.
1750		2572
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2573	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	2574	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	2575	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.	2576	there are many cases where libev has to resort to regular C<stat> polling,
		2577	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2578	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2579	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2580	xfs are fully working) libev usually gets away without polling.
1755		2581
1756	(There is no support for kqueue, as apparently it cannot be used to	2582	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	2583	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2584	descriptor open on the object at all times, and detecting renames, unlinks
		2585	etc. is difficult.
		2586
		2587	=head3 C<stat ()> is a synchronous operation
		2588
		2589	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2590	the process. The exception are C<ev_stat> watchers - those call C<stat
		2591	()>, which is a synchronous operation.
		2592
		2593	For local paths, this usually doesn't matter: unless the system is very
		2594	busy or the intervals between stat's are large, a stat call will be fast,
		2595	as the path data is usually in memory already (except when starting the
		2596	watcher).
		2597
		2598	For networked file systems, calling C<stat ()> can block an indefinite
		2599	time due to network issues, and even under good conditions, a stat call
		2600	often takes multiple milliseconds.
		2601
		2602	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2603	paths, although this is fully supported by libev.
1759		2604
1760	=head3 The special problem of stat time resolution	2605	=head3 The special problem of stat time resolution
1761		2606
1762	The C<stat ()> system call only supports full-second resolution portably, and	2607	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2608	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2609	still only support whole seconds.
1765		2610
1766	That means that, if the time is the only thing that changes, you can	2611	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	2612	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	2613	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	2614	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2615	stat data does change in other ways (e.g. file size).
1771		2616
1772	The solution to this is to delay acting on a change for slightly more	2617	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	2618	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);	2619	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2620	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2640	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	2641	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	2642	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.	2643	path for as long as the watcher is active.
1799		2644
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2645	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	2646	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2647	last change was detected).
1803		2648
1804	=item ev_stat_stat (loop, ev_stat *)	2649	=item ev_stat_stat (loop, ev_stat *)
1805		2650
1806	Updates the stat buffer immediately with new values. If you change the	2651	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	2652	watched path in your callback, you could call this function to avoid
…		…
1890		2735
1891		2736
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2737	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2738
1894	Idle watchers trigger events when no other events of the same or higher	2739	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	2740	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2741	as receiving "events").
1897		2742
1898	That is, as long as your process is busy handling sockets or timeouts	2743	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	2744	(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	2745	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	2746	are pending), the idle watchers are being called once per event loop
…		…
1912		2757
1913	=head3 Watcher-Specific Functions and Data Members	2758	=head3 Watcher-Specific Functions and Data Members
1914		2759
1915	=over 4	2760	=over 4
1916		2761
1917	=item ev_idle_init (ev_signal *, callback)	2762	=item ev_idle_init (ev_idle *, callback)
1918		2763
1919	Initialises and configures the idle watcher - it has no parameters of any	2764	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,	2765	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2766	believe me.
1922		2767
…		…
1926		2771
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2772	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2773	callback, free it. Also, use no error checking, as usual.
1929		2774
1930	static void	2775	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2776	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2777	{
1933	free (w);	2778	free (w);
1934	// now do something you wanted to do when the program has	2779	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2780	// no longer anything immediate to do.
1936	}	2781	}
1937		2782
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2783	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2784	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2785	ev_idle_start (loop, idle_watcher);
1941		2786
1942		2787
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2788	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2789
1945	Prepare and check watchers are usually (but not always) used in tandem:	2790	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2791	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2792	afterwards.
1948		2793
1949	You I<must not> call C<ev_loop> or similar functions that enter	2794	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>	2795	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	2796	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	2797	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,	2798	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	2799	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2800	called in pairs bracketing the blocking call.
1956		2801
1957	Their main purpose is to integrate other event mechanisms into libev and	2802	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	2803	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	2804	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2805	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,	2806	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>	2807	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2808	watcher).
1964		2809
1965	This is done by examining in each prepare call which file descriptors need	2810	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	2811	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	2812	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	2813	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2814	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	2815	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,	2816	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2817	nevertheless, because you never know, you know?).
1973		2818
1974	As another example, the Perl Coro module uses these hooks to integrate	2819	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2820	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2821	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	2822	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	2825	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2826	low-priority coroutines to idle/background tasks).
1982		2827
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2828	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	2829	priority, to ensure that they are being run before any other watchers
		2830	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2831
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2832	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	2833	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2834	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	2835	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	2836	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	2837	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2838	others).
1992		2839
1993	=head3 Watcher-Specific Functions and Data Members	2840	=head3 Watcher-Specific Functions and Data Members
1994		2841
1995	=over 4	2842	=over 4
1996		2843
…		…
1998		2845
1999	=item ev_check_init (ev_check *, callback)	2846	=item ev_check_init (ev_check *, callback)
2000		2847
2001	Initialises and configures the prepare or check watcher - they have no	2848	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>	2849	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.	2850	macros, but using them is utterly, utterly, utterly and completely
		2851	pointless.
2004		2852
2005	=back	2853	=back
2006		2854
2007	=head3 Examples	2855	=head3 Examples
2008		2856
…		…
2021		2869
2022	static ev_io iow [nfd];	2870	static ev_io iow [nfd];
2023	static ev_timer tw;	2871	static ev_timer tw;
2024		2872
2025	static void	2873	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2874	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2875	{
2028	}	2876	}
2029		2877
2030	// create io watchers for each fd and a timer before blocking	2878	// create io watchers for each fd and a timer before blocking
2031	static void	2879	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2880	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2881	{
2034	int timeout = 3600000;	2882	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2883	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2884	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2886
2039	/* the callback is illegal, but won't be called as we stop during check */	2887	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2888	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2889	ev_timer_start (loop, &tw);
2042		2890
2043	// create one ev_io per pollfd	2891	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2892	for (int i = 0; i < nfd; ++i)
2045	{	2893	{
…		…
2052	}	2900	}
2053	}	2901	}
2054		2902
2055	// stop all watchers after blocking	2903	// stop all watchers after blocking
2056	static void	2904	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2905	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2906	{
2059	ev_timer_stop (loop, &tw);	2907	ev_timer_stop (loop, &tw);
2060		2908
2061	for (int i = 0; i < nfd; ++i)	2909	for (int i = 0; i < nfd; ++i)
2062	{	2910	{
…		…
2101	}	2949	}
2102		2950
2103	// do not ever call adns_afterpoll	2951	// do not ever call adns_afterpoll
2104		2952
2105	Method 4: Do not use a prepare or check watcher because the module you	2953	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	2954	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	2955	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	2956	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2957	this approach, effectively embedding EV as a client into the horrible
		2958	libglib event loop.
2110		2959
2111	static gint	2960	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2961	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2962	{
2114	int got_events = 0;	2963	int got_events = 0;
…		…
2118		2967
2119	if (timeout >= 0)	2968	if (timeout >= 0)
2120	// create/start timer	2969	// create/start timer
2121		2970
2122	// poll	2971	// poll
2123	ev_loop (EV_A_ 0);	2972	ev_run (EV_A_ 0);
2124		2973
2125	// stop timer again	2974	// stop timer again
2126	if (timeout >= 0)	2975	if (timeout >= 0)
2127	ev_timer_stop (EV_A_ &to);	2976	ev_timer_stop (EV_A_ &to);
2128		2977
…		…
2145	prioritise I/O.	2994	prioritise I/O.
2146		2995
2147	As an example for a bug workaround, the kqueue backend might only support	2996	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	2997	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	2998	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	2999	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	3000	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	3001	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.	3002	C<kevent>, but at least you can use both mechanisms for what they are
		3003	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		3004
2155	As for prioritising I/O: rarely you have the case where some fds have	3005	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	3006	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	3007	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	3008	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.	3009	the rest in a second one, and embed the second one in the first.
2160		3010
2161	As long as the watcher is active, the callback will be invoked every time	3011	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	3012	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	3013	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	3014	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	3015	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	3016	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		3017
2169	As long as the watcher is started it will automatically handle events. The	3018	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	3019	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		3020
2174	Also, there have not currently been made special provisions for forking:	3021	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,	3022	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	3023	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	3024	C<ev_loop_fork> on the embedded loop.
2178		3025
2179	Unfortunately, not all backends are embeddable, only the ones returned by	3026	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3027	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	3028	portable one.
2182		3029
2183	So when you want to use this feature you will always have to be prepared	3030	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	3031	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	3032	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.	3033	create it, and if that fails, use the normal loop for everything.
		3034
		3035	=head3 C<ev_embed> and fork
		3036
		3037	While the C<ev_embed> watcher is running, forks in the embedding loop will
		3038	automatically be applied to the embedded loop as well, so no special
		3039	fork handling is required in that case. When the watcher is not running,
		3040	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		3041	as applicable.
2187		3042
2188	=head3 Watcher-Specific Functions and Data Members	3043	=head3 Watcher-Specific Functions and Data Members
2189		3044
2190	=over 4	3045	=over 4
2191		3046
…		…
2200	if you do not want that, you need to temporarily stop the embed watcher).	3055	if you do not want that, you need to temporarily stop the embed watcher).
2201		3056
2202	=item ev_embed_sweep (loop, ev_embed *)	3057	=item ev_embed_sweep (loop, ev_embed *)
2203		3058
2204	Make a single, non-blocking sweep over the embedded loop. This works	3059	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	3060	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2206	appropriate way for embedded loops.	3061	appropriate way for embedded loops.
2207		3062
2208	=item struct ev_loop *other [read-only]	3063	=item struct ev_loop *other [read-only]
2209		3064
2210	The embedded event loop.	3065	The embedded event loop.
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3074	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	3075	used).
2221		3076
2222	struct ev_loop *loop_hi = ev_default_init (0);	3077	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	3078	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	3079	ev_embed embed;
2225		3080
2226	// see if there is a chance of getting one that works	3081	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	3082	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3083	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3084	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	3098	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3099	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		3100
2246	struct ev_loop *loop = ev_default_init (0);	3101	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	3102	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	3103	ev_embed embed;
2249		3104
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3105	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3106	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	3107	{
2253	ev_embed_init (&embed, 0, loop_socket);	3108	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	3123	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	3124	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	3125	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	3126	handlers will be invoked, too, of course.
2272		3127
		3128	=head3 The special problem of life after fork - how is it possible?
		3129
		3130	Most uses of C<fork()> consist of forking, then some simple calls to set
		3131	up/change the process environment, followed by a call to C<exec()>. This
		3132	sequence should be handled by libev without any problems.
		3133
		3134	This changes when the application actually wants to do event handling
		3135	in the child, or both parent in child, in effect "continuing" after the
		3136	fork.
		3137
		3138	The default mode of operation (for libev, with application help to detect
		3139	forks) is to duplicate all the state in the child, as would be expected
		3140	when I<either> the parent I<or> the child process continues.
		3141
		3142	When both processes want to continue using libev, then this is usually the
		3143	wrong result. In that case, usually one process (typically the parent) is
		3144	supposed to continue with all watchers in place as before, while the other
		3145	process typically wants to start fresh, i.e. without any active watchers.
		3146
		3147	The cleanest and most efficient way to achieve that with libev is to
		3148	simply create a new event loop, which of course will be "empty", and
		3149	use that for new watchers. This has the advantage of not touching more
		3150	memory than necessary, and thus avoiding the copy-on-write, and the
		3151	disadvantage of having to use multiple event loops (which do not support
		3152	signal watchers).
		3153
		3154	When this is not possible, or you want to use the default loop for
		3155	other reasons, then in the process that wants to start "fresh", call
		3156	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3157	Destroying the default loop will "orphan" (not stop) all registered
		3158	watchers, so you have to be careful not to execute code that modifies
		3159	those watchers. Note also that in that case, you have to re-register any
		3160	signal watchers.
		3161
2273	=head3 Watcher-Specific Functions and Data Members	3162	=head3 Watcher-Specific Functions and Data Members
2274		3163
2275	=over 4	3164	=over 4
2276		3165
2277	=item ev_fork_init (ev_signal *, callback)	3166	=item ev_fork_init (ev_fork *, callback)
2278		3167
2279	Initialises and configures the fork watcher - it has no parameters of any	3168	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,	3169	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2281	believe me.	3170	really.
2282		3171
2283	=back	3172	=back
2284		3173
2285		3174
		3175	=head2 C<ev_cleanup> - even the best things end
		3176
		3177	Cleanup watchers are called just before the event loop is being destroyed
		3178	by a call to C<ev_loop_destroy>.
		3179
		3180	While there is no guarantee that the event loop gets destroyed, cleanup
		3181	watchers provide a convenient method to install cleanup hooks for your
		3182	program, worker threads and so on - you just to make sure to destroy the
		3183	loop when you want them to be invoked.
		3184
		3185	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3186	all other watchers, they do not keep a reference to the event loop (which
		3187	makes a lot of sense if you think about it). Like all other watchers, you
		3188	can call libev functions in the callback, except C<ev_cleanup_start>.
		3189
		3190	=head3 Watcher-Specific Functions and Data Members
		3191
		3192	=over 4
		3193
		3194	=item ev_cleanup_init (ev_cleanup *, callback)
		3195
		3196	Initialises and configures the cleanup watcher - it has no parameters of
		3197	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3198	pointless, I assure you.
		3199
		3200	=back
		3201
		3202	Example: Register an atexit handler to destroy the default loop, so any
		3203	cleanup functions are called.
		3204
		3205	static void
		3206	program_exits (void)
		3207	{
		3208	ev_loop_destroy (EV_DEFAULT_UC);
		3209	}
		3210
		3211	...
		3212	atexit (program_exits);
		3213
		3214
2286	=head2 C<ev_async> - how to wake up another event loop	3215	=head2 C<ev_async> - how to wake up an event loop
2287		3216
2288	In general, you cannot use an C<ev_loop> from multiple threads or other	3217	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	3218	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3219	loops - those are of course safe to use in different threads).
2291		3220
2292	Sometimes, however, you need to wake up another event loop you do not	3221	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	3222	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	3223	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	3224	it by calling C<ev_async_send>, which is thread- and signal safe.
2296	safe.
2297		3225
2298	This functionality is very similar to C<ev_signal> watchers, as signals,	3226	This functionality is very similar to C<ev_signal> watchers, as signals,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3227	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	3228	(i.e. the number of callback invocations may be less than the number of
2301	C<ev_async_sent> calls).	3229	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3230	of "global async watchers" by using a watcher on an otherwise unused
		3231	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3232	even without knowing which loop owns the signal.
2302		3233
2303	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2304	just the default loop.	3235	just the default loop.
2305		3236
2306	=head3 Queueing	3237	=head3 Queueing
2307		3238
2308	C<ev_async> does not support queueing of data in any way. The reason	3239	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	3240	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	3241	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	3242	need elaborate support such as pthreads or unportable memory access
		3243	semantics.
2312		3244
2313	That means that if you want to queue data, you have to provide your own	3245	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	3246	queue. But at least I can tell you how to implement locking around your
2315	queue:	3247	queue:
2316		3248
2317	=over 4	3249	=over 4
2318		3250
2319	=item queueing from a signal handler context	3251	=item queueing from a signal handler context
2320		3252
2321	To implement race-free queueing, you simply add to the queue in the signal	3253	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	3254	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3255	an example that does that for some fictitious SIGUSR1 handler:
2324		3256
2325	static ev_async mysig;	3257	static ev_async mysig;
2326		3258
2327	static void	3259	static void
2328	sigusr1_handler (void)	3260	sigusr1_handler (void)
…		…
2394	=over 4	3326	=over 4
2395		3327
2396	=item ev_async_init (ev_async *, callback)	3328	=item ev_async_init (ev_async *, callback)
2397		3329
2398	Initialises and configures the async watcher - it has no parameters of any	3330	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,	3331	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3332	trust me.
2401		3333
2402	=item ev_async_send (loop, ev_async *)	3334	=item ev_async_send (loop, ev_async *)
2403		3335
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3336	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	3337	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	3338	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	3339	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3340	section below on what exactly this means).
2409		3341
		3342	Note that, as with other watchers in libev, multiple events might get
		3343	compressed into a single callback invocation (another way to look at this
		3344	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3345	reset when the event loop detects that).
		3346
2410	This call incurs the overhead of a system call only once per loop iteration,	3347	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	3348	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3349	repeated calls to C<ev_async_send> for the same event loop.
2413		3350
2414	=item bool = ev_async_pending (ev_async *)	3351	=item bool = ev_async_pending (ev_async *)
2415		3352
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3353	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	3354	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	3357	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,	3358	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	3359	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.	3360	quickly check whether invoking the loop might be a good idea.
2424		3361
2425	Not that this does I<not> check whether the watcher itself is pending, only	3362	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3363	only whether it has been requested to make this watcher pending: there
		3364	is a time window between the event loop checking and resetting the async
		3365	notification, and the callback being invoked.
2427		3366
2428	=back	3367	=back
2429		3368
2430		3369
2431	=head1 OTHER FUNCTIONS	3370	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3374	=over 4
2436		3375
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3376	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3377
2439	This function combines a simple timer and an I/O watcher, calls your	3378	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3379	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	3380	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	3381	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3382	more watchers yourself.
2444		3383
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3384	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	3385	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3386	the given C<fd> and C<events> set will be created and started.
2448		3387
2449	If C<timeout> is less than 0, then no timeout watcher will be	3388	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	3389	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	3390	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3391
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3392	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	3393	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>	3394	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2457	value passed to C<ev_once>:	3395	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3396	a timeout and an io event at the same time - you probably should give io
		3397	events precedence.
		3398
		3399	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3400
2459	static void stdin_ready (int revents, void *arg)	3401	static void stdin_ready (int revents, void *arg)
2460	{	3402	{
		3403	if (revents & EV_READ)
		3404	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3405	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3406	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3407	}
2466		3408
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3409	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3410
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)	3411	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3412
2477	Feed an event on the given fd, as if a file descriptor backend detected	3413	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3414	the given events it.
2479		3415
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3416	=item ev_feed_signal_event (loop, int signum)
2481		3417
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3418	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2483	loop!).	3419	which is async-safe.
		3420
		3421	=back
		3422
		3423
		3424	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3425
		3426	This section explains some common idioms that are not immediately
		3427	obvious. Note that examples are sprinkled over the whole manual, and this
		3428	section only contains stuff that wouldn't fit anywhere else.
		3429
		3430	=over 4
		3431
		3432	=item Model/nested event loop invocations and exit conditions.
		3433
		3434	Often (especially in GUI toolkits) there are places where you have
		3435	I<modal> interaction, which is most easily implemented by recursively
		3436	invoking C<ev_run>.
		3437
		3438	This brings the problem of exiting - a callback might want to finish the
		3439	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3440	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3441	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3442	other combination: In these cases, C<ev_break> will not work alone.
		3443
		3444	The solution is to maintain "break this loop" variable for each C<ev_run>
		3445	invocation, and use a loop around C<ev_run> until the condition is
		3446	triggered, using C<EVRUN_ONCE>:
		3447
		3448	// main loop
		3449	int exit_main_loop = 0;
		3450
		3451	while (!exit_main_loop)
		3452	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3453
		3454	// in a model watcher
		3455	int exit_nested_loop = 0;
		3456
		3457	while (!exit_nested_loop)
		3458	ev_run (EV_A_ EVRUN_ONCE);
		3459
		3460	To exit from any of these loops, just set the corresponding exit variable:
		3461
		3462	// exit modal loop
		3463	exit_nested_loop = 1;
		3464
		3465	// exit main program, after modal loop is finished
		3466	exit_main_loop = 1;
		3467
		3468	// exit both
		3469	exit_main_loop = exit_nested_loop = 1;
2484		3470
2485	=back	3471	=back
2486		3472
2487		3473
2488	=head1 LIBEVENT EMULATION	3474	=head1 LIBEVENT EMULATION
2489		3475
2490	Libev offers a compatibility emulation layer for libevent. It cannot	3476	Libev offers a compatibility emulation layer for libevent. It cannot
2491	emulate the internals of libevent, so here are some usage hints:	3477	emulate the internals of libevent, so here are some usage hints:
2492		3478
2493	=over 4	3479	=over 4
		3480
		3481	=item * Only the libevent-1.4.1-beta API is being emulated.
		3482
		3483	This was the newest libevent version available when libev was implemented,
		3484	and is still mostly unchanged in 2010.
2494		3485
2495	=item * Use it by including <event.h>, as usual.	3486	=item * Use it by including <event.h>, as usual.
2496		3487
2497	=item * The following members are fully supported: ev_base, ev_callback,	3488	=item * The following members are fully supported: ev_base, ev_callback,
2498	ev_arg, ev_fd, ev_res, ev_events.	3489	ev_arg, ev_fd, ev_res, ev_events.
…		…
2504	=item * Priorities are not currently supported. Initialising priorities	3495	=item * Priorities are not currently supported. Initialising priorities
2505	will fail and all watchers will have the same priority, even though there	3496	will fail and all watchers will have the same priority, even though there
2506	is an ev_pri field.	3497	is an ev_pri field.
2507		3498
2508	=item * In libevent, the last base created gets the signals, in libev, the	3499	=item * In libevent, the last base created gets the signals, in libev, the
2509	first base created (== the default loop) gets the signals.	3500	base that registered the signal gets the signals.
2510		3501
2511	=item * Other members are not supported.	3502	=item * Other members are not supported.
2512		3503
2513	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3504	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2514	to use the libev header file and library.	3505	to use the libev header file and library.
…		…
2533	Care has been taken to keep the overhead low. The only data member the C++	3524	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	3525	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	3526	that the watcher is associated with (or no additional members at all if
2536	you disable C<EV_MULTIPLICITY> when embedding libev).	3527	you disable C<EV_MULTIPLICITY> when embedding libev).
2537		3528
2538	Currently, functions, and static and non-static member functions can be	3529	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	3530	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	3531	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	3532	you need support for other types of functors please contact the author
2542	it).	3533	(preferably after implementing it).
2543		3534
2544	Here is a list of things available in the C<ev> namespace:	3535	Here is a list of things available in the C<ev> namespace:
2545		3536
2546	=over 4	3537	=over 4
2547		3538
…		…
2565		3556
2566	=over 4	3557	=over 4
2567		3558
2568	=item ev::TYPE::TYPE ()	3559	=item ev::TYPE::TYPE ()
2569		3560
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3561	=item ev::TYPE::TYPE (loop)
2571		3562
2572	=item ev::TYPE::~TYPE	3563	=item ev::TYPE::~TYPE
2573		3564
2574	The constructor (optionally) takes an event loop to associate the watcher	3565	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3566	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3598
2608	myclass obj;	3599	myclass obj;
2609	ev::io iow;	3600	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3601	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3602
		3603	=item w->set (object *)
		3604
		3605	This is a variation of a method callback - leaving out the method to call
		3606	will default the method to C<operator ()>, which makes it possible to use
		3607	functor objects without having to manually specify the C<operator ()> all
		3608	the time. Incidentally, you can then also leave out the template argument
		3609	list.
		3610
		3611	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3612	int revents)>.
		3613
		3614	See the method-C<set> above for more details.
		3615
		3616	Example: use a functor object as callback.
		3617
		3618	struct myfunctor
		3619	{
		3620	void operator() (ev::io &w, int revents)
		3621	{
		3622	...
		3623	}
		3624	}
		3625
		3626	myfunctor f;
		3627
		3628	ev::io w;
		3629	w.set (&f);
		3630
2612	=item w->set<function> (void *data = 0)	3631	=item w->set<function> (void *data = 0)
2613		3632
2614	Also sets a callback, but uses a static method or plain function as	3633	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	3634	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3635	C<data> member and is free for you to use.
2617		3636
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3637	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3638
2620	See the method-C<set> above for more details.	3639	See the method-C<set> above for more details.
2621		3640
2622	Example:	3641	Example: Use a plain function as callback.
2623		3642
2624	static void io_cb (ev::io &w, int revents) { }	3643	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3644	iow.set <io_cb> ();
2626		3645
2627	=item w->set (struct ev_loop *)	3646	=item w->set (loop)
2628		3647
2629	Associates a different C<struct ev_loop> with this watcher. You can only	3648	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).	3649	do this when the watcher is inactive (and not pending either).
2631		3650
2632	=item w->set ([arguments])	3651	=item w->set ([arguments])
2633		3652
2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3653	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	3654	method or a suitable start method must be called at least once. Unlike the
2636	automatically stopped and restarted when reconfiguring it with this	3655	C counterpart, an active watcher gets automatically stopped and restarted
2637	method.	3656	when reconfiguring it with this method.
2638		3657
2639	=item w->start ()	3658	=item w->start ()
2640		3659
2641	Starts the watcher. Note that there is no C<loop> argument, as the	3660	Starts the watcher. Note that there is no C<loop> argument, as the
2642	constructor already stores the event loop.	3661	constructor already stores the event loop.
2643		3662
		3663	=item w->start ([arguments])
		3664
		3665	Instead of calling C<set> and C<start> methods separately, it is often
		3666	convenient to wrap them in one call. Uses the same type of arguments as
		3667	the configure C<set> method of the watcher.
		3668
2644	=item w->stop ()	3669	=item w->stop ()
2645		3670
2646	Stops the watcher if it is active. Again, no C<loop> argument.	3671	Stops the watcher if it is active. Again, no C<loop> argument.
2647		3672
2648	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3673	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2660		3685
2661	=back	3686	=back
2662		3687
2663	=back	3688	=back
2664		3689
2665	Example: Define a class with an IO and idle watcher, start one of them in	3690	Example: Define a class with two I/O and idle watchers, start the I/O
2666	the constructor.	3691	watchers in the constructor.
2667		3692
2668	class myclass	3693	class myclass
2669	{	3694	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3695	ev::io io ; void io_cb (ev::io &w, int revents);
		3696	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3697	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3698
2673	myclass (int fd)	3699	myclass (int fd)
2674	{	3700	{
2675	io .set <myclass, &myclass::io_cb > (this);	3701	io .set <myclass, &myclass::io_cb > (this);
		3702	io2 .set <myclass, &myclass::io2_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3703	idle.set <myclass, &myclass::idle_cb> (this);
2677		3704
2678	io.start (fd, ev::READ);	3705	io.set (fd, ev::WRITE); // configure the watcher
		3706	io.start (); // start it whenever convenient
		3707
		3708	io2.start (fd, ev::READ); // set + start in one call
2679	}	3709	}
2680	};	3710	};
2681		3711
2682		3712
2683	=head1 OTHER LANGUAGE BINDINGS	3713	=head1 OTHER LANGUAGE BINDINGS
…		…
2692	=item Perl	3722	=item Perl
2693		3723
2694	The EV module implements the full libev API and is actually used to test	3724	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,	3725	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3726	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	3727	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>).	3728	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3729	and C<EV::Glib>).
2699		3730
2700	It can be found and installed via CPAN, its homepage is at	3731	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3732	L<http://software.schmorp.de/pkg/EV>.
2702		3733
2703	=item Python	3734	=item Python
2704		3735
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3736	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	3737	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		3738
2712	=item Ruby	3739	=item Ruby
2713		3740
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3741	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	3742	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	3743	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3744	L<http://rev.rubyforge.org/>.
2718		3745
		3746	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3747	makes rev work even on mingw.
		3748
		3749	=item Haskell
		3750
		3751	A haskell binding to libev is available at
		3752	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3753
2719	=item D	3754	=item D
2720		3755
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3756	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>.	3757	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3758
		3759	=item Ocaml
		3760
		3761	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3762	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3763
		3764	=item Lua
		3765
		3766	Brian Maher has written a partial interface to libev for lua (at the
		3767	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3768	L<http://github.com/brimworks/lua-ev>.
2723		3769
2724	=back	3770	=back
2725		3771
2726		3772
2727	=head1 MACRO MAGIC	3773	=head1 MACRO MAGIC
…		…
2741	loop argument"). The C<EV_A> form is used when this is the sole argument,	3787	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:	3788	C<EV_A_> is used when other arguments are following. Example:
2743		3789
2744	ev_unref (EV_A);	3790	ev_unref (EV_A);
2745	ev_timer_add (EV_A_ watcher);	3791	ev_timer_add (EV_A_ watcher);
2746	ev_loop (EV_A_ 0);	3792	ev_run (EV_A_ 0);
2747		3793
2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3794	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2749	which is often provided by the following macro.	3795	which is often provided by the following macro.
2750		3796
2751	=item C<EV_P>, C<EV_P_>	3797	=item C<EV_P>, C<EV_P_>
…		…
2791	}	3837	}
2792		3838
2793	ev_check check;	3839	ev_check check;
2794	ev_check_init (&check, check_cb);	3840	ev_check_init (&check, check_cb);
2795	ev_check_start (EV_DEFAULT_ &check);	3841	ev_check_start (EV_DEFAULT_ &check);
2796	ev_loop (EV_DEFAULT_ 0);	3842	ev_run (EV_DEFAULT_ 0);
2797		3843
2798	=head1 EMBEDDING	3844	=head1 EMBEDDING
2799		3845
2800	Libev can (and often is) directly embedded into host	3846	Libev can (and often is) directly embedded into host
2801	applications. Examples of applications that embed it include the Deliantra	3847	applications. Examples of applications that embed it include the Deliantra
…		…
2828		3874
2829	#define EV_STANDALONE 1	3875	#define EV_STANDALONE 1
2830	#include "ev.h"	3876	#include "ev.h"
2831		3877
2832	Both header files and implementation files can be compiled with a C++	3878	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	3879	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3880	as a bug).
2835		3881
2836	You need the following files in your source tree, or in a directory	3882	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):	3883	in your include path (e.g. in libev/ when using -Ilibev):
2838		3884
…		…
2881	libev.m4	3927	libev.m4
2882		3928
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3929	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3930
2885	Libev can be configured via a variety of preprocessor symbols you have to	3931	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	3932	define before including (or compiling) any of its files. The default in
2887	autoconf is noted for every option.	3933	the absence of autoconf is documented for every option.
		3934
		3935	Symbols marked with "(h)" do not change the ABI, and can have different
		3936	values when compiling libev vs. including F<ev.h>, so it is permissible
		3937	to redefine them before including F<ev.h> without breaking compatibility
		3938	to a compiled library. All other symbols change the ABI, which means all
		3939	users of libev and the libev code itself must be compiled with compatible
		3940	settings.
2888		3941
2889	=over 4	3942	=over 4
2890		3943
		3944	=item EV_COMPAT3 (h)
		3945
		3946	Backwards compatibility is a major concern for libev. This is why this
		3947	release of libev comes with wrappers for the functions and symbols that
		3948	have been renamed between libev version 3 and 4.
		3949
		3950	You can disable these wrappers (to test compatibility with future
		3951	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3952	sources. This has the additional advantage that you can drop the C<struct>
		3953	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3954	typedef in that case.
		3955
		3956	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3957	and in some even more future version the compatibility code will be
		3958	removed completely.
		3959
2891	=item EV_STANDALONE	3960	=item EV_STANDALONE (h)
2892		3961
2893	Must always be C<1> if you do not use autoconf configuration, which	3962	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	3963	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3964	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	3965	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.	3966	F<event.h> that are not directly supported by the libev core alone.
2898		3967
		3968	In standalone mode, libev will still try to automatically deduce the
		3969	configuration, but has to be more conservative.
		3970
2899	=item EV_USE_MONOTONIC	3971	=item EV_USE_MONOTONIC
2900		3972
2901	If defined to be C<1>, libev will try to detect the availability of the	3973	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	3974	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	3975	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	3976	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3977	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>	3978	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3979	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3980
2909	=item EV_USE_REALTIME	3981	=item EV_USE_REALTIME
2910		3982
2911	If defined to be C<1>, libev will try to detect the availability of the	3983	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	3984	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	3985	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3986	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3987	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3988	correctness. See the note about libraries in the description of
		3989	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3990	C<EV_USE_CLOCK_SYSCALL>.
		3991
		3992	=item EV_USE_CLOCK_SYSCALL
		3993
		3994	If defined to be C<1>, libev will try to use a direct syscall instead
		3995	of calling the system-provided C<clock_gettime> function. This option
		3996	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3997	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3998	programs needlessly. Using a direct syscall is slightly slower (in
		3999	theory), because no optimised vdso implementation can be used, but avoids
		4000	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4001	higher, as it simplifies linking (no need for C<-lrt>).
2917		4002
2918	=item EV_USE_NANOSLEEP	4003	=item EV_USE_NANOSLEEP
2919		4004
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4005	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 ()>.	4006	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		4022
2938	=item EV_SELECT_USE_FD_SET	4023	=item EV_SELECT_USE_FD_SET
2939		4024
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	4025	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	4026	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	4027	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	4028	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	4029	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	4030	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	4031	configures the maximum size of the C<fd_set>.
2947		4032
2948	=item EV_SELECT_IS_WINSOCKET	4033	=item EV_SELECT_IS_WINSOCKET
2949		4034
2950	When defined to C<1>, the select backend will assume that	4035	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	4036	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	4038	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,	4039	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	4040	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	4041	on win32. Should not be defined on non-win32 platforms.
2957		4042
2958	=item EV_FD_TO_WIN32_HANDLE	4043	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		4044
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4045	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	4046	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	4047	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	4048	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.	4049	in which case they can provide this function to map fds to socket handles.
		4050
		4051	=item EV_WIN32_HANDLE_TO_FD(handle)
		4052
		4053	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4054	using the standard C<_open_osfhandle> function. For programs implementing
		4055	their own fd to handle mapping, overwriting this function makes it easier
		4056	to do so. This can be done by defining this macro to an appropriate value.
		4057
		4058	=item EV_WIN32_CLOSE_FD(fd)
		4059
		4060	If programs implement their own fd to handle mapping on win32, then this
		4061	macro can be used to override the C<close> function, useful to unregister
		4062	file descriptors again. Note that the replacement function has to close
		4063	the underlying OS handle.
2965		4064
2966	=item EV_USE_POLL	4065	=item EV_USE_POLL
2967		4066
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4067	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	4068	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.	4115	as well as for signal and thread safety in C<ev_async> watchers.
3017		4116
3018	In the absence of this define, libev will use C<sig_atomic_t volatile>	4117	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.	4118	(from F<signal.h>), which is usually good enough on most platforms.
3020		4119
3021	=item EV_H	4120	=item EV_H (h)
3022		4121
3023	The name of the F<ev.h> header file used to include it. The default if	4122	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	4123	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.	4124	used to virtually rename the F<ev.h> header file in case of conflicts.
3026		4125
3027	=item EV_CONFIG_H	4126	=item EV_CONFIG_H (h)
3028		4127
3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4128	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	4129	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3031	C<EV_H>, above.	4130	C<EV_H>, above.
3032		4131
3033	=item EV_EVENT_H	4132	=item EV_EVENT_H (h)
3034		4133
3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4134	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">.	4135	of how the F<event.h> header can be found, the default is C<"event.h">.
3037		4136
3038	=item EV_PROTOTYPES	4137	=item EV_PROTOTYPES (h)
3039		4138
3040	If defined to be C<0>, then F<ev.h> will not define any function	4139	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	4140	prototypes, but still define all the structs and other symbols. This is
3042	occasionally useful if you want to provide your own wrapper functions	4141	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	4142	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	4161	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	4162	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	4163	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	4164	fine.
3066		4165
3067	If your embedding application does not need any priorities, defining these both to	4166	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	4167	both to C<0> will save some memory and CPU.
3069		4168
3070	=item EV_PERIODIC_ENABLE	4169	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4170	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4171	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3071		4172
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	4173	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	4174	the respective watcher type is supported. If defined to be C<0>, then it
3074	code.	4175	is not. Disabling watcher types mainly saves code size.
3075		4176
3076	=item EV_IDLE_ENABLE	4177	=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		4178
3104	If you need to shave off some kilobytes of code at the expense of some	4179	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	4180	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	4181	certain subsets of functionality. The default is to enable all features
3107	much smaller 2-heap for timer management over the default 4-heap.	4182	that can be enabled on the platform.
		4183
		4184	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4185	with some broad features you want) and then selectively re-enable
		4186	additional parts you want, for example if you want everything minimal,
		4187	but multiple event loop support, async and child watchers and the poll
		4188	backend, use this:
		4189
		4190	#define EV_FEATURES 0
		4191	#define EV_MULTIPLICITY 1
		4192	#define EV_USE_POLL 1
		4193	#define EV_CHILD_ENABLE 1
		4194	#define EV_ASYNC_ENABLE 1
		4195
		4196	The actual value is a bitset, it can be a combination of the following
		4197	values:
		4198
		4199	=over 4
		4200
		4201	=item C<1> - faster/larger code
		4202
		4203	Use larger code to speed up some operations.
		4204
		4205	Currently this is used to override some inlining decisions (enlarging the
		4206	code size by roughly 30% on amd64).
		4207
		4208	When optimising for size, use of compiler flags such as C<-Os> with
		4209	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4210	assertions.
		4211
		4212	=item C<2> - faster/larger data structures
		4213
		4214	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4215	hash table sizes and so on. This will usually further increase code size
		4216	and can additionally have an effect on the size of data structures at
		4217	runtime.
		4218
		4219	=item C<4> - full API configuration
		4220
		4221	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4222	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4223
		4224	=item C<8> - full API
		4225
		4226	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4227	details on which parts of the API are still available without this
		4228	feature, and do not complain if this subset changes over time.
		4229
		4230	=item C<16> - enable all optional watcher types
		4231
		4232	Enables all optional watcher types. If you want to selectively enable
		4233	only some watcher types other than I/O and timers (e.g. prepare,
		4234	embed, async, child...) you can enable them manually by defining
		4235	C<EV_watchertype_ENABLE> to C<1> instead.
		4236
		4237	=item C<32> - enable all backends
		4238
		4239	This enables all backends - without this feature, you need to enable at
		4240	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4241
		4242	=item C<64> - enable OS-specific "helper" APIs
		4243
		4244	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4245	default.
		4246
		4247	=back
		4248
		4249	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4250	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4251	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4252	watchers, timers and monotonic clock support.
		4253
		4254	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4255	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4256	your program might be left out as well - a binary starting a timer and an
		4257	I/O watcher then might come out at only 5Kb.
		4258
		4259	=item EV_AVOID_STDIO
		4260
		4261	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4262	functions (printf, scanf, perror etc.). This will increase the code size
		4263	somewhat, but if your program doesn't otherwise depend on stdio and your
		4264	libc allows it, this avoids linking in the stdio library which is quite
		4265	big.
		4266
		4267	Note that error messages might become less precise when this option is
		4268	enabled.
		4269
		4270	=item EV_NSIG
		4271
		4272	The highest supported signal number, +1 (or, the number of
		4273	signals): Normally, libev tries to deduce the maximum number of signals
		4274	automatically, but sometimes this fails, in which case it can be
		4275	specified. Also, using a lower number than detected (C<32> should be
		4276	good for about any system in existence) can save some memory, as libev
		4277	statically allocates some 12-24 bytes per signal number.
3108		4278
3109	=item EV_PID_HASHSIZE	4279	=item EV_PID_HASHSIZE
3110		4280
3111	C<ev_child> watchers use a small hash table to distribute workload by	4281	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	4282	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	4283	usually more than enough. If you need to manage thousands of children you
3114	increase this value (I<must> be a power of two).	4284	might want to increase this value (I<must> be a power of two).
3115		4285
3116	=item EV_INOTIFY_HASHSIZE	4286	=item EV_INOTIFY_HASHSIZE
3117		4287
3118	C<ev_stat> watchers use a small hash table to distribute workload by	4288	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>),	4289	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>	4290	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	4291	C<ev_stat> watchers you might want to increase this value (I<must> be a
3122	two).	4292	power of two).
3123		4293
3124	=item EV_USE_4HEAP	4294	=item EV_USE_4HEAP
3125		4295
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4296	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	4297	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	4298	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4299	faster performance with many (thousands) of watchers.
3130		4300
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4301	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3132	(disabled).	4302	will be C<0>.
3133		4303
3134	=item EV_HEAP_CACHE_AT	4304	=item EV_HEAP_CACHE_AT
3135		4305
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4306	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	4307	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>),	4308	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,	4309	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	4310	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4311	noticeably with many (hundreds) of watchers.
3142		4312
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4313	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3144	(disabled).	4314	will be C<0>.
3145		4315
3146	=item EV_VERIFY	4316	=item EV_VERIFY
3147		4317
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4318	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	4319	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	4320	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	4321	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	4322	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	4323	verification code will be called very frequently, which will slow down
3154	libev considerably.	4324	libev considerably.
3155		4325
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4326	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3157	C<0.>	4327	will be C<0>.
3158		4328
3159	=item EV_COMMON	4329	=item EV_COMMON
3160		4330
3161	By default, all watchers have a C<void *data> member. By redefining	4331	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	4332	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,	4333	members. You have to define it each time you include one of the files,
3164	though, and it must be identical each time.	4334	though, and it must be identical each time.
3165		4335
3166	For example, the perl EV module uses something like this:	4336	For example, the perl EV module uses something like this:
3167		4337
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4349	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	4350	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	4351	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	4352	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++.	4353	method calls instead of plain function calls in C++.
		4354
		4355	=back
3184		4356
3185	=head2 EXPORTED API SYMBOLS	4357	=head2 EXPORTED API SYMBOLS
3186		4358
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4359	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	4360	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4390	file.
3219		4391
3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4392	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:	4393	that everybody includes and which overrides some configure choices:
3222		4394
3223	#define EV_MINIMAL 1	4395	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4396	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4397	#define EV_PREPARE_ENABLE 1
		4398	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4399	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4400	#define EV_CHILD_ENABLE 1
		4401	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4402	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4403
3233	#include "ev++.h"	4404	#include "ev++.h"
3234		4405
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4406	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4407
3237	#include "ev_cpp.h"	4408	#include "ev_cpp.h"
3238	#include "ev.c"	4409	#include "ev.c"
3239		4410
		4411	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4412
3241	=head1 THREADS AND COROUTINES	4413	=head2 THREADS AND COROUTINES
3242		4414
3243	=head2 THREADS	4415	=head3 THREADS
3244		4416
3245	Libev itself is thread-safe (unless the opposite is specifically	4417	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4418	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	4419	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:	4420	are no concurrent calls into any libev function with the same loop
		4421	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4422	of course): libev guarantees that different event loops share no data
3250	need locking.	4423	structures that need any locking.
3251		4424
3252	Or to put it differently: calls with different loop parameters can be done	4425	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4426	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	4427	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	4428	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4429	a mutex per loop).
3257		4430
3258	Specifically to support threads (and signal handlers), libev implements	4431	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4432	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4433	concurrency on the same event loop, namely waking it up "from the
		4434	outside".
3261		4435
3262	If you want to know which design (one loop, locking, or multiple loops	4436	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	4437	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4438	help you, but here is some generic advice:
3265		4439
3266	=over 4	4440	=over 4
3267		4441
3268	=item * most applications have a main thread: use the default libev loop	4442	=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.	4443	in that thread, or create a separate thread running only the default loop.
…		…
3281		4455
3282	Choosing a model is hard - look around, learn, know that usually you can do	4456	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	4457	better than you currently do :-)
3284		4458
3285	=item * often you need to talk to some other thread which blocks in the	4459	=item * often you need to talk to some other thread which blocks in the
		4460	event loop.
		4461
3286	event loop - C<ev_async> watchers can be used to wake them up from other	4462	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	4463	(or from signal contexts...).
3288		4464
3289	=item * some watcher types are only supported in the default loop - use	4465	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.	4466	work in the default loop by registering the signal watcher with the
		4467	default loop and triggering an C<ev_async> watcher from the default loop
		4468	watcher callback into the event loop interested in the signal.
3291		4469
3292	=back	4470	=back
3293		4471
		4472	=head4 THREAD LOCKING EXAMPLE
		4473
		4474	Here is a fictitious example of how to run an event loop in a different
		4475	thread than where callbacks are being invoked and watchers are
		4476	created/added/removed.
		4477
		4478	For a real-world example, see the C<EV::Loop::Async> perl module,
		4479	which uses exactly this technique (which is suited for many high-level
		4480	languages).
		4481
		4482	The example uses a pthread mutex to protect the loop data, a condition
		4483	variable to wait for callback invocations, an async watcher to notify the
		4484	event loop thread and an unspecified mechanism to wake up the main thread.
		4485
		4486	First, you need to associate some data with the event loop:
		4487
		4488	typedef struct {
		4489	mutex_t lock; /* global loop lock */
		4490	ev_async async_w;
		4491	thread_t tid;
		4492	cond_t invoke_cv;
		4493	} userdata;
		4494
		4495	void prepare_loop (EV_P)
		4496	{
		4497	// for simplicity, we use a static userdata struct.
		4498	static userdata u;
		4499
		4500	ev_async_init (&u->async_w, async_cb);
		4501	ev_async_start (EV_A_ &u->async_w);
		4502
		4503	pthread_mutex_init (&u->lock, 0);
		4504	pthread_cond_init (&u->invoke_cv, 0);
		4505
		4506	// now associate this with the loop
		4507	ev_set_userdata (EV_A_ u);
		4508	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4509	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4510
		4511	// then create the thread running ev_loop
		4512	pthread_create (&u->tid, 0, l_run, EV_A);
		4513	}
		4514
		4515	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4516	solely to wake up the event loop so it takes notice of any new watchers
		4517	that might have been added:
		4518
		4519	static void
		4520	async_cb (EV_P_ ev_async *w, int revents)
		4521	{
		4522	// just used for the side effects
		4523	}
		4524
		4525	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4526	protecting the loop data, respectively.
		4527
		4528	static void
		4529	l_release (EV_P)
		4530	{
		4531	userdata *u = ev_userdata (EV_A);
		4532	pthread_mutex_unlock (&u->lock);
		4533	}
		4534
		4535	static void
		4536	l_acquire (EV_P)
		4537	{
		4538	userdata *u = ev_userdata (EV_A);
		4539	pthread_mutex_lock (&u->lock);
		4540	}
		4541
		4542	The event loop thread first acquires the mutex, and then jumps straight
		4543	into C<ev_run>:
		4544
		4545	void *
		4546	l_run (void *thr_arg)
		4547	{
		4548	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4549
		4550	l_acquire (EV_A);
		4551	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4552	ev_run (EV_A_ 0);
		4553	l_release (EV_A);
		4554
		4555	return 0;
		4556	}
		4557
		4558	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4559	signal the main thread via some unspecified mechanism (signals? pipe
		4560	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4561	have been called (in a while loop because a) spurious wakeups are possible
		4562	and b) skipping inter-thread-communication when there are no pending
		4563	watchers is very beneficial):
		4564
		4565	static void
		4566	l_invoke (EV_P)
		4567	{
		4568	userdata *u = ev_userdata (EV_A);
		4569
		4570	while (ev_pending_count (EV_A))
		4571	{
		4572	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4573	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4574	}
		4575	}
		4576
		4577	Now, whenever the main thread gets told to invoke pending watchers, it
		4578	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4579	thread to continue:
		4580
		4581	static void
		4582	real_invoke_pending (EV_P)
		4583	{
		4584	userdata *u = ev_userdata (EV_A);
		4585
		4586	pthread_mutex_lock (&u->lock);
		4587	ev_invoke_pending (EV_A);
		4588	pthread_cond_signal (&u->invoke_cv);
		4589	pthread_mutex_unlock (&u->lock);
		4590	}
		4591
		4592	Whenever you want to start/stop a watcher or do other modifications to an
		4593	event loop, you will now have to lock:
		4594
		4595	ev_timer timeout_watcher;
		4596	userdata *u = ev_userdata (EV_A);
		4597
		4598	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4599
		4600	pthread_mutex_lock (&u->lock);
		4601	ev_timer_start (EV_A_ &timeout_watcher);
		4602	ev_async_send (EV_A_ &u->async_w);
		4603	pthread_mutex_unlock (&u->lock);
		4604
		4605	Note that sending the C<ev_async> watcher is required because otherwise
		4606	an event loop currently blocking in the kernel will have no knowledge
		4607	about the newly added timer. By waking up the loop it will pick up any new
		4608	watchers in the next event loop iteration.
		4609
3294	=head2 COROUTINES	4610	=head3 COROUTINES
3295		4611
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	4612	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	4613	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	4614	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	4615	different coroutines, and switch freely between both coroutines running
3300	loop, as long as you don't confuse yourself). The only exception is that	4616	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.	4617	that you must not do this from C<ev_periodic> reschedule callbacks.
3302		4618
3303	Care has been taken to ensure that libev does not keep local state inside	4619	Care has been taken to ensure that libev does not keep local state inside
3304	C<ev_loop>, and other calls do not usually allow coroutine switches.	4620	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4621	they do not call any callbacks.
3305		4622
		4623	=head2 COMPILER WARNINGS
3306		4624
3307	=head1 COMPLEXITIES	4625	Depending on your compiler and compiler settings, you might get no or a
		4626	lot of warnings when compiling libev code. Some people are apparently
		4627	scared by this.
3308		4628
3309	In this section the complexities of (many of) the algorithms used inside	4629	However, these are unavoidable for many reasons. For one, each compiler
3310	libev will be explained. For complexity discussions about backends see the	4630	has different warnings, and each user has different tastes regarding
3311	documentation for C<ev_default_init>.	4631	warning options. "Warn-free" code therefore cannot be a goal except when
		4632	targeting a specific compiler and compiler-version.
3312		4633
3313	All of the following are about amortised time: If an array needs to be	4634	Another reason is that some compiler warnings require elaborate
3314	extended, libev needs to realloc and move the whole array, but this	4635	workarounds, or other changes to the code that make it less clear and less
3315	happens asymptotically never with higher number of elements, so O(1) might	4636	maintainable.
3316	mean it might do a lengthy realloc operation in rare cases, but on average
3317	it is much faster and asymptotically approaches constant time.
3318		4637
3319	=over 4	4638	And of course, some compiler warnings are just plain stupid, or simply
		4639	wrong (because they don't actually warn about the condition their message
		4640	seems to warn about). For example, certain older gcc versions had some
		4641	warnings that resulted in an extreme number of false positives. These have
		4642	been fixed, but some people still insist on making code warn-free with
		4643	such buggy versions.
3320		4644
3321	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4645	While libev is written to generate as few warnings as possible,
		4646	"warn-free" code is not a goal, and it is recommended not to build libev
		4647	with any compiler warnings enabled unless you are prepared to cope with
		4648	them (e.g. by ignoring them). Remember that warnings are just that:
		4649	warnings, not errors, or proof of bugs.
3322		4650
3323	This means that, when you have a watcher that triggers in one hour and
3324	there are 100 watchers that would trigger before that then inserting will
3325	have to skip roughly seven (C<ld 100>) of these watchers.
3326		4651
3327	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4652	=head2 VALGRIND
3328		4653
3329	That means that changing a timer costs less than removing/adding them	4654	Valgrind has a special section here because it is a popular tool that is
3330	as only the relative motion in the event queue has to be paid for.	4655	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3331		4656
3332	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4657	If you think you found a bug (memory leak, uninitialised data access etc.)
		4658	in libev, then check twice: If valgrind reports something like:
3333		4659
3334	These just add the watcher into an array or at the head of a list.	4660	==2274== definitely lost: 0 bytes in 0 blocks.
		4661	==2274== possibly lost: 0 bytes in 0 blocks.
		4662	==2274== still reachable: 256 bytes in 1 blocks.
3335		4663
3336	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4664	Then there is no memory leak, just as memory accounted to global variables
		4665	is not a memleak - the memory is still being referenced, and didn't leak.
3337		4666
3338	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4667	Similarly, under some circumstances, valgrind might report kernel bugs
		4668	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4669	although an acceptable workaround has been found here), or it might be
		4670	confused.
3339		4671
3340	These watchers are stored in lists then need to be walked to find the	4672	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3341	correct watcher to remove. The lists are usually short (you don't usually	4673	make it into some kind of religion.
3342	have many watchers waiting for the same fd or signal).
3343		4674
3344	=item Finding the next timer in each loop iteration: O(1)	4675	If you are unsure about something, feel free to contact the mailing list
		4676	with the full valgrind report and an explanation on why you think this
		4677	is a bug in libev (best check the archives, too :). However, don't be
		4678	annoyed when you get a brisk "this is no bug" answer and take the chance
		4679	of learning how to interpret valgrind properly.
3345		4680
3346	By virtue of using a binary or 4-heap, the next timer is always found at a	4681	If you need, for some reason, empty reports from valgrind for your project
3347	fixed position in the storage array.	4682	I suggest using suppression lists.
3348		4683
3349	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3350		4684
3351	A change means an I/O watcher gets started or stopped, which requires	4685	=head1 PORTABILITY NOTES
3352	libev to recalculate its status (and possibly tell the kernel, depending
3353	on backend and whether C<ev_io_set> was used).
3354		4686
3355	=item Activating one watcher (putting it into the pending state): O(1)	4687	=head2 GNU/LINUX 32 BIT LIMITATIONS
3356		4688
3357	=item Priority handling: O(number_of_priorities)	4689	GNU/Linux is the only common platform that supports 64 bit file/large file
		4690	interfaces but I<disables> them by default.
3358		4691
3359	Priorities are implemented by allocating some space for each	4692	That means that libev compiled in the default environment doesn't support
3360	priority. When doing priority-based operations, libev usually has to	4693	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3361	linearly search all the priorities, but starting/stopping and activating
3362	watchers becomes O(1) w.r.t. priority handling.
3363		4694
3364	=item Sending an ev_async: O(1)	4695	Unfortunately, many programs try to work around this GNU/Linux issue
		4696	by enabling the large file API, which makes them incompatible with the
		4697	standard libev compiled for their system.
3365		4698
3366	=item Processing ev_async_send: O(number_of_async_watchers)	4699	Likewise, libev cannot enable the large file API itself as this would
		4700	suddenly make it incompatible to the default compile time environment,
		4701	i.e. all programs not using special compile switches.
3367		4702
3368	=item Processing signals: O(max_signal_number)	4703	=head2 OS/X AND DARWIN BUGS
3369		4704
3370	Sending involves a system call I<iff> there were no other C<ev_async_send>	4705	The whole thing is a bug if you ask me - basically any system interface
3371	calls in the current loop iteration. Checking for async and signal events	4706	you touch is broken, whether it is locales, poll, kqueue or even the
3372	involves iterating over all running async watchers or all signal numbers.	4707	OpenGL drivers.
3373		4708
3374	=back	4709	=head3 C<kqueue> is buggy
3375		4710
		4711	The kqueue syscall is broken in all known versions - most versions support
		4712	only sockets, many support pipes.
3376		4713
		4714	Libev tries to work around this by not using C<kqueue> by default on this
		4715	rotten platform, but of course you can still ask for it when creating a
		4716	loop - embedding a socket-only kqueue loop into a select-based one is
		4717	probably going to work well.
		4718
		4719	=head3 C<poll> is buggy
		4720
		4721	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4722	implementation by something calling C<kqueue> internally around the 10.5.6
		4723	release, so now C<kqueue> I<and> C<poll> are broken.
		4724
		4725	Libev tries to work around this by not using C<poll> by default on
		4726	this rotten platform, but of course you can still ask for it when creating
		4727	a loop.
		4728
		4729	=head3 C<select> is buggy
		4730
		4731	All that's left is C<select>, and of course Apple found a way to fuck this
		4732	one up as well: On OS/X, C<select> actively limits the number of file
		4733	descriptors you can pass in to 1024 - your program suddenly crashes when
		4734	you use more.
		4735
		4736	There is an undocumented "workaround" for this - defining
		4737	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4738	work on OS/X.
		4739
		4740	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4741
		4742	=head3 C<errno> reentrancy
		4743
		4744	The default compile environment on Solaris is unfortunately so
		4745	thread-unsafe that you can't even use components/libraries compiled
		4746	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4747	defined by default. A valid, if stupid, implementation choice.
		4748
		4749	If you want to use libev in threaded environments you have to make sure
		4750	it's compiled with C<_REENTRANT> defined.
		4751
		4752	=head3 Event port backend
		4753
		4754	The scalable event interface for Solaris is called "event
		4755	ports". Unfortunately, this mechanism is very buggy in all major
		4756	releases. If you run into high CPU usage, your program freezes or you get
		4757	a large number of spurious wakeups, make sure you have all the relevant
		4758	and latest kernel patches applied. No, I don't know which ones, but there
		4759	are multiple ones to apply, and afterwards, event ports actually work
		4760	great.
		4761
		4762	If you can't get it to work, you can try running the program by setting
		4763	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4764	C<select> backends.
		4765
		4766	=head2 AIX POLL BUG
		4767
		4768	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4769	this by trying to avoid the poll backend altogether (i.e. it's not even
		4770	compiled in), which normally isn't a big problem as C<select> works fine
		4771	with large bitsets on AIX, and AIX is dead anyway.
		4772
3377	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4773	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4774
		4775	=head3 General issues
3378		4776
3379	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4777	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3380	requires, and its I/O model is fundamentally incompatible with the POSIX	4778	requires, and its I/O model is fundamentally incompatible with the POSIX
3381	model. Libev still offers limited functionality on this platform in	4779	model. Libev still offers limited functionality on this platform in
3382	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4780	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3383	descriptors. This only applies when using Win32 natively, not when using	4781	descriptors. This only applies when using Win32 natively, not when using
3384	e.g. cygwin.	4782	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4783	as every compielr comes with a slightly differently broken/incompatible
		4784	environment.
3385		4785
3386	Lifting these limitations would basically require the full	4786	Lifting these limitations would basically require the full
3387	re-implementation of the I/O system. If you are into these kinds of	4787	re-implementation of the I/O system. If you are into this kind of thing,
3388	things, then note that glib does exactly that for you in a very portable	4788	then note that glib does exactly that for you in a very portable way (note
3389	way (note also that glib is the slowest event library known to man).	4789	also that glib is the slowest event library known to man).
3390		4790
3391	There is no supported compilation method available on windows except	4791	There is no supported compilation method available on windows except
3392	embedding it into other applications.	4792	embedding it into other applications.
		4793
		4794	Sensible signal handling is officially unsupported by Microsoft - libev
		4795	tries its best, but under most conditions, signals will simply not work.
3393		4796
3394	Not a libev limitation but worth mentioning: windows apparently doesn't	4797	Not a libev limitation but worth mentioning: windows apparently doesn't
3395	accept large writes: instead of resulting in a partial write, windows will	4798	accept large writes: instead of resulting in a partial write, windows will
3396	either accept everything or return C<ENOBUFS> if the buffer is too large,	4799	either accept everything or return C<ENOBUFS> if the buffer is too large,
3397	so make sure you only write small amounts into your sockets (less than a	4800	so make sure you only write small amounts into your sockets (less than a
3398	megabyte seems safe, but thsi apparently depends on the amount of memory	4801	megabyte seems safe, but this apparently depends on the amount of memory
3399	available).	4802	available).
3400		4803
3401	Due to the many, low, and arbitrary limits on the win32 platform and	4804	Due to the many, low, and arbitrary limits on the win32 platform and
3402	the abysmal performance of winsockets, using a large number of sockets	4805	the abysmal performance of winsockets, using a large number of sockets
3403	is not recommended (and not reasonable). If your program needs to use	4806	is not recommended (and not reasonable). If your program needs to use
3404	more than a hundred or so sockets, then likely it needs to use a totally	4807	more than a hundred or so sockets, then likely it needs to use a totally
3405	different implementation for windows, as libev offers the POSIX readiness	4808	different implementation for windows, as libev offers the POSIX readiness
3406	notification model, which cannot be implemented efficiently on windows	4809	notification model, which cannot be implemented efficiently on windows
3407	(Microsoft monopoly games).	4810	(due to Microsoft monopoly games).
3408		4811
3409	A typical way to use libev under windows is to embed it (see the embedding	4812	A typical way to use libev under windows is to embed it (see the embedding
3410	section for details) and use the following F<evwrap.h> header file instead	4813	section for details) and use the following F<evwrap.h> header file instead
3411	of F<ev.h>:	4814	of F<ev.h>:
3412		4815
…		…
3414	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4817	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3415		4818
3416	#include "ev.h"	4819	#include "ev.h"
3417		4820
3418	And compile the following F<evwrap.c> file into your project (make sure	4821	And compile the following F<evwrap.c> file into your project (make sure
3419	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4822	you do I<not> compile the F<ev.c> or any other embedded source files!):
3420		4823
3421	#include "evwrap.h"	4824	#include "evwrap.h"
3422	#include "ev.c"	4825	#include "ev.c"
3423		4826
3424	=over 4
3425
3426	=item The winsocket select function	4827	=head3 The winsocket C<select> function
3427		4828
3428	The winsocket C<select> function doesn't follow POSIX in that it	4829	The winsocket C<select> function doesn't follow POSIX in that it
3429	requires socket I<handles> and not socket I<file descriptors> (it is	4830	requires socket I<handles> and not socket I<file descriptors> (it is
3430	also extremely buggy). This makes select very inefficient, and also	4831	also extremely buggy). This makes select very inefficient, and also
3431	requires a mapping from file descriptors to socket handles (the Microsoft	4832	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3440	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4841	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3441		4842
3442	Note that winsockets handling of fd sets is O(n), so you can easily get a	4843	Note that winsockets handling of fd sets is O(n), so you can easily get a
3443	complexity in the O(n²) range when using win32.	4844	complexity in the O(n²) range when using win32.
3444		4845
3445	=item Limited number of file descriptors	4846	=head3 Limited number of file descriptors
3446		4847
3447	Windows has numerous arbitrary (and low) limits on things.	4848	Windows has numerous arbitrary (and low) limits on things.
3448		4849
3449	Early versions of winsocket's select only supported waiting for a maximum	4850	Early versions of winsocket's select only supported waiting for a maximum
3450	of C<64> handles (probably owning to the fact that all windows kernels	4851	of C<64> handles (probably owning to the fact that all windows kernels
3451	can only wait for C<64> things at the same time internally; Microsoft	4852	can only wait for C<64> things at the same time internally; Microsoft
3452	recommends spawning a chain of threads and wait for 63 handles and the	4853	recommends spawning a chain of threads and wait for 63 handles and the
3453	previous thread in each. Great).	4854	previous thread in each. Sounds great!).
3454		4855
3455	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4856	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3456	to some high number (e.g. C<2048>) before compiling the winsocket select	4857	to some high number (e.g. C<2048>) before compiling the winsocket select
3457	call (which might be in libev or elsewhere, for example, perl does its own	4858	call (which might be in libev or elsewhere, for example, perl and many
3458	select emulation on windows).	4859	other interpreters do their own select emulation on windows).
3459		4860
3460	Another limit is the number of file descriptors in the Microsoft runtime	4861	Another limit is the number of file descriptors in the Microsoft runtime
3461	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4862	libraries, which by default is C<64> (there must be a hidden I<64>
3462	or something like this inside Microsoft). You can increase this by calling	4863	fetish or something like this inside Microsoft). You can increase this
3463	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4864	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3464	arbitrary limit), but is broken in many versions of the Microsoft runtime	4865	(another arbitrary limit), but is broken in many versions of the Microsoft
3465	libraries.
3466
3467	This might get you to about C<512> or C<2048> sockets (depending on	4866	runtime libraries. This might get you to about C<512> or C<2048> sockets
3468	windows version and/or the phase of the moon). To get more, you need to	4867	(depending on windows version and/or the phase of the moon). To get more,
3469	wrap all I/O functions and provide your own fd management, but the cost of	4868	you need to wrap all I/O functions and provide your own fd management, but
3470	calling select (O(n²)) will likely make this unworkable.	4869	the cost of calling select (O(n²)) will likely make this unworkable.
3471		4870
3472	=back
3473
3474
3475	=head1 PORTABILITY REQUIREMENTS	4871	=head2 PORTABILITY REQUIREMENTS
3476		4872
3477	In addition to a working ISO-C implementation, libev relies on a few	4873	In addition to a working ISO-C implementation and of course the
3478	additional extensions:	4874	backend-specific APIs, libev relies on a few additional extensions:
3479		4875
3480	=over 4	4876	=over 4
3481		4877
3482	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4878	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3483	calling conventions regardless of C<ev_watcher_type *>.	4879	calling conventions regardless of C<ev_watcher_type *>.
…		…
3486	structure (guaranteed by POSIX but not by ISO C for example), but it also	4882	structure (guaranteed by POSIX but not by ISO C for example), but it also
3487	assumes that the same (machine) code can be used to call any watcher	4883	assumes that the same (machine) code can be used to call any watcher
3488	callback: The watcher callbacks have different type signatures, but libev	4884	callback: The watcher callbacks have different type signatures, but libev
3489	calls them using an C<ev_watcher *> internally.	4885	calls them using an C<ev_watcher *> internally.
3490		4886
		4887	=item pointer accesses must be thread-atomic
		4888
		4889	Accessing a pointer value must be atomic, it must both be readable and
		4890	writable in one piece - this is the case on all current architectures.
		4891
3491	=item C<sig_atomic_t volatile> must be thread-atomic as well	4892	=item C<sig_atomic_t volatile> must be thread-atomic as well
3492		4893
3493	The type C<sig_atomic_t volatile> (or whatever is defined as	4894	The type C<sig_atomic_t volatile> (or whatever is defined as
3494	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4895	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3495	threads. This is not part of the specification for C<sig_atomic_t>, but is	4896	threads. This is not part of the specification for C<sig_atomic_t>, but is
3496	believed to be sufficiently portable.	4897	believed to be sufficiently portable.
3497		4898
3498	=item C<sigprocmask> must work in a threaded environment	4899	=item C<sigprocmask> must work in a threaded environment
3499		4900
…		…
3508	except the initial one, and run the default loop in the initial thread as	4909	except the initial one, and run the default loop in the initial thread as
3509	well.	4910	well.
3510		4911
3511	=item C<long> must be large enough for common memory allocation sizes	4912	=item C<long> must be large enough for common memory allocation sizes
3512		4913
3513	To improve portability and simplify using libev, libev uses C<long>	4914	To improve portability and simplify its API, libev uses C<long> internally
3514	internally instead of C<size_t> when allocating its data structures. On	4915	instead of C<size_t> when allocating its data structures. On non-POSIX
3515	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4916	systems (Microsoft...) this might be unexpectedly low, but is still at
3516	is still at least 31 bits everywhere, which is enough for hundreds of	4917	least 31 bits everywhere, which is enough for hundreds of millions of
3517	millions of watchers.	4918	watchers.
3518		4919
3519	=item C<double> must hold a time value in seconds with enough accuracy	4920	=item C<double> must hold a time value in seconds with enough accuracy
3520		4921
3521	The type C<double> is used to represent timestamps. It is required to	4922	The type C<double> is used to represent timestamps. It is required to
3522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4923	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3523	enough for at least into the year 4000. This requirement is fulfilled by	4924	good enough for at least into the year 4000 with millisecond accuracy
		4925	(the design goal for libev). This requirement is overfulfilled by
3524	implementations implementing IEEE 754 (basically all existing ones).	4926	implementations using IEEE 754, which is basically all existing ones. With
		4927	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3525		4928
3526	=back	4929	=back
3527		4930
3528	If you know of other additional requirements drop me a note.	4931	If you know of other additional requirements drop me a note.
3529		4932
3530		4933
3531	=head1 COMPILER WARNINGS	4934	=head1 ALGORITHMIC COMPLEXITIES
3532		4935
3533	Depending on your compiler and compiler settings, you might get no or a	4936	In this section the complexities of (many of) the algorithms used inside
3534	lot of warnings when compiling libev code. Some people are apparently	4937	libev will be documented. For complexity discussions about backends see
3535	scared by this.	4938	the documentation for C<ev_default_init>.
3536		4939
3537	However, these are unavoidable for many reasons. For one, each compiler	4940	All of the following are about amortised time: If an array needs to be
3538	has different warnings, and each user has different tastes regarding	4941	extended, libev needs to realloc and move the whole array, but this
3539	warning options. "Warn-free" code therefore cannot be a goal except when	4942	happens asymptotically rarer with higher number of elements, so O(1) might
3540	targeting a specific compiler and compiler-version.	4943	mean that libev does a lengthy realloc operation in rare cases, but on
		4944	average it is much faster and asymptotically approaches constant time.
3541		4945
3542	Another reason is that some compiler warnings require elaborate	4946	=over 4
3543	workarounds, or other changes to the code that make it less clear and less
3544	maintainable.
3545		4947
3546	And of course, some compiler warnings are just plain stupid, or simply	4948	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3547	wrong (because they don't actually warn about the condition their message
3548	seems to warn about).
3549		4949
3550	While libev is written to generate as few warnings as possible,	4950	This means that, when you have a watcher that triggers in one hour and
3551	"warn-free" code is not a goal, and it is recommended not to build libev	4951	there are 100 watchers that would trigger before that, then inserting will
3552	with any compiler warnings enabled unless you are prepared to cope with	4952	have to skip roughly seven (C<ld 100>) of these watchers.
3553	them (e.g. by ignoring them). Remember that warnings are just that:
3554	warnings, not errors, or proof of bugs.
3555		4953
		4954	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3556		4955
3557	=head1 VALGRIND	4956	That means that changing a timer costs less than removing/adding them,
		4957	as only the relative motion in the event queue has to be paid for.
3558		4958
3559	Valgrind has a special section here because it is a popular tool that is	4959	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3560	highly useful, but valgrind reports are very hard to interpret.
3561		4960
3562	If you think you found a bug (memory leak, uninitialised data access etc.)	4961	These just add the watcher into an array or at the head of a list.
3563	in libev, then check twice: If valgrind reports something like:
3564		4962
3565	==2274== definitely lost: 0 bytes in 0 blocks.	4963	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3566	==2274== possibly lost: 0 bytes in 0 blocks.
3567	==2274== still reachable: 256 bytes in 1 blocks.
3568		4964
3569	Then there is no memory leak. Similarly, under some circumstances,	4965	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3570	valgrind might report kernel bugs as if it were a bug in libev, or it
3571	might be confused (it is a very good tool, but only a tool).
3572		4966
3573	If you are unsure about something, feel free to contact the mailing list	4967	These watchers are stored in lists, so they need to be walked to find the
3574	with the full valgrind report and an explanation on why you think this is	4968	correct watcher to remove. The lists are usually short (you don't usually
3575	a bug in libev. However, don't be annoyed when you get a brisk "this is	4969	have many watchers waiting for the same fd or signal: one is typical, two
3576	no bug" answer and take the chance of learning how to interpret valgrind	4970	is rare).
3577	properly.
3578		4971
3579	If you need, for some reason, empty reports from valgrind for your project	4972	=item Finding the next timer in each loop iteration: O(1)
3580	I suggest using suppression lists.
3581		4973
		4974	By virtue of using a binary or 4-heap, the next timer is always found at a
		4975	fixed position in the storage array.
		4976
		4977	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4978
		4979	A change means an I/O watcher gets started or stopped, which requires
		4980	libev to recalculate its status (and possibly tell the kernel, depending
		4981	on backend and whether C<ev_io_set> was used).
		4982
		4983	=item Activating one watcher (putting it into the pending state): O(1)
		4984
		4985	=item Priority handling: O(number_of_priorities)
		4986
		4987	Priorities are implemented by allocating some space for each
		4988	priority. When doing priority-based operations, libev usually has to
		4989	linearly search all the priorities, but starting/stopping and activating
		4990	watchers becomes O(1) with respect to priority handling.
		4991
		4992	=item Sending an ev_async: O(1)
		4993
		4994	=item Processing ev_async_send: O(number_of_async_watchers)
		4995
		4996	=item Processing signals: O(max_signal_number)
		4997
		4998	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4999	calls in the current loop iteration. Checking for async and signal events
		5000	involves iterating over all running async watchers or all signal numbers.
		5001
		5002	=back
		5003
		5004
		5005	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5006
		5007	The major version 4 introduced some incompatible changes to the API.
		5008
		5009	At the moment, the C<ev.h> header file provides compatibility definitions
		5010	for all changes, so most programs should still compile. The compatibility
		5011	layer might be removed in later versions of libev, so better update to the
		5012	new API early than late.
		5013
		5014	=over 4
		5015
		5016	=item C<EV_COMPAT3> backwards compatibility mechanism
		5017
		5018	The backward compatibility mechanism can be controlled by
		5019	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5020	section.
		5021
		5022	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5023
		5024	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5025
		5026	ev_loop_destroy (EV_DEFAULT_UC);
		5027	ev_loop_fork (EV_DEFAULT);
		5028
		5029	=item function/symbol renames
		5030
		5031	A number of functions and symbols have been renamed:
		5032
		5033	ev_loop => ev_run
		5034	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5035	EVLOOP_ONESHOT => EVRUN_ONCE
		5036
		5037	ev_unloop => ev_break
		5038	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5039	EVUNLOOP_ONE => EVBREAK_ONE
		5040	EVUNLOOP_ALL => EVBREAK_ALL
		5041
		5042	EV_TIMEOUT => EV_TIMER
		5043
		5044	ev_loop_count => ev_iteration
		5045	ev_loop_depth => ev_depth
		5046	ev_loop_verify => ev_verify
		5047
		5048	Most functions working on C<struct ev_loop> objects don't have an
		5049	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5050	associated constants have been renamed to not collide with the C<struct
		5051	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5052	as all other watcher types. Note that C<ev_loop_fork> is still called
		5053	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5054	typedef.
		5055
		5056	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5057
		5058	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5059	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5060	and work, but the library code will of course be larger.
		5061
		5062	=back
		5063
		5064
		5065	=head1 GLOSSARY
		5066
		5067	=over 4
		5068
		5069	=item active
		5070
		5071	A watcher is active as long as it has been started and not yet stopped.
		5072	See L<WATCHER STATES> for details.
		5073
		5074	=item application
		5075
		5076	In this document, an application is whatever is using libev.
		5077
		5078	=item backend
		5079
		5080	The part of the code dealing with the operating system interfaces.
		5081
		5082	=item callback
		5083
		5084	The address of a function that is called when some event has been
		5085	detected. Callbacks are being passed the event loop, the watcher that
		5086	received the event, and the actual event bitset.
		5087
		5088	=item callback/watcher invocation
		5089
		5090	The act of calling the callback associated with a watcher.
		5091
		5092	=item event
		5093
		5094	A change of state of some external event, such as data now being available
		5095	for reading on a file descriptor, time having passed or simply not having
		5096	any other events happening anymore.
		5097
		5098	In libev, events are represented as single bits (such as C<EV_READ> or
		5099	C<EV_TIMER>).
		5100
		5101	=item event library
		5102
		5103	A software package implementing an event model and loop.
		5104
		5105	=item event loop
		5106
		5107	An entity that handles and processes external events and converts them
		5108	into callback invocations.
		5109
		5110	=item event model
		5111
		5112	The model used to describe how an event loop handles and processes
		5113	watchers and events.
		5114
		5115	=item pending
		5116
		5117	A watcher is pending as soon as the corresponding event has been
		5118	detected. See L<WATCHER STATES> for details.
		5119
		5120	=item real time
		5121
		5122	The physical time that is observed. It is apparently strictly monotonic :)
		5123
		5124	=item wall-clock time
		5125
		5126	The time and date as shown on clocks. Unlike real time, it can actually
		5127	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5128	clock.
		5129
		5130	=item watcher
		5131
		5132	A data structure that describes interest in certain events. Watchers need
		5133	to be started (attached to an event loop) before they can receive events.
		5134
		5135	=back
3582		5136
3583	=head1 AUTHOR	5137	=head1 AUTHOR
3584		5138
3585	Marc Lehmann <libev@schmorp.de>.	5139	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5140	Magnusson and Emanuele Giaquinta.
3586		5141

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