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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		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;
…		…
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_ 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	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
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<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)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
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)); [NOT REENTRANT]	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 C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
284		324
285	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
287	not.	327	do not.
288		328
289	=over 4	329	=over 4
290		330
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		332
293	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
294	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
295	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
296	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".
297		343
298	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
299	function.	345	function (or via the C<EV_DEFAULT> macro).
300		346
301	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
302	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
303	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).
304		351
305	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,
306	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
307	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
308	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
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	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.
311		376
312	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
313	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>).
314		379
315	The following flags are supported:	380	The following flags are supported:
…		…
330	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
331	around bugs.	396	around bugs.
332		397
333	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
334		399
335	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
336	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.
337	enabling this flag.
338		402
339	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,
340	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
341	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
342	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
…		…
348	flag.	412	flag.
349		413
350	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>
351	environment variable.	415	environment variable.
352		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
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		450
355	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
356	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,
357	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
…		…
381	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
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		479
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
386	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,
387	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
388	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),
389	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
390		489
391	The epoll syscalls are the most misdesigned of the more advanced event	490	The epoll mechanism deserves honorable mention as the most misdesigned
392	mechanisms: problems include silently dropping fds, requiring a system	491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
393	call per change per fd (and unnecessary guessing of parameters), problems	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
394	with dup and so on. The biggest issue is fork races, however - if a	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
395	program forks then I<both> parent and child process have to recreate the	497	forks then I<both> parent and child process have to recreate the epoll
396	epoll set, which can take considerable time (one syscall per fd) and is of	498	set, which can take considerable time (one syscall per file descriptor)
397	course hard to detect.	499	and is of course hard to detect.
398		500
399	Epoll is also notoriously buggy - embedding epoll fds should work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
400	of course doesn't, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
401	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
402	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
403	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
404	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
405	events to filter out spurious ones.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
406		514
407	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
408	will result in some caching, there is still a system call per such incident	516	will result in some caching, there is still a system call per such
409	(because the fd could point to a different file description now), so its	517	incident (because the same I<file descriptor> could point to a different
410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
411	very well if you register events for both fds.	519	file descriptors might not work very well if you register events for both
		520	file descriptors.
412		521
413	Best performance from this backend is achieved by not unregistering all	522	Best performance from this backend is achieved by not unregistering all
414	watchers for a file descriptor until it has been closed, if possible,	523	watchers for a file descriptor until it has been closed, if possible,
415	i.e. keep at least one watcher active per fd at all times. Stopping and	524	i.e. keep at least one watcher active per fd at all times. Stopping and
416	starting a watcher (without re-setting it) also usually doesn't cause	525	starting a watcher (without re-setting it) also usually doesn't cause
417	extra overhead. A fork can both result in spurious notifications as well	526	extra overhead. A fork can both result in spurious notifications as well
418	as in libev having to destroy and recreate the epoll object, which can	527	as in libev having to destroy and recreate the epoll object, which can
419	take considerable time and thus should be avoided.	528	take considerable time and thus should be avoided.
420		529
		530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		531	faster than epoll for maybe up to a hundred file descriptors, depending on
		532	the usage. So sad.
		533
421	While nominally embeddable in other event loops, this feature is broken in	534	While nominally embeddable in other event loops, this feature is broken in
422	all kernel versions tested so far.	535	all kernel versions tested so far.
423		536
424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
425	C<EVBACKEND_POLL>.	538	C<EVBACKEND_POLL>.
426		539
427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
428		541
429	Kqueue deserves special mention, as at the time of this writing, it was	542	Kqueue deserves special mention, as at the time of this writing, it
430	broken on all BSDs except NetBSD (usually it doesn't work reliably with	543	was broken on all BSDs except NetBSD (usually it doesn't work reliably
431	anything but sockets and pipes, except on Darwin, where of course it's	544	with anything but sockets and pipes, except on Darwin, where of course
432	completely useless). For this reason it's not being "auto-detected" unless	545	it's completely useless). Unlike epoll, however, whose brokenness
433	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	546	is by design, these kqueue bugs can (and eventually will) be fixed
434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	547	without API changes to existing programs. For this reason it's not being
		548	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		550	system like NetBSD.
435		551
436	You still can embed kqueue into a normal poll or select backend and use it	552	You still can embed kqueue into a normal poll or select backend and use it
437	only for sockets (after having made sure that sockets work with kqueue on	553	only for sockets (after having made sure that sockets work with kqueue on
438	the target platform). See C<ev_embed> watchers for more info.	554	the target platform). See C<ev_embed> watchers for more info.
439		555
…		…
449		565
450	While nominally embeddable in other event loops, this doesn't work	566	While nominally embeddable in other event loops, this doesn't work
451	everywhere, so you might need to test for this. And since it is broken	567	everywhere, so you might need to test for this. And since it is broken
452	almost everywhere, you should only use it when you have a lot of sockets	568	almost everywhere, you should only use it when you have a lot of sockets
453	(for which it usually works), by embedding it into another event loop	569	(for which it usually works), by embedding it into another event loop
454	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	570	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
455	using it only for sockets.	571	also broken on OS X)) and, did I mention it, using it only for sockets.
456		572
457	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	573	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
458	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	574	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
459	C<NOTE_EOF>.	575	C<NOTE_EOF>.
460		576
…		…
468	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
469		585
470	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
471	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
472		588
473	Please note that Solaris event ports can deliver a lot of spurious
474	notifications, so you need to use non-blocking I/O or other means to avoid
475	blocking when no data (or space) is available.
476
477	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
478	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
480	might perform better.	592	might perform better.
481		593
482	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
483	notifications, this backend actually performed fully to specification
484	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
485	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
486		608
487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
488	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
489		611
490	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
491		613
492	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
493	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
494	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
495		617
496	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
497		627
498	=back	628	=back
499		629
500	If one or more of these are or'ed into the flags value, then only these	630	If one or more of the backend flags are or'ed into the flags value,
501	backends will be tried (in the reverse order as listed here). If none are	631	then only these backends will be tried (in the reverse order as listed
502	specified, all backends in C<ev_recommended_backends ()> will be tried.	632	here). If none are specified, all backends in C<ev_recommended_backends
503		633	()> will be tried.
504	Example: This is the most typical usage.
505
506	if (!ev_default_loop (0))
507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
508
509	Example: Restrict libev to the select and poll backends, and do not allow
510	environment settings to be taken into account:
511
512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
513
514	Example: Use whatever libev has to offer, but make sure that kqueue is
515	used if available (warning, breaks stuff, best use only with your own
516	private event loop and only if you know the OS supports your types of
517	fds):
518
519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
520
521	=item struct ev_loop *ev_loop_new (unsigned int flags)
522
523	Similar to C<ev_default_loop>, but always creates a new event loop that is
524	always distinct from the default loop. Unlike the default loop, it cannot
525	handle signal and child watchers, and attempts to do so will be greeted by
526	undefined behaviour (or a failed assertion if assertions are enabled).
527
528	Note that this function I<is> thread-safe, and the recommended way to use
529	libev with threads is indeed to create one loop per thread, and using the
530	default loop in the "main" or "initial" thread.
531		634
532	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
533		636
534	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
535	if (!epoller)	638	if (!epoller)
536	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
537		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
538	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
539		647
540	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
541	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
542	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
543	responsibility to either stop all watchers cleanly yourself I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
544	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
545	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
547		655
548	Note that certain global state, such as signal state (and installed signal	656	Note that certain global state, such as signal state (and installed signal
549	handlers), will not be freed by this function, and related watchers (such	657	handlers), will not be freed by this function, and related watchers (such
550	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
551		659
552	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
553	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
554	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
555	C<ev_loop_new> and C<ev_loop_destroy>).	667	and C<ev_loop_destroy>.
556		668
557	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
558		670
559	Like C<ev_default_destroy>, but destroys an event loop created by an
560	earlier call to C<ev_loop_new>.
561
562	=item ev_default_fork ()
563
564	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
565	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
566	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
567	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
568	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
569	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
570		681
571	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
572	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
573	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
574		688
575	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
576	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
577	quite nicely into a call to C<pthread_atfork>:
578		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
579	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
580
581	=item ev_loop_fork (loop)
582
583	Like C<ev_default_fork>, but acts on an event loop created by
584	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
585	after fork that you want to re-use in the child, and how you do this is
586	entirely your own problem.
587		703
588	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
589		705
590	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
591	otherwise.	707	otherwise.
592		708
593	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
594		710
595	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
596	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
597	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
598		714
599	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
600	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
601	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
602		733
603	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
604		735
605	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
606	use.	737	use.
…		…
615		746
616	=item ev_now_update (loop)	747	=item ev_now_update (loop)
617		748
618	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
619	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
620	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
621		752
622	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
623	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
624	the current time is a good idea.	755	the current time is a good idea.
625		756
626	See also "The special problem of time updates" in the C<ev_timer> section.	757	See also L<The special problem of time updates> in the C<ev_timer> section.
627		758
		759	=item ev_suspend (loop)
		760
		761	=item ev_resume (loop)
		762
		763	These two functions suspend and resume an event loop, for use when the
		764	loop is not used for a while and timeouts should not be processed.
		765
		766	A typical use case would be an interactive program such as a game: When
		767	the user presses C<^Z> to suspend the game and resumes it an hour later it
		768	would be best to handle timeouts as if no time had actually passed while
		769	the program was suspended. This can be achieved by calling C<ev_suspend>
		770	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		771	C<ev_resume> directly afterwards to resume timer processing.
		772
		773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		775	will be rescheduled (that is, they will lose any events that would have
		776	occurred while suspended).
		777
		778	After calling C<ev_suspend> you B<must not> call I<any> function on the
		779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		780	without a previous call to C<ev_suspend>.
		781
		782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		783	event loop time (see C<ev_now_update>).
		784
628	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
629		786
630	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
631	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
632	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
633		792
634	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
635	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
636		796
637	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
638	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
639	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
640	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
641	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
642	beauty.	802	beauty.
643		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
644	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
645	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
646	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
647	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
648		814
649	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
650	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
651	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
652	be an event internal to libev itself, so there is no guarentee that a	818	be an event internal to libev itself, so there is no guarantee that a
653	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
654	iteration of the loop.	820	iteration of the loop.
655		821
656	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
657	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
658	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
659	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
660		826
661	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
662		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
663	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
664	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
665	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
666	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
667	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
668	as to not disturb the other process.	838	as to not disturb the other process.
669	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
670	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
671	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
672	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
673	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
674	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
675	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
676	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
678	- Queue all expired timers.	849	- Queue all expired timers.
679	- Queue all expired periodics.	850	- Queue all expired periodics.
680	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
681	- Queue all check watchers.	852	- Queue all check watchers.
682	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
683	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
684	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
685	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
686	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
687	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
688		863
689	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
690	anymore.	865	anymore.
691		866
692	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
693	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
694	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
695	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
696		871
697	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
698		873
699	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
700	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
701	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
703		878
704	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
705		880
706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
707		883
708	=item ev_ref (loop)	884	=item ev_ref (loop)
709		885
710	=item ev_unref (loop)	886	=item ev_unref (loop)
711		887
712	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
713	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
714	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
715		891
716	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
717	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
718	stopping it.	895	before stopping it.
719		896
720	As an example, libev itself uses this for its internal signal pipe: It is	897	As an example, libev itself uses this for its internal signal pipe: It
721	not visible to the libev user and should not keep C<ev_loop> from exiting	898	is not visible to the libev user and should not keep C<ev_run> from
722	if no event watchers registered by it are active. It is also an excellent	899	exiting if no event watchers registered by it are active. It is also an
723	way to do this for generic recurring timers or from within third-party	900	excellent way to do this for generic recurring timers or from within
724	libraries. Just remember to I<unref after start> and I<ref before stop>	901	third-party libraries. Just remember to I<unref after start> and I<ref
725	(but only if the watcher wasn't active before, or was active before,	902	before stop> (but only if the watcher wasn't active before, or was active
726	respectively).	903	before, respectively. Note also that libev might stop watchers itself
		904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		905	in the callback).
727		906
728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
729	running when nothing else is active.	908	running when nothing else is active.
730		909
731	ev_signal exitsig;	910	ev_signal exitsig;
732	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
733	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
734	evf_unref (loop);	913	ev_unref (loop);
735		914
736	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
737		916
738	ev_ref (loop);	917	ev_ref (loop);
739	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
760		939
761	By setting a higher I<io collect interval> you allow libev to spend more	940	By setting a higher I<io collect interval> you allow libev to spend more
762	time collecting I/O events, so you can handle more events per iteration,	941	time collecting I/O events, so you can handle more events per iteration,
763	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
764	C<ev_timer>) will be not affected. Setting this to a non-null value will	943	C<ev_timer>) will be not affected. Setting this to a non-null value will
765	introduce an additional C<ev_sleep ()> call into most loop iterations.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
766		947
767	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
768	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
769	latency/jitter/inexactness (the watcher callback will be called	950	latency/jitter/inexactness (the watcher callback will be called
770	later). C<ev_io> watchers will not be affected. Setting this to a non-null	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
772		953
773	Many (busy) programs can usually benefit by setting the I/O collect	954	Many (busy) programs can usually benefit by setting the I/O collect
774	interval to a value near C<0.1> or so, which is often enough for	955	interval to a value near C<0.1> or so, which is often enough for
775	interactive servers (of course not for games), likewise for timeouts. It	956	interactive servers (of course not for games), likewise for timeouts. It
776	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
777	as this approaches the timing granularity of most systems.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
778		963
779	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
780	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
781	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
782	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
783	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
784	they fire on, say, one-second boundaries only.	969	they fire on, say, one-second boundaries only.
785		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
786	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
787		1047
788	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
789	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
790	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
791	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
802		1062
803	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
805	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
806		1066
807	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
808	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
809	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
810		1071
811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
812	{	1073	{
813	ev_io_stop (w);	1074	ev_io_stop (w);
814	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
815	}	1076	}
816		1077
817	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
818		1079
819	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
820		1081
821	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
823	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
824		1085
825	ev_loop (loop, 0);	1086	ev_run (loop, 0);
826		1087
827	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
828	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
829	stack).	1090	stack).
830		1091
831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
833		1094
834	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
835	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
836	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
837	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
838	is readable and/or writable).	1099	and/or writable).
839		1100
840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
841	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
842	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
843	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
866	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
867		1128
868	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
869	writable.	1130	writable.
870		1131
871	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
872		1133
873	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
874		1135
875	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
876		1137
…		…
894		1155
895	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
896		1157
897	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
898		1159
899	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
900	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
901	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
902	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
903	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
904	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
905	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
906		1167
907	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
908		1169
909	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
910		1171
911	=item C<EV_FORK>	1172	=item C<EV_FORK>
912		1173
913	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
914	C<ev_fork>).	1175	C<ev_fork>).
915		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
916	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
917		1182
918	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
		1184
		1185	=item C<EV_CUSTOM>
		1186
		1187	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1188	by libev users to signal watchers (e.g. via C<ev_feed_event>).
919		1189
920	=item C<EV_ERROR>	1190	=item C<EV_ERROR>
921		1191
922	An unspecified error has occurred, the watcher has been stopped. This might	1192	An unspecified error has occurred, the watcher has been stopped. This might
923	happen because the watcher could not be properly started because libev	1193	happen because the watcher could not be properly started because libev
…		…
961		1231
962	ev_io w;	1232	ev_io w;
963	ev_init (&w, my_cb);	1233	ev_init (&w, my_cb);
964	ev_io_set (&w, STDIN_FILENO, EV_READ);	1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
965		1235
966	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
967		1237
968	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
969	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
970	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
971	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
…		…
984		1254
985	Example: Initialise and set an C<ev_io> watcher in one step.	1255	Example: Initialise and set an C<ev_io> watcher in one step.
986		1256
987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
988		1258
989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
990		1260
991	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
992	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
993		1263
994	Example: Start the C<ev_io> watcher that is being abused as example in this	1264	Example: Start the C<ev_io> watcher that is being abused as example in this
995	whole section.	1265	whole section.
996		1266
997	ev_io_start (EV_DEFAULT_UC, &w);	1267	ev_io_start (EV_DEFAULT_UC, &w);
998		1268
999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1000		1270
1001	Stops the given watcher if active, and clears the pending status (whether	1271	Stops the given watcher if active, and clears the pending status (whether
1002	the watcher was active or not).	1272	the watcher was active or not).
1003		1273
1004	It is possible that stopped watchers are pending - for example,	1274	It is possible that stopped watchers are pending - for example,
…		…
1029	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
1030		1300
1031	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
1032	(modulo threads).	1302	(modulo threads).
1033		1303
1034	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
1035		1305
1036	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
1037		1307
1038	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
1039	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1040	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
1041	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
1042	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
1043		1313
1044	This means that priorities are I<only> used for ordering callback
1045	invocation after new events have been received. This is useful, for
1046	example, to reduce latency after idling, or more often, to bind two
1047	watchers on the same event and make sure one is called first.
1048
1049	If you need to suppress invocation when higher priority events are pending	1314	If you need to suppress invocation when higher priority events are pending
1050	you need to look at C<ev_idle> watchers, which provide this functionality.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
1051		1316
1052	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
1053	pending.	1318	pending.
1054
1055	The default priority used by watchers when no priority has been set is
1056	always C<0>, which is supposed to not be too high and not be too low :).
1057		1319
1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1059	fine, as long as you do not mind that the priority value you query might	1321	fine, as long as you do not mind that the priority value you query might
1060	or might not have been clamped to the valid range.	1322	or might not have been clamped to the valid range.
		1323
		1324	The default priority used by watchers when no priority has been set is
		1325	always C<0>, which is supposed to not be too high and not be too low :).
		1326
		1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1328	priorities.
1061		1329
1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1063		1331
1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1065	C<loop> nor C<revents> need to be valid as long as the watcher callback	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1073	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
1074		1342
1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1076	callback to be invoked, which can be accomplished with this function.	1344	callback to be invoked, which can be accomplished with this function.
1077		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
1078	=back	1360	=back
1079
1080		1361
1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1082		1363
1083	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
1084	and read at any time: libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
…		…
1130	#include <stddef.h>	1411	#include <stddef.h>
1131		1412
1132	static void	1413	static void
1133	t1_cb (EV_P_ ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1134	{	1415	{
1135	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1136	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1137	}	1418	}
1138		1419
1139	static void	1420	static void
1140	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1141	{	1422	{
1142	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1143	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1144	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
		1485
		1486	=head2 WATCHER PRIORITY MODELS
		1487
		1488	Many event loops support I<watcher priorities>, which are usually small
		1489	integers that influence the ordering of event callback invocation
		1490	between watchers in some way, all else being equal.
		1491
		1492	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1493	description for the more technical details such as the actual priority
		1494	range.
		1495
		1496	There are two common ways how these these priorities are being interpreted
		1497	by event loops:
		1498
		1499	In the more common lock-out model, higher priorities "lock out" invocation
		1500	of lower priority watchers, which means as long as higher priority
		1501	watchers receive events, lower priority watchers are not being invoked.
		1502
		1503	The less common only-for-ordering model uses priorities solely to order
		1504	callback invocation within a single event loop iteration: Higher priority
		1505	watchers are invoked before lower priority ones, but they all get invoked
		1506	before polling for new events.
		1507
		1508	Libev uses the second (only-for-ordering) model for all its watchers
		1509	except for idle watchers (which use the lock-out model).
		1510
		1511	The rationale behind this is that implementing the lock-out model for
		1512	watchers is not well supported by most kernel interfaces, and most event
		1513	libraries will just poll for the same events again and again as long as
		1514	their callbacks have not been executed, which is very inefficient in the
		1515	common case of one high-priority watcher locking out a mass of lower
		1516	priority ones.
		1517
		1518	Static (ordering) priorities are most useful when you have two or more
		1519	watchers handling the same resource: a typical usage example is having an
		1520	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1521	timeouts. Under load, data might be received while the program handles
		1522	other jobs, but since timers normally get invoked first, the timeout
		1523	handler will be executed before checking for data. In that case, giving
		1524	the timer a lower priority than the I/O watcher ensures that I/O will be
		1525	handled first even under adverse conditions (which is usually, but not
		1526	always, what you want).
		1527
		1528	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1529	will only be executed when no same or higher priority watchers have
		1530	received events, they can be used to implement the "lock-out" model when
		1531	required.
		1532
		1533	For example, to emulate how many other event libraries handle priorities,
		1534	you can associate an C<ev_idle> watcher to each such watcher, and in
		1535	the normal watcher callback, you just start the idle watcher. The real
		1536	processing is done in the idle watcher callback. This causes libev to
		1537	continuously poll and process kernel event data for the watcher, but when
		1538	the lock-out case is known to be rare (which in turn is rare :), this is
		1539	workable.
		1540
		1541	Usually, however, the lock-out model implemented that way will perform
		1542	miserably under the type of load it was designed to handle. In that case,
		1543	it might be preferable to stop the real watcher before starting the
		1544	idle watcher, so the kernel will not have to process the event in case
		1545	the actual processing will be delayed for considerable time.
		1546
		1547	Here is an example of an I/O watcher that should run at a strictly lower
		1548	priority than the default, and which should only process data when no
		1549	other events are pending:
		1550
		1551	ev_idle idle; // actual processing watcher
		1552	ev_io io; // actual event watcher
		1553
		1554	static void
		1555	io_cb (EV_P_ ev_io *w, int revents)
		1556	{
		1557	// stop the I/O watcher, we received the event, but
		1558	// are not yet ready to handle it.
		1559	ev_io_stop (EV_A_ w);
		1560
		1561	// start the idle watcher to handle the actual event.
		1562	// it will not be executed as long as other watchers
		1563	// with the default priority are receiving events.
		1564	ev_idle_start (EV_A_ &idle);
		1565	}
		1566
		1567	static void
		1568	idle_cb (EV_P_ ev_idle *w, int revents)
		1569	{
		1570	// actual processing
		1571	read (STDIN_FILENO, ...);
		1572
		1573	// have to start the I/O watcher again, as
		1574	// we have handled the event
		1575	ev_io_start (EV_P_ &io);
		1576	}
		1577
		1578	// initialisation
		1579	ev_idle_init (&idle, idle_cb);
		1580	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1581	ev_io_start (EV_DEFAULT_ &io);
		1582
		1583	In the "real" world, it might also be beneficial to start a timer, so that
		1584	low-priority connections can not be locked out forever under load. This
		1585	enables your program to keep a lower latency for important connections
		1586	during short periods of high load, while not completely locking out less
		1587	important ones.
1145		1588
1146		1589
1147	=head1 WATCHER TYPES	1590	=head1 WATCHER TYPES
1148		1591
1149	This section describes each watcher in detail, but will not repeat	1592	This section describes each watcher in detail, but will not repeat
…		…
1173	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1174	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1175	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1176	required if you know what you are doing).	1619	required if you know what you are doing).
1177		1620
1178	If you cannot use non-blocking mode, then force the use of a
1179	known-to-be-good backend (at the time of this writing, this includes only
1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1181
1182	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
1183	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1184	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
1185	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1186	lot of those (for example Solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1187	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1188	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1190		1628
1191	If you cannot run the fd in non-blocking mode (for example you should	1629	If you cannot run the fd in non-blocking mode (for example you should
1192	not play around with an Xlib connection), then you have to separately	1630	not play around with an Xlib connection), then you have to separately
1193	re-test whether a file descriptor is really ready with a known-to-be good	1631	re-test whether a file descriptor is really ready with a known-to-be good
1194	interface such as poll (fortunately in our Xlib example, Xlib already	1632	interface such as poll (fortunately in the case of Xlib, it already does
1195	does this on its own, so its quite safe to use). Some people additionally	1633	this on its own, so its quite safe to use). Some people additionally
1196	use C<SIGALRM> and an interval timer, just to be sure you won't block	1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
1197	indefinitely.	1635	indefinitely.
1198		1636
1199	But really, best use non-blocking mode.	1637	But really, best use non-blocking mode.
1200		1638
…		…
1228		1666
1229	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1230	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1231	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1232		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1233	=head3 The special problem of fork	1704	=head3 The special problem of fork
1234		1705
1235	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1236	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1237	it in the child.	1708	it in the child if you want to continue to use it in the child.
1238		1709
1239	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1240	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1242	C<EVBACKEND_POLL>.
1243		1713
1244	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1245		1715
1246	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1247	when writing to a pipe whose other end has been closed, your program gets	1717	when writing to a pipe whose other end has been closed, your program gets
…		…
1250		1720
1251	So when you encounter spurious, unexplained daemon exits, make sure you	1721	So when you encounter spurious, unexplained daemon exits, make sure you
1252	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1722	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1253	somewhere, as that would have given you a big clue).	1723	somewhere, as that would have given you a big clue).
1254		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1255		1763
1256	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1257		1765
1258	=over 4	1766	=over 4
1259		1767
…		…
1291	...	1799	...
1292	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1293	ev_io stdin_readable;	1801	ev_io stdin_readable;
1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1295	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1296	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1297		1805
1298		1806
1299	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1300		1808
1301	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
…		…
1306	year, it will still time out after (roughly) one hour. "Roughly" because	1814	year, it will still time out after (roughly) one hour. "Roughly" because
1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1308	monotonic clock option helps a lot here).	1816	monotonic clock option helps a lot here).
1309		1817
1310	The callback is guaranteed to be invoked only I<after> its timeout has	1818	The callback is guaranteed to be invoked only I<after> its timeout has
1311	passed, but if multiple timers become ready during the same loop iteration	1819	passed (not I<at>, so on systems with very low-resolution clocks this
1312	then order of execution is undefined.	1820	might introduce a small delay). If multiple timers become ready during the
		1821	same loop iteration then the ones with earlier time-out values are invoked
		1822	before ones of the same priority with later time-out values (but this is
		1823	no longer true when a callback calls C<ev_run> recursively).
1313		1824
1314	=head3 Be smart about timeouts	1825	=head3 Be smart about timeouts
1315		1826
1316	Many real-world problems involve some kind of timeout, usually for error	1827	Many real-world problems involve some kind of timeout, usually for error
1317	recovery. A typical example is an HTTP request - if the other side hangs,	1828	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1872	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1362	member and C<ev_timer_again>.	1873	member and C<ev_timer_again>.
1363		1874
1364	At start:	1875	At start:
1365		1876
1366	ev_timer_init (timer, callback);	1877	ev_init (timer, callback);
1367	timer->repeat = 60.;	1878	timer->repeat = 60.;
1368	ev_timer_again (loop, timer);	1879	ev_timer_again (loop, timer);
1369		1880
1370	Each time there is some activity:	1881	Each time there is some activity:
1371		1882
…		…
1403	ev_tstamp timeout = last_activity + 60.;	1914	ev_tstamp timeout = last_activity + 60.;
1404		1915
1405	// if last_activity + 60. is older than now, we did time out	1916	// if last_activity + 60. is older than now, we did time out
1406	if (timeout < now)	1917	if (timeout < now)
1407	{	1918	{
1408	// timeout occured, take action	1919	// timeout occurred, take action
1409	}	1920	}
1410	else	1921	else
1411	{	1922	{
1412	// callback was invoked, but there was some activity, re-arm	1923	// callback was invoked, but there was some activity, re-arm
1413	// the watcher to fire in last_activity + 60, which is	1924	// the watcher to fire in last_activity + 60, which is
1414	// guaranteed to be in the future, so "again" is positive:	1925	// guaranteed to be in the future, so "again" is positive:
1415	w->again = timeout - now;	1926	w->repeat = timeout - now;
1416	ev_timer_again (EV_A_ w);	1927	ev_timer_again (EV_A_ w);
1417	}	1928	}
1418	}	1929	}
1419		1930
1420	To summarise the callback: first calculate the real timeout (defined	1931	To summarise the callback: first calculate the real timeout (defined
…		…
1433		1944
1434	To start the timer, simply initialise the watcher and set C<last_activity>	1945	To start the timer, simply initialise the watcher and set C<last_activity>
1435	to the current time (meaning we just have some activity :), then call the	1946	to the current time (meaning we just have some activity :), then call the
1436	callback, which will "do the right thing" and start the timer:	1947	callback, which will "do the right thing" and start the timer:
1437		1948
1438	ev_timer_init (timer, callback);	1949	ev_init (timer, callback);
1439	last_activity = ev_now (loop);	1950	last_activity = ev_now (loop);
1440	callback (loop, timer, EV_TIMEOUT);	1951	callback (loop, timer, EV_TIMER);
1441		1952
1442	And when there is some activity, simply store the current time in	1953	And when there is some activity, simply store the current time in
1443	C<last_activity>, no libev calls at all:	1954	C<last_activity>, no libev calls at all:
1444		1955
1445	last_actiivty = ev_now (loop);	1956	last_activity = ev_now (loop);
1446		1957
1447	This technique is slightly more complex, but in most cases where the	1958	This technique is slightly more complex, but in most cases where the
1448	time-out is unlikely to be triggered, much more efficient.	1959	time-out is unlikely to be triggered, much more efficient.
1449		1960
1450	Changing the timeout is trivial as well (if it isn't hard-coded in the	1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1488		1999
1489	=head3 The special problem of time updates	2000	=head3 The special problem of time updates
1490		2001
1491	Establishing the current time is a costly operation (it usually takes at	2002	Establishing the current time is a costly operation (it usually takes at
1492	least two system calls): EV therefore updates its idea of the current	2003	least two system calls): EV therefore updates its idea of the current
1493	time only before and after C<ev_loop> collects new events, which causes a	2004	time only before and after C<ev_run> collects new events, which causes a
1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1495	lots of events in one iteration.	2006	lots of events in one iteration.
1496		2007
1497	The relative timeouts are calculated relative to the C<ev_now ()>	2008	The relative timeouts are calculated relative to the C<ev_now ()>
1498	time. This is usually the right thing as this timestamp refers to the time	2009	time. This is usually the right thing as this timestamp refers to the time
…		…
1504		2015
1505	If the event loop is suspended for a long time, you can also force an	2016	If the event loop is suspended for a long time, you can also force an
1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1507	()>.	2018	()>.
1508		2019
		2020	=head3 The special problems of suspended animation
		2021
		2022	When you leave the server world it is quite customary to hit machines that
		2023	can suspend/hibernate - what happens to the clocks during such a suspend?
		2024
		2025	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2026	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2027	to run until the system is suspended, but they will not advance while the
		2028	system is suspended. That means, on resume, it will be as if the program
		2029	was frozen for a few seconds, but the suspend time will not be counted
		2030	towards C<ev_timer> when a monotonic clock source is used. The real time
		2031	clock advanced as expected, but if it is used as sole clocksource, then a
		2032	long suspend would be detected as a time jump by libev, and timers would
		2033	be adjusted accordingly.
		2034
		2035	I would not be surprised to see different behaviour in different between
		2036	operating systems, OS versions or even different hardware.
		2037
		2038	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2039	time jump in the monotonic clocks and the realtime clock. If the program
		2040	is suspended for a very long time, and monotonic clock sources are in use,
		2041	then you can expect C<ev_timer>s to expire as the full suspension time
		2042	will be counted towards the timers. When no monotonic clock source is in
		2043	use, then libev will again assume a timejump and adjust accordingly.
		2044
		2045	It might be beneficial for this latter case to call C<ev_suspend>
		2046	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2047	deterministic behaviour in this case (you can do nothing against
		2048	C<SIGSTOP>).
		2049
1509	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1510		2051
1511	=over 4	2052	=over 4
1512		2053
1513	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1536	If the timer is started but non-repeating, stop it (as if it timed out).	2077	If the timer is started but non-repeating, stop it (as if it timed out).
1537		2078
1538	If the timer is repeating, either start it if necessary (with the	2079	If the timer is repeating, either start it if necessary (with the
1539	C<repeat> value), or reset the running timer to the C<repeat> value.	2080	C<repeat> value), or reset the running timer to the C<repeat> value.
1540		2081
1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1542	usage example.	2083	usage example.
		2084
		2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2086
		2087	Returns the remaining time until a timer fires. If the timer is active,
		2088	then this time is relative to the current event loop time, otherwise it's
		2089	the timeout value currently configured.
		2090
		2091	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2092	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2093	will return C<4>. When the timer expires and is restarted, it will return
		2094	roughly C<7> (likely slightly less as callback invocation takes some time,
		2095	too), and so on.
1543		2096
1544	=item ev_tstamp repeat [read-write]	2097	=item ev_tstamp repeat [read-write]
1545		2098
1546	The current C<repeat> value. Will be used each time the watcher times out	2099	The current C<repeat> value. Will be used each time the watcher times out
1547	or C<ev_timer_again> is called, and determines the next timeout (if any),	2100	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1573	}	2126	}
1574		2127
1575	ev_timer mytimer;	2128	ev_timer mytimer;
1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1577	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1578	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1579		2132
1580	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1581	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1582	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1583		2136
…		…
1585	=head2 C<ev_periodic> - to cron or not to cron?	2138	=head2 C<ev_periodic> - to cron or not to cron?
1586		2139
1587	Periodic watchers are also timers of a kind, but they are very versatile	2140	Periodic watchers are also timers of a kind, but they are very versatile
1588	(and unfortunately a bit complex).	2141	(and unfortunately a bit complex).
1589		2142
1590	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1591	but on wall clock time (absolute time). You can tell a periodic watcher	2144	relative time, the physical time that passes) but on wall clock time
1592	to trigger after some specific point in time. For example, if you tell a	2145	(absolute time, the thing you can read on your calender or clock). The
1593	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2146	difference is that wall clock time can run faster or slower than real
1594	+ 10.>, that is, an absolute time not a delay) and then reset your system	2147	time, and time jumps are not uncommon (e.g. when you adjust your
1595	clock to January of the previous year, then it will take more than year	2148	wrist-watch).
1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1597	roughly 10 seconds later as it uses a relative timeout).
1598		2149
		2150	You can tell a periodic watcher to trigger after some specific point
		2151	in time: for example, if you tell a periodic watcher to trigger "in 10
		2152	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2153	not a delay) and then reset your system clock to January of the previous
		2154	year, then it will take a year or more to trigger the event (unlike an
		2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2156	it, as it uses a relative timeout).
		2157
1599	C<ev_periodic>s can also be used to implement vastly more complex timers,	2158	C<ev_periodic> watchers can also be used to implement vastly more complex
1600	such as triggering an event on each "midnight, local time", or other	2159	timers, such as triggering an event on each "midnight, local time", or
1601	complicated rules.	2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2161	those cannot react to time jumps.
1602		2162
1603	As with timers, the callback is guaranteed to be invoked only when the	2163	As with timers, the callback is guaranteed to be invoked only when the
1604	time (C<at>) has passed, but if multiple periodic timers become ready	2164	point in time where it is supposed to trigger has passed. If multiple
1605	during the same loop iteration, then order of execution is undefined.	2165	timers become ready during the same loop iteration then the ones with
		2166	earlier time-out values are invoked before ones with later time-out values
		2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1606		2168
1607	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1608		2170
1609	=over 4	2171	=over 4
1610		2172
1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2173	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1612		2174
1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2175	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1614		2176
1615	Lots of arguments, lets sort it out... There are basically three modes of	2177	Lots of arguments, let's sort it out... There are basically three modes of
1616	operation, and we will explain them from simplest to most complex:	2178	operation, and we will explain them from simplest to most complex:
1617		2179
1618	=over 4	2180	=over 4
1619		2181
1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2182	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1621		2183
1622	In this configuration the watcher triggers an event after the wall clock	2184	In this configuration the watcher triggers an event after the wall clock
1623	time C<at> has passed. It will not repeat and will not adjust when a time	2185	time C<offset> has passed. It will not repeat and will not adjust when a
1624	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2186	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1625	only run when the system clock reaches or surpasses this time.	2187	will be stopped and invoked when the system clock reaches or surpasses
		2188	this point in time.
1626		2189
1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2190	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1628		2191
1629	In this mode the watcher will always be scheduled to time out at the next	2192	In this mode the watcher will always be scheduled to time out at the next
1630	C<at + N * interval> time (for some integer N, which can also be negative)	2193	C<offset + N * interval> time (for some integer N, which can also be
1631	and then repeat, regardless of any time jumps.	2194	negative) and then repeat, regardless of any time jumps. The C<offset>
		2195	argument is merely an offset into the C<interval> periods.
1632		2196
1633	This can be used to create timers that do not drift with respect to the	2197	This can be used to create timers that do not drift with respect to the
1634	system clock, for example, here is a C<ev_periodic> that triggers each	2198	system clock, for example, here is an C<ev_periodic> that triggers each
1635	hour, on the hour:	2199	hour, on the hour (with respect to UTC):
1636		2200
1637	ev_periodic_set (&periodic, 0., 3600., 0);	2201	ev_periodic_set (&periodic, 0., 3600., 0);
1638		2202
1639	This doesn't mean there will always be 3600 seconds in between triggers,	2203	This doesn't mean there will always be 3600 seconds in between triggers,
1640	but only that the callback will be called when the system time shows a	2204	but only that the callback will be called when the system time shows a
1641	full hour (UTC), or more correctly, when the system time is evenly divisible	2205	full hour (UTC), or more correctly, when the system time is evenly divisible
1642	by 3600.	2206	by 3600.
1643		2207
1644	Another way to think about it (for the mathematically inclined) is that	2208	Another way to think about it (for the mathematically inclined) is that
1645	C<ev_periodic> will try to run the callback in this mode at the next possible	2209	C<ev_periodic> will try to run the callback in this mode at the next possible
1646	time where C<time = at (mod interval)>, regardless of any time jumps.	2210	time where C<time = offset (mod interval)>, regardless of any time jumps.
1647		2211
1648	For numerical stability it is preferable that the C<at> value is near	2212	For numerical stability it is preferable that the C<offset> value is near
1649	C<ev_now ()> (the current time), but there is no range requirement for	2213	C<ev_now ()> (the current time), but there is no range requirement for
1650	this value, and in fact is often specified as zero.	2214	this value, and in fact is often specified as zero.
1651		2215
1652	Note also that there is an upper limit to how often a timer can fire (CPU	2216	Note also that there is an upper limit to how often a timer can fire (CPU
1653	speed for example), so if C<interval> is very small then timing stability	2217	speed for example), so if C<interval> is very small then timing stability
1654	will of course deteriorate. Libev itself tries to be exact to be about one	2218	will of course deteriorate. Libev itself tries to be exact to be about one
1655	millisecond (if the OS supports it and the machine is fast enough).	2219	millisecond (if the OS supports it and the machine is fast enough).
1656		2220
1657	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2221	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1658		2222
1659	In this mode the values for C<interval> and C<at> are both being	2223	In this mode the values for C<interval> and C<offset> are both being
1660	ignored. Instead, each time the periodic watcher gets scheduled, the	2224	ignored. Instead, each time the periodic watcher gets scheduled, the
1661	reschedule callback will be called with the watcher as first, and the	2225	reschedule callback will be called with the watcher as first, and the
1662	current time as second argument.	2226	current time as second argument.
1663		2227
1664	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2228	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1665	ever, or make ANY event loop modifications whatsoever>.	2229	or make ANY other event loop modifications whatsoever, unless explicitly
		2230	allowed by documentation here>.
1666		2231
1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2232	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2233	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1669	only event loop modification you are allowed to do).	2234	only event loop modification you are allowed to do).
1670		2235
…		…
1700	a different time than the last time it was called (e.g. in a crond like	2265	a different time than the last time it was called (e.g. in a crond like
1701	program when the crontabs have changed).	2266	program when the crontabs have changed).
1702		2267
1703	=item ev_tstamp ev_periodic_at (ev_periodic *)	2268	=item ev_tstamp ev_periodic_at (ev_periodic *)
1704		2269
1705	When active, returns the absolute time that the watcher is supposed to	2270	When active, returns the absolute time that the watcher is supposed
1706	trigger next.	2271	to trigger next. This is not the same as the C<offset> argument to
		2272	C<ev_periodic_set>, but indeed works even in interval and manual
		2273	rescheduling modes.
1707		2274
1708	=item ev_tstamp offset [read-write]	2275	=item ev_tstamp offset [read-write]
1709		2276
1710	When repeating, this contains the offset value, otherwise this is the	2277	When repeating, this contains the offset value, otherwise this is the
1711	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2278	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2279	although libev might modify this value for better numerical stability).
1712		2280
1713	Can be modified any time, but changes only take effect when the periodic	2281	Can be modified any time, but changes only take effect when the periodic
1714	timer fires or C<ev_periodic_again> is being called.	2282	timer fires or C<ev_periodic_again> is being called.
1715		2283
1716	=item ev_tstamp interval [read-write]	2284	=item ev_tstamp interval [read-write]
…		…
1732	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
1733	system time is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
1734	potentially a lot of jitter, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
1735		2303
1736	static void	2304	static void
1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1738	{	2306	{
1739	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
1740	}	2308	}
1741		2309
1742	ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
…		…
1765		2333
1766	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
1767		2335
1768	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
1769	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
1770	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
1771	normal event processing, like any other event.	2339	normal event processing, like any other event.
1772		2340
1773	If you want signals asynchronously, just use C<sigaction> as you would	2341	If you want signals to be delivered truly asynchronously, just use
1774	do without libev and forget about sharing the signal. You can even use	2342	C<sigaction> as you would do without libev and forget about sharing
1775	C<ev_async> from a signal handler to synchronously wake up an event loop.	2343	the signal. You can even use C<ev_async> from a signal handler to
		2344	synchronously wake up an event loop.
1776		2345
1777	You can configure as many watchers as you like per signal. Only when the	2346	You can configure as many watchers as you like for the same signal, but
		2347	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2348	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2349	C<SIGINT> in both the default loop and another loop at the same time. At
		2350	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2351
1778	first watcher gets started will libev actually register a signal handler	2352	When the first watcher gets started will libev actually register something
1779	with the kernel (thus it coexists with your own signal handlers as long as	2353	with the kernel (thus it coexists with your own signal handlers as long as
1780	you don't register any with libev for the same signal). Similarly, when	2354	you don't register any with libev for the same signal).
1781	the last signal watcher for a signal is stopped, libev will reset the
1782	signal handler to SIG_DFL (regardless of what it was set to before).
1783		2355
1784	If possible and supported, libev will install its handlers with	2356	If possible and supported, libev will install its handlers with
1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1786	interrupted. If you have a problem with system calls getting interrupted by	2358	not be unduly interrupted. If you have a problem with system calls getting
1787	signals you can block all signals in an C<ev_check> watcher and unblock	2359	interrupted by signals you can block all signals in an C<ev_check> watcher
1788	them in an C<ev_prepare> watcher.	2360	and unblock them in an C<ev_prepare> watcher.
		2361
		2362	=head3 The special problem of inheritance over fork/execve/pthread_create
		2363
		2364	Both the signal mask (C<sigprocmask>) and the signal disposition
		2365	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2366	stopping it again), that is, libev might or might not block the signal,
		2367	and might or might not set or restore the installed signal handler.
		2368
		2369	While this does not matter for the signal disposition (libev never
		2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2371	C<execve>), this matters for the signal mask: many programs do not expect
		2372	certain signals to be blocked.
		2373
		2374	This means that before calling C<exec> (from the child) you should reset
		2375	the signal mask to whatever "default" you expect (all clear is a good
		2376	choice usually).
		2377
		2378	The simplest way to ensure that the signal mask is reset in the child is
		2379	to install a fork handler with C<pthread_atfork> that resets it. That will
		2380	catch fork calls done by libraries (such as the libc) as well.
		2381
		2382	In current versions of libev, the signal will not be blocked indefinitely
		2383	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2384	the window of opportunity for problems, it will not go away, as libev
		2385	I<has> to modify the signal mask, at least temporarily.
		2386
		2387	So I can't stress this enough: I<If you do not reset your signal mask when
		2388	you expect it to be empty, you have a race condition in your code>. This
		2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
1789		2404
1790	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
1791		2406
1792	=over 4	2407	=over 4
1793		2408
…		…
1809	Example: Try to exit cleanly on SIGINT.	2424	Example: Try to exit cleanly on SIGINT.
1810		2425
1811	static void	2426	static void
1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1813	{	2428	{
1814	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
1815	}	2430	}
1816		2431
1817	ev_signal signal_watcher;	2432	ev_signal signal_watcher;
1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1819	ev_signal_start (loop, &signal_watcher);	2434	ev_signal_start (loop, &signal_watcher);
…		…
1825	some child status changes (most typically when a child of yours dies or	2440	some child status changes (most typically when a child of yours dies or
1826	exits). It is permissible to install a child watcher I<after> the child	2441	exits). It is permissible to install a child watcher I<after> the child
1827	has been forked (which implies it might have already exited), as long	2442	has been forked (which implies it might have already exited), as long
1828	as the event loop isn't entered (or is continued from a watcher), i.e.,	2443	as the event loop isn't entered (or is continued from a watcher), i.e.,
1829	forking and then immediately registering a watcher for the child is fine,	2444	forking and then immediately registering a watcher for the child is fine,
1830	but forking and registering a watcher a few event loop iterations later is	2445	but forking and registering a watcher a few event loop iterations later or
1831	not.	2446	in the next callback invocation is not.
1832		2447
1833	Only the default event loop is capable of handling signals, and therefore	2448	Only the default event loop is capable of handling signals, and therefore
1834	you can only register child watchers in the default event loop.	2449	you can only register child watchers in the default event loop.
1835		2450
		2451	Due to some design glitches inside libev, child watchers will always be
		2452	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2453	libev)
		2454
1836	=head3 Process Interaction	2455	=head3 Process Interaction
1837		2456
1838	Libev grabs C<SIGCHLD> as soon as the default event loop is	2457	Libev grabs C<SIGCHLD> as soon as the default event loop is
1839	initialised. This is necessary to guarantee proper behaviour even if	2458	initialised. This is necessary to guarantee proper behaviour even if the
1840	the first child watcher is started after the child exits. The occurrence	2459	first child watcher is started after the child exits. The occurrence
1841	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2460	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1842	synchronously as part of the event loop processing. Libev always reaps all	2461	synchronously as part of the event loop processing. Libev always reaps all
1843	children, even ones not watched.	2462	children, even ones not watched.
1844		2463
1845	=head3 Overriding the Built-In Processing	2464	=head3 Overriding the Built-In Processing
…		…
1855	=head3 Stopping the Child Watcher	2474	=head3 Stopping the Child Watcher
1856		2475
1857	Currently, the child watcher never gets stopped, even when the	2476	Currently, the child watcher never gets stopped, even when the
1858	child terminates, so normally one needs to stop the watcher in the	2477	child terminates, so normally one needs to stop the watcher in the
1859	callback. Future versions of libev might stop the watcher automatically	2478	callback. Future versions of libev might stop the watcher automatically
1860	when a child exit is detected.	2479	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2480	problem).
1861		2481
1862	=head3 Watcher-Specific Functions and Data Members	2482	=head3 Watcher-Specific Functions and Data Members
1863		2483
1864	=over 4	2484	=over 4
1865		2485
…		…
1922		2542
1923		2543
1924	=head2 C<ev_stat> - did the file attributes just change?	2544	=head2 C<ev_stat> - did the file attributes just change?
1925		2545
1926	This watches a file system path for attribute changes. That is, it calls	2546	This watches a file system path for attribute changes. That is, it calls
1927	C<stat> regularly (or when the OS says it changed) and sees if it changed	2547	C<stat> on that path in regular intervals (or when the OS says it changed)
1928	compared to the last time, invoking the callback if it did.	2548	and sees if it changed compared to the last time, invoking the callback if
		2549	it did.
1929		2550
1930	The path does not need to exist: changing from "path exists" to "path does	2551	The path does not need to exist: changing from "path exists" to "path does
1931	not exist" is a status change like any other. The condition "path does	2552	not exist" is a status change like any other. The condition "path does not
1932	not exist" is signified by the C<st_nlink> field being zero (which is	2553	exist" (or more correctly "path cannot be stat'ed") is signified by the
1933	otherwise always forced to be at least one) and all the other fields of	2554	C<st_nlink> field being zero (which is otherwise always forced to be at
1934	the stat buffer having unspecified contents.	2555	least one) and all the other fields of the stat buffer having unspecified
		2556	contents.
1935		2557
1936	The path I<should> be absolute and I<must not> end in a slash. If it is	2558	The path I<must not> end in a slash or contain special components such as
		2559	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1937	relative and your working directory changes, the behaviour is undefined.	2560	your working directory changes, then the behaviour is undefined.
1938		2561
1939	Since there is no standard kernel interface to do this, the portable	2562	Since there is no portable change notification interface available, the
1940	implementation simply calls C<stat (2)> regularly on the path to see if	2563	portable implementation simply calls C<stat(2)> regularly on the path
1941	it changed somehow. You can specify a recommended polling interval for	2564	to see if it changed somehow. You can specify a recommended polling
1942	this case. If you specify a polling interval of C<0> (highly recommended!)	2565	interval for this case. If you specify a polling interval of C<0> (highly
1943	then a I<suitable, unspecified default> value will be used (which	2566	recommended!) then a I<suitable, unspecified default> value will be used
1944	you can expect to be around five seconds, although this might change	2567	(which you can expect to be around five seconds, although this might
1945	dynamically). Libev will also impose a minimum interval which is currently	2568	change dynamically). Libev will also impose a minimum interval which is
1946	around C<0.1>, but thats usually overkill.	2569	currently around C<0.1>, but that's usually overkill.
1947		2570
1948	This watcher type is not meant for massive numbers of stat watchers,	2571	This watcher type is not meant for massive numbers of stat watchers,
1949	as even with OS-supported change notifications, this can be	2572	as even with OS-supported change notifications, this can be
1950	resource-intensive.	2573	resource-intensive.
1951		2574
1952	At the time of this writing, the only OS-specific interface implemented	2575	At the time of this writing, the only OS-specific interface implemented
1953	is the Linux inotify interface (implementing kqueue support is left as	2576	is the Linux inotify interface (implementing kqueue support is left as an
1954	an exercise for the reader. Note, however, that the author sees no way	2577	exercise for the reader. Note, however, that the author sees no way of
1955	of implementing C<ev_stat> semantics with kqueue).	2578	implementing C<ev_stat> semantics with kqueue, except as a hint).
1956		2579
1957	=head3 ABI Issues (Largefile Support)	2580	=head3 ABI Issues (Largefile Support)
1958		2581
1959	Libev by default (unless the user overrides this) uses the default	2582	Libev by default (unless the user overrides this) uses the default
1960	compilation environment, which means that on systems with large file	2583	compilation environment, which means that on systems with large file
1961	support disabled by default, you get the 32 bit version of the stat	2584	support disabled by default, you get the 32 bit version of the stat
1962	structure. When using the library from programs that change the ABI to	2585	structure. When using the library from programs that change the ABI to
1963	use 64 bit file offsets the programs will fail. In that case you have to	2586	use 64 bit file offsets the programs will fail. In that case you have to
1964	compile libev with the same flags to get binary compatibility. This is	2587	compile libev with the same flags to get binary compatibility. This is
1965	obviously the case with any flags that change the ABI, but the problem is	2588	obviously the case with any flags that change the ABI, but the problem is
1966	most noticeably disabled with ev_stat and large file support.	2589	most noticeably displayed with ev_stat and large file support.
1967		2590
1968	The solution for this is to lobby your distribution maker to make large	2591	The solution for this is to lobby your distribution maker to make large
1969	file interfaces available by default (as e.g. FreeBSD does) and not	2592	file interfaces available by default (as e.g. FreeBSD does) and not
1970	optional. Libev cannot simply switch on large file support because it has	2593	optional. Libev cannot simply switch on large file support because it has
1971	to exchange stat structures with application programs compiled using the	2594	to exchange stat structures with application programs compiled using the
1972	default compilation environment.	2595	default compilation environment.
1973		2596
1974	=head3 Inotify and Kqueue	2597	=head3 Inotify and Kqueue
1975		2598
1976	When C<inotify (7)> support has been compiled into libev (generally	2599	When C<inotify (7)> support has been compiled into libev and present at
1977	only available with Linux 2.6.25 or above due to bugs in earlier	2600	runtime, it will be used to speed up change detection where possible. The
1978	implementations) and present at runtime, it will be used to speed up	2601	inotify descriptor will be created lazily when the first C<ev_stat>
1979	change detection where possible. The inotify descriptor will be created	2602	watcher is being started.
1980	lazily when the first C<ev_stat> watcher is being started.
1981		2603
1982	Inotify presence does not change the semantics of C<ev_stat> watchers	2604	Inotify presence does not change the semantics of C<ev_stat> watchers
1983	except that changes might be detected earlier, and in some cases, to avoid	2605	except that changes might be detected earlier, and in some cases, to avoid
1984	making regular C<stat> calls. Even in the presence of inotify support	2606	making regular C<stat> calls. Even in the presence of inotify support
1985	there are many cases where libev has to resort to regular C<stat> polling,	2607	there are many cases where libev has to resort to regular C<stat> polling,
1986	but as long as the path exists, libev usually gets away without polling.	2608	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2609	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2610	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2611	xfs are fully working) libev usually gets away without polling.
1987		2612
1988	There is no support for kqueue, as apparently it cannot be used to	2613	There is no support for kqueue, as apparently it cannot be used to
1989	implement this functionality, due to the requirement of having a file	2614	implement this functionality, due to the requirement of having a file
1990	descriptor open on the object at all times, and detecting renames, unlinks	2615	descriptor open on the object at all times, and detecting renames, unlinks
1991	etc. is difficult.	2616	etc. is difficult.
1992		2617
		2618	=head3 C<stat ()> is a synchronous operation
		2619
		2620	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2621	the process. The exception are C<ev_stat> watchers - those call C<stat
		2622	()>, which is a synchronous operation.
		2623
		2624	For local paths, this usually doesn't matter: unless the system is very
		2625	busy or the intervals between stat's are large, a stat call will be fast,
		2626	as the path data is usually in memory already (except when starting the
		2627	watcher).
		2628
		2629	For networked file systems, calling C<stat ()> can block an indefinite
		2630	time due to network issues, and even under good conditions, a stat call
		2631	often takes multiple milliseconds.
		2632
		2633	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2634	paths, although this is fully supported by libev.
		2635
1993	=head3 The special problem of stat time resolution	2636	=head3 The special problem of stat time resolution
1994		2637
1995	The C<stat ()> system call only supports full-second resolution portably, and	2638	The C<stat ()> system call only supports full-second resolution portably,
1996	even on systems where the resolution is higher, most file systems still	2639	and even on systems where the resolution is higher, most file systems
1997	only support whole seconds.	2640	still only support whole seconds.
1998		2641
1999	That means that, if the time is the only thing that changes, you can	2642	That means that, if the time is the only thing that changes, you can
2000	easily miss updates: on the first update, C<ev_stat> detects a change and	2643	easily miss updates: on the first update, C<ev_stat> detects a change and
2001	calls your callback, which does something. When there is another update	2644	calls your callback, which does something. When there is another update
2002	within the same second, C<ev_stat> will be unable to detect unless the	2645	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2145		2788
2146	=head3 Watcher-Specific Functions and Data Members	2789	=head3 Watcher-Specific Functions and Data Members
2147		2790
2148	=over 4	2791	=over 4
2149		2792
2150	=item ev_idle_init (ev_signal *, callback)	2793	=item ev_idle_init (ev_idle *, callback)
2151		2794
2152	Initialises and configures the idle watcher - it has no parameters of any	2795	Initialises and configures the idle watcher - it has no parameters of any
2153	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2796	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2154	believe me.	2797	believe me.
2155		2798
…		…
2168	// no longer anything immediate to do.	2811	// no longer anything immediate to do.
2169	}	2812	}
2170		2813
2171	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2172	ev_idle_init (idle_watcher, idle_cb);	2815	ev_idle_init (idle_watcher, idle_cb);
2173	ev_idle_start (loop, idle_cb);	2816	ev_idle_start (loop, idle_watcher);
2174		2817
2175		2818
2176	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2177		2820
2178	Prepare and check watchers are usually (but not always) used in pairs:	2821	Prepare and check watchers are usually (but not always) used in pairs:
2179	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
2180	afterwards.	2823	afterwards.
2181		2824
2182	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
2183	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
2184	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
2185	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
2186	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2187	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2271	struct pollfd fds [nfd];	2914	struct pollfd fds [nfd];
2272	// actual code will need to loop here and realloc etc.	2915	// actual code will need to loop here and realloc etc.
2273	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2274		2917
2275	/* the callback is illegal, but won't be called as we stop during check */	2918	/* the callback is illegal, but won't be called as we stop during check */
2276	ev_timer_init (&tw, 0, timeout * 1e-3);	2919	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2277	ev_timer_start (loop, &tw);	2920	ev_timer_start (loop, &tw);
2278		2921
2279	// create one ev_io per pollfd	2922	// create one ev_io per pollfd
2280	for (int i = 0; i < nfd; ++i)	2923	for (int i = 0; i < nfd; ++i)
2281	{	2924	{
…		…
2355		2998
2356	if (timeout >= 0)	2999	if (timeout >= 0)
2357	// create/start timer	3000	// create/start timer
2358		3001
2359	// poll	3002	// poll
2360	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
2361		3004
2362	// stop timer again	3005	// stop timer again
2363	if (timeout >= 0)	3006	if (timeout >= 0)
2364	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2365		3008
…		…
2394	some fds have to be watched and handled very quickly (with low latency),	3037	some fds have to be watched and handled very quickly (with low latency),
2395	and even priorities and idle watchers might have too much overhead. In	3038	and even priorities and idle watchers might have too much overhead. In
2396	this case you would put all the high priority stuff in one loop and all	3039	this case you would put all the high priority stuff in one loop and all
2397	the rest in a second one, and embed the second one in the first.	3040	the rest in a second one, and embed the second one in the first.
2398		3041
2399	As long as the watcher is active, the callback will be invoked every time	3042	As long as the watcher is active, the callback will be invoked every
2400	there might be events pending in the embedded loop. The callback must then	3043	time there might be events pending in the embedded loop. The callback
2401	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3044	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2402	their callbacks (you could also start an idle watcher to give the embedded	3045	sweep and invoke their callbacks (the callback doesn't need to invoke the
2403	loop strictly lower priority for example). You can also set the callback	3046	C<ev_embed_sweep> function directly, it could also start an idle watcher
2404	to C<0>, in which case the embed watcher will automatically execute the	3047	to give the embedded loop strictly lower priority for example).
2405	embedded loop sweep.
2406		3048
2407	As long as the watcher is started it will automatically handle events. The	3049	You can also set the callback to C<0>, in which case the embed watcher
2408	callback will be invoked whenever some events have been handled. You can	3050	will automatically execute the embedded loop sweep whenever necessary.
2409	set the callback to C<0> to avoid having to specify one if you are not
2410	interested in that.
2411		3051
2412	Also, there have not currently been made special provisions for forking:	3052	Fork detection will be handled transparently while the C<ev_embed> watcher
2413	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3053	is active, i.e., the embedded loop will automatically be forked when the
2414	but you will also have to stop and restart any C<ev_embed> watchers	3054	embedding loop forks. In other cases, the user is responsible for calling
2415	yourself - but you can use a fork watcher to handle this automatically,	3055	C<ev_loop_fork> on the embedded loop.
2416	and future versions of libev might do just that.
2417		3056
2418	Unfortunately, not all backends are embeddable: only the ones returned by	3057	Unfortunately, not all backends are embeddable: only the ones returned by
2419	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3058	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2420	portable one.	3059	portable one.
2421		3060
…		…
2447	if you do not want that, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2448		3087
2449	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2450		3089
2451	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2452	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2453	appropriate way for embedded loops.	3092	appropriate way for embedded loops.
2454		3093
2455	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2456		3095
2457	The embedded event loop.	3096	The embedded event loop.
…		…
2515	event loop blocks next and before C<ev_check> watchers are being called,	3154	event loop blocks next and before C<ev_check> watchers are being called,
2516	and only in the child after the fork. If whoever good citizen calling	3155	and only in the child after the fork. If whoever good citizen calling
2517	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2518	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2519		3158
		3159	=head3 The special problem of life after fork - how is it possible?
		3160
		3161	Most uses of C<fork()> consist of forking, then some simple calls to set
		3162	up/change the process environment, followed by a call to C<exec()>. This
		3163	sequence should be handled by libev without any problems.
		3164
		3165	This changes when the application actually wants to do event handling
		3166	in the child, or both parent in child, in effect "continuing" after the
		3167	fork.
		3168
		3169	The default mode of operation (for libev, with application help to detect
		3170	forks) is to duplicate all the state in the child, as would be expected
		3171	when I<either> the parent I<or> the child process continues.
		3172
		3173	When both processes want to continue using libev, then this is usually the
		3174	wrong result. In that case, usually one process (typically the parent) is
		3175	supposed to continue with all watchers in place as before, while the other
		3176	process typically wants to start fresh, i.e. without any active watchers.
		3177
		3178	The cleanest and most efficient way to achieve that with libev is to
		3179	simply create a new event loop, which of course will be "empty", and
		3180	use that for new watchers. This has the advantage of not touching more
		3181	memory than necessary, and thus avoiding the copy-on-write, and the
		3182	disadvantage of having to use multiple event loops (which do not support
		3183	signal watchers).
		3184
		3185	When this is not possible, or you want to use the default loop for
		3186	other reasons, then in the process that wants to start "fresh", call
		3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3188	Destroying the default loop will "orphan" (not stop) all registered
		3189	watchers, so you have to be careful not to execute code that modifies
		3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
		3192
2520	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2521		3194
2522	=over 4	3195	=over 4
2523		3196
2524	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2525		3198
2526	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2527	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2528	believe me.	3201	really.
2529		3202
2530	=back	3203	=back
2531		3204
2532		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2533	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2534		3247
2535	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2536	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2537	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2538		3251
2539	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2540	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2541	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2542	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2543	safe.
2544		3256
2545	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2546	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2547	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2548	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2549		3264
2550	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2551	just the default loop.	3266	just the default loop.
2552		3267
2553	=head3 Queueing	3268	=head3 Queueing
2554		3269
2555	C<ev_async> does not support queueing of data in any way. The reason	3270	C<ev_async> does not support queueing of data in any way. The reason
2556	is that the author does not know of a simple (or any) algorithm for a	3271	is that the author does not know of a simple (or any) algorithm for a
2557	multiple-writer-single-reader queue that works in all cases and doesn't	3272	multiple-writer-single-reader queue that works in all cases and doesn't
2558	need elaborate support such as pthreads.	3273	need elaborate support such as pthreads or unportable memory access
		3274	semantics.
2559		3275
2560	That means that if you want to queue data, you have to provide your own	3276	That means that if you want to queue data, you have to provide your own
2561	queue. But at least I can tell you how to implement locking around your	3277	queue. But at least I can tell you how to implement locking around your
2562	queue:	3278	queue:
2563		3279
…		…
2641	=over 4	3357	=over 4
2642		3358
2643	=item ev_async_init (ev_async *, callback)	3359	=item ev_async_init (ev_async *, callback)
2644		3360
2645	Initialises and configures the async watcher - it has no parameters of any	3361	Initialises and configures the async watcher - it has no parameters of any
2646	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3362	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2647	trust me.	3363	trust me.
2648		3364
2649	=item ev_async_send (loop, ev_async *)	3365	=item ev_async_send (loop, ev_async *)
2650		3366
2651	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2652	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2653	C<ev_feed_event>, this call is safe to do from other threads, signal or	3369	C<ev_feed_event>, this call is safe to do from other threads, signal or
2654	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2655	section below on what exactly this means).	3371	section below on what exactly this means).
2656		3372
		3373	Note that, as with other watchers in libev, multiple events might get
		3374	compressed into a single callback invocation (another way to look at this
		3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3376	reset when the event loop detects that).
		3377
2657	This call incurs the overhead of a system call only once per loop iteration,	3378	This call incurs the overhead of a system call only once per event loop
2658	so while the overhead might be noticeable, it doesn't apply to repeated	3379	iteration, so while the overhead might be noticeable, it doesn't apply to
2659	calls to C<ev_async_send>.	3380	repeated calls to C<ev_async_send> for the same event loop.
2660		3381
2661	=item bool = ev_async_pending (ev_async *)	3382	=item bool = ev_async_pending (ev_async *)
2662		3383
2663	Returns a non-zero value when C<ev_async_send> has been called on the	3384	Returns a non-zero value when C<ev_async_send> has been called on the
2664	watcher but the event has not yet been processed (or even noted) by the	3385	watcher but the event has not yet been processed (or even noted) by the
…		…
2667	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3388	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2668	the loop iterates next and checks for the watcher to have become active,	3389	the loop iterates next and checks for the watcher to have become active,
2669	it will reset the flag again. C<ev_async_pending> can be used to very	3390	it will reset the flag again. C<ev_async_pending> can be used to very
2670	quickly check whether invoking the loop might be a good idea.	3391	quickly check whether invoking the loop might be a good idea.
2671		3392
2672	Not that this does I<not> check whether the watcher itself is pending, only	3393	Not that this does I<not> check whether the watcher itself is pending,
2673	whether it has been requested to make this watcher pending.	3394	only whether it has been requested to make this watcher pending: there
		3395	is a time window between the event loop checking and resetting the async
		3396	notification, and the callback being invoked.
2674		3397
2675	=back	3398	=back
2676		3399
2677		3400
2678	=head1 OTHER FUNCTIONS	3401	=head1 OTHER FUNCTIONS
…		…
2695		3418
2696	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
2697	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2698	repeat = 0) will be started. C<0> is a valid timeout.	3421	repeat = 0) will be started. C<0> is a valid timeout.
2699		3422
2700	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2701	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
2702	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2703	value passed to C<ev_once>. Note that it is possible to receive I<both>	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
2704	a timeout and an io event at the same time - you probably should give io	3427	a timeout and an io event at the same time - you probably should give io
2705	events precedence.	3428	events precedence.
2706		3429
2707	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2708		3431
2709	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
2710	{	3433	{
2711	if (revents & EV_READ)	3434	if (revents & EV_READ)
2712	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
2713	else if (revents & EV_TIMEOUT)	3436	else if (revents & EV_TIMER)
2714	/* doh, nothing entered */;	3437	/* doh, nothing entered */;
2715	}	3438	}
2716		3439
2717	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2718		3441
2719	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2720
2721	Feeds the given event set into the event loop, as if the specified event
2722	had happened for the specified watcher (which must be a pointer to an
2723	initialised but not necessarily started event watcher).
2724
2725	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3442	=item ev_feed_fd_event (loop, int fd, int revents)
2726		3443
2727	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
2728	the given events it.	3445	the given events it.
2729		3446
2730	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
2731		3448
2732	Feed an event as if the given signal occurred (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2733	loop!).	3450	which is async-safe.
		3451
		3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=over 4
		3462
		3463	=item Model/nested event loop invocations and exit conditions.
		3464
		3465	Often (especially in GUI toolkits) there are places where you have
		3466	I<modal> interaction, which is most easily implemented by recursively
		3467	invoking C<ev_run>.
		3468
		3469	This brings the problem of exiting - a callback might want to finish the
		3470	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3471	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3472	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3473	other combination: In these cases, C<ev_break> will not work alone.
		3474
		3475	The solution is to maintain "break this loop" variable for each C<ev_run>
		3476	invocation, and use a loop around C<ev_run> until the condition is
		3477	triggered, using C<EVRUN_ONCE>:
		3478
		3479	// main loop
		3480	int exit_main_loop = 0;
		3481
		3482	while (!exit_main_loop)
		3483	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3484
		3485	// in a model watcher
		3486	int exit_nested_loop = 0;
		3487
		3488	while (!exit_nested_loop)
		3489	ev_run (EV_A_ EVRUN_ONCE);
		3490
		3491	To exit from any of these loops, just set the corresponding exit variable:
		3492
		3493	// exit modal loop
		3494	exit_nested_loop = 1;
		3495
		3496	// exit main program, after modal loop is finished
		3497	exit_main_loop = 1;
		3498
		3499	// exit both
		3500	exit_main_loop = exit_nested_loop = 1;
		3501
		3502	=item Thread locking example
		3503
		3504	Here is a fictitious example of how to run an event loop in a different
		3505	thread than where callbacks are being invoked and watchers are
		3506	created/added/removed.
		3507
		3508	For a real-world example, see the C<EV::Loop::Async> perl module,
		3509	which uses exactly this technique (which is suited for many high-level
		3510	languages).
		3511
		3512	The example uses a pthread mutex to protect the loop data, a condition
		3513	variable to wait for callback invocations, an async watcher to notify the
		3514	event loop thread and an unspecified mechanism to wake up the main thread.
		3515
		3516	First, you need to associate some data with the event loop:
		3517
		3518	typedef struct {
		3519	mutex_t lock; /* global loop lock */
		3520	ev_async async_w;
		3521	thread_t tid;
		3522	cond_t invoke_cv;
		3523	} userdata;
		3524
		3525	void prepare_loop (EV_P)
		3526	{
		3527	// for simplicity, we use a static userdata struct.
		3528	static userdata u;
		3529
		3530	ev_async_init (&u->async_w, async_cb);
		3531	ev_async_start (EV_A_ &u->async_w);
		3532
		3533	pthread_mutex_init (&u->lock, 0);
		3534	pthread_cond_init (&u->invoke_cv, 0);
		3535
		3536	// now associate this with the loop
		3537	ev_set_userdata (EV_A_ u);
		3538	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3539	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3540
		3541	// then create the thread running ev_loop
		3542	pthread_create (&u->tid, 0, l_run, EV_A);
		3543	}
		3544
		3545	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3546	solely to wake up the event loop so it takes notice of any new watchers
		3547	that might have been added:
		3548
		3549	static void
		3550	async_cb (EV_P_ ev_async *w, int revents)
		3551	{
		3552	// just used for the side effects
		3553	}
		3554
		3555	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3556	protecting the loop data, respectively.
		3557
		3558	static void
		3559	l_release (EV_P)
		3560	{
		3561	userdata *u = ev_userdata (EV_A);
		3562	pthread_mutex_unlock (&u->lock);
		3563	}
		3564
		3565	static void
		3566	l_acquire (EV_P)
		3567	{
		3568	userdata *u = ev_userdata (EV_A);
		3569	pthread_mutex_lock (&u->lock);
		3570	}
		3571
		3572	The event loop thread first acquires the mutex, and then jumps straight
		3573	into C<ev_run>:
		3574
		3575	void *
		3576	l_run (void *thr_arg)
		3577	{
		3578	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3579
		3580	l_acquire (EV_A);
		3581	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3582	ev_run (EV_A_ 0);
		3583	l_release (EV_A);
		3584
		3585	return 0;
		3586	}
		3587
		3588	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3589	signal the main thread via some unspecified mechanism (signals? pipe
		3590	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3591	have been called (in a while loop because a) spurious wakeups are possible
		3592	and b) skipping inter-thread-communication when there are no pending
		3593	watchers is very beneficial):
		3594
		3595	static void
		3596	l_invoke (EV_P)
		3597	{
		3598	userdata *u = ev_userdata (EV_A);
		3599
		3600	while (ev_pending_count (EV_A))
		3601	{
		3602	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3603	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3604	}
		3605	}
		3606
		3607	Now, whenever the main thread gets told to invoke pending watchers, it
		3608	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3609	thread to continue:
		3610
		3611	static void
		3612	real_invoke_pending (EV_P)
		3613	{
		3614	userdata *u = ev_userdata (EV_A);
		3615
		3616	pthread_mutex_lock (&u->lock);
		3617	ev_invoke_pending (EV_A);
		3618	pthread_cond_signal (&u->invoke_cv);
		3619	pthread_mutex_unlock (&u->lock);
		3620	}
		3621
		3622	Whenever you want to start/stop a watcher or do other modifications to an
		3623	event loop, you will now have to lock:
		3624
		3625	ev_timer timeout_watcher;
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3629
		3630	pthread_mutex_lock (&u->lock);
		3631	ev_timer_start (EV_A_ &timeout_watcher);
		3632	ev_async_send (EV_A_ &u->async_w);
		3633	pthread_mutex_unlock (&u->lock);
		3634
		3635	Note that sending the C<ev_async> watcher is required because otherwise
		3636	an event loop currently blocking in the kernel will have no knowledge
		3637	about the newly added timer. By waking up the loop it will pick up any new
		3638	watchers in the next event loop iteration.
2734		3639
2735	=back	3640	=back
2736		3641
2737		3642
2738	=head1 LIBEVENT EMULATION	3643	=head1 LIBEVENT EMULATION
2739		3644
2740	Libev offers a compatibility emulation layer for libevent. It cannot	3645	Libev offers a compatibility emulation layer for libevent. It cannot
2741	emulate the internals of libevent, so here are some usage hints:	3646	emulate the internals of libevent, so here are some usage hints:
2742		3647
2743	=over 4	3648	=over 4
		3649
		3650	=item * Only the libevent-1.4.1-beta API is being emulated.
		3651
		3652	This was the newest libevent version available when libev was implemented,
		3653	and is still mostly unchanged in 2010.
2744		3654
2745	=item * Use it by including <event.h>, as usual.	3655	=item * Use it by including <event.h>, as usual.
2746		3656
2747	=item * The following members are fully supported: ev_base, ev_callback,	3657	=item * The following members are fully supported: ev_base, ev_callback,
2748	ev_arg, ev_fd, ev_res, ev_events.	3658	ev_arg, ev_fd, ev_res, ev_events.
…		…
2754	=item * Priorities are not currently supported. Initialising priorities	3664	=item * Priorities are not currently supported. Initialising priorities
2755	will fail and all watchers will have the same priority, even though there	3665	will fail and all watchers will have the same priority, even though there
2756	is an ev_pri field.	3666	is an ev_pri field.
2757		3667
2758	=item * In libevent, the last base created gets the signals, in libev, the	3668	=item * In libevent, the last base created gets the signals, in libev, the
2759	first base created (== the default loop) gets the signals.	3669	base that registered the signal gets the signals.
2760		3670
2761	=item * Other members are not supported.	3671	=item * Other members are not supported.
2762		3672
2763	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3673	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2764	to use the libev header file and library.	3674	to use the libev header file and library.
…		…
2783	Care has been taken to keep the overhead low. The only data member the C++	3693	Care has been taken to keep the overhead low. The only data member the C++
2784	classes add (compared to plain C-style watchers) is the event loop pointer	3694	classes add (compared to plain C-style watchers) is the event loop pointer
2785	that the watcher is associated with (or no additional members at all if	3695	that the watcher is associated with (or no additional members at all if
2786	you disable C<EV_MULTIPLICITY> when embedding libev).	3696	you disable C<EV_MULTIPLICITY> when embedding libev).
2787		3697
2788	Currently, functions, and static and non-static member functions can be	3698	Currently, functions, static and non-static member functions and classes
2789	used as callbacks. Other types should be easy to add as long as they only	3699	with C<operator ()> can be used as callbacks. Other types should be easy
2790	need one additional pointer for context. If you need support for other	3700	to add as long as they only need one additional pointer for context. If
2791	types of functors please contact the author (preferably after implementing	3701	you need support for other types of functors please contact the author
2792	it).	3702	(preferably after implementing it).
2793		3703
2794	Here is a list of things available in the C<ev> namespace:	3704	Here is a list of things available in the C<ev> namespace:
2795		3705
2796	=over 4	3706	=over 4
2797		3707
…		…
2815		3725
2816	=over 4	3726	=over 4
2817		3727
2818	=item ev::TYPE::TYPE ()	3728	=item ev::TYPE::TYPE ()
2819		3729
2820	=item ev::TYPE::TYPE (struct ev_loop *)	3730	=item ev::TYPE::TYPE (loop)
2821		3731
2822	=item ev::TYPE::~TYPE	3732	=item ev::TYPE::~TYPE
2823		3733
2824	The constructor (optionally) takes an event loop to associate the watcher	3734	The constructor (optionally) takes an event loop to associate the watcher
2825	with. If it is omitted, it will use C<EV_DEFAULT>.	3735	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2857		3767
2858	myclass obj;	3768	myclass obj;
2859	ev::io iow;	3769	ev::io iow;
2860	iow.set <myclass, &myclass::io_cb> (&obj);	3770	iow.set <myclass, &myclass::io_cb> (&obj);
2861		3771
		3772	=item w->set (object *)
		3773
		3774	This is a variation of a method callback - leaving out the method to call
		3775	will default the method to C<operator ()>, which makes it possible to use
		3776	functor objects without having to manually specify the C<operator ()> all
		3777	the time. Incidentally, you can then also leave out the template argument
		3778	list.
		3779
		3780	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3781	int revents)>.
		3782
		3783	See the method-C<set> above for more details.
		3784
		3785	Example: use a functor object as callback.
		3786
		3787	struct myfunctor
		3788	{
		3789	void operator() (ev::io &w, int revents)
		3790	{
		3791	...
		3792	}
		3793	}
		3794
		3795	myfunctor f;
		3796
		3797	ev::io w;
		3798	w.set (&f);
		3799
2862	=item w->set<function> (void *data = 0)	3800	=item w->set<function> (void *data = 0)
2863		3801
2864	Also sets a callback, but uses a static method or plain function as	3802	Also sets a callback, but uses a static method or plain function as
2865	callback. The optional C<data> argument will be stored in the watcher's	3803	callback. The optional C<data> argument will be stored in the watcher's
2866	C<data> member and is free for you to use.	3804	C<data> member and is free for you to use.
…		…
2872	Example: Use a plain function as callback.	3810	Example: Use a plain function as callback.
2873		3811
2874	static void io_cb (ev::io &w, int revents) { }	3812	static void io_cb (ev::io &w, int revents) { }
2875	iow.set <io_cb> ();	3813	iow.set <io_cb> ();
2876		3814
2877	=item w->set (struct ev_loop *)	3815	=item w->set (loop)
2878		3816
2879	Associates a different C<struct ev_loop> with this watcher. You can only	3817	Associates a different C<struct ev_loop> with this watcher. You can only
2880	do this when the watcher is inactive (and not pending either).	3818	do this when the watcher is inactive (and not pending either).
2881		3819
2882	=item w->set ([arguments])	3820	=item w->set ([arguments])
2883		3821
2884	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3822	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2885	called at least once. Unlike the C counterpart, an active watcher gets	3823	method or a suitable start method must be called at least once. Unlike the
2886	automatically stopped and restarted when reconfiguring it with this	3824	C counterpart, an active watcher gets automatically stopped and restarted
2887	method.	3825	when reconfiguring it with this method.
2888		3826
2889	=item w->start ()	3827	=item w->start ()
2890		3828
2891	Starts the watcher. Note that there is no C<loop> argument, as the	3829	Starts the watcher. Note that there is no C<loop> argument, as the
2892	constructor already stores the event loop.	3830	constructor already stores the event loop.
2893		3831
		3832	=item w->start ([arguments])
		3833
		3834	Instead of calling C<set> and C<start> methods separately, it is often
		3835	convenient to wrap them in one call. Uses the same type of arguments as
		3836	the configure C<set> method of the watcher.
		3837
2894	=item w->stop ()	3838	=item w->stop ()
2895		3839
2896	Stops the watcher if it is active. Again, no C<loop> argument.	3840	Stops the watcher if it is active. Again, no C<loop> argument.
2897		3841
2898	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3842	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2910		3854
2911	=back	3855	=back
2912		3856
2913	=back	3857	=back
2914		3858
2915	Example: Define a class with an IO and idle watcher, start one of them in	3859	Example: Define a class with two I/O and idle watchers, start the I/O
2916	the constructor.	3860	watchers in the constructor.
2917		3861
2918	class myclass	3862	class myclass
2919	{	3863	{
2920	ev::io io ; void io_cb (ev::io &w, int revents);	3864	ev::io io ; void io_cb (ev::io &w, int revents);
		3865	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2921	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3866	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2922		3867
2923	myclass (int fd)	3868	myclass (int fd)
2924	{	3869	{
2925	io .set <myclass, &myclass::io_cb > (this);	3870	io .set <myclass, &myclass::io_cb > (this);
		3871	io2 .set <myclass, &myclass::io2_cb > (this);
2926	idle.set <myclass, &myclass::idle_cb> (this);	3872	idle.set <myclass, &myclass::idle_cb> (this);
2927		3873
2928	io.start (fd, ev::READ);	3874	io.set (fd, ev::WRITE); // configure the watcher
		3875	io.start (); // start it whenever convenient
		3876
		3877	io2.start (fd, ev::READ); // set + start in one call
2929	}	3878	}
2930	};	3879	};
2931		3880
2932		3881
2933	=head1 OTHER LANGUAGE BINDINGS	3882	=head1 OTHER LANGUAGE BINDINGS
…		…
2952	L<http://software.schmorp.de/pkg/EV>.	3901	L<http://software.schmorp.de/pkg/EV>.
2953		3902
2954	=item Python	3903	=item Python
2955		3904
2956	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3905	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2957	seems to be quite complete and well-documented. Note, however, that the	3906	seems to be quite complete and well-documented.
2958	patch they require for libev is outright dangerous as it breaks the ABI
2959	for everybody else, and therefore, should never be applied in an installed
2960	libev (if python requires an incompatible ABI then it needs to embed
2961	libev).
2962		3907
2963	=item Ruby	3908	=item Ruby
2964		3909
2965	Tony Arcieri has written a ruby extension that offers access to a subset	3910	Tony Arcieri has written a ruby extension that offers access to a subset
2966	of the libev API and adds file handle abstractions, asynchronous DNS and	3911	of the libev API and adds file handle abstractions, asynchronous DNS and
2967	more on top of it. It can be found via gem servers. Its homepage is at	3912	more on top of it. It can be found via gem servers. Its homepage is at
2968	L<http://rev.rubyforge.org/>.	3913	L<http://rev.rubyforge.org/>.
2969		3914
		3915	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3916	makes rev work even on mingw.
		3917
		3918	=item Haskell
		3919
		3920	A haskell binding to libev is available at
		3921	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3922
2970	=item D	3923	=item D
2971		3924
2972	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3925	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2973	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3926	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2974		3927
2975	=item Ocaml	3928	=item Ocaml
2976		3929
2977	Erkki Seppala has written Ocaml bindings for libev, to be found at	3930	Erkki Seppala has written Ocaml bindings for libev, to be found at
2978	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3931	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3932
		3933	=item Lua
		3934
		3935	Brian Maher has written a partial interface to libev for lua (at the
		3936	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3937	L<http://github.com/brimworks/lua-ev>.
2979		3938
2980	=back	3939	=back
2981		3940
2982		3941
2983	=head1 MACRO MAGIC	3942	=head1 MACRO MAGIC
…		…
2997	loop argument"). The C<EV_A> form is used when this is the sole argument,	3956	loop argument"). The C<EV_A> form is used when this is the sole argument,
2998	C<EV_A_> is used when other arguments are following. Example:	3957	C<EV_A_> is used when other arguments are following. Example:
2999		3958
3000	ev_unref (EV_A);	3959	ev_unref (EV_A);
3001	ev_timer_add (EV_A_ watcher);	3960	ev_timer_add (EV_A_ watcher);
3002	ev_loop (EV_A_ 0);	3961	ev_run (EV_A_ 0);
3003		3962
3004	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3963	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3005	which is often provided by the following macro.	3964	which is often provided by the following macro.
3006		3965
3007	=item C<EV_P>, C<EV_P_>	3966	=item C<EV_P>, C<EV_P_>
…		…
3047	}	4006	}
3048		4007
3049	ev_check check;	4008	ev_check check;
3050	ev_check_init (&check, check_cb);	4009	ev_check_init (&check, check_cb);
3051	ev_check_start (EV_DEFAULT_ &check);	4010	ev_check_start (EV_DEFAULT_ &check);
3052	ev_loop (EV_DEFAULT_ 0);	4011	ev_run (EV_DEFAULT_ 0);
3053		4012
3054	=head1 EMBEDDING	4013	=head1 EMBEDDING
3055		4014
3056	Libev can (and often is) directly embedded into host	4015	Libev can (and often is) directly embedded into host
3057	applications. Examples of applications that embed it include the Deliantra	4016	applications. Examples of applications that embed it include the Deliantra
…		…
3084		4043
3085	#define EV_STANDALONE 1	4044	#define EV_STANDALONE 1
3086	#include "ev.h"	4045	#include "ev.h"
3087		4046
3088	Both header files and implementation files can be compiled with a C++	4047	Both header files and implementation files can be compiled with a C++
3089	compiler (at least, thats a stated goal, and breakage will be treated	4048	compiler (at least, that's a stated goal, and breakage will be treated
3090	as a bug).	4049	as a bug).
3091		4050
3092	You need the following files in your source tree, or in a directory	4051	You need the following files in your source tree, or in a directory
3093	in your include path (e.g. in libev/ when using -Ilibev):	4052	in your include path (e.g. in libev/ when using -Ilibev):
3094		4053
…		…
3137	libev.m4	4096	libev.m4
3138		4097
3139	=head2 PREPROCESSOR SYMBOLS/MACROS	4098	=head2 PREPROCESSOR SYMBOLS/MACROS
3140		4099
3141	Libev can be configured via a variety of preprocessor symbols you have to	4100	Libev can be configured via a variety of preprocessor symbols you have to
3142	define before including any of its files. The default in the absence of	4101	define before including (or compiling) any of its files. The default in
3143	autoconf is documented for every option.	4102	the absence of autoconf is documented for every option.
		4103
		4104	Symbols marked with "(h)" do not change the ABI, and can have different
		4105	values when compiling libev vs. including F<ev.h>, so it is permissible
		4106	to redefine them before including F<ev.h> without breaking compatibility
		4107	to a compiled library. All other symbols change the ABI, which means all
		4108	users of libev and the libev code itself must be compiled with compatible
		4109	settings.
3144		4110
3145	=over 4	4111	=over 4
3146		4112
		4113	=item EV_COMPAT3 (h)
		4114
		4115	Backwards compatibility is a major concern for libev. This is why this
		4116	release of libev comes with wrappers for the functions and symbols that
		4117	have been renamed between libev version 3 and 4.
		4118
		4119	You can disable these wrappers (to test compatibility with future
		4120	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4121	sources. This has the additional advantage that you can drop the C<struct>
		4122	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4123	typedef in that case.
		4124
		4125	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4126	and in some even more future version the compatibility code will be
		4127	removed completely.
		4128
3147	=item EV_STANDALONE	4129	=item EV_STANDALONE (h)
3148		4130
3149	Must always be C<1> if you do not use autoconf configuration, which	4131	Must always be C<1> if you do not use autoconf configuration, which
3150	keeps libev from including F<config.h>, and it also defines dummy	4132	keeps libev from including F<config.h>, and it also defines dummy
3151	implementations for some libevent functions (such as logging, which is not	4133	implementations for some libevent functions (such as logging, which is not
3152	supported). It will also not define any of the structs usually found in	4134	supported). It will also not define any of the structs usually found in
3153	F<event.h> that are not directly supported by the libev core alone.	4135	F<event.h> that are not directly supported by the libev core alone.
3154		4136
		4137	In standalone mode, libev will still try to automatically deduce the
		4138	configuration, but has to be more conservative.
		4139
3155	=item EV_USE_MONOTONIC	4140	=item EV_USE_MONOTONIC
3156		4141
3157	If defined to be C<1>, libev will try to detect the availability of the	4142	If defined to be C<1>, libev will try to detect the availability of the
3158	monotonic clock option at both compile time and runtime. Otherwise no use	4143	monotonic clock option at both compile time and runtime. Otherwise no
3159	of the monotonic clock option will be attempted. If you enable this, you	4144	use of the monotonic clock option will be attempted. If you enable this,
3160	usually have to link against librt or something similar. Enabling it when	4145	you usually have to link against librt or something similar. Enabling it
3161	the functionality isn't available is safe, though, although you have	4146	when the functionality isn't available is safe, though, although you have
3162	to make sure you link against any libraries where the C<clock_gettime>	4147	to make sure you link against any libraries where the C<clock_gettime>
3163	function is hiding in (often F<-lrt>).	4148	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3164		4149
3165	=item EV_USE_REALTIME	4150	=item EV_USE_REALTIME
3166		4151
3167	If defined to be C<1>, libev will try to detect the availability of the	4152	If defined to be C<1>, libev will try to detect the availability of the
3168	real-time clock option at compile time (and assume its availability at	4153	real-time clock option at compile time (and assume its availability
3169	runtime if successful). Otherwise no use of the real-time clock option will	4154	at runtime if successful). Otherwise no use of the real-time clock
3170	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4155	option will be attempted. This effectively replaces C<gettimeofday>
3171	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4156	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3172	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4157	correctness. See the note about libraries in the description of
		4158	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4159	C<EV_USE_CLOCK_SYSCALL>.
		4160
		4161	=item EV_USE_CLOCK_SYSCALL
		4162
		4163	If defined to be C<1>, libev will try to use a direct syscall instead
		4164	of calling the system-provided C<clock_gettime> function. This option
		4165	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4166	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4167	programs needlessly. Using a direct syscall is slightly slower (in
		4168	theory), because no optimised vdso implementation can be used, but avoids
		4169	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4170	higher, as it simplifies linking (no need for C<-lrt>).
3173		4171
3174	=item EV_USE_NANOSLEEP	4172	=item EV_USE_NANOSLEEP
3175		4173
3176	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4174	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3177	and will use it for delays. Otherwise it will use C<select ()>.	4175	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3193		4191
3194	=item EV_SELECT_USE_FD_SET	4192	=item EV_SELECT_USE_FD_SET
3195		4193
3196	If defined to C<1>, then the select backend will use the system C<fd_set>	4194	If defined to C<1>, then the select backend will use the system C<fd_set>
3197	structure. This is useful if libev doesn't compile due to a missing	4195	structure. This is useful if libev doesn't compile due to a missing
3198	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4196	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3199	exotic systems. This usually limits the range of file descriptors to some	4197	on exotic systems. This usually limits the range of file descriptors to
3200	low limit such as 1024 or might have other limitations (winsocket only	4198	some low limit such as 1024 or might have other limitations (winsocket
3201	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4199	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3202	influence the size of the C<fd_set> used.	4200	configures the maximum size of the C<fd_set>.
3203		4201
3204	=item EV_SELECT_IS_WINSOCKET	4202	=item EV_SELECT_IS_WINSOCKET
3205		4203
3206	When defined to C<1>, the select backend will assume that	4204	When defined to C<1>, the select backend will assume that
3207	select/socket/connect etc. don't understand file descriptors but	4205	select/socket/connect etc. don't understand file descriptors but
…		…
3209	be used is the winsock select). This means that it will call	4207	be used is the winsock select). This means that it will call
3210	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4208	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3211	it is assumed that all these functions actually work on fds, even	4209	it is assumed that all these functions actually work on fds, even
3212	on win32. Should not be defined on non-win32 platforms.	4210	on win32. Should not be defined on non-win32 platforms.
3213		4211
3214	=item EV_FD_TO_WIN32_HANDLE	4212	=item EV_FD_TO_WIN32_HANDLE(fd)
3215		4213
3216	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4214	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3217	file descriptors to socket handles. When not defining this symbol (the	4215	file descriptors to socket handles. When not defining this symbol (the
3218	default), then libev will call C<_get_osfhandle>, which is usually	4216	default), then libev will call C<_get_osfhandle>, which is usually
3219	correct. In some cases, programs use their own file descriptor management,	4217	correct. In some cases, programs use their own file descriptor management,
3220	in which case they can provide this function to map fds to socket handles.	4218	in which case they can provide this function to map fds to socket handles.
		4219
		4220	=item EV_WIN32_HANDLE_TO_FD(handle)
		4221
		4222	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4223	using the standard C<_open_osfhandle> function. For programs implementing
		4224	their own fd to handle mapping, overwriting this function makes it easier
		4225	to do so. This can be done by defining this macro to an appropriate value.
		4226
		4227	=item EV_WIN32_CLOSE_FD(fd)
		4228
		4229	If programs implement their own fd to handle mapping on win32, then this
		4230	macro can be used to override the C<close> function, useful to unregister
		4231	file descriptors again. Note that the replacement function has to close
		4232	the underlying OS handle.
3221		4233
3222	=item EV_USE_POLL	4234	=item EV_USE_POLL
3223		4235
3224	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4236	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3225	backend. Otherwise it will be enabled on non-win32 platforms. It	4237	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3272	as well as for signal and thread safety in C<ev_async> watchers.	4284	as well as for signal and thread safety in C<ev_async> watchers.
3273		4285
3274	In the absence of this define, libev will use C<sig_atomic_t volatile>	4286	In the absence of this define, libev will use C<sig_atomic_t volatile>
3275	(from F<signal.h>), which is usually good enough on most platforms.	4287	(from F<signal.h>), which is usually good enough on most platforms.
3276		4288
3277	=item EV_H	4289	=item EV_H (h)
3278		4290
3279	The name of the F<ev.h> header file used to include it. The default if	4291	The name of the F<ev.h> header file used to include it. The default if
3280	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4292	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3281	used to virtually rename the F<ev.h> header file in case of conflicts.	4293	used to virtually rename the F<ev.h> header file in case of conflicts.
3282		4294
3283	=item EV_CONFIG_H	4295	=item EV_CONFIG_H (h)
3284		4296
3285	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4297	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3286	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4298	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3287	C<EV_H>, above.	4299	C<EV_H>, above.
3288		4300
3289	=item EV_EVENT_H	4301	=item EV_EVENT_H (h)
3290		4302
3291	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4303	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3292	of how the F<event.h> header can be found, the default is C<"event.h">.	4304	of how the F<event.h> header can be found, the default is C<"event.h">.
3293		4305
3294	=item EV_PROTOTYPES	4306	=item EV_PROTOTYPES (h)
3295		4307
3296	If defined to be C<0>, then F<ev.h> will not define any function	4308	If defined to be C<0>, then F<ev.h> will not define any function
3297	prototypes, but still define all the structs and other symbols. This is	4309	prototypes, but still define all the structs and other symbols. This is
3298	occasionally useful if you want to provide your own wrapper functions	4310	occasionally useful if you want to provide your own wrapper functions
3299	around libev functions.	4311	around libev functions.
…		…
3321	fine.	4333	fine.
3322		4334
3323	If your embedding application does not need any priorities, defining these	4335	If your embedding application does not need any priorities, defining these
3324	both to C<0> will save some memory and CPU.	4336	both to C<0> will save some memory and CPU.
3325		4337
3326	=item EV_PERIODIC_ENABLE	4338	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4339	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4340	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3327		4341
3328	If undefined or defined to be C<1>, then periodic timers are supported. If	4342	If undefined or defined to be C<1> (and the platform supports it), then
3329	defined to be C<0>, then they are not. Disabling them saves a few kB of	4343	the respective watcher type is supported. If defined to be C<0>, then it
3330	code.	4344	is not. Disabling watcher types mainly saves code size.
3331		4345
3332	=item EV_IDLE_ENABLE	4346	=item EV_FEATURES
3333
3334	If undefined or defined to be C<1>, then idle watchers are supported. If
3335	defined to be C<0>, then they are not. Disabling them saves a few kB of
3336	code.
3337
3338	=item EV_EMBED_ENABLE
3339
3340	If undefined or defined to be C<1>, then embed watchers are supported. If
3341	defined to be C<0>, then they are not. Embed watchers rely on most other
3342	watcher types, which therefore must not be disabled.
3343
3344	=item EV_STAT_ENABLE
3345
3346	If undefined or defined to be C<1>, then stat watchers are supported. If
3347	defined to be C<0>, then they are not.
3348
3349	=item EV_FORK_ENABLE
3350
3351	If undefined or defined to be C<1>, then fork watchers are supported. If
3352	defined to be C<0>, then they are not.
3353
3354	=item EV_ASYNC_ENABLE
3355
3356	If undefined or defined to be C<1>, then async watchers are supported. If
3357	defined to be C<0>, then they are not.
3358
3359	=item EV_MINIMAL
3360		4347
3361	If you need to shave off some kilobytes of code at the expense of some	4348	If you need to shave off some kilobytes of code at the expense of some
3362	speed, define this symbol to C<1>. Currently this is used to override some	4349	speed (but with the full API), you can define this symbol to request
3363	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4350	certain subsets of functionality. The default is to enable all features
3364	much smaller 2-heap for timer management over the default 4-heap.	4351	that can be enabled on the platform.
		4352
		4353	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4354	with some broad features you want) and then selectively re-enable
		4355	additional parts you want, for example if you want everything minimal,
		4356	but multiple event loop support, async and child watchers and the poll
		4357	backend, use this:
		4358
		4359	#define EV_FEATURES 0
		4360	#define EV_MULTIPLICITY 1
		4361	#define EV_USE_POLL 1
		4362	#define EV_CHILD_ENABLE 1
		4363	#define EV_ASYNC_ENABLE 1
		4364
		4365	The actual value is a bitset, it can be a combination of the following
		4366	values:
		4367
		4368	=over 4
		4369
		4370	=item C<1> - faster/larger code
		4371
		4372	Use larger code to speed up some operations.
		4373
		4374	Currently this is used to override some inlining decisions (enlarging the
		4375	code size by roughly 30% on amd64).
		4376
		4377	When optimising for size, use of compiler flags such as C<-Os> with
		4378	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4379	assertions.
		4380
		4381	=item C<2> - faster/larger data structures
		4382
		4383	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4384	hash table sizes and so on. This will usually further increase code size
		4385	and can additionally have an effect on the size of data structures at
		4386	runtime.
		4387
		4388	=item C<4> - full API configuration
		4389
		4390	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4391	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4392
		4393	=item C<8> - full API
		4394
		4395	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4396	details on which parts of the API are still available without this
		4397	feature, and do not complain if this subset changes over time.
		4398
		4399	=item C<16> - enable all optional watcher types
		4400
		4401	Enables all optional watcher types. If you want to selectively enable
		4402	only some watcher types other than I/O and timers (e.g. prepare,
		4403	embed, async, child...) you can enable them manually by defining
		4404	C<EV_watchertype_ENABLE> to C<1> instead.
		4405
		4406	=item C<32> - enable all backends
		4407
		4408	This enables all backends - without this feature, you need to enable at
		4409	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4410
		4411	=item C<64> - enable OS-specific "helper" APIs
		4412
		4413	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4414	default.
		4415
		4416	=back
		4417
		4418	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4419	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4420	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4421	watchers, timers and monotonic clock support.
		4422
		4423	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4424	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4425	your program might be left out as well - a binary starting a timer and an
		4426	I/O watcher then might come out at only 5Kb.
		4427
		4428	=item EV_AVOID_STDIO
		4429
		4430	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4431	functions (printf, scanf, perror etc.). This will increase the code size
		4432	somewhat, but if your program doesn't otherwise depend on stdio and your
		4433	libc allows it, this avoids linking in the stdio library which is quite
		4434	big.
		4435
		4436	Note that error messages might become less precise when this option is
		4437	enabled.
		4438
		4439	=item EV_NSIG
		4440
		4441	The highest supported signal number, +1 (or, the number of
		4442	signals): Normally, libev tries to deduce the maximum number of signals
		4443	automatically, but sometimes this fails, in which case it can be
		4444	specified. Also, using a lower number than detected (C<32> should be
		4445	good for about any system in existence) can save some memory, as libev
		4446	statically allocates some 12-24 bytes per signal number.
3365		4447
3366	=item EV_PID_HASHSIZE	4448	=item EV_PID_HASHSIZE
3367		4449
3368	C<ev_child> watchers use a small hash table to distribute workload by	4450	C<ev_child> watchers use a small hash table to distribute workload by
3369	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4451	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3370	than enough. If you need to manage thousands of children you might want to	4452	usually more than enough. If you need to manage thousands of children you
3371	increase this value (I<must> be a power of two).	4453	might want to increase this value (I<must> be a power of two).
3372		4454
3373	=item EV_INOTIFY_HASHSIZE	4455	=item EV_INOTIFY_HASHSIZE
3374		4456
3375	C<ev_stat> watchers use a small hash table to distribute workload by	4457	C<ev_stat> watchers use a small hash table to distribute workload by
3376	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4458	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3377	usually more than enough. If you need to manage thousands of C<ev_stat>	4459	disabled), usually more than enough. If you need to manage thousands of
3378	watchers you might want to increase this value (I<must> be a power of	4460	C<ev_stat> watchers you might want to increase this value (I<must> be a
3379	two).	4461	power of two).
3380		4462
3381	=item EV_USE_4HEAP	4463	=item EV_USE_4HEAP
3382		4464
3383	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4465	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3384	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4466	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3385	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4467	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3386	faster performance with many (thousands) of watchers.	4468	faster performance with many (thousands) of watchers.
3387		4469
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4470	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4471	will be C<0>.
3390		4472
3391	=item EV_HEAP_CACHE_AT	4473	=item EV_HEAP_CACHE_AT
3392		4474
3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4475	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3394	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4476	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3395	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4477	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3396	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4478	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3397	but avoids random read accesses on heap changes. This improves performance	4479	but avoids random read accesses on heap changes. This improves performance
3398	noticeably with many (hundreds) of watchers.	4480	noticeably with many (hundreds) of watchers.
3399		4481
3400	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4482	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3401	(disabled).	4483	will be C<0>.
3402		4484
3403	=item EV_VERIFY	4485	=item EV_VERIFY
3404		4486
3405	Controls how much internal verification (see C<ev_loop_verify ()>) will	4487	Controls how much internal verification (see C<ev_verify ()>) will
3406	be done: If set to C<0>, no internal verification code will be compiled	4488	be done: If set to C<0>, no internal verification code will be compiled
3407	in. If set to C<1>, then verification code will be compiled in, but not	4489	in. If set to C<1>, then verification code will be compiled in, but not
3408	called. If set to C<2>, then the internal verification code will be	4490	called. If set to C<2>, then the internal verification code will be
3409	called once per loop, which can slow down libev. If set to C<3>, then the	4491	called once per loop, which can slow down libev. If set to C<3>, then the
3410	verification code will be called very frequently, which will slow down	4492	verification code will be called very frequently, which will slow down
3411	libev considerably.	4493	libev considerably.
3412		4494
3413	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4495	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3414	C<0>.	4496	will be C<0>.
3415		4497
3416	=item EV_COMMON	4498	=item EV_COMMON
3417		4499
3418	By default, all watchers have a C<void *data> member. By redefining	4500	By default, all watchers have a C<void *data> member. By redefining
3419	this macro to a something else you can include more and other types of	4501	this macro to something else you can include more and other types of
3420	members. You have to define it each time you include one of the files,	4502	members. You have to define it each time you include one of the files,
3421	though, and it must be identical each time.	4503	though, and it must be identical each time.
3422		4504
3423	For example, the perl EV module uses something like this:	4505	For example, the perl EV module uses something like this:
3424		4506
…		…
3477	file.	4559	file.
3478		4560
3479	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4561	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3480	that everybody includes and which overrides some configure choices:	4562	that everybody includes and which overrides some configure choices:
3481		4563
3482	#define EV_MINIMAL 1	4564	#define EV_FEATURES 8
3483	#define EV_USE_POLL 0	4565	#define EV_USE_SELECT 1
3484	#define EV_MULTIPLICITY 0
3485	#define EV_PERIODIC_ENABLE 0	4566	#define EV_PREPARE_ENABLE 1
		4567	#define EV_IDLE_ENABLE 1
3486	#define EV_STAT_ENABLE 0	4568	#define EV_SIGNAL_ENABLE 1
3487	#define EV_FORK_ENABLE 0	4569	#define EV_CHILD_ENABLE 1
		4570	#define EV_USE_STDEXCEPT 0
3488	#define EV_CONFIG_H <config.h>	4571	#define EV_CONFIG_H <config.h>
3489	#define EV_MINPRI 0
3490	#define EV_MAXPRI 0
3491		4572
3492	#include "ev++.h"	4573	#include "ev++.h"
3493		4574
3494	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4575	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3495		4576
…		…
3555	default loop and triggering an C<ev_async> watcher from the default loop	4636	default loop and triggering an C<ev_async> watcher from the default loop
3556	watcher callback into the event loop interested in the signal.	4637	watcher callback into the event loop interested in the signal.
3557		4638
3558	=back	4639	=back
3559		4640
		4641	See also L<Thread locking example>.
		4642
3560	=head3 COROUTINES	4643	=head3 COROUTINES
3561		4644
3562	Libev is very accommodating to coroutines ("cooperative threads"):	4645	Libev is very accommodating to coroutines ("cooperative threads"):
3563	libev fully supports nesting calls to its functions from different	4646	libev fully supports nesting calls to its functions from different
3564	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4647	coroutines (e.g. you can call C<ev_run> on the same loop from two
3565	different coroutines, and switch freely between both coroutines running the	4648	different coroutines, and switch freely between both coroutines running
3566	loop, as long as you don't confuse yourself). The only exception is that	4649	the loop, as long as you don't confuse yourself). The only exception is
3567	you must not do this from C<ev_periodic> reschedule callbacks.	4650	that you must not do this from C<ev_periodic> reschedule callbacks.
3568		4651
3569	Care has been taken to ensure that libev does not keep local state inside	4652	Care has been taken to ensure that libev does not keep local state inside
3570	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4653	C<ev_run>, and other calls do not usually allow for coroutine switches as
3571	they do not clal any callbacks.	4654	they do not call any callbacks.
3572		4655
3573	=head2 COMPILER WARNINGS	4656	=head2 COMPILER WARNINGS
3574		4657
3575	Depending on your compiler and compiler settings, you might get no or a	4658	Depending on your compiler and compiler settings, you might get no or a
3576	lot of warnings when compiling libev code. Some people are apparently	4659	lot of warnings when compiling libev code. Some people are apparently
…		…
3586	maintainable.	4669	maintainable.
3587		4670
3588	And of course, some compiler warnings are just plain stupid, or simply	4671	And of course, some compiler warnings are just plain stupid, or simply
3589	wrong (because they don't actually warn about the condition their message	4672	wrong (because they don't actually warn about the condition their message
3590	seems to warn about). For example, certain older gcc versions had some	4673	seems to warn about). For example, certain older gcc versions had some
3591	warnings that resulted an extreme number of false positives. These have	4674	warnings that resulted in an extreme number of false positives. These have
3592	been fixed, but some people still insist on making code warn-free with	4675	been fixed, but some people still insist on making code warn-free with
3593	such buggy versions.	4676	such buggy versions.
3594		4677
3595	While libev is written to generate as few warnings as possible,	4678	While libev is written to generate as few warnings as possible,
3596	"warn-free" code is not a goal, and it is recommended not to build libev	4679	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3610	==2274== definitely lost: 0 bytes in 0 blocks.	4693	==2274== definitely lost: 0 bytes in 0 blocks.
3611	==2274== possibly lost: 0 bytes in 0 blocks.	4694	==2274== possibly lost: 0 bytes in 0 blocks.
3612	==2274== still reachable: 256 bytes in 1 blocks.	4695	==2274== still reachable: 256 bytes in 1 blocks.
3613		4696
3614	Then there is no memory leak, just as memory accounted to global variables	4697	Then there is no memory leak, just as memory accounted to global variables
3615	is not a memleak - the memory is still being refernced, and didn't leak.	4698	is not a memleak - the memory is still being referenced, and didn't leak.
3616		4699
3617	Similarly, under some circumstances, valgrind might report kernel bugs	4700	Similarly, under some circumstances, valgrind might report kernel bugs
3618	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4701	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3619	although an acceptable workaround has been found here), or it might be	4702	although an acceptable workaround has been found here), or it might be
3620	confused.	4703	confused.
…		…
3632	I suggest using suppression lists.	4715	I suggest using suppression lists.
3633		4716
3634		4717
3635	=head1 PORTABILITY NOTES	4718	=head1 PORTABILITY NOTES
3636		4719
		4720	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4721
		4722	GNU/Linux is the only common platform that supports 64 bit file/large file
		4723	interfaces but I<disables> them by default.
		4724
		4725	That means that libev compiled in the default environment doesn't support
		4726	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4727
		4728	Unfortunately, many programs try to work around this GNU/Linux issue
		4729	by enabling the large file API, which makes them incompatible with the
		4730	standard libev compiled for their system.
		4731
		4732	Likewise, libev cannot enable the large file API itself as this would
		4733	suddenly make it incompatible to the default compile time environment,
		4734	i.e. all programs not using special compile switches.
		4735
		4736	=head2 OS/X AND DARWIN BUGS
		4737
		4738	The whole thing is a bug if you ask me - basically any system interface
		4739	you touch is broken, whether it is locales, poll, kqueue or even the
		4740	OpenGL drivers.
		4741
		4742	=head3 C<kqueue> is buggy
		4743
		4744	The kqueue syscall is broken in all known versions - most versions support
		4745	only sockets, many support pipes.
		4746
		4747	Libev tries to work around this by not using C<kqueue> by default on this
		4748	rotten platform, but of course you can still ask for it when creating a
		4749	loop - embedding a socket-only kqueue loop into a select-based one is
		4750	probably going to work well.
		4751
		4752	=head3 C<poll> is buggy
		4753
		4754	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4755	implementation by something calling C<kqueue> internally around the 10.5.6
		4756	release, so now C<kqueue> I<and> C<poll> are broken.
		4757
		4758	Libev tries to work around this by not using C<poll> by default on
		4759	this rotten platform, but of course you can still ask for it when creating
		4760	a loop.
		4761
		4762	=head3 C<select> is buggy
		4763
		4764	All that's left is C<select>, and of course Apple found a way to fuck this
		4765	one up as well: On OS/X, C<select> actively limits the number of file
		4766	descriptors you can pass in to 1024 - your program suddenly crashes when
		4767	you use more.
		4768
		4769	There is an undocumented "workaround" for this - defining
		4770	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4771	work on OS/X.
		4772
		4773	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4774
		4775	=head3 C<errno> reentrancy
		4776
		4777	The default compile environment on Solaris is unfortunately so
		4778	thread-unsafe that you can't even use components/libraries compiled
		4779	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4780	defined by default. A valid, if stupid, implementation choice.
		4781
		4782	If you want to use libev in threaded environments you have to make sure
		4783	it's compiled with C<_REENTRANT> defined.
		4784
		4785	=head3 Event port backend
		4786
		4787	The scalable event interface for Solaris is called "event
		4788	ports". Unfortunately, this mechanism is very buggy in all major
		4789	releases. If you run into high CPU usage, your program freezes or you get
		4790	a large number of spurious wakeups, make sure you have all the relevant
		4791	and latest kernel patches applied. No, I don't know which ones, but there
		4792	are multiple ones to apply, and afterwards, event ports actually work
		4793	great.
		4794
		4795	If you can't get it to work, you can try running the program by setting
		4796	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4797	C<select> backends.
		4798
		4799	=head2 AIX POLL BUG
		4800
		4801	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4802	this by trying to avoid the poll backend altogether (i.e. it's not even
		4803	compiled in), which normally isn't a big problem as C<select> works fine
		4804	with large bitsets on AIX, and AIX is dead anyway.
		4805
3637	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4806	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4807
		4808	=head3 General issues
3638		4809
3639	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4810	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3640	requires, and its I/O model is fundamentally incompatible with the POSIX	4811	requires, and its I/O model is fundamentally incompatible with the POSIX
3641	model. Libev still offers limited functionality on this platform in	4812	model. Libev still offers limited functionality on this platform in
3642	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4813	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3643	descriptors. This only applies when using Win32 natively, not when using	4814	descriptors. This only applies when using Win32 natively, not when using
3644	e.g. cygwin.	4815	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4816	as every compielr comes with a slightly differently broken/incompatible
		4817	environment.
3645		4818
3646	Lifting these limitations would basically require the full	4819	Lifting these limitations would basically require the full
3647	re-implementation of the I/O system. If you are into these kinds of	4820	re-implementation of the I/O system. If you are into this kind of thing,
3648	things, then note that glib does exactly that for you in a very portable	4821	then note that glib does exactly that for you in a very portable way (note
3649	way (note also that glib is the slowest event library known to man).	4822	also that glib is the slowest event library known to man).
3650		4823
3651	There is no supported compilation method available on windows except	4824	There is no supported compilation method available on windows except
3652	embedding it into other applications.	4825	embedding it into other applications.
		4826
		4827	Sensible signal handling is officially unsupported by Microsoft - libev
		4828	tries its best, but under most conditions, signals will simply not work.
3653		4829
3654	Not a libev limitation but worth mentioning: windows apparently doesn't	4830	Not a libev limitation but worth mentioning: windows apparently doesn't
3655	accept large writes: instead of resulting in a partial write, windows will	4831	accept large writes: instead of resulting in a partial write, windows will
3656	either accept everything or return C<ENOBUFS> if the buffer is too large,	4832	either accept everything or return C<ENOBUFS> if the buffer is too large,
3657	so make sure you only write small amounts into your sockets (less than a	4833	so make sure you only write small amounts into your sockets (less than a
…		…
3662	the abysmal performance of winsockets, using a large number of sockets	4838	the abysmal performance of winsockets, using a large number of sockets
3663	is not recommended (and not reasonable). If your program needs to use	4839	is not recommended (and not reasonable). If your program needs to use
3664	more than a hundred or so sockets, then likely it needs to use a totally	4840	more than a hundred or so sockets, then likely it needs to use a totally
3665	different implementation for windows, as libev offers the POSIX readiness	4841	different implementation for windows, as libev offers the POSIX readiness
3666	notification model, which cannot be implemented efficiently on windows	4842	notification model, which cannot be implemented efficiently on windows
3667	(Microsoft monopoly games).	4843	(due to Microsoft monopoly games).
3668		4844
3669	A typical way to use libev under windows is to embed it (see the embedding	4845	A typical way to use libev under windows is to embed it (see the embedding
3670	section for details) and use the following F<evwrap.h> header file instead	4846	section for details) and use the following F<evwrap.h> header file instead
3671	of F<ev.h>:	4847	of F<ev.h>:
3672		4848
…		…
3679	you do I<not> compile the F<ev.c> or any other embedded source files!):	4855	you do I<not> compile the F<ev.c> or any other embedded source files!):
3680		4856
3681	#include "evwrap.h"	4857	#include "evwrap.h"
3682	#include "ev.c"	4858	#include "ev.c"
3683		4859
3684	=over 4
3685
3686	=item The winsocket select function	4860	=head3 The winsocket C<select> function
3687		4861
3688	The winsocket C<select> function doesn't follow POSIX in that it	4862	The winsocket C<select> function doesn't follow POSIX in that it
3689	requires socket I<handles> and not socket I<file descriptors> (it is	4863	requires socket I<handles> and not socket I<file descriptors> (it is
3690	also extremely buggy). This makes select very inefficient, and also	4864	also extremely buggy). This makes select very inefficient, and also
3691	requires a mapping from file descriptors to socket handles (the Microsoft	4865	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3700	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4874	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3701		4875
3702	Note that winsockets handling of fd sets is O(n), so you can easily get a	4876	Note that winsockets handling of fd sets is O(n), so you can easily get a
3703	complexity in the O(n²) range when using win32.	4877	complexity in the O(n²) range when using win32.
3704		4878
3705	=item Limited number of file descriptors	4879	=head3 Limited number of file descriptors
3706		4880
3707	Windows has numerous arbitrary (and low) limits on things.	4881	Windows has numerous arbitrary (and low) limits on things.
3708		4882
3709	Early versions of winsocket's select only supported waiting for a maximum	4883	Early versions of winsocket's select only supported waiting for a maximum
3710	of C<64> handles (probably owning to the fact that all windows kernels	4884	of C<64> handles (probably owning to the fact that all windows kernels
3711	can only wait for C<64> things at the same time internally; Microsoft	4885	can only wait for C<64> things at the same time internally; Microsoft
3712	recommends spawning a chain of threads and wait for 63 handles and the	4886	recommends spawning a chain of threads and wait for 63 handles and the
3713	previous thread in each. Great).	4887	previous thread in each. Sounds great!).
3714		4888
3715	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4889	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3716	to some high number (e.g. C<2048>) before compiling the winsocket select	4890	to some high number (e.g. C<2048>) before compiling the winsocket select
3717	call (which might be in libev or elsewhere, for example, perl does its own	4891	call (which might be in libev or elsewhere, for example, perl and many
3718	select emulation on windows).	4892	other interpreters do their own select emulation on windows).
3719		4893
3720	Another limit is the number of file descriptors in the Microsoft runtime	4894	Another limit is the number of file descriptors in the Microsoft runtime
3721	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4895	libraries, which by default is C<64> (there must be a hidden I<64>
3722	or something like this inside Microsoft). You can increase this by calling	4896	fetish or something like this inside Microsoft). You can increase this
3723	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4897	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3724	arbitrary limit), but is broken in many versions of the Microsoft runtime	4898	(another arbitrary limit), but is broken in many versions of the Microsoft
3725	libraries.
3726
3727	This might get you to about C<512> or C<2048> sockets (depending on	4899	runtime libraries. This might get you to about C<512> or C<2048> sockets
3728	windows version and/or the phase of the moon). To get more, you need to	4900	(depending on windows version and/or the phase of the moon). To get more,
3729	wrap all I/O functions and provide your own fd management, but the cost of	4901	you need to wrap all I/O functions and provide your own fd management, but
3730	calling select (O(n²)) will likely make this unworkable.	4902	the cost of calling select (O(n²)) will likely make this unworkable.
3731
3732	=back
3733		4903
3734	=head2 PORTABILITY REQUIREMENTS	4904	=head2 PORTABILITY REQUIREMENTS
3735		4905
3736	In addition to a working ISO-C implementation and of course the	4906	In addition to a working ISO-C implementation and of course the
3737	backend-specific APIs, libev relies on a few additional extensions:	4907	backend-specific APIs, libev relies on a few additional extensions:
…		…
3744	Libev assumes not only that all watcher pointers have the same internal	4914	Libev assumes not only that all watcher pointers have the same internal
3745	structure (guaranteed by POSIX but not by ISO C for example), but it also	4915	structure (guaranteed by POSIX but not by ISO C for example), but it also
3746	assumes that the same (machine) code can be used to call any watcher	4916	assumes that the same (machine) code can be used to call any watcher
3747	callback: The watcher callbacks have different type signatures, but libev	4917	callback: The watcher callbacks have different type signatures, but libev
3748	calls them using an C<ev_watcher *> internally.	4918	calls them using an C<ev_watcher *> internally.
		4919
		4920	=item pointer accesses must be thread-atomic
		4921
		4922	Accessing a pointer value must be atomic, it must both be readable and
		4923	writable in one piece - this is the case on all current architectures.
3749		4924
3750	=item C<sig_atomic_t volatile> must be thread-atomic as well	4925	=item C<sig_atomic_t volatile> must be thread-atomic as well
3751		4926
3752	The type C<sig_atomic_t volatile> (or whatever is defined as	4927	The type C<sig_atomic_t volatile> (or whatever is defined as
3753	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4928	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3776	watchers.	4951	watchers.
3777		4952
3778	=item C<double> must hold a time value in seconds with enough accuracy	4953	=item C<double> must hold a time value in seconds with enough accuracy
3779		4954
3780	The type C<double> is used to represent timestamps. It is required to	4955	The type C<double> is used to represent timestamps. It is required to
3781	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4956	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3782	enough for at least into the year 4000. This requirement is fulfilled by	4957	good enough for at least into the year 4000 with millisecond accuracy
		4958	(the design goal for libev). This requirement is overfulfilled by
3783	implementations implementing IEEE 754 (basically all existing ones).	4959	implementations using IEEE 754, which is basically all existing ones. With
		4960	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3784		4961
3785	=back	4962	=back
3786		4963
3787	If you know of other additional requirements drop me a note.	4964	If you know of other additional requirements drop me a note.
3788		4965
…		…
3856	involves iterating over all running async watchers or all signal numbers.	5033	involves iterating over all running async watchers or all signal numbers.
3857		5034
3858	=back	5035	=back
3859		5036
3860		5037
		5038	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5039
		5040	The major version 4 introduced some incompatible changes to the API.
		5041
		5042	At the moment, the C<ev.h> header file provides compatibility definitions
		5043	for all changes, so most programs should still compile. The compatibility
		5044	layer might be removed in later versions of libev, so better update to the
		5045	new API early than late.
		5046
		5047	=over 4
		5048
		5049	=item C<EV_COMPAT3> backwards compatibility mechanism
		5050
		5051	The backward compatibility mechanism can be controlled by
		5052	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5053	section.
		5054
		5055	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5056
		5057	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5058
		5059	ev_loop_destroy (EV_DEFAULT_UC);
		5060	ev_loop_fork (EV_DEFAULT);
		5061
		5062	=item function/symbol renames
		5063
		5064	A number of functions and symbols have been renamed:
		5065
		5066	ev_loop => ev_run
		5067	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5068	EVLOOP_ONESHOT => EVRUN_ONCE
		5069
		5070	ev_unloop => ev_break
		5071	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5072	EVUNLOOP_ONE => EVBREAK_ONE
		5073	EVUNLOOP_ALL => EVBREAK_ALL
		5074
		5075	EV_TIMEOUT => EV_TIMER
		5076
		5077	ev_loop_count => ev_iteration
		5078	ev_loop_depth => ev_depth
		5079	ev_loop_verify => ev_verify
		5080
		5081	Most functions working on C<struct ev_loop> objects don't have an
		5082	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5083	associated constants have been renamed to not collide with the C<struct
		5084	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5085	as all other watcher types. Note that C<ev_loop_fork> is still called
		5086	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5087	typedef.
		5088
		5089	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5090
		5091	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5092	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5093	and work, but the library code will of course be larger.
		5094
		5095	=back
		5096
		5097
		5098	=head1 GLOSSARY
		5099
		5100	=over 4
		5101
		5102	=item active
		5103
		5104	A watcher is active as long as it has been started and not yet stopped.
		5105	See L<WATCHER STATES> for details.
		5106
		5107	=item application
		5108
		5109	In this document, an application is whatever is using libev.
		5110
		5111	=item backend
		5112
		5113	The part of the code dealing with the operating system interfaces.
		5114
		5115	=item callback
		5116
		5117	The address of a function that is called when some event has been
		5118	detected. Callbacks are being passed the event loop, the watcher that
		5119	received the event, and the actual event bitset.
		5120
		5121	=item callback/watcher invocation
		5122
		5123	The act of calling the callback associated with a watcher.
		5124
		5125	=item event
		5126
		5127	A change of state of some external event, such as data now being available
		5128	for reading on a file descriptor, time having passed or simply not having
		5129	any other events happening anymore.
		5130
		5131	In libev, events are represented as single bits (such as C<EV_READ> or
		5132	C<EV_TIMER>).
		5133
		5134	=item event library
		5135
		5136	A software package implementing an event model and loop.
		5137
		5138	=item event loop
		5139
		5140	An entity that handles and processes external events and converts them
		5141	into callback invocations.
		5142
		5143	=item event model
		5144
		5145	The model used to describe how an event loop handles and processes
		5146	watchers and events.
		5147
		5148	=item pending
		5149
		5150	A watcher is pending as soon as the corresponding event has been
		5151	detected. See L<WATCHER STATES> for details.
		5152
		5153	=item real time
		5154
		5155	The physical time that is observed. It is apparently strictly monotonic :)
		5156
		5157	=item wall-clock time
		5158
		5159	The time and date as shown on clocks. Unlike real time, it can actually
		5160	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5161	clock.
		5162
		5163	=item watcher
		5164
		5165	A data structure that describes interest in certain events. Watchers need
		5166	to be started (attached to an event loop) before they can receive events.
		5167
		5168	=back
		5169
3861	=head1 AUTHOR	5170	=head1 AUTHOR
3862		5171
3863	Marc Lehmann <libev@schmorp.de>.	5172	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5173	Magnusson and Emanuele Giaquinta.
3864		5174

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