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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	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);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	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
70	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
71	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
72		92
73	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
74	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
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	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
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	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
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	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
96	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
97	(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>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	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
101	for example).	122	for example).
102		123
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	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
118	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
119	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
120	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
121	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
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	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
155	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
156	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
161	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
162	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
163		192
164	=item int ev_version_major ()	193	=item int ev_version_major ()
165		194
166	=item int ev_version_minor ()	195	=item int ev_version_minor ()
167		196
…		…
178	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	209	not a problem.
181		210
182	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
184		214
185	assert (("libev version mismatch",	215	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
188		218
…		…
199	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
201		231
202	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
203		233
204	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
210		241
211	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
212		243
213	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
218		249
219	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
220		251
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
222		253
223	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
252	}	283	}
253		284
254	...	285	...
255	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
256		287
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
258		289
259	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
260	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	305	}
275		306
276	...	307	...
277	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
278		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
279	=back	323	=back
280		324
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		326
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
286		330
287	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
289	not.	333	do not.
290		334
291	=over 4	335	=over 4
292		336
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		338
295	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
299		349
300	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
301	function.	351	function (or via the C<EV_DEFAULT> macro).
302		352
303	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
306		357
307	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
313		382
314	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		385
317	The following flags are supported:	386	The following flags are supported:
…		…
332	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
333	around bugs.	402	around bugs.
334		403
335	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
336		405
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		408
341	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	418	flag.
351		419
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	421	environment variable.
354		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		459
357	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		488
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
388	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
389	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
390	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
391	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
392		498
393	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	508	and is of course hard to detect.
401		509
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
403	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
404	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
405	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
406	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
409		526
410	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
450		567
451	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
452	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
453	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
455	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
457	cases	574	drops fds silently in similarly hard-to-detect cases
458		575
459	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
460		577
461	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
462	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		597
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
483		600
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	604	might perform better.
492		605
493	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
497		620
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
500		623
501	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
502		625
503	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		629
507	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		639
509	=back	640	=back
510		641
511	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
514		645	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		646
543	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
544		648
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	650	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
548		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
549	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
550		659
551	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		667
559	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
562		671
563	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
567		680
568	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
569		682
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
581		693
582	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
585		700
586	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
590	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		715
599	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
600		717
601	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	719	otherwise.
603		720
604	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
605		722
606	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
609		726
610	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
613		745
614	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
615		747
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	749	use.
…		…
626		758
627	=item ev_now_update (loop)	759	=item ev_now_update (loop)
628		760
629	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
632		764
633	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	767	the current time is a good idea.
636		768
637	See also "The special problem of time updates" in the C<ev_timer> section.	769	See also L<The special problem of time updates> in the C<ev_timer> section.
638		770
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
639	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
640		798
641	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
643	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
644		804
645	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
647		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
648	Please note that an explicit C<ev_unloop> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	818	beauty.
654		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	826	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	827	block your process in case there are no events and will return after one
658	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
659		830
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	833	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	834	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
665	iteration of the loop.	836	iteration of the loop.
666		837
667	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
671		842
672	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
673		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	856	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	867	- Queue all expired timers.
690	- Queue all expired periodics.	868	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	870	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	872	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
699		881
700	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	883	anymore.
702		884
703	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
707		889
708	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
709		891
710	Can be used to make a call to C<ev_loop> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		896
715	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
716		898
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
718		901
719	=item ev_ref (loop)	902	=item ev_ref (loop)
720		903
721	=item ev_unref (loop)	904	=item ev_unref (loop)
722		905
723	Ref/unref can be used to add or remove a reference count on the event	906	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	907	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	908	count is nonzero, C<ev_run> will not return on its own.
726		909
727	If you have a watcher you never unregister that should not keep C<ev_loop>	910	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	911	unregister, but that nevertheless should not keep C<ev_run> from
		912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	913	before stopping it.
730		914
731	As an example, libev itself uses this for its internal signal pipe: It is	915	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	916	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	917	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	918	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	919	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	920	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	921	before, respectively. Note also that libev might stop watchers itself
		922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		923	in the callback).
738		924
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	926	running when nothing else is active.
741		927
742	ev_signal exitsig;	928	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	931	ev_unref (loop);
746		932
747	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
748		934
749	ev_ref (loop);	935	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
770	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
771		957
772	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		963	sleep time ensures that libev will not poll for I/O events more often then
		964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
777		966
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		972
784	Many (busy) programs can usually benefit by setting the I/O collect	973	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	974	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	975	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	976	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	977	as this approaches the timing granularity of most systems. Note that if
		978	you do transactions with the outside world and you can't increase the
		979	parallelity, then this setting will limit your transaction rate (if you
		980	need to poll once per transaction and the I/O collect interval is 0.01,
		981	then you can't do more than 100 transactions per second).
789		982
790	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	985	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	986	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	987	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	988	they fire on, say, one-second boundaries only.
796		989
		990	Example: we only need 0.1s timeout granularity, and we wish not to poll
		991	more often than 100 times per second:
		992
		993	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		995
		996	=item ev_invoke_pending (loop)
		997
		998	This call will simply invoke all pending watchers while resetting their
		999	pending state. Normally, C<ev_run> does this automatically when required,
		1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1005
		1006	=item int ev_pending_count (loop)
		1007
		1008	Returns the number of pending watchers - zero indicates that no watchers
		1009	are pending.
		1010
		1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1012
		1013	This overrides the invoke pending functionality of the loop: Instead of
		1014	invoking all pending watchers when there are any, C<ev_run> will call
		1015	this callback instead. This is useful, for example, when you want to
		1016	invoke the actual watchers inside another context (another thread etc.).
		1017
		1018	If you want to reset the callback, use C<ev_invoke_pending> as new
		1019	callback.
		1020
		1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1022
		1023	Sometimes you want to share the same loop between multiple threads. This
		1024	can be done relatively simply by putting mutex_lock/unlock calls around
		1025	each call to a libev function.
		1026
		1027	However, C<ev_run> can run an indefinite time, so it is not feasible
		1028	to wait for it to return. One way around this is to wake up the event
		1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1030	I<release> and I<acquire> callbacks on the loop.
		1031
		1032	When set, then C<release> will be called just before the thread is
		1033	suspended waiting for new events, and C<acquire> is called just
		1034	afterwards.
		1035
		1036	Ideally, C<release> will just call your mutex_unlock function, and
		1037	C<acquire> will just call the mutex_lock function again.
		1038
		1039	While event loop modifications are allowed between invocations of
		1040	C<release> and C<acquire> (that's their only purpose after all), no
		1041	modifications done will affect the event loop, i.e. adding watchers will
		1042	have no effect on the set of file descriptors being watched, or the time
		1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1044	to take note of any changes you made.
		1045
		1046	In theory, threads executing C<ev_run> will be async-cancel safe between
		1047	invocations of C<release> and C<acquire>.
		1048
		1049	See also the locking example in the C<THREADS> section later in this
		1050	document.
		1051
		1052	=item ev_set_userdata (loop, void *data)
		1053
		1054	=item void *ev_userdata (loop)
		1055
		1056	Set and retrieve a single C<void *> associated with a loop. When
		1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1058	C<0>.
		1059
		1060	These two functions can be used to associate arbitrary data with a loop,
		1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1062	C<acquire> callbacks described above, but of course can be (ab-)used for
		1063	any other purpose as well.
		1064
797	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
798		1066
799	This function only does something when C<EV_VERIFY> support has been	1067	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1068	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1070	is found to be inconsistent, it will print an error message to standard
…		…
813		1081
814	In the following description, uppercase C<TYPE> in names stands for the	1082	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
817		1085
818	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
821		1090
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1092	{
824	ev_io_stop (w);	1093	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
826	}	1095	}
827		1096
828	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
829		1098
830	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
831		1100
832	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
835		1104
836	ev_loop (loop, 0);	1105	ev_run (loop, 0);
837		1106
838	As you can see, you are responsible for allocating the memory for your	1107	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1108	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1109	stack).
841		1110
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1113
845	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1116	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1117	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1118	and/or writable).
850		1119
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1121	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1122	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
878		1147
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1149	writable.
881		1150
882	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
883		1152
884	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
885		1154
886	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
887		1156
…		…
905		1174
906	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
907		1176
908	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
909		1178
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
911	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
913	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
914	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
916	C<ev_loop> from blocking).	1190	blocking).
917		1191
918	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
919		1193
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1195
922	=item C<EV_FORK>	1196	=item C<EV_FORK>
923		1197
924	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1199	C<ev_fork>).
926		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
		1204
927	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
928		1206
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
		1208
		1209	=item C<EV_CUSTOM>
		1210
		1211	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1212	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1213
931	=item C<EV_ERROR>	1214	=item C<EV_ERROR>
932		1215
933	An unspecified error has occurred, the watcher has been stopped. This might	1216	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1217	happen because the watcher could not be properly started because libev
…		…
972		1255
973	ev_io w;	1256	ev_io w;
974	ev_init (&w, my_cb);	1257	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1259
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1261
979	This macro initialises the type-specific parts of a watcher. You need to	1262	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1263	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1264	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1265	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1278
996	Example: Initialise and set an C<ev_io> watcher in one step.	1279	Example: Initialise and set an C<ev_io> watcher in one step.
997		1280
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1282
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1284
1002	Starts (activates) the given watcher. Only active watchers will receive	1285	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1286	events. If the watcher is already active nothing will happen.
1004		1287
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1288	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1289	whole section.
1007		1290
1008	ev_io_start (EV_DEFAULT_UC, &w);	1291	ev_io_start (EV_DEFAULT_UC, &w);
1009		1292
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1294
1012	Stops the given watcher if active, and clears the pending status (whether	1295	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1296	the watcher was active or not).
1014		1297
1015	It is possible that stopped watchers are pending - for example,	1298	It is possible that stopped watchers are pending - for example,
…		…
1035		1318
1036	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1037		1320
1038	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1039		1322
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1041		1324
1042	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1326	(modulo threads).
1044		1327
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1329
1047	=item int ev_priority (ev_TYPE *watcher)	1330	=item int ev_priority (ev_TYPE *watcher)
1048		1331
1049	Set and query the priority of the watcher. The priority is a small	1332	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1334	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1335	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1336	from being executed (except for C<ev_idle> watchers).
1054		1337
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1338	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1339	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1340
1063	You I<must not> change the priority of a watcher as long as it is active or	1341	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1342	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1343
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1344	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1345	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
		1347
		1348	The default priority used by watchers when no priority has been set is
		1349	always C<0>, which is supposed to not be too high and not be too low :).
		1350
		1351	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1352	priorities.
1072		1353
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1355
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1357	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1365	watcher isn't pending it does nothing and returns C<0>.
1085		1366
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1367	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1368	callback to be invoked, which can be accomplished with this function.
1088		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
1089	=back	1384	=back
1090		1385
		1386	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1091		1388
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1093		1390
1094	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1095	and read at any time: libev will completely ignore it. This can be used	1392	active, pending and so on. In this section these states and the rules to
1096	to associate arbitrary data with your watcher. If you need more data and	1393	transition between them will be described in more detail - and while these
1097	don't want to allocate memory and store a pointer to it in that data	1394	rules might look complicated, they usually do "the right thing".
1098	member, you can also "subclass" the watcher type and provide your own
1099	data:
1100		1395
1101	struct my_io	1396	=over 4
		1397
		1398	=item initialiased
		1399
		1400	Before a watcher can be registered with the event loop it has to be
		1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1403
		1404	In this state it is simply some block of memory that is suitable for
		1405	use in an event loop. It can be moved around, freed, reused etc. at
		1406	will - as long as you either keep the memory contents intact, or call
		1407	C<ev_TYPE_init> again.
		1408
		1409	=item started/running/active
		1410
		1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
		1416
		1417	=item pending
		1418
		1419	If a watcher is active and libev determines that an event it is interested
		1420	in has occurred (such as a timer expiring), it will become pending. It will
		1421	stay in this pending state until either it is stopped or its callback is
		1422	about to be invoked, so it is not normally pending inside the watcher
		1423	callback.
		1424
		1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
		1431
		1432	It is also possible to feed an event on a watcher that is not active (e.g.
		1433	via C<ev_feed_event>), in which case it becomes pending without being
		1434	active.
		1435
		1436	=item stopped
		1437
		1438	A watcher can be stopped implicitly by libev (in which case it might still
		1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1440	latter will clear any pending state the watcher might be in, regardless
		1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
		1450
		1451	=head2 WATCHER PRIORITY MODELS
		1452
		1453	Many event loops support I<watcher priorities>, which are usually small
		1454	integers that influence the ordering of event callback invocation
		1455	between watchers in some way, all else being equal.
		1456
		1457	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1458	description for the more technical details such as the actual priority
		1459	range.
		1460
		1461	There are two common ways how these these priorities are being interpreted
		1462	by event loops:
		1463
		1464	In the more common lock-out model, higher priorities "lock out" invocation
		1465	of lower priority watchers, which means as long as higher priority
		1466	watchers receive events, lower priority watchers are not being invoked.
		1467
		1468	The less common only-for-ordering model uses priorities solely to order
		1469	callback invocation within a single event loop iteration: Higher priority
		1470	watchers are invoked before lower priority ones, but they all get invoked
		1471	before polling for new events.
		1472
		1473	Libev uses the second (only-for-ordering) model for all its watchers
		1474	except for idle watchers (which use the lock-out model).
		1475
		1476	The rationale behind this is that implementing the lock-out model for
		1477	watchers is not well supported by most kernel interfaces, and most event
		1478	libraries will just poll for the same events again and again as long as
		1479	their callbacks have not been executed, which is very inefficient in the
		1480	common case of one high-priority watcher locking out a mass of lower
		1481	priority ones.
		1482
		1483	Static (ordering) priorities are most useful when you have two or more
		1484	watchers handling the same resource: a typical usage example is having an
		1485	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1486	timeouts. Under load, data might be received while the program handles
		1487	other jobs, but since timers normally get invoked first, the timeout
		1488	handler will be executed before checking for data. In that case, giving
		1489	the timer a lower priority than the I/O watcher ensures that I/O will be
		1490	handled first even under adverse conditions (which is usually, but not
		1491	always, what you want).
		1492
		1493	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1494	will only be executed when no same or higher priority watchers have
		1495	received events, they can be used to implement the "lock-out" model when
		1496	required.
		1497
		1498	For example, to emulate how many other event libraries handle priorities,
		1499	you can associate an C<ev_idle> watcher to each such watcher, and in
		1500	the normal watcher callback, you just start the idle watcher. The real
		1501	processing is done in the idle watcher callback. This causes libev to
		1502	continuously poll and process kernel event data for the watcher, but when
		1503	the lock-out case is known to be rare (which in turn is rare :), this is
		1504	workable.
		1505
		1506	Usually, however, the lock-out model implemented that way will perform
		1507	miserably under the type of load it was designed to handle. In that case,
		1508	it might be preferable to stop the real watcher before starting the
		1509	idle watcher, so the kernel will not have to process the event in case
		1510	the actual processing will be delayed for considerable time.
		1511
		1512	Here is an example of an I/O watcher that should run at a strictly lower
		1513	priority than the default, and which should only process data when no
		1514	other events are pending:
		1515
		1516	ev_idle idle; // actual processing watcher
		1517	ev_io io; // actual event watcher
		1518
		1519	static void
		1520	io_cb (EV_P_ ev_io *w, int revents)
1102	{	1521	{
1103	ev_io io;	1522	// stop the I/O watcher, we received the event, but
1104	int otherfd;	1523	// are not yet ready to handle it.
1105	void *somedata;	1524	ev_io_stop (EV_A_ w);
1106	struct whatever *mostinteresting;	1525
		1526	// start the idle watcher to handle the actual event.
		1527	// it will not be executed as long as other watchers
		1528	// with the default priority are receiving events.
		1529	ev_idle_start (EV_A_ &idle);
1107	};	1530	}
1108		1531
1109	...	1532	static void
1110	struct my_io w;	1533	idle_cb (EV_P_ ev_idle *w, int revents)
1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1112
1113	And since your callback will be called with a pointer to the watcher, you
1114	can cast it back to your own type:
1115
1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1117	{	1534	{
1118	struct my_io *w = (struct my_io *)w_;	1535	// actual processing
1119	...	1536	read (STDIN_FILENO, ...);
		1537
		1538	// have to start the I/O watcher again, as
		1539	// we have handled the event
		1540	ev_io_start (EV_P_ &io);
1120	}	1541	}
1121		1542
1122	More interesting and less C-conformant ways of casting your callback type	1543	// initialisation
1123	instead have been omitted.	1544	ev_idle_init (&idle, idle_cb);
		1545	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1546	ev_io_start (EV_DEFAULT_ &io);
1124		1547
1125	Another common scenario is to use some data structure with multiple	1548	In the "real" world, it might also be beneficial to start a timer, so that
1126	embedded watchers:	1549	low-priority connections can not be locked out forever under load. This
1127		1550	enables your program to keep a lower latency for important connections
1128	struct my_biggy	1551	during short periods of high load, while not completely locking out less
1129	{	1552	important ones.
1130	int some_data;
1131	ev_timer t1;
1132	ev_timer t2;
1133	}
1134
1135	In this case getting the pointer to C<my_biggy> is a bit more
1136	complicated: Either you store the address of your C<my_biggy> struct
1137	in the C<data> member of the watcher (for woozies), or you need to use
1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
1139	programmers):
1140
1141	#include <stddef.h>
1142
1143	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{
1146	struct my_biggy big = (struct my_biggy *
1147	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}
1149
1150	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{
1153	struct my_biggy big = (struct my_biggy *
1154	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}
1156		1553
1157		1554
1158	=head1 WATCHER TYPES	1555	=head1 WATCHER TYPES
1159		1556
1160	This section describes each watcher in detail, but will not repeat	1557	This section describes each watcher in detail, but will not repeat
…		…
1184	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1185	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1186	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1584	required if you know what you are doing).
1188		1585
1189	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1192
1193	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1197	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1198	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1201		1593
1202	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1203	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1204	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1205	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1206	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1207	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1208	indefinitely.	1600	indefinitely.
1209		1601
1210	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1211		1603
…		…
1239		1631
1240	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1244	=head3 The special problem of fork	1669	=head3 The special problem of fork
1245		1670
1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1247	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1248	it in the child.	1673	it in the child if you want to continue to use it in the child.
1249		1674
1250	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1678
1255	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1256		1680
1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1258	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1261		1685
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1686	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1687	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1688	somewhere, as that would have given you a big clue).
1265		1689
		1690	=head3 The special problem of accept()ing when you can't
		1691
		1692	Many implementations of the POSIX C<accept> function (for example,
		1693	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1694	connection from the pending queue in all error cases.
		1695
		1696	For example, larger servers often run out of file descriptors (because
		1697	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1698	rejecting the connection, leading to libev signalling readiness on
		1699	the next iteration again (the connection still exists after all), and
		1700	typically causing the program to loop at 100% CPU usage.
		1701
		1702	Unfortunately, the set of errors that cause this issue differs between
		1703	operating systems, there is usually little the app can do to remedy the
		1704	situation, and no known thread-safe method of removing the connection to
		1705	cope with overload is known (to me).
		1706
		1707	One of the easiest ways to handle this situation is to just ignore it
		1708	- when the program encounters an overload, it will just loop until the
		1709	situation is over. While this is a form of busy waiting, no OS offers an
		1710	event-based way to handle this situation, so it's the best one can do.
		1711
		1712	A better way to handle the situation is to log any errors other than
		1713	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1714	messages, and continue as usual, which at least gives the user an idea of
		1715	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1716	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1717	usage.
		1718
		1719	If your program is single-threaded, then you could also keep a dummy file
		1720	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1721	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1722	close that fd, and create a new dummy fd. This will gracefully refuse
		1723	clients under typical overload conditions.
		1724
		1725	The last way to handle it is to simply log the error and C<exit>, as
		1726	is often done with C<malloc> failures, but this results in an easy
		1727	opportunity for a DoS attack.
1266		1728
1267	=head3 Watcher-Specific Functions	1729	=head3 Watcher-Specific Functions
1268		1730
1269	=over 4	1731	=over 4
1270		1732
…		…
1302	...	1764	...
1303	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1766	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1767	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1308		1770
1309		1771
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1773
1312	Timer watchers are simple relative timers that generate an event after a	1774	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1779	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1320		1782
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
		1787	iteration then the ones with earlier time-out values are invoked before
		1788	ones of the same priority with later time-out values (but this is no
		1789	longer true when a callback calls C<ev_run> recursively).
1324		1790
1325	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1326		1792
1327	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1838	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1839	member and C<ev_timer_again>.
1374		1840
1375	At start:	1841	At start:
1376		1842
1377	ev_timer_init (timer, callback);	1843	ev_init (timer, callback);
1378	timer->repeat = 60.;	1844	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1845	ev_timer_again (loop, timer);
1380		1846
1381	Each time there is some activity:	1847	Each time there is some activity:
1382		1848
…		…
1403		1869
1404	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1405	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1406	within the callback:	1872	within the callback:
1407		1873
		1874	ev_tstamp timeout = 60.;
1408	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1409		1877
1410	static void	1878	static void
1411	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1412	{	1880	{
1413	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1414	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1415		1883
1416	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1417	if (timeout < now)	1885	if (after < 0.)
1418	{	1886	{
1419	// timeout occured, take action	1887	// timeout occurred, take action
1420	}	1888	}
1421	else	1889	else
1422	{	1890	{
1423	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1424	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1425	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1426	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1427	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1428	}	1897	}
1429	}	1898	}
1430		1899
1431	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1432	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1433	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1434	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1435	re-schedule the timer to fire at that future time, to see if maybe we have
1436	a timeout then.
1437		1904
1438	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1439	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1440		1914
1441	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1442	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1443	libev to change the timeout.	1917	libev to change the timeout.
1444		1918
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1446	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1447	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1448		1923
		1924	last_activity = ev_now (EV_A);
1449	ev_timer_init (timer, callback);	1925	ev_init (&timer, callback);
1450	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1451	callback (loop, timer, EV_TIMEOUT);
1452		1927
1453	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1455		1930
		1931	if (activity detected)
1456	last_actiivty = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1457		1941
1458	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1460
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
1462	callback :) - just change the timeout and invoke the callback, which will
1463	fix things for you.
1464		1944
1465	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1466		1946
1467	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1468	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1496	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1497	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1498	overkill :)	1978	overkill :)
1499		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1500	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1501		2018
1502	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1503	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2023	lots of events in one iteration.
1507		2024
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	2026	time. This is usually the right thing as this timestamp refers to the time
…		…
1515		2032
1516	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2035	()>.
1519		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
		2069
		2070	=head3 The special problems of suspended animation
		2071
		2072	When you leave the server world it is quite customary to hit machines that
		2073	can suspend/hibernate - what happens to the clocks during such a suspend?
		2074
		2075	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2076	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2077	to run until the system is suspended, but they will not advance while the
		2078	system is suspended. That means, on resume, it will be as if the program
		2079	was frozen for a few seconds, but the suspend time will not be counted
		2080	towards C<ev_timer> when a monotonic clock source is used. The real time
		2081	clock advanced as expected, but if it is used as sole clocksource, then a
		2082	long suspend would be detected as a time jump by libev, and timers would
		2083	be adjusted accordingly.
		2084
		2085	I would not be surprised to see different behaviour in different between
		2086	operating systems, OS versions or even different hardware.
		2087
		2088	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2089	time jump in the monotonic clocks and the realtime clock. If the program
		2090	is suspended for a very long time, and monotonic clock sources are in use,
		2091	then you can expect C<ev_timer>s to expire as the full suspension time
		2092	will be counted towards the timers. When no monotonic clock source is in
		2093	use, then libev will again assume a timejump and adjust accordingly.
		2094
		2095	It might be beneficial for this latter case to call C<ev_suspend>
		2096	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2097	deterministic behaviour in this case (you can do nothing against
		2098	C<SIGSTOP>).
		2099
1520	=head3 Watcher-Specific Functions and Data Members	2100	=head3 Watcher-Specific Functions and Data Members
1521		2101
1522	=over 4	2102	=over 4
1523		2103
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2104	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1537	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1538	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1539		2119
1540	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1541		2121
1542	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1543	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1544		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1545	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1546		2132
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1548		2135
1549	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1551		2138
		2139	=back
		2140
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2141	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1553	usage example.	2142	usage example.
		2143
		2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2145
		2146	Returns the remaining time until a timer fires. If the timer is active,
		2147	then this time is relative to the current event loop time, otherwise it's
		2148	the timeout value currently configured.
		2149
		2150	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2151	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2152	will return C<4>. When the timer expires and is restarted, it will return
		2153	roughly C<7> (likely slightly less as callback invocation takes some time,
		2154	too), and so on.
1554		2155
1555	=item ev_tstamp repeat [read-write]	2156	=item ev_tstamp repeat [read-write]
1556		2157
1557	The current C<repeat> value. Will be used each time the watcher times out	2158	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2159	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2185	}
1585		2186
1586	ev_timer mytimer;	2187	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2188	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1590		2191
1591	// and in some piece of code that gets executed on any "activity":	2192	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1594		2195
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2197	=head2 C<ev_periodic> - to cron or not to cron?
1597		2198
1598	Periodic watchers are also timers of a kind, but they are very versatile	2199	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2200	(and unfortunately a bit complex).
1600		2201
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2202	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2203	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2204	(absolute time, the thing you can read on your calender or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2205	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2206	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2207	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2208
		2209	You can tell a periodic watcher to trigger after some specific point
		2210	in time: for example, if you tell a periodic watcher to trigger "in 10
		2211	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2212	not a delay) and then reset your system clock to January of the previous
		2213	year, then it will take a year or more to trigger the event (unlike an
		2214	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2215	it, as it uses a relative timeout).
		2216
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2217	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2218	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2219	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2220	those cannot react to time jumps.
1613		2221
1614	As with timers, the callback is guaranteed to be invoked only when the	2222	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2223	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2224	timers become ready during the same loop iteration then the ones with
		2225	earlier time-out values are invoked before ones with later time-out values
		2226	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2227
1618	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1619		2229
1620	=over 4	2230	=over 4
1621		2231
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2232	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2233
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2234	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2235
1626	Lots of arguments, lets sort it out... There are basically three modes of	2236	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2237	operation, and we will explain them from simplest to most complex:
1628		2238
1629	=over 4	2239	=over 4
1630		2240
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2241	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2242
1633	In this configuration the watcher triggers an event after the wall clock	2243	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2244	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2245	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2246	will be stopped and invoked when the system clock reaches or surpasses
		2247	this point in time.
1637		2248
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2249	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2250
1640	In this mode the watcher will always be scheduled to time out at the next	2251	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2252	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2253	negative) and then repeat, regardless of any time jumps. The C<offset>
		2254	argument is merely an offset into the C<interval> periods.
1643		2255
1644	This can be used to create timers that do not drift with respect to the	2256	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2257	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2258	hour, on the hour (with respect to UTC):
1647		2259
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2260	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2261
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2262	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2263	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2264	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2265	by 3600.
1654		2266
1655	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2270
1659	For numerical stability it is preferable that the C<at> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
1660	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
1661	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
1662		2277
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
1667		2282
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2283	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2284
1670	In this mode the values for C<interval> and C<at> are both being	2285	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2286	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2287	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2288	current time as second argument.
1674		2289
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2290	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY event loop modifications whatsoever>.	2291	or make ANY other event loop modifications whatsoever, unless explicitly
		2292	allowed by documentation here>.
1677		2293
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2294	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2295	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2296	only event loop modification you are allowed to do).
1681		2297
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2327	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2328	program when the crontabs have changed).
1713		2329
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2330	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2331
1716	When active, returns the absolute time that the watcher is supposed to	2332	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2333	to trigger next. This is not the same as the C<offset> argument to
		2334	C<ev_periodic_set>, but indeed works even in interval and manual
		2335	rescheduling modes.
1718		2336
1719	=item ev_tstamp offset [read-write]	2337	=item ev_tstamp offset [read-write]
1720		2338
1721	When repeating, this contains the offset value, otherwise this is the	2339	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2340	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2341	although libev might modify this value for better numerical stability).
1723		2342
1724	Can be modified any time, but changes only take effect when the periodic	2343	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2344	timer fires or C<ev_periodic_again> is being called.
1726		2345
1727	=item ev_tstamp interval [read-write]	2346	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
1746		2365
1747	static void	2366	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2368	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2369	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2370	}
1752		2371
1753	ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
…		…
1776		2395
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2397
1779	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2401	normal event processing, like any other event.
1783		2402
1784	If you want signals asynchronously, just use C<sigaction> as you would	2403	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2404	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2405	the signal. You can even use C<ev_async> from a signal handler to
		2406	synchronously wake up an event loop.
1787		2407
1788	You can configure as many watchers as you like per signal. Only when the	2408	You can configure as many watchers as you like for the same signal, but
		2409	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2410	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2411	C<SIGINT> in both the default loop and another loop at the same time. At
		2412	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2413
1789	first watcher gets started will libev actually register a signal handler	2414	When the first watcher gets started will libev actually register something
1790	with the kernel (thus it coexists with your own signal handlers as long as	2415	with the kernel (thus it coexists with your own signal handlers as long as
1791	you don't register any with libev for the same signal). Similarly, when	2416	you don't register any with libev for the same signal).
1792	the last signal watcher for a signal is stopped, libev will reset the
1793	signal handler to SIG_DFL (regardless of what it was set to before).
1794		2417
1795	If possible and supported, libev will install its handlers with	2418	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2419	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2420	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2421	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2422	and unblock them in an C<ev_prepare> watcher.
		2423
		2424	=head3 The special problem of inheritance over fork/execve/pthread_create
		2425
		2426	Both the signal mask (C<sigprocmask>) and the signal disposition
		2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2428	stopping it again), that is, libev might or might not block the signal,
		2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
		2431
		2432	While this does not matter for the signal disposition (libev never
		2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2434	C<execve>), this matters for the signal mask: many programs do not expect
		2435	certain signals to be blocked.
		2436
		2437	This means that before calling C<exec> (from the child) you should reset
		2438	the signal mask to whatever "default" you expect (all clear is a good
		2439	choice usually).
		2440
		2441	The simplest way to ensure that the signal mask is reset in the child is
		2442	to install a fork handler with C<pthread_atfork> that resets it. That will
		2443	catch fork calls done by libraries (such as the libc) as well.
		2444
		2445	In current versions of libev, the signal will not be blocked indefinitely
		2446	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2447	the window of opportunity for problems, it will not go away, as libev
		2448	I<has> to modify the signal mask, at least temporarily.
		2449
		2450	So I can't stress this enough: I<If you do not reset your signal mask when
		2451	you expect it to be empty, you have a race condition in your code>. This
		2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
1800		2467
1801	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
1802		2469
1803	=over 4	2470	=over 4
1804		2471
…		…
1820	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
1821		2488
1822	static void	2489	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2491	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
1826	}	2493	}
1827		2494
1828	ev_signal signal_watcher;	2495	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2503	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2504	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2505	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2506	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2507	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2508	but forking and registering a watcher a few event loop iterations later or
1842	not.	2509	in the next callback invocation is not.
1843		2510
1844	Only the default event loop is capable of handling signals, and therefore	2511	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2512	you can only register child watchers in the default event loop.
1846		2513
		2514	Due to some design glitches inside libev, child watchers will always be
		2515	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2516	libev)
		2517
1847	=head3 Process Interaction	2518	=head3 Process Interaction
1848		2519
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2520	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2521	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2522	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2523	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2524	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2525	children, even ones not watched.
1855		2526
1856	=head3 Overriding the Built-In Processing	2527	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2537	=head3 Stopping the Child Watcher
1867		2538
1868	Currently, the child watcher never gets stopped, even when the	2539	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2540	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2541	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2542	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2543	problem).
1872		2544
1873	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1874		2546
1875	=over 4	2547	=over 4
1876		2548
…		…
2175	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2176	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2177	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2178	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2179		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L<Abusing an ev_check watcher for its side-effect> for a longer
		2864	example.
		2865
2180	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2181		2867
2182	=over 4	2868	=over 4
2183		2869
2184	=item ev_idle_init (ev_signal *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
2185		2871
2186	Initialises and configures the idle watcher - it has no parameters of any	2872	Initialises and configures the idle watcher - it has no parameters of any
2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2188	believe me.	2874	believe me.
2189		2875
…		…
2195	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2196		2882
2197	static void	2883	static void
2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2199	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2200	free (w);	2890	free (w);
		2891
2201	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2202	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2203	}	2894	}
2204		2895
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2897	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2898	ev_idle_start (loop, idle_watcher);
2208		2899
2209		2900
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2902
2212	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2905	afterwards.
2215		2906
2216	You I<must not> call C<ev_loop> or similar functions that enter	2907	You I<must not> call C<ev_run> or similar functions that enter
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2908	the current event loop from either C<ev_prepare> or C<ev_check>
2218	watchers. Other loops than the current one are fine, however. The	2909	watchers. Other loops than the current one are fine, however. The
2219	rationale behind this is that you do not need to check for recursion in	2910	rationale behind this is that you do not need to check for recursion in
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2911	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2221	C<ev_check> so if you have one watcher of each kind they will always be	2912	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2245	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2246	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2247	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2248	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2249		2940
2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2251	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2252	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2253		2945
2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2255	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2256	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2257	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2258	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2260	others).	2952	others).
		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2261		2973
2262	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2263		2975
2264	=over 4	2976	=over 4
2265		2977
…		…
2305	struct pollfd fds [nfd];	3017	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	3018	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3019	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		3020
2309	/* the callback is illegal, but won't be called as we stop during check */	3021	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	3022	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	3023	ev_timer_start (loop, &tw);
2312		3024
2313	// create one ev_io per pollfd	3025	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	3026	for (int i = 0; i < nfd; ++i)
2315	{	3027	{
…		…
2389		3101
2390	if (timeout >= 0)	3102	if (timeout >= 0)
2391	// create/start timer	3103	// create/start timer
2392		3104
2393	// poll	3105	// poll
2394	ev_loop (EV_A_ 0);	3106	ev_run (EV_A_ 0);
2395		3107
2396	// stop timer again	3108	// stop timer again
2397	if (timeout >= 0)	3109	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3110	ev_timer_stop (EV_A_ &to);
2399		3111
…		…
2477	if you do not want that, you need to temporarily stop the embed watcher).	3189	if you do not want that, you need to temporarily stop the embed watcher).
2478		3190
2479	=item ev_embed_sweep (loop, ev_embed *)	3191	=item ev_embed_sweep (loop, ev_embed *)
2480		3192
2481	Make a single, non-blocking sweep over the embedded loop. This works	3193	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3194	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3195	appropriate way for embedded loops.
2484		3196
2485	=item struct ev_loop *other [read-only]	3197	=item struct ev_loop *other [read-only]
2486		3198
2487	The embedded event loop.	3199	The embedded event loop.
…		…
2545	event loop blocks next and before C<ev_check> watchers are being called,	3257	event loop blocks next and before C<ev_check> watchers are being called,
2546	and only in the child after the fork. If whoever good citizen calling	3258	and only in the child after the fork. If whoever good citizen calling
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2548	handlers will be invoked, too, of course.	3260	handlers will be invoked, too, of course.
2549		3261
		3262	=head3 The special problem of life after fork - how is it possible?
		3263
		3264	Most uses of C<fork()> consist of forking, then some simple calls to set
		3265	up/change the process environment, followed by a call to C<exec()>. This
		3266	sequence should be handled by libev without any problems.
		3267
		3268	This changes when the application actually wants to do event handling
		3269	in the child, or both parent in child, in effect "continuing" after the
		3270	fork.
		3271
		3272	The default mode of operation (for libev, with application help to detect
		3273	forks) is to duplicate all the state in the child, as would be expected
		3274	when I<either> the parent I<or> the child process continues.
		3275
		3276	When both processes want to continue using libev, then this is usually the
		3277	wrong result. In that case, usually one process (typically the parent) is
		3278	supposed to continue with all watchers in place as before, while the other
		3279	process typically wants to start fresh, i.e. without any active watchers.
		3280
		3281	The cleanest and most efficient way to achieve that with libev is to
		3282	simply create a new event loop, which of course will be "empty", and
		3283	use that for new watchers. This has the advantage of not touching more
		3284	memory than necessary, and thus avoiding the copy-on-write, and the
		3285	disadvantage of having to use multiple event loops (which do not support
		3286	signal watchers).
		3287
		3288	When this is not possible, or you want to use the default loop for
		3289	other reasons, then in the process that wants to start "fresh", call
		3290	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3291	Destroying the default loop will "orphan" (not stop) all registered
		3292	watchers, so you have to be careful not to execute code that modifies
		3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
		3295
2550	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
2551		3297
2552	=over 4	3298	=over 4
2553		3299
2554	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
2555		3301
2556	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3304	really.
2559		3305
2560	=back	3306	=back
2561		3307
2562		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
2563	=head2 C<ev_async> - how to wake up another event loop	3349	=head2 C<ev_async> - how to wake up an event loop
2564		3350
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
2568		3354
2569	Sometimes, however, you need to wake up another event loop you do not	3355	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3356	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3357	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3359
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2579		3364	of "global async watchers" by using a watcher on an otherwise unused
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2581	just the default loop.	3366	even without knowing which loop owns the signal.
2582		3367
2583	=head3 Queueing	3368	=head3 Queueing
2584		3369
2585	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3372	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3373	need elaborate support such as pthreads or unportable memory access
		3374	semantics.
2589		3375
2590	That means that if you want to queue data, you have to provide your own	3376	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3377	queue. But at least I can tell you how to implement locking around your
2592	queue:	3378	queue:
2593		3379
…		…
2677	trust me.	3463	trust me.
2678		3464
2679	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
2680		3466
2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2685	section below on what exactly this means).	3473	embedding section below on what exactly this means).
2686		3474
2687	This call incurs the overhead of a system call only once per loop iteration,	3475	Note that, as with other watchers in libev, multiple events might get
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3476	compressed into a single callback invocation (another way to look at
2689	calls to C<ev_async_send>.	3477	this is that C<ev_async> watchers are level-triggered: they are set on
		3478	C<ev_async_send>, reset when the event loop detects that).
		3479
		3480	This call incurs the overhead of at most one extra system call per event
		3481	loop iteration, if the event loop is blocked, and no syscall at all if
		3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
2690		3486
2691	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
2692		3488
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3493	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3494	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3495	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3496	quickly check whether invoking the loop might be a good idea.
2701		3497
2702	Not that this does I<not> check whether the watcher itself is pending, only	3498	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3499	only whether it has been requested to make this watcher pending: there
		3500	is a time window between the event loop checking and resetting the async
		3501	notification, and the callback being invoked.
2704		3502
2705	=back	3503	=back
2706		3504
2707		3505
2708	=head1 OTHER FUNCTIONS	3506	=head1 OTHER FUNCTIONS
…		…
2725		3523
2726	If C<timeout> is less than 0, then no timeout watcher will be	3524	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3525	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3526	repeat = 0) will be started. C<0> is a valid timeout.
2729		3527
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3528	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3529	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3530	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3531	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3532	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3533	events precedence.
2736		3534
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3535	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3536
2739	static void stdin_ready (int revents, void *arg)	3537	static void stdin_ready (int revents, void *arg)
2740	{	3538	{
2741	if (revents & EV_READ)	3539	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3540	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3541	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3542	/* doh, nothing entered */;
2745	}	3543	}
2746		3544
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3546
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3548
2757	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3550	the given events.
2759		3551
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
2761		3553
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3555	which is async-safe.
2764		3556
2765	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, C<ev_break> will not work alone.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
2766		3908
2767		3909
2768	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
2769		3911
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
2772		3914
2773	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
2774		3921
2775	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
2776		3923
2777	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3933	is an ev_pri field.
2787		3934
2788	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
2790		3937
2791	=item * Other members are not supported.	3938	=item * Other members are not supported.
2792		3939
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3941	to use the libev header file and library.
2795		3942
2796	=back	3943	=back
2797		3944
2798	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
2799		3979
2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2801	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
2802	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
2803		3983
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		3997
2818	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
2822	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
2823		4007
2824	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
2825		4009
2826	=over 4	4010	=over 4
2827		4011
…		…
2837	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2838		4022
2839	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2840	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2841	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2842	defines by many implementations.	4026	defined by many implementations.
2843		4027
2844	All of those classes have these methods:	4028	All of those classes have these methods:
2845		4029
2846	=over 4	4030	=over 4
2847		4031
2848	=item ev::TYPE::TYPE ()	4032	=item ev::TYPE::TYPE ()
2849		4033
2850	=item ev::TYPE::TYPE (struct ev_loop *)	4034	=item ev::TYPE::TYPE (loop)
2851		4035
2852	=item ev::TYPE::~TYPE	4036	=item ev::TYPE::~TYPE
2853		4037
2854	The constructor (optionally) takes an event loop to associate the watcher	4038	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	4039	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	4072	myclass obj;
2889	ev::io iow;	4073	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	4074	iow.set <myclass, &myclass::io_cb> (&obj);
2891		4075
2892	=item w->set (object *)	4076	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		4077
2896	This is a variation of a method callback - leaving out the method to call	4078	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	4079	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	4080	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	4081	the time. Incidentally, you can then also leave out the template argument
…		…
2932	Example: Use a plain function as callback.	4114	Example: Use a plain function as callback.
2933		4115
2934	static void io_cb (ev::io &w, int revents) { }	4116	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	4117	iow.set <io_cb> ();
2936		4118
2937	=item w->set (struct ev_loop *)	4119	=item w->set (loop)
2938		4120
2939	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
2941		4123
2942	=item w->set ([arguments])	4124	=item w->set ([arguments])
2943		4125
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4126	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2945	called at least once. Unlike the C counterpart, an active watcher gets	4127	method or a suitable start method must be called at least once. Unlike the
2946	automatically stopped and restarted when reconfiguring it with this	4128	C counterpart, an active watcher gets automatically stopped and restarted
2947	method.	4129	when reconfiguring it with this method.
2948		4130
2949	=item w->start ()	4131	=item w->start ()
2950		4132
2951	Starts the watcher. Note that there is no C<loop> argument, as the	4133	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	4134	constructor already stores the event loop.
2953		4135
		4136	=item w->start ([arguments])
		4137
		4138	Instead of calling C<set> and C<start> methods separately, it is often
		4139	convenient to wrap them in one call. Uses the same type of arguments as
		4140	the configure C<set> method of the watcher.
		4141
2954	=item w->stop ()	4142	=item w->stop ()
2955		4143
2956	Stops the watcher if it is active. Again, no C<loop> argument.	4144	Stops the watcher if it is active. Again, no C<loop> argument.
2957		4145
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4146	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		4158
2971	=back	4159	=back
2972		4160
2973	=back	4161	=back
2974		4162
2975	Example: Define a class with an IO and idle watcher, start one of them in	4163	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	4164	watchers in the constructor.
2977		4165
2978	class myclass	4166	class myclass
2979	{	4167	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	4168	ev::io io ; void io_cb (ev::io &w, int revents);
		4169	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4170	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		4171
2983	myclass (int fd)	4172	myclass (int fd)
2984	{	4173	{
2985	io .set <myclass, &myclass::io_cb > (this);	4174	io .set <myclass, &myclass::io_cb > (this);
		4175	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	4176	idle.set <myclass, &myclass::idle_cb> (this);
2987		4177
2988	io.start (fd, ev::READ);	4178	io.set (fd, ev::WRITE); // configure the watcher
		4179	io.start (); // start it whenever convenient
		4180
		4181	io2.start (fd, ev::READ); // set + start in one call
2989	}	4182	}
2990	};	4183	};
2991		4184
2992		4185
2993	=head1 OTHER LANGUAGE BINDINGS	4186	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	4205	L<http://software.schmorp.de/pkg/EV>.
3013		4206
3014	=item Python	4207	=item Python
3015		4208
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4209	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	4210	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		4211
3023	=item Ruby	4212	=item Ruby
3024		4213
3025	Tony Arcieri has written a ruby extension that offers access to a subset	4214	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	4215	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	4217	L<http://rev.rubyforge.org/>.
3029		4218
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	4219	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	4220	makes rev work even on mingw.
3032		4221
		4222	=item Haskell
		4223
		4224	A haskell binding to libev is available at
		4225	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4226
3033	=item D	4227	=item D
3034		4228
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4229	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4230	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3037		4231
3038	=item Ocaml	4232	=item Ocaml
3039		4233
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	4234	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4235	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4236
		4237	=item Lua
		4238
		4239	Brian Maher has written a partial interface to libev for lua (at the
		4240	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4241	L<http://github.com/brimworks/lua-ev>.
3042		4242
3043	=back	4243	=back
3044		4244
3045		4245
3046	=head1 MACRO MAGIC	4246	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	4260	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	4261	C<EV_A_> is used when other arguments are following. Example:
3062		4262
3063	ev_unref (EV_A);	4263	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	4264	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	4265	ev_run (EV_A_ 0);
3066		4266
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4267	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	4268	which is often provided by the following macro.
3069		4269
3070	=item C<EV_P>, C<EV_P_>	4270	=item C<EV_P>, C<EV_P_>
…		…
3083	suitable for use with C<EV_A>.	4283	suitable for use with C<EV_A>.
3084		4284
3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4285	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3086		4286
3087	Similar to the other two macros, this gives you the value of the default	4287	Similar to the other two macros, this gives you the value of the default
3088	loop, if multiple loops are supported ("ev loop default").	4288	loop, if multiple loops are supported ("ev loop default"). The default loop
		4289	will be initialised if it isn't already initialised.
		4290
		4291	For non-multiplicity builds, these macros do nothing, so you always have
		4292	to initialise the loop somewhere.
3089		4293
3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4294	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3091		4295
3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4296	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3093	default loop has been initialised (C<UC> == unchecked). Their behaviour	4297	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3110	}	4314	}
3111		4315
3112	ev_check check;	4316	ev_check check;
3113	ev_check_init (&check, check_cb);	4317	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4318	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4319	ev_run (EV_DEFAULT_ 0);
3116		4320
3117	=head1 EMBEDDING	4321	=head1 EMBEDDING
3118		4322
3119	Libev can (and often is) directly embedded into host	4323	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4324	applications. Examples of applications that embed it include the Deliantra
…		…
3200	libev.m4	4404	libev.m4
3201		4405
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4406	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4407
3204	Libev can be configured via a variety of preprocessor symbols you have to	4408	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	4409	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4410	the absence of autoconf is documented for every option.
		4411
		4412	Symbols marked with "(h)" do not change the ABI, and can have different
		4413	values when compiling libev vs. including F<ev.h>, so it is permissible
		4414	to redefine them before including F<ev.h> without breaking compatibility
		4415	to a compiled library. All other symbols change the ABI, which means all
		4416	users of libev and the libev code itself must be compiled with compatible
		4417	settings.
3207		4418
3208	=over 4	4419	=over 4
3209		4420
		4421	=item EV_COMPAT3 (h)
		4422
		4423	Backwards compatibility is a major concern for libev. This is why this
		4424	release of libev comes with wrappers for the functions and symbols that
		4425	have been renamed between libev version 3 and 4.
		4426
		4427	You can disable these wrappers (to test compatibility with future
		4428	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4429	sources. This has the additional advantage that you can drop the C<struct>
		4430	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4431	typedef in that case.
		4432
		4433	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4434	and in some even more future version the compatibility code will be
		4435	removed completely.
		4436
3210	=item EV_STANDALONE	4437	=item EV_STANDALONE (h)
3211		4438
3212	Must always be C<1> if you do not use autoconf configuration, which	4439	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	4440	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4441	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	4442	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	4443	F<event.h> that are not directly supported by the libev core alone.
3217		4444
3218	In stanbdalone mode, libev will still try to automatically deduce the	4445	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4446	configuration, but has to be more conservative.
		4447
		4448	=item EV_USE_FLOOR
		4449
		4450	If defined to be C<1>, libev will use the C<floor ()> function for its
		4451	periodic reschedule calculations, otherwise libev will fall back on a
		4452	portable (slower) implementation. If you enable this, you usually have to
		4453	link against libm or something equivalent. Enabling this when the C<floor>
		4454	function is not available will fail, so the safe default is to not enable
		4455	this.
3220		4456
3221	=item EV_USE_MONOTONIC	4457	=item EV_USE_MONOTONIC
3222		4458
3223	If defined to be C<1>, libev will try to detect the availability of the	4459	If defined to be C<1>, libev will try to detect the availability of the
3224	monotonic clock option at both compile time and runtime. Otherwise no	4460	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3288	be used is the winsock select). This means that it will call	4524	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4525	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4526	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4527	on win32. Should not be defined on non-win32 platforms.
3292		4528
3293	=item EV_FD_TO_WIN32_HANDLE	4529	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4530
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4531	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4532	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4533	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4534	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4535	in which case they can provide this function to map fds to socket handles.
		4536
		4537	=item EV_WIN32_HANDLE_TO_FD(handle)
		4538
		4539	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4540	using the standard C<_open_osfhandle> function. For programs implementing
		4541	their own fd to handle mapping, overwriting this function makes it easier
		4542	to do so. This can be done by defining this macro to an appropriate value.
		4543
		4544	=item EV_WIN32_CLOSE_FD(fd)
		4545
		4546	If programs implement their own fd to handle mapping on win32, then this
		4547	macro can be used to override the C<close> function, useful to unregister
		4548	file descriptors again. Note that the replacement function has to close
		4549	the underlying OS handle.
3300		4550
3301	=item EV_USE_POLL	4551	=item EV_USE_POLL
3302		4552
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4553	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4554	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3340	If defined to be C<1>, libev will compile in support for the Linux inotify	4590	If defined to be C<1>, libev will compile in support for the Linux inotify
3341	interface to speed up C<ev_stat> watchers. Its actual availability will	4591	interface to speed up C<ev_stat> watchers. Its actual availability will
3342	be detected at runtime. If undefined, it will be enabled if the headers	4592	be detected at runtime. If undefined, it will be enabled if the headers
3343	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4593	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3344		4594
		4595	=item EV_NO_SMP
		4596
		4597	If defined to be C<1>, libev will assume that memory is always coherent
		4598	between threads, that is, threads can be used, but threads never run on
		4599	different cpus (or different cpu cores). This reduces dependencies
		4600	and makes libev faster.
		4601
		4602	=item EV_NO_THREADS
		4603
		4604	If defined to be C<1>, libev will assume that it will never be called
		4605	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4606	above. This reduces dependencies and makes libev faster.
		4607
3345	=item EV_ATOMIC_T	4608	=item EV_ATOMIC_T
3346		4609
3347	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4610	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3348	access is atomic with respect to other threads or signal contexts. No such	4611	access is atomic and serialised with respect to other threads or signal
3349	type is easily found in the C language, so you can provide your own type	4612	contexts. No such type is easily found in the C language, so you can
3350	that you know is safe for your purposes. It is used both for signal handler "locking"	4613	provide your own type that you know is safe for your purposes. It is used
3351	as well as for signal and thread safety in C<ev_async> watchers.	4614	both for signal handler "locking" as well as for signal and thread safety
		4615	in C<ev_async> watchers.
3352		4616
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4617	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4618	(from F<signal.h>), which is usually good enough on most platforms,
		4619	although strictly speaking using a type that also implies a memory fence
		4620	is required.
3355		4621
3356	=item EV_H	4622	=item EV_H (h)
3357		4623
3358	The name of the F<ev.h> header file used to include it. The default if	4624	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4625	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4626	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4627
3362	=item EV_CONFIG_H	4628	=item EV_CONFIG_H (h)
3363		4629
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4630	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4631	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4632	C<EV_H>, above.
3367		4633
3368	=item EV_EVENT_H	4634	=item EV_EVENT_H (h)
3369		4635
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4636	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4637	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4638
3373	=item EV_PROTOTYPES	4639	=item EV_PROTOTYPES (h)
3374		4640
3375	If defined to be C<0>, then F<ev.h> will not define any function	4641	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4642	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4643	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4644	around libev functions.
…		…
3383	will have the C<struct ev_loop *> as first argument, and you can create	4649	will have the C<struct ev_loop *> as first argument, and you can create
3384	additional independent event loops. Otherwise there will be no support	4650	additional independent event loops. Otherwise there will be no support
3385	for multiple event loops and there is no first event loop pointer	4651	for multiple event loops and there is no first event loop pointer
3386	argument. Instead, all functions act on the single default loop.	4652	argument. Instead, all functions act on the single default loop.
3387		4653
		4654	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4655	default loop when multiplicity is switched off - you always have to
		4656	initialise the loop manually in this case.
		4657
3388	=item EV_MINPRI	4658	=item EV_MINPRI
3389		4659
3390	=item EV_MAXPRI	4660	=item EV_MAXPRI
3391		4661
3392	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4662	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3400	fine.	4670	fine.
3401		4671
3402	If your embedding application does not need any priorities, defining these	4672	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4673	both to C<0> will save some memory and CPU.
3404		4674
3405	=item EV_PERIODIC_ENABLE	4675	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4676	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4677	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4678
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4679	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4680	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4681	is not. Disabling watcher types mainly saves code size.
3410		4682
3411	=item EV_IDLE_ENABLE	4683	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4684
3440	If you need to shave off some kilobytes of code at the expense of some	4685	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4686	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4687	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4688	that can be enabled on the platform.
		4689
		4690	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4691	with some broad features you want) and then selectively re-enable
		4692	additional parts you want, for example if you want everything minimal,
		4693	but multiple event loop support, async and child watchers and the poll
		4694	backend, use this:
		4695
		4696	#define EV_FEATURES 0
		4697	#define EV_MULTIPLICITY 1
		4698	#define EV_USE_POLL 1
		4699	#define EV_CHILD_ENABLE 1
		4700	#define EV_ASYNC_ENABLE 1
		4701
		4702	The actual value is a bitset, it can be a combination of the following
		4703	values (by default, all of these are enabled):
		4704
		4705	=over 4
		4706
		4707	=item C<1> - faster/larger code
		4708
		4709	Use larger code to speed up some operations.
		4710
		4711	Currently this is used to override some inlining decisions (enlarging the
		4712	code size by roughly 30% on amd64).
		4713
		4714	When optimising for size, use of compiler flags such as C<-Os> with
		4715	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4716	assertions.
		4717
		4718	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4719	(e.g. gcc with C<-Os>).
		4720
		4721	=item C<2> - faster/larger data structures
		4722
		4723	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4724	hash table sizes and so on. This will usually further increase code size
		4725	and can additionally have an effect on the size of data structures at
		4726	runtime.
		4727
		4728	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4729	(e.g. gcc with C<-Os>).
		4730
		4731	=item C<4> - full API configuration
		4732
		4733	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4734	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4735
		4736	=item C<8> - full API
		4737
		4738	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4739	details on which parts of the API are still available without this
		4740	feature, and do not complain if this subset changes over time.
		4741
		4742	=item C<16> - enable all optional watcher types
		4743
		4744	Enables all optional watcher types. If you want to selectively enable
		4745	only some watcher types other than I/O and timers (e.g. prepare,
		4746	embed, async, child...) you can enable them manually by defining
		4747	C<EV_watchertype_ENABLE> to C<1> instead.
		4748
		4749	=item C<32> - enable all backends
		4750
		4751	This enables all backends - without this feature, you need to enable at
		4752	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4753
		4754	=item C<64> - enable OS-specific "helper" APIs
		4755
		4756	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4757	default.
		4758
		4759	=back
		4760
		4761	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4762	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4763	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4764	watchers, timers and monotonic clock support.
		4765
		4766	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4767	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4768	your program might be left out as well - a binary starting a timer and an
		4769	I/O watcher then might come out at only 5Kb.
		4770
		4771	=item EV_API_STATIC
		4772
		4773	If this symbol is defined (by default it is not), then all identifiers
		4774	will have static linkage. This means that libev will not export any
		4775	identifiers, and you cannot link against libev anymore. This can be useful
		4776	when you embed libev, only want to use libev functions in a single file,
		4777	and do not want its identifiers to be visible.
		4778
		4779	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4780	wants to use libev.
		4781
		4782	This option only works when libev is compiled with a C compiler, as C++
		4783	doesn't support the required declaration syntax.
		4784
		4785	=item EV_AVOID_STDIO
		4786
		4787	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4788	functions (printf, scanf, perror etc.). This will increase the code size
		4789	somewhat, but if your program doesn't otherwise depend on stdio and your
		4790	libc allows it, this avoids linking in the stdio library which is quite
		4791	big.
		4792
		4793	Note that error messages might become less precise when this option is
		4794	enabled.
		4795
		4796	=item EV_NSIG
		4797
		4798	The highest supported signal number, +1 (or, the number of
		4799	signals): Normally, libev tries to deduce the maximum number of signals
		4800	automatically, but sometimes this fails, in which case it can be
		4801	specified. Also, using a lower number than detected (C<32> should be
		4802	good for about any system in existence) can save some memory, as libev
		4803	statically allocates some 12-24 bytes per signal number.
3444		4804
3445	=item EV_PID_HASHSIZE	4805	=item EV_PID_HASHSIZE
3446		4806
3447	C<ev_child> watchers use a small hash table to distribute workload by	4807	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4808	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4809	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4810	might want to increase this value (I<must> be a power of two).
3451		4811
3452	=item EV_INOTIFY_HASHSIZE	4812	=item EV_INOTIFY_HASHSIZE
3453		4813
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4814	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4815	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4816	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4817	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4818	power of two).
3459		4819
3460	=item EV_USE_4HEAP	4820	=item EV_USE_4HEAP
3461		4821
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4822	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4823	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4824	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4825	faster performance with many (thousands) of watchers.
3466		4826
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4827	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4828	will be C<0>.
3469		4829
3470	=item EV_HEAP_CACHE_AT	4830	=item EV_HEAP_CACHE_AT
3471		4831
3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4832	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4833	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4834	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4835	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4836	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4837	noticeably with many (hundreds) of watchers.
3478		4838
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4839	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4840	will be C<0>.
3481		4841
3482	=item EV_VERIFY	4842	=item EV_VERIFY
3483		4843
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4844	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4845	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4846	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4847	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4848	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4849	verification code will be called very frequently, which will slow down
3490	libev considerably.	4850	libev considerably.
3491		4851
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4852	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4853	will be C<0>.
3494		4854
3495	=item EV_COMMON	4855	=item EV_COMMON
3496		4856
3497	By default, all watchers have a C<void *data> member. By redefining	4857	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4858	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4859	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4860	though, and it must be identical each time.
3501		4861
3502	For example, the perl EV module uses something like this:	4862	For example, the perl EV module uses something like this:
3503		4863
…		…
3556	file.	4916	file.
3557		4917
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4918	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	4919	that everybody includes and which overrides some configure choices:
3560		4920
3561	#define EV_MINIMAL 1	4921	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	4922	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	4923	#define EV_PREPARE_ENABLE 1
		4924	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	4925	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	4926	#define EV_CHILD_ENABLE 1
		4927	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	4928	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		4929
3571	#include "ev++.h"	4930	#include "ev++.h"
3572		4931
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4932	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		4933
3575	#include "ev_cpp.h"	4934	#include "ev_cpp.h"
3576	#include "ev.c"	4935	#include "ev.c"
3577		4936
3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4937	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3579		4938
3580	=head2 THREADS AND COROUTINES	4939	=head2 THREADS AND COROUTINES
3581		4940
3582	=head3 THREADS	4941	=head3 THREADS
3583		4942
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	4993	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	4994	watcher callback into the event loop interested in the signal.
3636		4995
3637	=back	4996	=back
3638		4997
		4998	See also L<THREAD LOCKING EXAMPLE>.
		4999
3639	=head3 COROUTINES	5000	=head3 COROUTINES
3640		5001
3641	Libev is very accommodating to coroutines ("cooperative threads"):	5002	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	5003	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5004	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	5005	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	5006	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	5007	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		5008
3648	Care has been taken to ensure that libev does not keep local state inside	5009	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5010	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	5011	they do not call any callbacks.
3651		5012
3652	=head2 COMPILER WARNINGS	5013	=head2 COMPILER WARNINGS
3653		5014
3654	Depending on your compiler and compiler settings, you might get no or a	5015	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	5026	maintainable.
3666		5027
3667	And of course, some compiler warnings are just plain stupid, or simply	5028	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	5029	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	5030	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	5031	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	5032	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	5033	such buggy versions.
3673		5034
3674	While libev is written to generate as few warnings as possible,	5035	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	5036	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	5072	I suggest using suppression lists.
3712		5073
3713		5074
3714	=head1 PORTABILITY NOTES	5075	=head1 PORTABILITY NOTES
3715		5076
		5077	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5078
		5079	GNU/Linux is the only common platform that supports 64 bit file/large file
		5080	interfaces but I<disables> them by default.
		5081
		5082	That means that libev compiled in the default environment doesn't support
		5083	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5084
		5085	Unfortunately, many programs try to work around this GNU/Linux issue
		5086	by enabling the large file API, which makes them incompatible with the
		5087	standard libev compiled for their system.
		5088
		5089	Likewise, libev cannot enable the large file API itself as this would
		5090	suddenly make it incompatible to the default compile time environment,
		5091	i.e. all programs not using special compile switches.
		5092
		5093	=head2 OS/X AND DARWIN BUGS
		5094
		5095	The whole thing is a bug if you ask me - basically any system interface
		5096	you touch is broken, whether it is locales, poll, kqueue or even the
		5097	OpenGL drivers.
		5098
		5099	=head3 C<kqueue> is buggy
		5100
		5101	The kqueue syscall is broken in all known versions - most versions support
		5102	only sockets, many support pipes.
		5103
		5104	Libev tries to work around this by not using C<kqueue> by default on this
		5105	rotten platform, but of course you can still ask for it when creating a
		5106	loop - embedding a socket-only kqueue loop into a select-based one is
		5107	probably going to work well.
		5108
		5109	=head3 C<poll> is buggy
		5110
		5111	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5112	implementation by something calling C<kqueue> internally around the 10.5.6
		5113	release, so now C<kqueue> I<and> C<poll> are broken.
		5114
		5115	Libev tries to work around this by not using C<poll> by default on
		5116	this rotten platform, but of course you can still ask for it when creating
		5117	a loop.
		5118
		5119	=head3 C<select> is buggy
		5120
		5121	All that's left is C<select>, and of course Apple found a way to fuck this
		5122	one up as well: On OS/X, C<select> actively limits the number of file
		5123	descriptors you can pass in to 1024 - your program suddenly crashes when
		5124	you use more.
		5125
		5126	There is an undocumented "workaround" for this - defining
		5127	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5128	work on OS/X.
		5129
		5130	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5131
		5132	=head3 C<errno> reentrancy
		5133
		5134	The default compile environment on Solaris is unfortunately so
		5135	thread-unsafe that you can't even use components/libraries compiled
		5136	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5137	defined by default. A valid, if stupid, implementation choice.
		5138
		5139	If you want to use libev in threaded environments you have to make sure
		5140	it's compiled with C<_REENTRANT> defined.
		5141
		5142	=head3 Event port backend
		5143
		5144	The scalable event interface for Solaris is called "event
		5145	ports". Unfortunately, this mechanism is very buggy in all major
		5146	releases. If you run into high CPU usage, your program freezes or you get
		5147	a large number of spurious wakeups, make sure you have all the relevant
		5148	and latest kernel patches applied. No, I don't know which ones, but there
		5149	are multiple ones to apply, and afterwards, event ports actually work
		5150	great.
		5151
		5152	If you can't get it to work, you can try running the program by setting
		5153	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5154	C<select> backends.
		5155
		5156	=head2 AIX POLL BUG
		5157
		5158	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5159	this by trying to avoid the poll backend altogether (i.e. it's not even
		5160	compiled in), which normally isn't a big problem as C<select> works fine
		5161	with large bitsets on AIX, and AIX is dead anyway.
		5162
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5163	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5164
		5165	=head3 General issues
3717		5166
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5167	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	5168	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	5169	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5170	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	5171	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	5172	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5173	as every compiler comes with a slightly differently broken/incompatible
		5174	environment.
3724		5175
3725	Lifting these limitations would basically require the full	5176	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	5177	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	5178	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	5179	also that glib is the slowest event library known to man).
3729		5180
3730	There is no supported compilation method available on windows except	5181	There is no supported compilation method available on windows except
3731	embedding it into other applications.	5182	embedding it into other applications.
		5183
		5184	Sensible signal handling is officially unsupported by Microsoft - libev
		5185	tries its best, but under most conditions, signals will simply not work.
3732		5186
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	5187	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	5188	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	5189	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	5190	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	5195	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	5196	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	5197	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	5198	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	5199	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	5200	(due to Microsoft monopoly games).
3747		5201
3748	A typical way to use libev under windows is to embed it (see the embedding	5202	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	5203	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	5204	of F<ev.h>:
3751		5205
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	5212	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		5213
3760	#include "evwrap.h"	5214	#include "evwrap.h"
3761	#include "ev.c"	5215	#include "ev.c"
3762		5216
3763	=over 4
3764
3765	=item The winsocket select function	5217	=head3 The winsocket C<select> function
3766		5218
3767	The winsocket C<select> function doesn't follow POSIX in that it	5219	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	5220	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	5221	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	5222	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5231	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		5232
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	5233	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	5234	complexity in the O(n²) range when using win32.
3783		5235
3784	=item Limited number of file descriptors	5236	=head3 Limited number of file descriptors
3785		5237
3786	Windows has numerous arbitrary (and low) limits on things.	5238	Windows has numerous arbitrary (and low) limits on things.
3787		5239
3788	Early versions of winsocket's select only supported waiting for a maximum	5240	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	5241	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	5242	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	5243	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	5244	previous thread in each. Sounds great!).
3793		5245
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5246	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	5247	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	5248	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	5249	other interpreters do their own select emulation on windows).
3798		5250
3799	Another limit is the number of file descriptors in the Microsoft runtime	5251	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5252	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	5253	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5254	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	5255	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	5256	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	5257	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	5258	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	5259	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		5260
3813	=head2 PORTABILITY REQUIREMENTS	5261	=head2 PORTABILITY REQUIREMENTS
3814		5262
3815	In addition to a working ISO-C implementation and of course the	5263	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	5264	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	5271	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	5272	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	5273	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	5274	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	5275	calls them using an C<ev_watcher *> internally.
		5276
		5277	=item pointer accesses must be thread-atomic
		5278
		5279	Accessing a pointer value must be atomic, it must both be readable and
		5280	writable in one piece - this is the case on all current architectures.
3828		5281
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	5282	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		5283
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	5284	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5285	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3855	watchers.	5308	watchers.
3856		5309
3857	=item C<double> must hold a time value in seconds with enough accuracy	5310	=item C<double> must hold a time value in seconds with enough accuracy
3858		5311
3859	The type C<double> is used to represent timestamps. It is required to	5312	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5313	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	5314	good enough for at least into the year 4000 with millisecond accuracy
		5315	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	5316	implementations using IEEE 754, which is basically all existing ones.
		5317
		5318	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5319	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5320	is either obsolete or somebody patched it to use C<long double> or
		5321	something like that, just kidding).
3863		5322
3864	=back	5323	=back
3865		5324
3866	If you know of other additional requirements drop me a note.	5325	If you know of other additional requirements drop me a note.
3867		5326
…		…
3929	=item Processing ev_async_send: O(number_of_async_watchers)	5388	=item Processing ev_async_send: O(number_of_async_watchers)
3930		5389
3931	=item Processing signals: O(max_signal_number)	5390	=item Processing signals: O(max_signal_number)
3932		5391
3933	Sending involves a system call I<iff> there were no other C<ev_async_send>	5392	Sending involves a system call I<iff> there were no other C<ev_async_send>
3934	calls in the current loop iteration. Checking for async and signal events	5393	calls in the current loop iteration and the loop is currently
		5394	blocked. Checking for async and signal events involves iterating over all
3935	involves iterating over all running async watchers or all signal numbers.	5395	running async watchers or all signal numbers.
3936		5396
3937	=back	5397	=back
3938		5398
3939		5399
		5400	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5401
		5402	The major version 4 introduced some incompatible changes to the API.
		5403
		5404	At the moment, the C<ev.h> header file provides compatibility definitions
		5405	for all changes, so most programs should still compile. The compatibility
		5406	layer might be removed in later versions of libev, so better update to the
		5407	new API early than late.
		5408
		5409	=over 4
		5410
		5411	=item C<EV_COMPAT3> backwards compatibility mechanism
		5412
		5413	The backward compatibility mechanism can be controlled by
		5414	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5415	section.
		5416
		5417	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5418
		5419	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5420
		5421	ev_loop_destroy (EV_DEFAULT_UC);
		5422	ev_loop_fork (EV_DEFAULT);
		5423
		5424	=item function/symbol renames
		5425
		5426	A number of functions and symbols have been renamed:
		5427
		5428	ev_loop => ev_run
		5429	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5430	EVLOOP_ONESHOT => EVRUN_ONCE
		5431
		5432	ev_unloop => ev_break
		5433	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5434	EVUNLOOP_ONE => EVBREAK_ONE
		5435	EVUNLOOP_ALL => EVBREAK_ALL
		5436
		5437	EV_TIMEOUT => EV_TIMER
		5438
		5439	ev_loop_count => ev_iteration
		5440	ev_loop_depth => ev_depth
		5441	ev_loop_verify => ev_verify
		5442
		5443	Most functions working on C<struct ev_loop> objects don't have an
		5444	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5445	associated constants have been renamed to not collide with the C<struct
		5446	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5447	as all other watcher types. Note that C<ev_loop_fork> is still called
		5448	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5449	typedef.
		5450
		5451	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5452
		5453	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5454	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5455	and work, but the library code will of course be larger.
		5456
		5457	=back
		5458
		5459
		5460	=head1 GLOSSARY
		5461
		5462	=over 4
		5463
		5464	=item active
		5465
		5466	A watcher is active as long as it has been started and not yet stopped.
		5467	See L<WATCHER STATES> for details.
		5468
		5469	=item application
		5470
		5471	In this document, an application is whatever is using libev.
		5472
		5473	=item backend
		5474
		5475	The part of the code dealing with the operating system interfaces.
		5476
		5477	=item callback
		5478
		5479	The address of a function that is called when some event has been
		5480	detected. Callbacks are being passed the event loop, the watcher that
		5481	received the event, and the actual event bitset.
		5482
		5483	=item callback/watcher invocation
		5484
		5485	The act of calling the callback associated with a watcher.
		5486
		5487	=item event
		5488
		5489	A change of state of some external event, such as data now being available
		5490	for reading on a file descriptor, time having passed or simply not having
		5491	any other events happening anymore.
		5492
		5493	In libev, events are represented as single bits (such as C<EV_READ> or
		5494	C<EV_TIMER>).
		5495
		5496	=item event library
		5497
		5498	A software package implementing an event model and loop.
		5499
		5500	=item event loop
		5501
		5502	An entity that handles and processes external events and converts them
		5503	into callback invocations.
		5504
		5505	=item event model
		5506
		5507	The model used to describe how an event loop handles and processes
		5508	watchers and events.
		5509
		5510	=item pending
		5511
		5512	A watcher is pending as soon as the corresponding event has been
		5513	detected. See L<WATCHER STATES> for details.
		5514
		5515	=item real time
		5516
		5517	The physical time that is observed. It is apparently strictly monotonic :)
		5518
		5519	=item wall-clock time
		5520
		5521	The time and date as shown on clocks. Unlike real time, it can actually
		5522	be wrong and jump forwards and backwards, e.g. when you adjust your
		5523	clock.
		5524
		5525	=item watcher
		5526
		5527	A data structure that describes interest in certain events. Watchers need
		5528	to be started (attached to an event loop) before they can receive events.
		5529
		5530	=back
		5531
3940	=head1 AUTHOR	5532	=head1 AUTHOR
3941		5533
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5534	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5535	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3943		5536

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