ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.211 by root, Mon Nov 3 14:34:16 2008 UTC vs.
Revision 1.436 by root, Sun Oct 11 15:46:42 2015 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
8		10
9	=head2 EXAMPLE PROGRAM	11	=head2 EXAMPLE PROGRAM
10		12
11	// a single header file is required	13	// a single header file is required
12	#include <ev.h>	14	#include <ev.h>
		15
		16	#include <stdio.h> // for puts
13		17
14	// every watcher type has its own typedef'd struct	18	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	19	// with the name ev_TYPE
16	ev_io stdin_watcher;	20	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	21	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	28	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	30	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
28		32
29	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
31	}	35	}
32		36
33	// another callback, this time for a time-out	37	// another callback, this time for a time-out
34	static void	38	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	40	{
37	puts ("timeout");	41	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
40	}	44	}
41		45
42	int	46	int
43	main (void)	47	main (void)
44	{	48	{
45	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
47		51
48	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
57		61
58	// now wait for events to arrive	62	// now wait for events to arrive
59	ev_loop (loop, 0);	63	ev_run (loop, 0);
60		64
61	// unloop was called, so exit	65	// break was called, so exit
62	return 0;	66	return 0;
63	}	67	}
64		68
65	=head1 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
66		72
67	The newest version of this document is also available as an html-formatted	73	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	74	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	75	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		76
		77	While this document tries to be as complete as possible in documenting
		78	libev, its usage and the rationale behind its design, it is not a tutorial
		79	on event-based programming, nor will it introduce event-based programming
		80	with libev.
		81
		82	Familiarity with event based programming techniques in general is assumed
		83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
		93	=head1 ABOUT LIBEV
70		94
71	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	97	these event sources and provide your program with events.
74		98
…		…
84	=head2 FEATURES	108	=head2 FEATURES
85		109
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	117	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	119	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		120	limited support for fork events (C<ev_fork>).
96		121
97	It also is quite fast (see this	122	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	123	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	124	for example).
100		125
…		…
103	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	134	this argument.
110		135
111	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
112		137
113	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
119	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	146	time differences (e.g. delays) throughout libev.
121		147
122	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
123		149
124	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	151	and internal errors (bugs).
…		…
149		175
150	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
151		177
152	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
155		182
156	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
157		184
158	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
160	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
161		194
162	=item int ev_version_major ()	195	=item int ev_version_major ()
163		196
164	=item int ev_version_minor ()	197	=item int ev_version_minor ()
165		198
…		…
176	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	211	not a problem.
179		212
180	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
182		216
183	assert (("libev version mismatch",	217	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
186		220
…		…
197	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
199		233
200	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
201		235
202	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
208		243
209	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
210		245
211	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
216		251
217	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
218		253
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		255
221	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	285	}
251		286
252	...	287	...
253	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
254		289
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		291
257	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	307	}
273		308
274	...	309	...
275	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
276		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
277	=back	325	=back
278		326
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		328
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
284		332
285	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
287	not.	335	do not.
288		336
289	=over 4	337	=over 4
290		338
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		340
293	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
297		351
298	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
299	function.	353	function (or via the C<EV_DEFAULT> macro).
300		354
301	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
304		359
305	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
311		384
312	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		387
315	The following flags are supported:	388	The following flags are supported:
…		…
325		398
326	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
327	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
329	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
330	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
331	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
332		407
333	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
334		409
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	411	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		412
339	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
343	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	without a system call and thus I<very> fast, but my GNU/Linux system also has
344	C<pthread_atfork> which is even faster).	418	C<pthread_atfork> which is even faster).
345		419
346	The big advantage of this flag is that you can forget about fork (and	420	The big advantage of this flag is that you can forget about fork (and
347	forget about forgetting to tell libev about forking) when you use this	421	forget about forgetting to tell libev about forking, although you still
348	flag.	422	have to ignore C<SIGPIPE>) when you use this flag.
349		423
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	424	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	425	environment variable.
		426
		427	=item C<EVFLAG_NOINOTIFY>
		428
		429	When this flag is specified, then libev will not attempt to use the
		430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		431	testing, this flag can be useful to conserve inotify file descriptors, as
		432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		433
		434	=item C<EVFLAG_SIGNALFD>
		435
		436	When this flag is specified, then libev will attempt to use the
		437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		438	delivers signals synchronously, which makes it both faster and might make
		439	it possible to get the queued signal data. It can also simplify signal
		440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
		442
		443	Signalfd will not be used by default as this changes your signal mask, and
		444	there are a lot of shoddy libraries and programs (glib's threadpool for
		445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
352		461
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		463
355	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	490	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	491	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		492
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		494
		495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		496	kernels).
		497
386	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
387	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
388	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
389	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
390		502
391	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
395	so on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
396	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
397	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
398	hard to detect.	512	and is of course hard to detect.
399		513
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
401	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
402	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
403	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
404	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
405	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
406	events to filter out spurious ones, recreating the set when required.	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
		524	not least, it also refuses to work with some file descriptors which work
		525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
407		530
408	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
417	i.e. keep at least one watcher active per fd at all times. Stopping and	540	i.e. keep at least one watcher active per fd at all times. Stopping and
418	starting a watcher (without re-setting it) also usually doesn't cause	541	starting a watcher (without re-setting it) also usually doesn't cause
419	extra overhead. A fork can both result in spurious notifications as well	542	extra overhead. A fork can both result in spurious notifications as well
420	as in libev having to destroy and recreate the epoll object, which can	543	as in libev having to destroy and recreate the epoll object, which can
421	take considerable time and thus should be avoided.	544	take considerable time and thus should be avoided.
		545
		546	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		547	faster than epoll for maybe up to a hundred file descriptors, depending on
		548	the usage. So sad.
422		549
423	While nominally embeddable in other event loops, this feature is broken in	550	While nominally embeddable in other event loops, this feature is broken in
424	all kernel versions tested so far.	551	all kernel versions tested so far.
425		552
426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	553	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
444		571
445	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
446	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
447	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
448	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
449	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
451	cases	578	drops fds silently in similarly hard-to-detect cases.
452		579
453	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
454		581
455	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
456	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
457	almost everywhere, you should only use it when you have a lot of sockets	584	almost everywhere, you should only use it when you have a lot of sockets
458	(for which it usually works), by embedding it into another event loop	585	(for which it usually works), by embedding it into another event loop
459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	586	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
460	using it only for sockets.	587	also broken on OS X)) and, did I mention it, using it only for sockets.
461		588
462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	589	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	590	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
464	C<NOTE_EOF>.	591	C<NOTE_EOF>.
465		592
…		…
473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
474		601
475	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
476	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
477		604
478	Please note that Solaris event ports can deliver a lot of spurious
479	notifications, so you need to use non-blocking I/O or other means to avoid
480	blocking when no data (or space) is available.
481
482	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
483	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
485	might perform better.	608	might perform better.
486		609
487	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
488	notifications, this backend actually performed fully to specification
489	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
490	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
491		624
492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
493	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
494		627
495	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
496		629
497	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
499	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
500		633
501	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
502		643
503	=back	644	=back
504		645
505	If one or more of these are or'ed into the flags value, then only these	646	If one or more of the backend flags are or'ed into the flags value,
506	backends will be tried (in the reverse order as listed here). If none are	647	then only these backends will be tried (in the reverse order as listed
507	specified, all backends in C<ev_recommended_backends ()> will be tried.	648	here). If none are specified, all backends in C<ev_recommended_backends
508		649	()> will be tried.
509	Example: This is the most typical usage.
510
511	if (!ev_default_loop (0))
512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
513
514	Example: Restrict libev to the select and poll backends, and do not allow
515	environment settings to be taken into account:
516
517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
518
519	Example: Use whatever libev has to offer, but make sure that kqueue is
520	used if available (warning, breaks stuff, best use only with your own
521	private event loop and only if you know the OS supports your types of
522	fds):
523
524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
525
526	=item struct ev_loop *ev_loop_new (unsigned int flags)
527
528	Similar to C<ev_default_loop>, but always creates a new event loop that is
529	always distinct from the default loop. Unlike the default loop, it cannot
530	handle signal and child watchers, and attempts to do so will be greeted by
531	undefined behaviour (or a failed assertion if assertions are enabled).
532
533	Note that this function I<is> thread-safe, and the recommended way to use
534	libev with threads is indeed to create one loop per thread, and using the
535	default loop in the "main" or "initial" thread.
536		650
537	Example: Try to create a event loop that uses epoll and nothing else.	651	Example: Try to create a event loop that uses epoll and nothing else.
538		652
539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
540	if (!epoller)	654	if (!epoller)
541	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
542		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
543	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
544		663
545	Destroys the default loop again (frees all memory and kernel state	664	Destroys an event loop object (frees all memory and kernel state
546	etc.). None of the active event watchers will be stopped in the normal	665	etc.). None of the active event watchers will be stopped in the normal
547	sense, so e.g. C<ev_is_active> might still return true. It is your	666	sense, so e.g. C<ev_is_active> might still return true. It is your
548	responsibility to either stop all watchers cleanly yourself I<before>	667	responsibility to either stop all watchers cleanly yourself I<before>
549	calling this function, or cope with the fact afterwards (which is usually	668	calling this function, or cope with the fact afterwards (which is usually
550	the easiest thing, you can just ignore the watchers and/or C<free ()> them	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
552		671
553	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
554	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
555	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
556		675
557	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
558	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
559	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
560	C<ev_loop_new> and C<ev_loop_destroy>).	683	and C<ev_loop_destroy>.
561		684
562	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
563		686
564	Like C<ev_default_destroy>, but destroys an event loop created by an
565	earlier call to C<ev_loop_new>.
566
567	=item ev_default_fork ()
568
569	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations
570	to reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
571	name, you can call it anytime, but it makes most sense after forking, in	689	the name, you can call it anytime you are allowed to start or stop
572	the child process (or both child and parent, but that again makes little	690	watchers (except inside an C<ev_prepare> callback), but it makes most
573	sense). You I<must> call it in the child before using any of the libev	691	sense after forking, in the child process. You I<must> call it (or use
574	functions, and it will only take effect at the next C<ev_loop> iteration.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		693
		694	In addition, if you want to reuse a loop (via this function of
		695	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		696
		697	Again, you I<have> to call it on I<any> loop that you want to re-use after
		698	a fork, I<even if you do not plan to use the loop in the parent>. This is
		699	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		700	during fork.
575		701
576	On the other hand, you only need to call this function in the child	702	On the other hand, you only need to call this function in the child
577	process if and only if you want to use the event library in the child. If	703	process if and only if you want to use the event loop in the child. If
578	you just fork+exec, you don't have to call it at all.	704	you just fork+exec or create a new loop in the child, you don't have to
		705	call it at all (in fact, C<epoll> is so badly broken that it makes a
		706	difference, but libev will usually detect this case on its own and do a
		707	costly reset of the backend).
579		708
580	The function itself is quite fast and it's usually not a problem to call	709	The function itself is quite fast and it's usually not a problem to call
581	it just in case after a fork. To make this easy, the function will fit in	710	it just in case after a fork.
582	quite nicely into a call to C<pthread_atfork>:
583		711
		712	Example: Automate calling C<ev_loop_fork> on the default loop when
		713	using pthreads.
		714
		715	static void
		716	post_fork_child (void)
		717	{
		718	ev_loop_fork (EV_DEFAULT);
		719	}
		720
		721	...
584	pthread_atfork (0, 0, ev_default_fork);	722	pthread_atfork (0, 0, post_fork_child);
585
586	=item ev_loop_fork (loop)
587
588	Like C<ev_default_fork>, but acts on an event loop created by
589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
590	after fork that you want to re-use in the child, and how you do this is
591	entirely your own problem.
592		723
593	=item int ev_is_default_loop (loop)	724	=item int ev_is_default_loop (loop)
594		725
595	Returns true when the given loop is, in fact, the default loop, and false	726	Returns true when the given loop is, in fact, the default loop, and false
596	otherwise.	727	otherwise.
597		728
598	=item unsigned int ev_loop_count (loop)	729	=item unsigned int ev_iteration (loop)
599		730
600	Returns the count of loop iterations for the loop, which is identical to	731	Returns the current iteration count for the event loop, which is identical
601	the number of times libev did poll for new events. It starts at C<0> and	732	to the number of times libev did poll for new events. It starts at C<0>
602	happily wraps around with enough iterations.	733	and happily wraps around with enough iterations.
603		734
604	This value can sometimes be useful as a generation counter of sorts (it	735	This value can sometimes be useful as a generation counter of sorts (it
605	"ticks" the number of loop iterations), as it roughly corresponds with	736	"ticks" the number of loop iterations), as it roughly corresponds with
606	C<ev_prepare> and C<ev_check> calls.	737	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		738	prepare and check phases.
		739
		740	=item unsigned int ev_depth (loop)
		741
		742	Returns the number of times C<ev_run> was entered minus the number of
		743	times C<ev_run> was exited normally, in other words, the recursion depth.
		744
		745	Outside C<ev_run>, this number is zero. In a callback, this number is
		746	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		747	in which case it is higher.
		748
		749	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		750	throwing an exception etc.), doesn't count as "exit" - consider this
		751	as a hint to avoid such ungentleman-like behaviour unless it's really
		752	convenient, in which case it is fully supported.
607		753
608	=item unsigned int ev_backend (loop)	754	=item unsigned int ev_backend (loop)
609		755
610	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	756	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
611	use.	757	use.
…		…
620		766
621	=item ev_now_update (loop)	767	=item ev_now_update (loop)
622		768
623	Establishes the current time by querying the kernel, updating the time	769	Establishes the current time by querying the kernel, updating the time
624	returned by C<ev_now ()> in the progress. This is a costly operation and	770	returned by C<ev_now ()> in the progress. This is a costly operation and
625	is usually done automatically within C<ev_loop ()>.	771	is usually done automatically within C<ev_run ()>.
626		772
627	This function is rarely useful, but when some event callback runs for a	773	This function is rarely useful, but when some event callback runs for a
628	very long time without entering the event loop, updating libev's idea of	774	very long time without entering the event loop, updating libev's idea of
629	the current time is a good idea.	775	the current time is a good idea.
630		776
631	See also "The special problem of time updates" in the C<ev_timer> section.	777	See also L</The special problem of time updates> in the C<ev_timer> section.
632		778
		779	=item ev_suspend (loop)
		780
		781	=item ev_resume (loop)
		782
		783	These two functions suspend and resume an event loop, for use when the
		784	loop is not used for a while and timeouts should not be processed.
		785
		786	A typical use case would be an interactive program such as a game: When
		787	the user presses C<^Z> to suspend the game and resumes it an hour later it
		788	would be best to handle timeouts as if no time had actually passed while
		789	the program was suspended. This can be achieved by calling C<ev_suspend>
		790	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		791	C<ev_resume> directly afterwards to resume timer processing.
		792
		793	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		794	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		795	will be rescheduled (that is, they will lose any events that would have
		796	occurred while suspended).
		797
		798	After calling C<ev_suspend> you B<must not> call I<any> function on the
		799	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		800	without a previous call to C<ev_suspend>.
		801
		802	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		803	event loop time (see C<ev_now_update>).
		804
633	=item ev_loop (loop, int flags)	805	=item bool ev_run (loop, int flags)
634		806
635	Finally, this is it, the event handler. This function usually is called	807	Finally, this is it, the event handler. This function usually is called
636	after you initialised all your watchers and you want to start handling	808	after you have initialised all your watchers and you want to start
637	events.	809	handling events. It will ask the operating system for any new events, call
		810	the watcher callbacks, and then repeat the whole process indefinitely: This
		811	is why event loops are called I<loops>.
638		812
639	If the flags argument is specified as C<0>, it will not return until	813	If the flags argument is specified as C<0>, it will keep handling events
640	either no event watchers are active anymore or C<ev_unloop> was called.	814	until either no event watchers are active anymore or C<ev_break> was
		815	called.
641		816
		817	The return value is false if there are no more active watchers (which
		818	usually means "all jobs done" or "deadlock"), and true in all other cases
		819	(which usually means " you should call C<ev_run> again").
		820
642	Please note that an explicit C<ev_unloop> is usually better than	821	Please note that an explicit C<ev_break> is usually better than
643	relying on all watchers to be stopped when deciding when a program has	822	relying on all watchers to be stopped when deciding when a program has
644	finished (especially in interactive programs), but having a program	823	finished (especially in interactive programs), but having a program
645	that automatically loops as long as it has to and no longer by virtue	824	that automatically loops as long as it has to and no longer by virtue
646	of relying on its watchers stopping correctly, that is truly a thing of	825	of relying on its watchers stopping correctly, that is truly a thing of
647	beauty.	826	beauty.
648		827
		828	This function is I<mostly> exception-safe - you can break out of a
		829	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		830	exception and so on. This does not decrement the C<ev_depth> value, nor
		831	will it clear any outstanding C<EVBREAK_ONE> breaks.
		832
649	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	833	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
650	those events and any already outstanding ones, but will not block your	834	those events and any already outstanding ones, but will not wait and
651	process in case there are no events and will return after one iteration of	835	block your process in case there are no events and will return after one
652	the loop.	836	iteration of the loop. This is sometimes useful to poll and handle new
		837	events while doing lengthy calculations, to keep the program responsive.
653		838
654	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	839	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
655	necessary) and will handle those and any already outstanding ones. It	840	necessary) and will handle those and any already outstanding ones. It
656	will block your process until at least one new event arrives (which could	841	will block your process until at least one new event arrives (which could
657	be an event internal to libev itself, so there is no guarantee that a	842	be an event internal to libev itself, so there is no guarantee that a
658	user-registered callback will be called), and will return after one	843	user-registered callback will be called), and will return after one
659	iteration of the loop.	844	iteration of the loop.
660		845
661	This is useful if you are waiting for some external event in conjunction	846	This is useful if you are waiting for some external event in conjunction
662	with something not expressible using other libev watchers (i.e. "roll your	847	with something not expressible using other libev watchers (i.e. "roll your
663	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	848	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
664	usually a better approach for this kind of thing.	849	usually a better approach for this kind of thing.
665		850
666	Here are the gory details of what C<ev_loop> does:	851	Here are the gory details of what C<ev_run> does (this is for your
		852	understanding, not a guarantee that things will work exactly like this in
		853	future versions):
667		854
		855	- Increment loop depth.
		856	- Reset the ev_break status.
668	- Before the first iteration, call any pending watchers.	857	- Before the first iteration, call any pending watchers.
		858	LOOP:
669	* If EVFLAG_FORKCHECK was used, check for a fork.	859	- If EVFLAG_FORKCHECK was used, check for a fork.
670	- If a fork was detected (by any means), queue and call all fork watchers.	860	- If a fork was detected (by any means), queue and call all fork watchers.
671	- Queue and call all prepare watchers.	861	- Queue and call all prepare watchers.
		862	- If ev_break was called, goto FINISH.
672	- If we have been forked, detach and recreate the kernel state	863	- If we have been forked, detach and recreate the kernel state
673	as to not disturb the other process.	864	as to not disturb the other process.
674	- Update the kernel state with all outstanding changes.	865	- Update the kernel state with all outstanding changes.
675	- Update the "event loop time" (ev_now ()).	866	- Update the "event loop time" (ev_now ()).
676	- Calculate for how long to sleep or block, if at all	867	- Calculate for how long to sleep or block, if at all
677	(active idle watchers, EVLOOP_NONBLOCK or not having	868	(active idle watchers, EVRUN_NOWAIT or not having
678	any active watchers at all will result in not sleeping).	869	any active watchers at all will result in not sleeping).
679	- Sleep if the I/O and timer collect interval say so.	870	- Sleep if the I/O and timer collect interval say so.
		871	- Increment loop iteration counter.
680	- Block the process, waiting for any events.	872	- Block the process, waiting for any events.
681	- Queue all outstanding I/O (fd) events.	873	- Queue all outstanding I/O (fd) events.
682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	874	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
683	- Queue all expired timers.	875	- Queue all expired timers.
684	- Queue all expired periodics.	876	- Queue all expired periodics.
685	- Unless any events are pending now, queue all idle watchers.	877	- Queue all idle watchers with priority higher than that of pending events.
686	- Queue all check watchers.	878	- Queue all check watchers.
687	- Call all queued watchers in reverse order (i.e. check watchers first).	879	- Call all queued watchers in reverse order (i.e. check watchers first).
688	Signals and child watchers are implemented as I/O watchers, and will	880	Signals and child watchers are implemented as I/O watchers, and will
689	be handled here by queueing them when their watcher gets executed.	881	be handled here by queueing them when their watcher gets executed.
690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	882	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
691	were used, or there are no active watchers, return, otherwise	883	were used, or there are no active watchers, goto FINISH, otherwise
692	continue with step *.	884	continue with step LOOP.
		885	FINISH:
		886	- Reset the ev_break status iff it was EVBREAK_ONE.
		887	- Decrement the loop depth.
		888	- Return.
693		889
694	Example: Queue some jobs and then loop until no events are outstanding	890	Example: Queue some jobs and then loop until no events are outstanding
695	anymore.	891	anymore.
696		892
697	... queue jobs here, make sure they register event watchers as long	893	... queue jobs here, make sure they register event watchers as long
698	... as they still have work to do (even an idle watcher will do..)	894	... as they still have work to do (even an idle watcher will do..)
699	ev_loop (my_loop, 0);	895	ev_run (my_loop, 0);
700	... jobs done or somebody called unloop. yeah!	896	... jobs done or somebody called break. yeah!
701		897
702	=item ev_unloop (loop, how)	898	=item ev_break (loop, how)
703		899
704	Can be used to make a call to C<ev_loop> return early (but only after it	900	Can be used to make a call to C<ev_run> return early (but only after it
705	has processed all outstanding events). The C<how> argument must be either	901	has processed all outstanding events). The C<how> argument must be either
706	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	902	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	903	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
708		904
709	This "unloop state" will be cleared when entering C<ev_loop> again.	905	This "break state" will be cleared on the next call to C<ev_run>.
710		906
711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	907	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		908	which case it will have no effect.
712		909
713	=item ev_ref (loop)	910	=item ev_ref (loop)
714		911
715	=item ev_unref (loop)	912	=item ev_unref (loop)
716		913
717	Ref/unref can be used to add or remove a reference count on the event	914	Ref/unref can be used to add or remove a reference count on the event
718	loop: Every watcher keeps one reference, and as long as the reference	915	loop: Every watcher keeps one reference, and as long as the reference
719	count is nonzero, C<ev_loop> will not return on its own.	916	count is nonzero, C<ev_run> will not return on its own.
720		917
721	If you have a watcher you never unregister that should not keep C<ev_loop>	918	This is useful when you have a watcher that you never intend to
722	from returning, call ev_unref() after starting, and ev_ref() before	919	unregister, but that nevertheless should not keep C<ev_run> from
		920	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
723	stopping it.	921	before stopping it.
724		922
725	As an example, libev itself uses this for its internal signal pipe: It is	923	As an example, libev itself uses this for its internal signal pipe: It
726	not visible to the libev user and should not keep C<ev_loop> from exiting	924	is not visible to the libev user and should not keep C<ev_run> from
727	if no event watchers registered by it are active. It is also an excellent	925	exiting if no event watchers registered by it are active. It is also an
728	way to do this for generic recurring timers or from within third-party	926	excellent way to do this for generic recurring timers or from within
729	libraries. Just remember to I<unref after start> and I<ref before stop>	927	third-party libraries. Just remember to I<unref after start> and I<ref
730	(but only if the watcher wasn't active before, or was active before,	928	before stop> (but only if the watcher wasn't active before, or was active
731	respectively).	929	before, respectively. Note also that libev might stop watchers itself
		930	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		931	in the callback).
732		932
733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	933	Example: Create a signal watcher, but keep it from keeping C<ev_run>
734	running when nothing else is active.	934	running when nothing else is active.
735		935
736	ev_signal exitsig;	936	ev_signal exitsig;
737	ev_signal_init (&exitsig, sig_cb, SIGINT);	937	ev_signal_init (&exitsig, sig_cb, SIGINT);
738	ev_signal_start (loop, &exitsig);	938	ev_signal_start (loop, &exitsig);
739	evf_unref (loop);	939	ev_unref (loop);
740		940
741	Example: For some weird reason, unregister the above signal handler again.	941	Example: For some weird reason, unregister the above signal handler again.
742		942
743	ev_ref (loop);	943	ev_ref (loop);
744	ev_signal_stop (loop, &exitsig);	944	ev_signal_stop (loop, &exitsig);
…		…
764	overhead for the actual polling but can deliver many events at once.	964	overhead for the actual polling but can deliver many events at once.
765		965
766	By setting a higher I<io collect interval> you allow libev to spend more	966	By setting a higher I<io collect interval> you allow libev to spend more
767	time collecting I/O events, so you can handle more events per iteration,	967	time collecting I/O events, so you can handle more events per iteration,
768	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	968	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
769	C<ev_timer>) will be not affected. Setting this to a non-null value will	969	C<ev_timer>) will not be affected. Setting this to a non-null value will
770	introduce an additional C<ev_sleep ()> call into most loop iterations.	970	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		971	sleep time ensures that libev will not poll for I/O events more often then
		972	once per this interval, on average (as long as the host time resolution is
		973	good enough).
771		974
772	Likewise, by setting a higher I<timeout collect interval> you allow libev	975	Likewise, by setting a higher I<timeout collect interval> you allow libev
773	to spend more time collecting timeouts, at the expense of increased	976	to spend more time collecting timeouts, at the expense of increased
774	latency/jitter/inexactness (the watcher callback will be called	977	latency/jitter/inexactness (the watcher callback will be called
775	later). C<ev_io> watchers will not be affected. Setting this to a non-null	978	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
777		980
778	Many (busy) programs can usually benefit by setting the I/O collect	981	Many (busy) programs can usually benefit by setting the I/O collect
779	interval to a value near C<0.1> or so, which is often enough for	982	interval to a value near C<0.1> or so, which is often enough for
780	interactive servers (of course not for games), likewise for timeouts. It	983	interactive servers (of course not for games), likewise for timeouts. It
781	usually doesn't make much sense to set it to a lower value than C<0.01>,	984	usually doesn't make much sense to set it to a lower value than C<0.01>,
782	as this approaches the timing granularity of most systems.	985	as this approaches the timing granularity of most systems. Note that if
		986	you do transactions with the outside world and you can't increase the
		987	parallelity, then this setting will limit your transaction rate (if you
		988	need to poll once per transaction and the I/O collect interval is 0.01,
		989	then you can't do more than 100 transactions per second).
783		990
784	Setting the I<timeout collect interval> can improve the opportunity for	991	Setting the I<timeout collect interval> can improve the opportunity for
785	saving power, as the program will "bundle" timer callback invocations that	992	saving power, as the program will "bundle" timer callback invocations that
786	are "near" in time together, by delaying some, thus reducing the number of	993	are "near" in time together, by delaying some, thus reducing the number of
787	times the process sleeps and wakes up again. Another useful technique to	994	times the process sleeps and wakes up again. Another useful technique to
788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	995	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
789	they fire on, say, one-second boundaries only.	996	they fire on, say, one-second boundaries only.
790		997
		998	Example: we only need 0.1s timeout granularity, and we wish not to poll
		999	more often than 100 times per second:
		1000
		1001	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1002	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1003
		1004	=item ev_invoke_pending (loop)
		1005
		1006	This call will simply invoke all pending watchers while resetting their
		1007	pending state. Normally, C<ev_run> does this automatically when required,
		1008	but when overriding the invoke callback this call comes handy. This
		1009	function can be invoked from a watcher - this can be useful for example
		1010	when you want to do some lengthy calculation and want to pass further
		1011	event handling to another thread (you still have to make sure only one
		1012	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1013
		1014	=item int ev_pending_count (loop)
		1015
		1016	Returns the number of pending watchers - zero indicates that no watchers
		1017	are pending.
		1018
		1019	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1020
		1021	This overrides the invoke pending functionality of the loop: Instead of
		1022	invoking all pending watchers when there are any, C<ev_run> will call
		1023	this callback instead. This is useful, for example, when you want to
		1024	invoke the actual watchers inside another context (another thread etc.).
		1025
		1026	If you want to reset the callback, use C<ev_invoke_pending> as new
		1027	callback.
		1028
		1029	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1030
		1031	Sometimes you want to share the same loop between multiple threads. This
		1032	can be done relatively simply by putting mutex_lock/unlock calls around
		1033	each call to a libev function.
		1034
		1035	However, C<ev_run> can run an indefinite time, so it is not feasible
		1036	to wait for it to return. One way around this is to wake up the event
		1037	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1038	I<release> and I<acquire> callbacks on the loop.
		1039
		1040	When set, then C<release> will be called just before the thread is
		1041	suspended waiting for new events, and C<acquire> is called just
		1042	afterwards.
		1043
		1044	Ideally, C<release> will just call your mutex_unlock function, and
		1045	C<acquire> will just call the mutex_lock function again.
		1046
		1047	While event loop modifications are allowed between invocations of
		1048	C<release> and C<acquire> (that's their only purpose after all), no
		1049	modifications done will affect the event loop, i.e. adding watchers will
		1050	have no effect on the set of file descriptors being watched, or the time
		1051	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1052	to take note of any changes you made.
		1053
		1054	In theory, threads executing C<ev_run> will be async-cancel safe between
		1055	invocations of C<release> and C<acquire>.
		1056
		1057	See also the locking example in the C<THREADS> section later in this
		1058	document.
		1059
		1060	=item ev_set_userdata (loop, void *data)
		1061
		1062	=item void *ev_userdata (loop)
		1063
		1064	Set and retrieve a single C<void *> associated with a loop. When
		1065	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1066	C<0>.
		1067
		1068	These two functions can be used to associate arbitrary data with a loop,
		1069	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1070	C<acquire> callbacks described above, but of course can be (ab-)used for
		1071	any other purpose as well.
		1072
791	=item ev_loop_verify (loop)	1073	=item ev_verify (loop)
792		1074
793	This function only does something when C<EV_VERIFY> support has been	1075	This function only does something when C<EV_VERIFY> support has been
794	compiled in, which is the default for non-minimal builds. It tries to go	1076	compiled in, which is the default for non-minimal builds. It tries to go
795	through all internal structures and checks them for validity. If anything	1077	through all internal structures and checks them for validity. If anything
796	is found to be inconsistent, it will print an error message to standard	1078	is found to be inconsistent, it will print an error message to standard
…		…
807		1089
808	In the following description, uppercase C<TYPE> in names stands for the	1090	In the following description, uppercase C<TYPE> in names stands for the
809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1091	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
810	watchers and C<ev_io_start> for I/O watchers.	1092	watchers and C<ev_io_start> for I/O watchers.
811		1093
812	A watcher is a structure that you create and register to record your	1094	A watcher is an opaque structure that you allocate and register to record
813	interest in some event. For instance, if you want to wait for STDIN to	1095	your interest in some event. To make a concrete example, imagine you want
814	become readable, you would create an C<ev_io> watcher for that:	1096	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1097	for that:
815		1098
816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
817	{	1100	{
818	ev_io_stop (w);	1101	ev_io_stop (w);
819	ev_unloop (loop, EVUNLOOP_ALL);	1102	ev_break (loop, EVBREAK_ALL);
820	}	1103	}
821		1104
822	struct ev_loop *loop = ev_default_loop (0);	1105	struct ev_loop *loop = ev_default_loop (0);
823		1106
824	ev_io stdin_watcher;	1107	ev_io stdin_watcher;
825		1108
826	ev_init (&stdin_watcher, my_cb);	1109	ev_init (&stdin_watcher, my_cb);
827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1110	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
828	ev_io_start (loop, &stdin_watcher);	1111	ev_io_start (loop, &stdin_watcher);
829		1112
830	ev_loop (loop, 0);	1113	ev_run (loop, 0);
831		1114
832	As you can see, you are responsible for allocating the memory for your	1115	As you can see, you are responsible for allocating the memory for your
833	watcher structures (and it is I<usually> a bad idea to do this on the	1116	watcher structures (and it is I<usually> a bad idea to do this on the
834	stack).	1117	stack).
835		1118
836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1119	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1120	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
838		1121
839	Each watcher structure must be initialised by a call to C<ev_init	1122	Each watcher structure must be initialised by a call to C<ev_init (watcher
840	(watcher *, callback)>, which expects a callback to be provided. This	1123	*, callback)>, which expects a callback to be provided. This callback is
841	callback gets invoked each time the event occurs (or, in the case of I/O	1124	invoked each time the event occurs (or, in the case of I/O watchers, each
842	watchers, each time the event loop detects that the file descriptor given	1125	time the event loop detects that the file descriptor given is readable
843	is readable and/or writable).	1126	and/or writable).
844		1127
845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1128	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
846	macro to configure it, with arguments specific to the watcher type. There	1129	macro to configure it, with arguments specific to the watcher type. There
847	is also a macro to combine initialisation and setting in one call: C<<	1130	is also a macro to combine initialisation and setting in one call: C<<
848	ev_TYPE_init (watcher *, callback, ...) >>.	1131	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
871	=item C<EV_WRITE>	1154	=item C<EV_WRITE>
872		1155
873	The file descriptor in the C<ev_io> watcher has become readable and/or	1156	The file descriptor in the C<ev_io> watcher has become readable and/or
874	writable.	1157	writable.
875		1158
876	=item C<EV_TIMEOUT>	1159	=item C<EV_TIMER>
877		1160
878	The C<ev_timer> watcher has timed out.	1161	The C<ev_timer> watcher has timed out.
879		1162
880	=item C<EV_PERIODIC>	1163	=item C<EV_PERIODIC>
881		1164
…		…
899		1182
900	=item C<EV_PREPARE>	1183	=item C<EV_PREPARE>
901		1184
902	=item C<EV_CHECK>	1185	=item C<EV_CHECK>
903		1186
904	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1187	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
905	to gather new events, and all C<ev_check> watchers are invoked just after	1188	gather new events, and all C<ev_check> watchers are queued (not invoked)
906	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1189	just after C<ev_run> has gathered them, but before it queues any callbacks
		1190	for any received events. That means C<ev_prepare> watchers are the last
		1191	watchers invoked before the event loop sleeps or polls for new events, and
		1192	C<ev_check> watchers will be invoked before any other watchers of the same
		1193	or lower priority within an event loop iteration.
		1194
907	received events. Callbacks of both watcher types can start and stop as	1195	Callbacks of both watcher types can start and stop as many watchers as
908	many watchers as they want, and all of them will be taken into account	1196	they want, and all of them will be taken into account (for example, a
909	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1197	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
910	C<ev_loop> from blocking).	1198	blocking).
911		1199
912	=item C<EV_EMBED>	1200	=item C<EV_EMBED>
913		1201
914	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1202	The embedded event loop specified in the C<ev_embed> watcher needs attention.
915		1203
916	=item C<EV_FORK>	1204	=item C<EV_FORK>
917		1205
918	The event loop has been resumed in the child process after fork (see	1206	The event loop has been resumed in the child process after fork (see
919	C<ev_fork>).	1207	C<ev_fork>).
920		1208
		1209	=item C<EV_CLEANUP>
		1210
		1211	The event loop is about to be destroyed (see C<ev_cleanup>).
		1212
921	=item C<EV_ASYNC>	1213	=item C<EV_ASYNC>
922		1214
923	The given async watcher has been asynchronously notified (see C<ev_async>).	1215	The given async watcher has been asynchronously notified (see C<ev_async>).
		1216
		1217	=item C<EV_CUSTOM>
		1218
		1219	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1220	by libev users to signal watchers (e.g. via C<ev_feed_event>).
924		1221
925	=item C<EV_ERROR>	1222	=item C<EV_ERROR>
926		1223
927	An unspecified error has occurred, the watcher has been stopped. This might	1224	An unspecified error has occurred, the watcher has been stopped. This might
928	happen because the watcher could not be properly started because libev	1225	happen because the watcher could not be properly started because libev
…		…
966		1263
967	ev_io w;	1264	ev_io w;
968	ev_init (&w, my_cb);	1265	ev_init (&w, my_cb);
969	ev_io_set (&w, STDIN_FILENO, EV_READ);	1266	ev_io_set (&w, STDIN_FILENO, EV_READ);
970		1267
971	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1268	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
972		1269
973	This macro initialises the type-specific parts of a watcher. You need to	1270	This macro initialises the type-specific parts of a watcher. You need to
974	call C<ev_init> at least once before you call this macro, but you can	1271	call C<ev_init> at least once before you call this macro, but you can
975	call C<ev_TYPE_set> any number of times. You must not, however, call this	1272	call C<ev_TYPE_set> any number of times. You must not, however, call this
976	macro on a watcher that is active (it can be pending, however, which is a	1273	macro on a watcher that is active (it can be pending, however, which is a
…		…
989		1286
990	Example: Initialise and set an C<ev_io> watcher in one step.	1287	Example: Initialise and set an C<ev_io> watcher in one step.
991		1288
992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1289	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
993		1290
994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1291	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
995		1292
996	Starts (activates) the given watcher. Only active watchers will receive	1293	Starts (activates) the given watcher. Only active watchers will receive
997	events. If the watcher is already active nothing will happen.	1294	events. If the watcher is already active nothing will happen.
998		1295
999	Example: Start the C<ev_io> watcher that is being abused as example in this	1296	Example: Start the C<ev_io> watcher that is being abused as example in this
1000	whole section.	1297	whole section.
1001		1298
1002	ev_io_start (EV_DEFAULT_UC, &w);	1299	ev_io_start (EV_DEFAULT_UC, &w);
1003		1300
1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1301	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1005		1302
1006	Stops the given watcher if active, and clears the pending status (whether	1303	Stops the given watcher if active, and clears the pending status (whether
1007	the watcher was active or not).	1304	the watcher was active or not).
1008		1305
1009	It is possible that stopped watchers are pending - for example,	1306	It is possible that stopped watchers are pending - for example,
…		…
1029		1326
1030	=item callback ev_cb (ev_TYPE *watcher)	1327	=item callback ev_cb (ev_TYPE *watcher)
1031		1328
1032	Returns the callback currently set on the watcher.	1329	Returns the callback currently set on the watcher.
1033		1330
1034	=item ev_cb_set (ev_TYPE *watcher, callback)	1331	=item ev_set_cb (ev_TYPE *watcher, callback)
1035		1332
1036	Change the callback. You can change the callback at virtually any time	1333	Change the callback. You can change the callback at virtually any time
1037	(modulo threads).	1334	(modulo threads).
1038		1335
1039	=item ev_set_priority (ev_TYPE *watcher, priority)	1336	=item ev_set_priority (ev_TYPE *watcher, int priority)
1040		1337
1041	=item int ev_priority (ev_TYPE *watcher)	1338	=item int ev_priority (ev_TYPE *watcher)
1042		1339
1043	Set and query the priority of the watcher. The priority is a small	1340	Set and query the priority of the watcher. The priority is a small
1044	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1341	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1045	(default: C<-2>). Pending watchers with higher priority will be invoked	1342	(default: C<-2>). Pending watchers with higher priority will be invoked
1046	before watchers with lower priority, but priority will not keep watchers	1343	before watchers with lower priority, but priority will not keep watchers
1047	from being executed (except for C<ev_idle> watchers).	1344	from being executed (except for C<ev_idle> watchers).
1048		1345
1049	This means that priorities are I<only> used for ordering callback
1050	invocation after new events have been received. This is useful, for
1051	example, to reduce latency after idling, or more often, to bind two
1052	watchers on the same event and make sure one is called first.
1053
1054	If you need to suppress invocation when higher priority events are pending	1346	If you need to suppress invocation when higher priority events are pending
1055	you need to look at C<ev_idle> watchers, which provide this functionality.	1347	you need to look at C<ev_idle> watchers, which provide this functionality.
1056		1348
1057	You I<must not> change the priority of a watcher as long as it is active or	1349	You I<must not> change the priority of a watcher as long as it is active or
1058	pending.	1350	pending.
1059
1060	The default priority used by watchers when no priority has been set is
1061	always C<0>, which is supposed to not be too high and not be too low :).
1062		1351
1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1352	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1064	fine, as long as you do not mind that the priority value you query might	1353	fine, as long as you do not mind that the priority value you query might
1065	or might not have been clamped to the valid range.	1354	or might not have been clamped to the valid range.
		1355
		1356	The default priority used by watchers when no priority has been set is
		1357	always C<0>, which is supposed to not be too high and not be too low :).
		1358
		1359	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1360	priorities.
1066		1361
1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1362	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1068		1363
1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1364	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1070	C<loop> nor C<revents> need to be valid as long as the watcher callback	1365	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1078	watcher isn't pending it does nothing and returns C<0>.	1373	watcher isn't pending it does nothing and returns C<0>.
1079		1374
1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1375	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1081	callback to be invoked, which can be accomplished with this function.	1376	callback to be invoked, which can be accomplished with this function.
1082		1377
		1378	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1379
		1380	Feeds the given event set into the event loop, as if the specified event
		1381	had happened for the specified watcher (which must be a pointer to an
		1382	initialised but not necessarily started event watcher). Obviously you must
		1383	not free the watcher as long as it has pending events.
		1384
		1385	Stopping the watcher, letting libev invoke it, or calling
		1386	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1387	not started in the first place.
		1388
		1389	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1390	functions that do not need a watcher.
		1391
1083	=back	1392	=back
1084		1393
		1394	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1395	OWN COMPOSITE WATCHERS> idioms.
1085		1396
1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1397	=head2 WATCHER STATES
1087		1398
1088	Each watcher has, by default, a member C<void *data> that you can change	1399	There are various watcher states mentioned throughout this manual -
1089	and read at any time: libev will completely ignore it. This can be used	1400	active, pending and so on. In this section these states and the rules to
1090	to associate arbitrary data with your watcher. If you need more data and	1401	transition between them will be described in more detail - and while these
1091	don't want to allocate memory and store a pointer to it in that data	1402	rules might look complicated, they usually do "the right thing".
1092	member, you can also "subclass" the watcher type and provide your own
1093	data:
1094		1403
1095	struct my_io	1404	=over 4
		1405
		1406	=item initialised
		1407
		1408	Before a watcher can be registered with the event loop it has to be
		1409	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1410	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1411
		1412	In this state it is simply some block of memory that is suitable for
		1413	use in an event loop. It can be moved around, freed, reused etc. at
		1414	will - as long as you either keep the memory contents intact, or call
		1415	C<ev_TYPE_init> again.
		1416
		1417	=item started/running/active
		1418
		1419	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1420	property of the event loop, and is actively waiting for events. While in
		1421	this state it cannot be accessed (except in a few documented ways), moved,
		1422	freed or anything else - the only legal thing is to keep a pointer to it,
		1423	and call libev functions on it that are documented to work on active watchers.
		1424
		1425	=item pending
		1426
		1427	If a watcher is active and libev determines that an event it is interested
		1428	in has occurred (such as a timer expiring), it will become pending. It will
		1429	stay in this pending state until either it is stopped or its callback is
		1430	about to be invoked, so it is not normally pending inside the watcher
		1431	callback.
		1432
		1433	The watcher might or might not be active while it is pending (for example,
		1434	an expired non-repeating timer can be pending but no longer active). If it
		1435	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1436	but it is still property of the event loop at this time, so cannot be
		1437	moved, freed or reused. And if it is active the rules described in the
		1438	previous item still apply.
		1439
		1440	It is also possible to feed an event on a watcher that is not active (e.g.
		1441	via C<ev_feed_event>), in which case it becomes pending without being
		1442	active.
		1443
		1444	=item stopped
		1445
		1446	A watcher can be stopped implicitly by libev (in which case it might still
		1447	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1448	latter will clear any pending state the watcher might be in, regardless
		1449	of whether it was active or not, so stopping a watcher explicitly before
		1450	freeing it is often a good idea.
		1451
		1452	While stopped (and not pending) the watcher is essentially in the
		1453	initialised state, that is, it can be reused, moved, modified in any way
		1454	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1455	it again).
		1456
		1457	=back
		1458
		1459	=head2 WATCHER PRIORITY MODELS
		1460
		1461	Many event loops support I<watcher priorities>, which are usually small
		1462	integers that influence the ordering of event callback invocation
		1463	between watchers in some way, all else being equal.
		1464
		1465	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1466	description for the more technical details such as the actual priority
		1467	range.
		1468
		1469	There are two common ways how these these priorities are being interpreted
		1470	by event loops:
		1471
		1472	In the more common lock-out model, higher priorities "lock out" invocation
		1473	of lower priority watchers, which means as long as higher priority
		1474	watchers receive events, lower priority watchers are not being invoked.
		1475
		1476	The less common only-for-ordering model uses priorities solely to order
		1477	callback invocation within a single event loop iteration: Higher priority
		1478	watchers are invoked before lower priority ones, but they all get invoked
		1479	before polling for new events.
		1480
		1481	Libev uses the second (only-for-ordering) model for all its watchers
		1482	except for idle watchers (which use the lock-out model).
		1483
		1484	The rationale behind this is that implementing the lock-out model for
		1485	watchers is not well supported by most kernel interfaces, and most event
		1486	libraries will just poll for the same events again and again as long as
		1487	their callbacks have not been executed, which is very inefficient in the
		1488	common case of one high-priority watcher locking out a mass of lower
		1489	priority ones.
		1490
		1491	Static (ordering) priorities are most useful when you have two or more
		1492	watchers handling the same resource: a typical usage example is having an
		1493	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1494	timeouts. Under load, data might be received while the program handles
		1495	other jobs, but since timers normally get invoked first, the timeout
		1496	handler will be executed before checking for data. In that case, giving
		1497	the timer a lower priority than the I/O watcher ensures that I/O will be
		1498	handled first even under adverse conditions (which is usually, but not
		1499	always, what you want).
		1500
		1501	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1502	will only be executed when no same or higher priority watchers have
		1503	received events, they can be used to implement the "lock-out" model when
		1504	required.
		1505
		1506	For example, to emulate how many other event libraries handle priorities,
		1507	you can associate an C<ev_idle> watcher to each such watcher, and in
		1508	the normal watcher callback, you just start the idle watcher. The real
		1509	processing is done in the idle watcher callback. This causes libev to
		1510	continuously poll and process kernel event data for the watcher, but when
		1511	the lock-out case is known to be rare (which in turn is rare :), this is
		1512	workable.
		1513
		1514	Usually, however, the lock-out model implemented that way will perform
		1515	miserably under the type of load it was designed to handle. In that case,
		1516	it might be preferable to stop the real watcher before starting the
		1517	idle watcher, so the kernel will not have to process the event in case
		1518	the actual processing will be delayed for considerable time.
		1519
		1520	Here is an example of an I/O watcher that should run at a strictly lower
		1521	priority than the default, and which should only process data when no
		1522	other events are pending:
		1523
		1524	ev_idle idle; // actual processing watcher
		1525	ev_io io; // actual event watcher
		1526
		1527	static void
		1528	io_cb (EV_P_ ev_io *w, int revents)
1096	{	1529	{
1097	ev_io io;	1530	// stop the I/O watcher, we received the event, but
1098	int otherfd;	1531	// are not yet ready to handle it.
1099	void *somedata;	1532	ev_io_stop (EV_A_ w);
1100	struct whatever *mostinteresting;	1533
		1534	// start the idle watcher to handle the actual event.
		1535	// it will not be executed as long as other watchers
		1536	// with the default priority are receiving events.
		1537	ev_idle_start (EV_A_ &idle);
1101	};	1538	}
1102		1539
1103	...	1540	static void
1104	struct my_io w;	1541	idle_cb (EV_P_ ev_idle *w, int revents)
1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1106
1107	And since your callback will be called with a pointer to the watcher, you
1108	can cast it back to your own type:
1109
1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1111	{	1542	{
1112	struct my_io *w = (struct my_io *)w_;	1543	// actual processing
1113	...	1544	read (STDIN_FILENO, ...);
		1545
		1546	// have to start the I/O watcher again, as
		1547	// we have handled the event
		1548	ev_io_start (EV_P_ &io);
1114	}	1549	}
1115		1550
1116	More interesting and less C-conformant ways of casting your callback type	1551	// initialisation
1117	instead have been omitted.	1552	ev_idle_init (&idle, idle_cb);
		1553	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1554	ev_io_start (EV_DEFAULT_ &io);
1118		1555
1119	Another common scenario is to use some data structure with multiple	1556	In the "real" world, it might also be beneficial to start a timer, so that
1120	embedded watchers:	1557	low-priority connections can not be locked out forever under load. This
1121		1558	enables your program to keep a lower latency for important connections
1122	struct my_biggy	1559	during short periods of high load, while not completely locking out less
1123	{	1560	important ones.
1124	int some_data;
1125	ev_timer t1;
1126	ev_timer t2;
1127	}
1128
1129	In this case getting the pointer to C<my_biggy> is a bit more
1130	complicated: Either you store the address of your C<my_biggy> struct
1131	in the C<data> member of the watcher (for woozies), or you need to use
1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
1133	programmers):
1134
1135	#include <stddef.h>
1136
1137	static void
1138	t1_cb (EV_P_ ev_timer *w, int revents)
1139	{
1140	struct my_biggy big = (struct my_biggy *
1141	(((char *)w) - offsetof (struct my_biggy, t1));
1142	}
1143
1144	static void
1145	t2_cb (EV_P_ ev_timer *w, int revents)
1146	{
1147	struct my_biggy big = (struct my_biggy *
1148	(((char *)w) - offsetof (struct my_biggy, t2));
1149	}
1150		1561
1151		1562
1152	=head1 WATCHER TYPES	1563	=head1 WATCHER TYPES
1153		1564
1154	This section describes each watcher in detail, but will not repeat	1565	This section describes each watcher in detail, but will not repeat
…		…
1178	In general you can register as many read and/or write event watchers per	1589	In general you can register as many read and/or write event watchers per
1179	fd as you want (as long as you don't confuse yourself). Setting all file	1590	fd as you want (as long as you don't confuse yourself). Setting all file
1180	descriptors to non-blocking mode is also usually a good idea (but not	1591	descriptors to non-blocking mode is also usually a good idea (but not
1181	required if you know what you are doing).	1592	required if you know what you are doing).
1182		1593
1183	If you cannot use non-blocking mode, then force the use of a
1184	known-to-be-good backend (at the time of this writing, this includes only
1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1186
1187	Another thing you have to watch out for is that it is quite easy to	1594	Another thing you have to watch out for is that it is quite easy to
1188	receive "spurious" readiness notifications, that is your callback might	1595	receive "spurious" readiness notifications, that is, your callback might
1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1596	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1190	because there is no data. Not only are some backends known to create a	1597	because there is no data. It is very easy to get into this situation even
1191	lot of those (for example Solaris ports), it is very easy to get into	1598	with a relatively standard program structure. Thus it is best to always
1192	this situation even with a relatively standard program structure. Thus	1599	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1600	preferable to a program hanging until some data arrives.
1195		1601
1196	If you cannot run the fd in non-blocking mode (for example you should	1602	If you cannot run the fd in non-blocking mode (for example you should
1197	not play around with an Xlib connection), then you have to separately	1603	not play around with an Xlib connection), then you have to separately
1198	re-test whether a file descriptor is really ready with a known-to-be good	1604	re-test whether a file descriptor is really ready with a known-to-be good
1199	interface such as poll (fortunately in our Xlib example, Xlib already	1605	interface such as poll (fortunately in the case of Xlib, it already does
1200	does this on its own, so its quite safe to use). Some people additionally	1606	this on its own, so its quite safe to use). Some people additionally
1201	use C<SIGALRM> and an interval timer, just to be sure you won't block	1607	use C<SIGALRM> and an interval timer, just to be sure you won't block
1202	indefinitely.	1608	indefinitely.
1203		1609
1204	But really, best use non-blocking mode.	1610	But really, best use non-blocking mode.
1205		1611
…		…
1233		1639
1234	There is no workaround possible except not registering events	1640	There is no workaround possible except not registering events
1235	for potentially C<dup ()>'ed file descriptors, or to resort to	1641	for potentially C<dup ()>'ed file descriptors, or to resort to
1236	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1642	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1237		1643
		1644	=head3 The special problem of files
		1645
		1646	Many people try to use C<select> (or libev) on file descriptors
		1647	representing files, and expect it to become ready when their program
		1648	doesn't block on disk accesses (which can take a long time on their own).
		1649
		1650	However, this cannot ever work in the "expected" way - you get a readiness
		1651	notification as soon as the kernel knows whether and how much data is
		1652	there, and in the case of open files, that's always the case, so you
		1653	always get a readiness notification instantly, and your read (or possibly
		1654	write) will still block on the disk I/O.
		1655
		1656	Another way to view it is that in the case of sockets, pipes, character
		1657	devices and so on, there is another party (the sender) that delivers data
		1658	on its own, but in the case of files, there is no such thing: the disk
		1659	will not send data on its own, simply because it doesn't know what you
		1660	wish to read - you would first have to request some data.
		1661
		1662	Since files are typically not-so-well supported by advanced notification
		1663	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1664	to files, even though you should not use it. The reason for this is
		1665	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1666	usually a tty, often a pipe, but also sometimes files or special devices
		1667	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1668	F</dev/urandom>), and even though the file might better be served with
		1669	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1670	it "just works" instead of freezing.
		1671
		1672	So avoid file descriptors pointing to files when you know it (e.g. use
		1673	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1674	when you rarely read from a file instead of from a socket, and want to
		1675	reuse the same code path.
		1676
1238	=head3 The special problem of fork	1677	=head3 The special problem of fork
1239		1678
1240	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1679	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1241	useless behaviour. Libev fully supports fork, but needs to be told about	1680	useless behaviour. Libev fully supports fork, but needs to be told about
1242	it in the child.	1681	it in the child if you want to continue to use it in the child.
1243		1682
1244	To support fork in your programs, you either have to call	1683	To support fork in your child processes, you have to call C<ev_loop_fork
1245	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1684	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1685	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1247	C<EVBACKEND_POLL>.
1248		1686
1249	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1250		1688
1251	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1689	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1252	when writing to a pipe whose other end has been closed, your program gets	1690	when writing to a pipe whose other end has been closed, your program gets
…		…
1255		1693
1256	So when you encounter spurious, unexplained daemon exits, make sure you	1694	So when you encounter spurious, unexplained daemon exits, make sure you
1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1695	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1258	somewhere, as that would have given you a big clue).	1696	somewhere, as that would have given you a big clue).
1259		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1260		1736
1261	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1262		1738
1263	=over 4	1739	=over 4
1264		1740
…		…
1296	...	1772	...
1297	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1298	ev_io stdin_readable;	1774	ev_io stdin_readable;
1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1300	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1301	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1302		1778
1303		1779
1304	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1305		1781
1306	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1311	year, it will still time out after (roughly) one hour. "Roughly" because	1787	year, it will still time out after (roughly) one hour. "Roughly" because
1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1313	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1314		1790
1315	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1316	passed, but if multiple timers become ready during the same loop iteration	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1317	then order of execution is undefined.	1793	might introduce a small delay, see "the special problem of being too
		1794	early", below). If multiple timers become ready during the same loop
		1795	iteration then the ones with earlier time-out values are invoked before
		1796	ones of the same priority with later time-out values (but this is no
		1797	longer true when a callback calls C<ev_run> recursively).
1318		1798
1319	=head3 Be smart about timeouts	1799	=head3 Be smart about timeouts
1320		1800
1321	Many real-world problems involve some kind of timeout, usually for error	1801	Many real-world problems involve some kind of timeout, usually for error
1322	recovery. A typical example is an HTTP request - if the other side hangs,	1802	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1846	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1367	member and C<ev_timer_again>.	1847	member and C<ev_timer_again>.
1368		1848
1369	At start:	1849	At start:
1370		1850
1371	ev_timer_init (timer, callback);	1851	ev_init (timer, callback);
1372	timer->repeat = 60.;	1852	timer->repeat = 60.;
1373	ev_timer_again (loop, timer);	1853	ev_timer_again (loop, timer);
1374		1854
1375	Each time there is some activity:	1855	Each time there is some activity:
1376		1856
…		…
1397		1877
1398	In this case, it would be more efficient to leave the C<ev_timer> alone,	1878	In this case, it would be more efficient to leave the C<ev_timer> alone,
1399	but remember the time of last activity, and check for a real timeout only	1879	but remember the time of last activity, and check for a real timeout only
1400	within the callback:	1880	within the callback:
1401		1881
		1882	ev_tstamp timeout = 60.;
1402	ev_tstamp last_activity; // time of last activity	1883	ev_tstamp last_activity; // time of last activity
		1884	ev_timer timer;
1403		1885
1404	static void	1886	static void
1405	callback (EV_P_ ev_timer *w, int revents)	1887	callback (EV_P_ ev_timer *w, int revents)
1406	{	1888	{
1407	ev_tstamp now = ev_now (EV_A);	1889	// calculate when the timeout would happen
1408	ev_tstamp timeout = last_activity + 60.;	1890	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1409		1891
1410	// if last_activity + 60. is older than now, we did time out	1892	// if negative, it means we the timeout already occurred
1411	if (timeout < now)	1893	if (after < 0.)
1412	{	1894	{
1413	// timeout occured, take action	1895	// timeout occurred, take action
1414	}	1896	}
1415	else	1897	else
1416	{	1898	{
1417	// callback was invoked, but there was some activity, re-arm	1899	// callback was invoked, but there was some recent
1418	// the watcher to fire in last_activity + 60, which is	1900	// activity. simply restart the timer to time out
1419	// guaranteed to be in the future, so "again" is positive:	1901	// after "after" seconds, which is the earliest time
1420	w->again = timeout - now;	1902	// the timeout can occur.
		1903	ev_timer_set (w, after, 0.);
1421	ev_timer_again (EV_A_ w);	1904	ev_timer_start (EV_A_ w);
1422	}	1905	}
1423	}	1906	}
1424		1907
1425	To summarise the callback: first calculate the real timeout (defined	1908	To summarise the callback: first calculate in how many seconds the
1426	as "60 seconds after the last activity"), then check if that time has	1909	timeout will occur (by calculating the absolute time when it would occur,
1427	been reached, which means something I<did>, in fact, time out. Otherwise	1910	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1428	the callback was invoked too early (C<timeout> is in the future), so	1911	(EV_A)> from that).
1429	re-schedule the timer to fire at that future time, to see if maybe we have
1430	a timeout then.
1431		1912
1432	Note how C<ev_timer_again> is used, taking advantage of the	1913	If this value is negative, then we are already past the timeout, i.e. we
1433	C<ev_timer_again> optimisation when the timer is already running.	1914	timed out, and need to do whatever is needed in this case.
		1915
		1916	Otherwise, we now the earliest time at which the timeout would trigger,
		1917	and simply start the timer with this timeout value.
		1918
		1919	In other words, each time the callback is invoked it will check whether
		1920	the timeout occurred. If not, it will simply reschedule itself to check
		1921	again at the earliest time it could time out. Rinse. Repeat.
1434		1922
1435	This scheme causes more callback invocations (about one every 60 seconds	1923	This scheme causes more callback invocations (about one every 60 seconds
1436	minus half the average time between activity), but virtually no calls to	1924	minus half the average time between activity), but virtually no calls to
1437	libev to change the timeout.	1925	libev to change the timeout.
1438		1926
1439	To start the timer, simply initialise the watcher and set C<last_activity>	1927	To start the machinery, simply initialise the watcher and set
1440	to the current time (meaning we just have some activity :), then call the	1928	C<last_activity> to the current time (meaning there was some activity just
1441	callback, which will "do the right thing" and start the timer:	1929	now), then call the callback, which will "do the right thing" and start
		1930	the timer:
1442		1931
		1932	last_activity = ev_now (EV_A);
1443	ev_timer_init (timer, callback);	1933	ev_init (&timer, callback);
1444	last_activity = ev_now (loop);	1934	callback (EV_A_ &timer, 0);
1445	callback (loop, timer, EV_TIMEOUT);
1446		1935
1447	And when there is some activity, simply store the current time in	1936	When there is some activity, simply store the current time in
1448	C<last_activity>, no libev calls at all:	1937	C<last_activity>, no libev calls at all:
1449		1938
		1939	if (activity detected)
1450	last_actiivty = ev_now (loop);	1940	last_activity = ev_now (EV_A);
		1941
		1942	When your timeout value changes, then the timeout can be changed by simply
		1943	providing a new value, stopping the timer and calling the callback, which
		1944	will again do the right thing (for example, time out immediately :).
		1945
		1946	timeout = new_value;
		1947	ev_timer_stop (EV_A_ &timer);
		1948	callback (EV_A_ &timer, 0);
1451		1949
1452	This technique is slightly more complex, but in most cases where the	1950	This technique is slightly more complex, but in most cases where the
1453	time-out is unlikely to be triggered, much more efficient.	1951	time-out is unlikely to be triggered, much more efficient.
1454
1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
1456	callback :) - just change the timeout and invoke the callback, which will
1457	fix things for you.
1458		1952
1459	=item 4. Wee, just use a double-linked list for your timeouts.	1953	=item 4. Wee, just use a double-linked list for your timeouts.
1460		1954
1461	If there is not one request, but many thousands (millions...), all	1955	If there is not one request, but many thousands (millions...), all
1462	employing some kind of timeout with the same timeout value, then one can	1956	employing some kind of timeout with the same timeout value, then one can
…		…
1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1983	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1490	rather complicated, but extremely efficient, something that really pays	1984	rather complicated, but extremely efficient, something that really pays
1491	off after the first million or so of active timers, i.e. it's usually	1985	off after the first million or so of active timers, i.e. it's usually
1492	overkill :)	1986	overkill :)
1493		1987
		1988	=head3 The special problem of being too early
		1989
		1990	If you ask a timer to call your callback after three seconds, then
		1991	you expect it to be invoked after three seconds - but of course, this
		1992	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1993	guaranteed to any precision by libev - imagine somebody suspending the
		1994	process with a STOP signal for a few hours for example.
		1995
		1996	So, libev tries to invoke your callback as soon as possible I<after> the
		1997	delay has occurred, but cannot guarantee this.
		1998
		1999	A less obvious failure mode is calling your callback too early: many event
		2000	loops compare timestamps with a "elapsed delay >= requested delay", but
		2001	this can cause your callback to be invoked much earlier than you would
		2002	expect.
		2003
		2004	To see why, imagine a system with a clock that only offers full second
		2005	resolution (think windows if you can't come up with a broken enough OS
		2006	yourself). If you schedule a one-second timer at the time 500.9, then the
		2007	event loop will schedule your timeout to elapse at a system time of 500
		2008	(500.9 truncated to the resolution) + 1, or 501.
		2009
		2010	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2011	501" and invoke the callback 0.1s after it was started, even though a
		2012	one-second delay was requested - this is being "too early", despite best
		2013	intentions.
		2014
		2015	This is the reason why libev will never invoke the callback if the elapsed
		2016	delay equals the requested delay, but only when the elapsed delay is
		2017	larger than the requested delay. In the example above, libev would only invoke
		2018	the callback at system time 502, or 1.1s after the timer was started.
		2019
		2020	So, while libev cannot guarantee that your callback will be invoked
		2021	exactly when requested, it I<can> and I<does> guarantee that the requested
		2022	delay has actually elapsed, or in other words, it always errs on the "too
		2023	late" side of things.
		2024
1494	=head3 The special problem of time updates	2025	=head3 The special problem of time updates
1495		2026
1496	Establishing the current time is a costly operation (it usually takes at	2027	Establishing the current time is a costly operation (it usually takes
1497	least two system calls): EV therefore updates its idea of the current	2028	at least one system call): EV therefore updates its idea of the current
1498	time only before and after C<ev_loop> collects new events, which causes a	2029	time only before and after C<ev_run> collects new events, which causes a
1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2030	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1500	lots of events in one iteration.	2031	lots of events in one iteration.
1501		2032
1502	The relative timeouts are calculated relative to the C<ev_now ()>	2033	The relative timeouts are calculated relative to the C<ev_now ()>
1503	time. This is usually the right thing as this timestamp refers to the time	2034	time. This is usually the right thing as this timestamp refers to the time
1504	of the event triggering whatever timeout you are modifying/starting. If	2035	of the event triggering whatever timeout you are modifying/starting. If
1505	you suspect event processing to be delayed and you I<need> to base the	2036	you suspect event processing to be delayed and you I<need> to base the
1506	timeout on the current time, use something like this to adjust for this:	2037	timeout on the current time, use something like the following to adjust
		2038	for it:
1507		2039
1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2040	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1509		2041
1510	If the event loop is suspended for a long time, you can also force an	2042	If the event loop is suspended for a long time, you can also force an
1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2043	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1512	()>.	2044	()>, although that will push the event time of all outstanding events
		2045	further into the future.
		2046
		2047	=head3 The special problem of unsynchronised clocks
		2048
		2049	Modern systems have a variety of clocks - libev itself uses the normal
		2050	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2051	jumps).
		2052
		2053	Neither of these clocks is synchronised with each other or any other clock
		2054	on the system, so C<ev_time ()> might return a considerably different time
		2055	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2056	a call to C<gettimeofday> might return a second count that is one higher
		2057	than a directly following call to C<time>.
		2058
		2059	The moral of this is to only compare libev-related timestamps with
		2060	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2061	a second or so.
		2062
		2063	One more problem arises due to this lack of synchronisation: if libev uses
		2064	the system monotonic clock and you compare timestamps from C<ev_time>
		2065	or C<ev_now> from when you started your timer and when your callback is
		2066	invoked, you will find that sometimes the callback is a bit "early".
		2067
		2068	This is because C<ev_timer>s work in real time, not wall clock time, so
		2069	libev makes sure your callback is not invoked before the delay happened,
		2070	I<measured according to the real time>, not the system clock.
		2071
		2072	If your timeouts are based on a physical timescale (e.g. "time out this
		2073	connection after 100 seconds") then this shouldn't bother you as it is
		2074	exactly the right behaviour.
		2075
		2076	If you want to compare wall clock/system timestamps to your timers, then
		2077	you need to use C<ev_periodic>s, as these are based on the wall clock
		2078	time, where your comparisons will always generate correct results.
		2079
		2080	=head3 The special problems of suspended animation
		2081
		2082	When you leave the server world it is quite customary to hit machines that
		2083	can suspend/hibernate - what happens to the clocks during such a suspend?
		2084
		2085	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2086	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2087	to run until the system is suspended, but they will not advance while the
		2088	system is suspended. That means, on resume, it will be as if the program
		2089	was frozen for a few seconds, but the suspend time will not be counted
		2090	towards C<ev_timer> when a monotonic clock source is used. The real time
		2091	clock advanced as expected, but if it is used as sole clocksource, then a
		2092	long suspend would be detected as a time jump by libev, and timers would
		2093	be adjusted accordingly.
		2094
		2095	I would not be surprised to see different behaviour in different between
		2096	operating systems, OS versions or even different hardware.
		2097
		2098	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2099	time jump in the monotonic clocks and the realtime clock. If the program
		2100	is suspended for a very long time, and monotonic clock sources are in use,
		2101	then you can expect C<ev_timer>s to expire as the full suspension time
		2102	will be counted towards the timers. When no monotonic clock source is in
		2103	use, then libev will again assume a timejump and adjust accordingly.
		2104
		2105	It might be beneficial for this latter case to call C<ev_suspend>
		2106	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2107	deterministic behaviour in this case (you can do nothing against
		2108	C<SIGSTOP>).
1513		2109
1514	=head3 Watcher-Specific Functions and Data Members	2110	=head3 Watcher-Specific Functions and Data Members
1515		2111
1516	=over 4	2112	=over 4
1517		2113
…		…
1531	keep up with the timer (because it takes longer than those 10 seconds to	2127	keep up with the timer (because it takes longer than those 10 seconds to
1532	do stuff) the timer will not fire more than once per event loop iteration.	2128	do stuff) the timer will not fire more than once per event loop iteration.
1533		2129
1534	=item ev_timer_again (loop, ev_timer *)	2130	=item ev_timer_again (loop, ev_timer *)
1535		2131
1536	This will act as if the timer timed out and restart it again if it is	2132	This will act as if the timer timed out, and restarts it again if it is
1537	repeating. The exact semantics are:	2133	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2134	timeout to the C<repeat> value and calling C<ev_timer_start>.
1538		2135
		2136	The exact semantics are as in the following rules, all of which will be
		2137	applied to the watcher:
		2138
		2139	=over 4
		2140
1539	If the timer is pending, its pending status is cleared.	2141	=item If the timer is pending, the pending status is always cleared.
1540		2142
1541	If the timer is started but non-repeating, stop it (as if it timed out).	2143	=item If the timer is started but non-repeating, stop it (as if it timed
		2144	out, without invoking it).
1542		2145
1543	If the timer is repeating, either start it if necessary (with the	2146	=item If the timer is repeating, make the C<repeat> value the new timeout
1544	C<repeat> value), or reset the running timer to the C<repeat> value.	2147	and start the timer, if necessary.
1545		2148
		2149	=back
		2150
1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2151	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1547	usage example.	2152	usage example.
		2153
		2154	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2155
		2156	Returns the remaining time until a timer fires. If the timer is active,
		2157	then this time is relative to the current event loop time, otherwise it's
		2158	the timeout value currently configured.
		2159
		2160	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2161	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2162	will return C<4>. When the timer expires and is restarted, it will return
		2163	roughly C<7> (likely slightly less as callback invocation takes some time,
		2164	too), and so on.
1548		2165
1549	=item ev_tstamp repeat [read-write]	2166	=item ev_tstamp repeat [read-write]
1550		2167
1551	The current C<repeat> value. Will be used each time the watcher times out	2168	The current C<repeat> value. Will be used each time the watcher times out
1552	or C<ev_timer_again> is called, and determines the next timeout (if any),	2169	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1578	}	2195	}
1579		2196
1580	ev_timer mytimer;	2197	ev_timer mytimer;
1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2198	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1582	ev_timer_again (&mytimer); /* start timer */	2199	ev_timer_again (&mytimer); /* start timer */
1583	ev_loop (loop, 0);	2200	ev_run (loop, 0);
1584		2201
1585	// and in some piece of code that gets executed on any "activity":	2202	// and in some piece of code that gets executed on any "activity":
1586	// reset the timeout to start ticking again at 10 seconds	2203	// reset the timeout to start ticking again at 10 seconds
1587	ev_timer_again (&mytimer);	2204	ev_timer_again (&mytimer);
1588		2205
…		…
1590	=head2 C<ev_periodic> - to cron or not to cron?	2207	=head2 C<ev_periodic> - to cron or not to cron?
1591		2208
1592	Periodic watchers are also timers of a kind, but they are very versatile	2209	Periodic watchers are also timers of a kind, but they are very versatile
1593	(and unfortunately a bit complex).	2210	(and unfortunately a bit complex).
1594		2211
1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2212	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1596	but on wall clock time (absolute time). You can tell a periodic watcher	2213	relative time, the physical time that passes) but on wall clock time
1597	to trigger after some specific point in time. For example, if you tell a	2214	(absolute time, the thing you can read on your calender or clock). The
1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2215	difference is that wall clock time can run faster or slower than real
1599	+ 10.>, that is, an absolute time not a delay) and then reset your system	2216	time, and time jumps are not uncommon (e.g. when you adjust your
1600	clock to January of the previous year, then it will take more than year	2217	wrist-watch).
1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1602	roughly 10 seconds later as it uses a relative timeout).
1603		2218
		2219	You can tell a periodic watcher to trigger after some specific point
		2220	in time: for example, if you tell a periodic watcher to trigger "in 10
		2221	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2222	not a delay) and then reset your system clock to January of the previous
		2223	year, then it will take a year or more to trigger the event (unlike an
		2224	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2225	it, as it uses a relative timeout).
		2226
1604	C<ev_periodic>s can also be used to implement vastly more complex timers,	2227	C<ev_periodic> watchers can also be used to implement vastly more complex
1605	such as triggering an event on each "midnight, local time", or other	2228	timers, such as triggering an event on each "midnight, local time", or
1606	complicated rules.	2229	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2230	those cannot react to time jumps.
1607		2231
1608	As with timers, the callback is guaranteed to be invoked only when the	2232	As with timers, the callback is guaranteed to be invoked only when the
1609	time (C<at>) has passed, but if multiple periodic timers become ready	2233	point in time where it is supposed to trigger has passed. If multiple
1610	during the same loop iteration, then order of execution is undefined.	2234	timers become ready during the same loop iteration then the ones with
		2235	earlier time-out values are invoked before ones with later time-out values
		2236	(but this is no longer true when a callback calls C<ev_run> recursively).
1611		2237
1612	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1613		2239
1614	=over 4	2240	=over 4
1615		2241
1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2242	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1617		2243
1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2244	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1619		2245
1620	Lots of arguments, lets sort it out... There are basically three modes of	2246	Lots of arguments, let's sort it out... There are basically three modes of
1621	operation, and we will explain them from simplest to most complex:	2247	operation, and we will explain them from simplest to most complex:
1622		2248
1623	=over 4	2249	=over 4
1624		2250
1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2251	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1626		2252
1627	In this configuration the watcher triggers an event after the wall clock	2253	In this configuration the watcher triggers an event after the wall clock
1628	time C<at> has passed. It will not repeat and will not adjust when a time	2254	time C<offset> has passed. It will not repeat and will not adjust when a
1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2255	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1630	only run when the system clock reaches or surpasses this time.	2256	will be stopped and invoked when the system clock reaches or surpasses
		2257	this point in time.
1631		2258
1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2259	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1633		2260
1634	In this mode the watcher will always be scheduled to time out at the next	2261	In this mode the watcher will always be scheduled to time out at the next
1635	C<at + N * interval> time (for some integer N, which can also be negative)	2262	C<offset + N * interval> time (for some integer N, which can also be
1636	and then repeat, regardless of any time jumps.	2263	negative) and then repeat, regardless of any time jumps. The C<offset>
		2264	argument is merely an offset into the C<interval> periods.
1637		2265
1638	This can be used to create timers that do not drift with respect to the	2266	This can be used to create timers that do not drift with respect to the
1639	system clock, for example, here is a C<ev_periodic> that triggers each	2267	system clock, for example, here is an C<ev_periodic> that triggers each
1640	hour, on the hour:	2268	hour, on the hour (with respect to UTC):
1641		2269
1642	ev_periodic_set (&periodic, 0., 3600., 0);	2270	ev_periodic_set (&periodic, 0., 3600., 0);
1643		2271
1644	This doesn't mean there will always be 3600 seconds in between triggers,	2272	This doesn't mean there will always be 3600 seconds in between triggers,
1645	but only that the callback will be called when the system time shows a	2273	but only that the callback will be called when the system time shows a
1646	full hour (UTC), or more correctly, when the system time is evenly divisible	2274	full hour (UTC), or more correctly, when the system time is evenly divisible
1647	by 3600.	2275	by 3600.
1648		2276
1649	Another way to think about it (for the mathematically inclined) is that	2277	Another way to think about it (for the mathematically inclined) is that
1650	C<ev_periodic> will try to run the callback in this mode at the next possible	2278	C<ev_periodic> will try to run the callback in this mode at the next possible
1651	time where C<time = at (mod interval)>, regardless of any time jumps.	2279	time where C<time = offset (mod interval)>, regardless of any time jumps.
1652		2280
1653	For numerical stability it is preferable that the C<at> value is near	2281	The C<interval> I<MUST> be positive, and for numerical stability, the
1654	C<ev_now ()> (the current time), but there is no range requirement for	2282	interval value should be higher than C<1/8192> (which is around 100
1655	this value, and in fact is often specified as zero.	2283	microseconds) and C<offset> should be higher than C<0> and should have
		2284	at most a similar magnitude as the current time (say, within a factor of
		2285	ten). Typical values for offset are, in fact, C<0> or something between
		2286	C<0> and C<interval>, which is also the recommended range.
1656		2287
1657	Note also that there is an upper limit to how often a timer can fire (CPU	2288	Note also that there is an upper limit to how often a timer can fire (CPU
1658	speed for example), so if C<interval> is very small then timing stability	2289	speed for example), so if C<interval> is very small then timing stability
1659	will of course deteriorate. Libev itself tries to be exact to be about one	2290	will of course deteriorate. Libev itself tries to be exact to be about one
1660	millisecond (if the OS supports it and the machine is fast enough).	2291	millisecond (if the OS supports it and the machine is fast enough).
1661		2292
1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2293	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1663		2294
1664	In this mode the values for C<interval> and C<at> are both being	2295	In this mode the values for C<interval> and C<offset> are both being
1665	ignored. Instead, each time the periodic watcher gets scheduled, the	2296	ignored. Instead, each time the periodic watcher gets scheduled, the
1666	reschedule callback will be called with the watcher as first, and the	2297	reschedule callback will be called with the watcher as first, and the
1667	current time as second argument.	2298	current time as second argument.
1668		2299
1669	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2300	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1670	ever, or make ANY event loop modifications whatsoever>.	2301	or make ANY other event loop modifications whatsoever, unless explicitly
		2302	allowed by documentation here>.
1671		2303
1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2304	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2305	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1674	only event loop modification you are allowed to do).	2306	only event loop modification you are allowed to do).
1675		2307
…		…
1705	a different time than the last time it was called (e.g. in a crond like	2337	a different time than the last time it was called (e.g. in a crond like
1706	program when the crontabs have changed).	2338	program when the crontabs have changed).
1707		2339
1708	=item ev_tstamp ev_periodic_at (ev_periodic *)	2340	=item ev_tstamp ev_periodic_at (ev_periodic *)
1709		2341
1710	When active, returns the absolute time that the watcher is supposed to	2342	When active, returns the absolute time that the watcher is supposed
1711	trigger next.	2343	to trigger next. This is not the same as the C<offset> argument to
		2344	C<ev_periodic_set>, but indeed works even in interval and manual
		2345	rescheduling modes.
1712		2346
1713	=item ev_tstamp offset [read-write]	2347	=item ev_tstamp offset [read-write]
1714		2348
1715	When repeating, this contains the offset value, otherwise this is the	2349	When repeating, this contains the offset value, otherwise this is the
1716	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2350	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2351	although libev might modify this value for better numerical stability).
1717		2352
1718	Can be modified any time, but changes only take effect when the periodic	2353	Can be modified any time, but changes only take effect when the periodic
1719	timer fires or C<ev_periodic_again> is being called.	2354	timer fires or C<ev_periodic_again> is being called.
1720		2355
1721	=item ev_tstamp interval [read-write]	2356	=item ev_tstamp interval [read-write]
…		…
1737	Example: Call a callback every hour, or, more precisely, whenever the	2372	Example: Call a callback every hour, or, more precisely, whenever the
1738	system time is divisible by 3600. The callback invocation times have	2373	system time is divisible by 3600. The callback invocation times have
1739	potentially a lot of jitter, but good long-term stability.	2374	potentially a lot of jitter, but good long-term stability.
1740		2375
1741	static void	2376	static void
1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2377	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1743	{	2378	{
1744	... its now a full hour (UTC, or TAI or whatever your clock follows)	2379	... its now a full hour (UTC, or TAI or whatever your clock follows)
1745	}	2380	}
1746		2381
1747	ev_periodic hourly_tick;	2382	ev_periodic hourly_tick;
…		…
1764		2399
1765	ev_periodic hourly_tick;	2400	ev_periodic hourly_tick;
1766	ev_periodic_init (&hourly_tick, clock_cb,	2401	ev_periodic_init (&hourly_tick, clock_cb,
1767	fmod (ev_now (loop), 3600.), 3600., 0);	2402	fmod (ev_now (loop), 3600.), 3600., 0);
1768	ev_periodic_start (loop, &hourly_tick);	2403	ev_periodic_start (loop, &hourly_tick);
1769		2404
1770		2405
1771	=head2 C<ev_signal> - signal me when a signal gets signalled!	2406	=head2 C<ev_signal> - signal me when a signal gets signalled!
1772		2407
1773	Signal watchers will trigger an event when the process receives a specific	2408	Signal watchers will trigger an event when the process receives a specific
1774	signal one or more times. Even though signals are very asynchronous, libev	2409	signal one or more times. Even though signals are very asynchronous, libev
1775	will try it's best to deliver signals synchronously, i.e. as part of the	2410	will try its best to deliver signals synchronously, i.e. as part of the
1776	normal event processing, like any other event.	2411	normal event processing, like any other event.
1777		2412
1778	If you want signals asynchronously, just use C<sigaction> as you would	2413	If you want signals to be delivered truly asynchronously, just use
1779	do without libev and forget about sharing the signal. You can even use	2414	C<sigaction> as you would do without libev and forget about sharing
1780	C<ev_async> from a signal handler to synchronously wake up an event loop.	2415	the signal. You can even use C<ev_async> from a signal handler to
		2416	synchronously wake up an event loop.
1781		2417
1782	You can configure as many watchers as you like per signal. Only when the	2418	You can configure as many watchers as you like for the same signal, but
1783	first watcher gets started will libev actually register a signal handler	2419	only within the same loop, i.e. you can watch for C<SIGINT> in your
1784	with the kernel (thus it coexists with your own signal handlers as long as	2420	default loop and for C<SIGIO> in another loop, but you cannot watch for
1785	you don't register any with libev for the same signal). Similarly, when	2421	C<SIGINT> in both the default loop and another loop at the same time. At
1786	the last signal watcher for a signal is stopped, libev will reset the	2422	the moment, C<SIGCHLD> is permanently tied to the default loop.
1787	signal handler to SIG_DFL (regardless of what it was set to before).	2423
		2424	Only after the first watcher for a signal is started will libev actually
		2425	register something with the kernel. It thus coexists with your own signal
		2426	handlers as long as you don't register any with libev for the same signal.
1788		2427
1789	If possible and supported, libev will install its handlers with	2428	If possible and supported, libev will install its handlers with
1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2429	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1791	interrupted. If you have a problem with system calls getting interrupted by	2430	not be unduly interrupted. If you have a problem with system calls getting
1792	signals you can block all signals in an C<ev_check> watcher and unblock	2431	interrupted by signals you can block all signals in an C<ev_check> watcher
1793	them in an C<ev_prepare> watcher.	2432	and unblock them in an C<ev_prepare> watcher.
		2433
		2434	=head3 The special problem of inheritance over fork/execve/pthread_create
		2435
		2436	Both the signal mask (C<sigprocmask>) and the signal disposition
		2437	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2438	stopping it again), that is, libev might or might not block the signal,
		2439	and might or might not set or restore the installed signal handler (but
		2440	see C<EVFLAG_NOSIGMASK>).
		2441
		2442	While this does not matter for the signal disposition (libev never
		2443	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2444	C<execve>), this matters for the signal mask: many programs do not expect
		2445	certain signals to be blocked.
		2446
		2447	This means that before calling C<exec> (from the child) you should reset
		2448	the signal mask to whatever "default" you expect (all clear is a good
		2449	choice usually).
		2450
		2451	The simplest way to ensure that the signal mask is reset in the child is
		2452	to install a fork handler with C<pthread_atfork> that resets it. That will
		2453	catch fork calls done by libraries (such as the libc) as well.
		2454
		2455	In current versions of libev, the signal will not be blocked indefinitely
		2456	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2457	the window of opportunity for problems, it will not go away, as libev
		2458	I<has> to modify the signal mask, at least temporarily.
		2459
		2460	So I can't stress this enough: I<If you do not reset your signal mask when
		2461	you expect it to be empty, you have a race condition in your code>. This
		2462	is not a libev-specific thing, this is true for most event libraries.
		2463
		2464	=head3 The special problem of threads signal handling
		2465
		2466	POSIX threads has problematic signal handling semantics, specifically,
		2467	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2468	threads in a process block signals, which is hard to achieve.
		2469
		2470	When you want to use sigwait (or mix libev signal handling with your own
		2471	for the same signals), you can tackle this problem by globally blocking
		2472	all signals before creating any threads (or creating them with a fully set
		2473	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2474	loops. Then designate one thread as "signal receiver thread" which handles
		2475	these signals. You can pass on any signals that libev might be interested
		2476	in by calling C<ev_feed_signal>.
1794		2477
1795	=head3 Watcher-Specific Functions and Data Members	2478	=head3 Watcher-Specific Functions and Data Members
1796		2479
1797	=over 4	2480	=over 4
1798		2481
…		…
1814	Example: Try to exit cleanly on SIGINT.	2497	Example: Try to exit cleanly on SIGINT.
1815		2498
1816	static void	2499	static void
1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2500	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1818	{	2501	{
1819	ev_unloop (loop, EVUNLOOP_ALL);	2502	ev_break (loop, EVBREAK_ALL);
1820	}	2503	}
1821		2504
1822	ev_signal signal_watcher;	2505	ev_signal signal_watcher;
1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2506	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1824	ev_signal_start (loop, &signal_watcher);	2507	ev_signal_start (loop, &signal_watcher);
…		…
1830	some child status changes (most typically when a child of yours dies or	2513	some child status changes (most typically when a child of yours dies or
1831	exits). It is permissible to install a child watcher I<after> the child	2514	exits). It is permissible to install a child watcher I<after> the child
1832	has been forked (which implies it might have already exited), as long	2515	has been forked (which implies it might have already exited), as long
1833	as the event loop isn't entered (or is continued from a watcher), i.e.,	2516	as the event loop isn't entered (or is continued from a watcher), i.e.,
1834	forking and then immediately registering a watcher for the child is fine,	2517	forking and then immediately registering a watcher for the child is fine,
1835	but forking and registering a watcher a few event loop iterations later is	2518	but forking and registering a watcher a few event loop iterations later or
1836	not.	2519	in the next callback invocation is not.
1837		2520
1838	Only the default event loop is capable of handling signals, and therefore	2521	Only the default event loop is capable of handling signals, and therefore
1839	you can only register child watchers in the default event loop.	2522	you can only register child watchers in the default event loop.
1840		2523
		2524	Due to some design glitches inside libev, child watchers will always be
		2525	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2526	libev)
		2527
1841	=head3 Process Interaction	2528	=head3 Process Interaction
1842		2529
1843	Libev grabs C<SIGCHLD> as soon as the default event loop is	2530	Libev grabs C<SIGCHLD> as soon as the default event loop is
1844	initialised. This is necessary to guarantee proper behaviour even if	2531	initialised. This is necessary to guarantee proper behaviour even if the
1845	the first child watcher is started after the child exits. The occurrence	2532	first child watcher is started after the child exits. The occurrence
1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2533	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1847	synchronously as part of the event loop processing. Libev always reaps all	2534	synchronously as part of the event loop processing. Libev always reaps all
1848	children, even ones not watched.	2535	children, even ones not watched.
1849		2536
1850	=head3 Overriding the Built-In Processing	2537	=head3 Overriding the Built-In Processing
…		…
1860	=head3 Stopping the Child Watcher	2547	=head3 Stopping the Child Watcher
1861		2548
1862	Currently, the child watcher never gets stopped, even when the	2549	Currently, the child watcher never gets stopped, even when the
1863	child terminates, so normally one needs to stop the watcher in the	2550	child terminates, so normally one needs to stop the watcher in the
1864	callback. Future versions of libev might stop the watcher automatically	2551	callback. Future versions of libev might stop the watcher automatically
1865	when a child exit is detected.	2552	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2553	problem).
1866		2554
1867	=head3 Watcher-Specific Functions and Data Members	2555	=head3 Watcher-Specific Functions and Data Members
1868		2556
1869	=over 4	2557	=over 4
1870		2558
…		…
1928		2616
1929	=head2 C<ev_stat> - did the file attributes just change?	2617	=head2 C<ev_stat> - did the file attributes just change?
1930		2618
1931	This watches a file system path for attribute changes. That is, it calls	2619	This watches a file system path for attribute changes. That is, it calls
1932	C<stat> on that path in regular intervals (or when the OS says it changed)	2620	C<stat> on that path in regular intervals (or when the OS says it changed)
1933	and sees if it changed compared to the last time, invoking the callback if	2621	and sees if it changed compared to the last time, invoking the callback
1934	it did.	2622	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2623	happen after the watcher has been started will be reported.
1935		2624
1936	The path does not need to exist: changing from "path exists" to "path does	2625	The path does not need to exist: changing from "path exists" to "path does
1937	not exist" is a status change like any other. The condition "path does not	2626	not exist" is a status change like any other. The condition "path does not
1938	exist" (or more correctly "path cannot be stat'ed") is signified by the	2627	exist" (or more correctly "path cannot be stat'ed") is signified by the
1939	C<st_nlink> field being zero (which is otherwise always forced to be at	2628	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
1997		2686
1998	There is no support for kqueue, as apparently it cannot be used to	2687	There is no support for kqueue, as apparently it cannot be used to
1999	implement this functionality, due to the requirement of having a file	2688	implement this functionality, due to the requirement of having a file
2000	descriptor open on the object at all times, and detecting renames, unlinks	2689	descriptor open on the object at all times, and detecting renames, unlinks
2001	etc. is difficult.	2690	etc. is difficult.
		2691
		2692	=head3 C<stat ()> is a synchronous operation
		2693
		2694	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2695	the process. The exception are C<ev_stat> watchers - those call C<stat
		2696	()>, which is a synchronous operation.
		2697
		2698	For local paths, this usually doesn't matter: unless the system is very
		2699	busy or the intervals between stat's are large, a stat call will be fast,
		2700	as the path data is usually in memory already (except when starting the
		2701	watcher).
		2702
		2703	For networked file systems, calling C<stat ()> can block an indefinite
		2704	time due to network issues, and even under good conditions, a stat call
		2705	often takes multiple milliseconds.
		2706
		2707	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2708	paths, although this is fully supported by libev.
2002		2709
2003	=head3 The special problem of stat time resolution	2710	=head3 The special problem of stat time resolution
2004		2711
2005	The C<stat ()> system call only supports full-second resolution portably,	2712	The C<stat ()> system call only supports full-second resolution portably,
2006	and even on systems where the resolution is higher, most file systems	2713	and even on systems where the resolution is higher, most file systems
…		…
2151	Apart from keeping your process non-blocking (which is a useful	2858	Apart from keeping your process non-blocking (which is a useful
2152	effect on its own sometimes), idle watchers are a good place to do	2859	effect on its own sometimes), idle watchers are a good place to do
2153	"pseudo-background processing", or delay processing stuff to after the	2860	"pseudo-background processing", or delay processing stuff to after the
2154	event loop has handled all outstanding events.	2861	event loop has handled all outstanding events.
2155		2862
		2863	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2864
		2865	As long as there is at least one active idle watcher, libev will never
		2866	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2867	For this to work, the idle watcher doesn't need to be invoked at all - the
		2868	lowest priority will do.
		2869
		2870	This mode of operation can be useful together with an C<ev_check> watcher,
		2871	to do something on each event loop iteration - for example to balance load
		2872	between different connections.
		2873
		2874	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2875	example.
		2876
2156	=head3 Watcher-Specific Functions and Data Members	2877	=head3 Watcher-Specific Functions and Data Members
2157		2878
2158	=over 4	2879	=over 4
2159		2880
2160	=item ev_idle_init (ev_signal *, callback)	2881	=item ev_idle_init (ev_idle *, callback)
2161		2882
2162	Initialises and configures the idle watcher - it has no parameters of any	2883	Initialises and configures the idle watcher - it has no parameters of any
2163	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2884	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2164	believe me.	2885	believe me.
2165		2886
…		…
2171	callback, free it. Also, use no error checking, as usual.	2892	callback, free it. Also, use no error checking, as usual.
2172		2893
2173	static void	2894	static void
2174	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2895	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2175	{	2896	{
		2897	// stop the watcher
		2898	ev_idle_stop (loop, w);
		2899
		2900	// now we can free it
2176	free (w);	2901	free (w);
		2902
2177	// now do something you wanted to do when the program has	2903	// now do something you wanted to do when the program has
2178	// no longer anything immediate to do.	2904	// no longer anything immediate to do.
2179	}	2905	}
2180		2906
2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2907	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2182	ev_idle_init (idle_watcher, idle_cb);	2908	ev_idle_init (idle_watcher, idle_cb);
2183	ev_idle_start (loop, idle_cb);	2909	ev_idle_start (loop, idle_watcher);
2184		2910
2185		2911
2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2912	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2187		2913
2188	Prepare and check watchers are usually (but not always) used in pairs:	2914	Prepare and check watchers are often (but not always) used in pairs:
2189	prepare watchers get invoked before the process blocks and check watchers	2915	prepare watchers get invoked before the process blocks and check watchers
2190	afterwards.	2916	afterwards.
2191		2917
2192	You I<must not> call C<ev_loop> or similar functions that enter	2918	You I<must not> call C<ev_run> (or similar functions that enter the
2193	the current event loop from either C<ev_prepare> or C<ev_check>	2919	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2194	watchers. Other loops than the current one are fine, however. The	2920	C<ev_check> watchers. Other loops than the current one are fine,
2195	rationale behind this is that you do not need to check for recursion in	2921	however. The rationale behind this is that you do not need to check
2196	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2922	for recursion in those watchers, i.e. the sequence will always be
2197	C<ev_check> so if you have one watcher of each kind they will always be	2923	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2198	called in pairs bracketing the blocking call.	2924	kind they will always be called in pairs bracketing the blocking call.
2199		2925
2200	Their main purpose is to integrate other event mechanisms into libev and	2926	Their main purpose is to integrate other event mechanisms into libev and
2201	their use is somewhat advanced. They could be used, for example, to track	2927	their use is somewhat advanced. They could be used, for example, to track
2202	variable changes, implement your own watchers, integrate net-snmp or a	2928	variable changes, implement your own watchers, integrate net-snmp or a
2203	coroutine library and lots more. They are also occasionally useful if	2929	coroutine library and lots more. They are also occasionally useful if
…		…
2221	with priority higher than or equal to the event loop and one coroutine	2947	with priority higher than or equal to the event loop and one coroutine
2222	of lower priority, but only once, using idle watchers to keep the event	2948	of lower priority, but only once, using idle watchers to keep the event
2223	loop from blocking if lower-priority coroutines are active, thus mapping	2949	loop from blocking if lower-priority coroutines are active, thus mapping
2224	low-priority coroutines to idle/background tasks).	2950	low-priority coroutines to idle/background tasks).
2225		2951
2226	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2952	When used for this purpose, it is recommended to give C<ev_check> watchers
2227	priority, to ensure that they are being run before any other watchers	2953	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2228	after the poll (this doesn't matter for C<ev_prepare> watchers).	2954	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2955	watchers).
2229		2956
2230	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2957	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2231	activate ("feed") events into libev. While libev fully supports this, they	2958	activate ("feed") events into libev. While libev fully supports this, they
2232	might get executed before other C<ev_check> watchers did their job. As	2959	might get executed before other C<ev_check> watchers did their job. As
2233	C<ev_check> watchers are often used to embed other (non-libev) event	2960	C<ev_check> watchers are often used to embed other (non-libev) event
2234	loops those other event loops might be in an unusable state until their	2961	loops those other event loops might be in an unusable state until their
2235	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2962	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2236	others).	2963	others).
		2964
		2965	=head3 Abusing an C<ev_check> watcher for its side-effect
		2966
		2967	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2968	useful because they are called once per event loop iteration. For
		2969	example, if you want to handle a large number of connections fairly, you
		2970	normally only do a bit of work for each active connection, and if there
		2971	is more work to do, you wait for the next event loop iteration, so other
		2972	connections have a chance of making progress.
		2973
		2974	Using an C<ev_check> watcher is almost enough: it will be called on the
		2975	next event loop iteration. However, that isn't as soon as possible -
		2976	without external events, your C<ev_check> watcher will not be invoked.
		2977
		2978	This is where C<ev_idle> watchers come in handy - all you need is a
		2979	single global idle watcher that is active as long as you have one active
		2980	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2981	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2982	invoked. Neither watcher alone can do that.
2237		2983
2238	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2239		2985
2240	=over 4	2986	=over 4
2241		2987
…		…
2281	struct pollfd fds [nfd];	3027	struct pollfd fds [nfd];
2282	// actual code will need to loop here and realloc etc.	3028	// actual code will need to loop here and realloc etc.
2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3029	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2284		3030
2285	/* the callback is illegal, but won't be called as we stop during check */	3031	/* the callback is illegal, but won't be called as we stop during check */
2286	ev_timer_init (&tw, 0, timeout * 1e-3);	3032	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2287	ev_timer_start (loop, &tw);	3033	ev_timer_start (loop, &tw);
2288		3034
2289	// create one ev_io per pollfd	3035	// create one ev_io per pollfd
2290	for (int i = 0; i < nfd; ++i)	3036	for (int i = 0; i < nfd; ++i)
2291	{	3037	{
…		…
2365		3111
2366	if (timeout >= 0)	3112	if (timeout >= 0)
2367	// create/start timer	3113	// create/start timer
2368		3114
2369	// poll	3115	// poll
2370	ev_loop (EV_A_ 0);	3116	ev_run (EV_A_ 0);
2371		3117
2372	// stop timer again	3118	// stop timer again
2373	if (timeout >= 0)	3119	if (timeout >= 0)
2374	ev_timer_stop (EV_A_ &to);	3120	ev_timer_stop (EV_A_ &to);
2375		3121
…		…
2404	some fds have to be watched and handled very quickly (with low latency),	3150	some fds have to be watched and handled very quickly (with low latency),
2405	and even priorities and idle watchers might have too much overhead. In	3151	and even priorities and idle watchers might have too much overhead. In
2406	this case you would put all the high priority stuff in one loop and all	3152	this case you would put all the high priority stuff in one loop and all
2407	the rest in a second one, and embed the second one in the first.	3153	the rest in a second one, and embed the second one in the first.
2408		3154
2409	As long as the watcher is active, the callback will be invoked every time	3155	As long as the watcher is active, the callback will be invoked every
2410	there might be events pending in the embedded loop. The callback must then	3156	time there might be events pending in the embedded loop. The callback
2411	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3157	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2412	their callbacks (you could also start an idle watcher to give the embedded	3158	sweep and invoke their callbacks (the callback doesn't need to invoke the
2413	loop strictly lower priority for example). You can also set the callback	3159	C<ev_embed_sweep> function directly, it could also start an idle watcher
2414	to C<0>, in which case the embed watcher will automatically execute the	3160	to give the embedded loop strictly lower priority for example).
2415	embedded loop sweep.
2416		3161
2417	As long as the watcher is started it will automatically handle events. The	3162	You can also set the callback to C<0>, in which case the embed watcher
2418	callback will be invoked whenever some events have been handled. You can	3163	will automatically execute the embedded loop sweep whenever necessary.
2419	set the callback to C<0> to avoid having to specify one if you are not
2420	interested in that.
2421		3164
2422	Also, there have not currently been made special provisions for forking:	3165	Fork detection will be handled transparently while the C<ev_embed> watcher
2423	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3166	is active, i.e., the embedded loop will automatically be forked when the
2424	but you will also have to stop and restart any C<ev_embed> watchers	3167	embedding loop forks. In other cases, the user is responsible for calling
2425	yourself - but you can use a fork watcher to handle this automatically,	3168	C<ev_loop_fork> on the embedded loop.
2426	and future versions of libev might do just that.
2427		3169
2428	Unfortunately, not all backends are embeddable: only the ones returned by	3170	Unfortunately, not all backends are embeddable: only the ones returned by
2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3171	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2430	portable one.	3172	portable one.
2431		3173
…		…
2446		3188
2447	=over 4	3189	=over 4
2448		3190
2449	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3191	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2450		3192
2451	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3193	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2452		3194
2453	Configures the watcher to embed the given loop, which must be	3195	Configures the watcher to embed the given loop, which must be
2454	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3196	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2455	invoked automatically, otherwise it is the responsibility of the callback	3197	invoked automatically, otherwise it is the responsibility of the callback
2456	to invoke it (it will continue to be called until the sweep has been done,	3198	to invoke it (it will continue to be called until the sweep has been done,
2457	if you do not want that, you need to temporarily stop the embed watcher).	3199	if you do not want that, you need to temporarily stop the embed watcher).
2458		3200
2459	=item ev_embed_sweep (loop, ev_embed *)	3201	=item ev_embed_sweep (loop, ev_embed *)
2460		3202
2461	Make a single, non-blocking sweep over the embedded loop. This works	3203	Make a single, non-blocking sweep over the embedded loop. This works
2462	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3204	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2463	appropriate way for embedded loops.	3205	appropriate way for embedded loops.
2464		3206
2465	=item struct ev_loop *other [read-only]	3207	=item struct ev_loop *other [read-only]
2466		3208
2467	The embedded event loop.	3209	The embedded event loop.
…		…
2477	used).	3219	used).
2478		3220
2479	struct ev_loop *loop_hi = ev_default_init (0);	3221	struct ev_loop *loop_hi = ev_default_init (0);
2480	struct ev_loop *loop_lo = 0;	3222	struct ev_loop *loop_lo = 0;
2481	ev_embed embed;	3223	ev_embed embed;
2482		3224
2483	// see if there is a chance of getting one that works	3225	// see if there is a chance of getting one that works
2484	// (remember that a flags value of 0 means autodetection)	3226	// (remember that a flags value of 0 means autodetection)
2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3227	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3228	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2487	: 0;	3229	: 0;
…		…
2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3243	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2502		3244
2503	struct ev_loop *loop = ev_default_init (0);	3245	struct ev_loop *loop = ev_default_init (0);
2504	struct ev_loop *loop_socket = 0;	3246	struct ev_loop *loop_socket = 0;
2505	ev_embed embed;	3247	ev_embed embed;
2506		3248
2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3249	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3250	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2509	{	3251	{
2510	ev_embed_init (&embed, 0, loop_socket);	3252	ev_embed_init (&embed, 0, loop_socket);
2511	ev_embed_start (loop, &embed);	3253	ev_embed_start (loop, &embed);
…		…
2519		3261
2520	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3262	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2521		3263
2522	Fork watchers are called when a C<fork ()> was detected (usually because	3264	Fork watchers are called when a C<fork ()> was detected (usually because
2523	whoever is a good citizen cared to tell libev about it by calling	3265	whoever is a good citizen cared to tell libev about it by calling
2524	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3266	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2525	event loop blocks next and before C<ev_check> watchers are being called,	3267	and before C<ev_check> watchers are being called, and only in the child
2526	and only in the child after the fork. If whoever good citizen calling	3268	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2527	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3269	and calls it in the wrong process, the fork handlers will be invoked, too,
2528	handlers will be invoked, too, of course.	3270	of course.
		3271
		3272	=head3 The special problem of life after fork - how is it possible?
		3273
		3274	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3275	up/change the process environment, followed by a call to C<exec()>. This
		3276	sequence should be handled by libev without any problems.
		3277
		3278	This changes when the application actually wants to do event handling
		3279	in the child, or both parent in child, in effect "continuing" after the
		3280	fork.
		3281
		3282	The default mode of operation (for libev, with application help to detect
		3283	forks) is to duplicate all the state in the child, as would be expected
		3284	when I<either> the parent I<or> the child process continues.
		3285
		3286	When both processes want to continue using libev, then this is usually the
		3287	wrong result. In that case, usually one process (typically the parent) is
		3288	supposed to continue with all watchers in place as before, while the other
		3289	process typically wants to start fresh, i.e. without any active watchers.
		3290
		3291	The cleanest and most efficient way to achieve that with libev is to
		3292	simply create a new event loop, which of course will be "empty", and
		3293	use that for new watchers. This has the advantage of not touching more
		3294	memory than necessary, and thus avoiding the copy-on-write, and the
		3295	disadvantage of having to use multiple event loops (which do not support
		3296	signal watchers).
		3297
		3298	When this is not possible, or you want to use the default loop for
		3299	other reasons, then in the process that wants to start "fresh", call
		3300	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3301	Destroying the default loop will "orphan" (not stop) all registered
		3302	watchers, so you have to be careful not to execute code that modifies
		3303	those watchers. Note also that in that case, you have to re-register any
		3304	signal watchers.
2529		3305
2530	=head3 Watcher-Specific Functions and Data Members	3306	=head3 Watcher-Specific Functions and Data Members
2531		3307
2532	=over 4	3308	=over 4
2533		3309
2534	=item ev_fork_init (ev_signal *, callback)	3310	=item ev_fork_init (ev_fork *, callback)
2535		3311
2536	Initialises and configures the fork watcher - it has no parameters of any	3312	Initialises and configures the fork watcher - it has no parameters of any
2537	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3313	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2538	believe me.	3314	really.
2539		3315
2540	=back	3316	=back
2541		3317
2542		3318
		3319	=head2 C<ev_cleanup> - even the best things end
		3320
		3321	Cleanup watchers are called just before the event loop is being destroyed
		3322	by a call to C<ev_loop_destroy>.
		3323
		3324	While there is no guarantee that the event loop gets destroyed, cleanup
		3325	watchers provide a convenient method to install cleanup hooks for your
		3326	program, worker threads and so on - you just to make sure to destroy the
		3327	loop when you want them to be invoked.
		3328
		3329	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3330	all other watchers, they do not keep a reference to the event loop (which
		3331	makes a lot of sense if you think about it). Like all other watchers, you
		3332	can call libev functions in the callback, except C<ev_cleanup_start>.
		3333
		3334	=head3 Watcher-Specific Functions and Data Members
		3335
		3336	=over 4
		3337
		3338	=item ev_cleanup_init (ev_cleanup *, callback)
		3339
		3340	Initialises and configures the cleanup watcher - it has no parameters of
		3341	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3342	pointless, I assure you.
		3343
		3344	=back
		3345
		3346	Example: Register an atexit handler to destroy the default loop, so any
		3347	cleanup functions are called.
		3348
		3349	static void
		3350	program_exits (void)
		3351	{
		3352	ev_loop_destroy (EV_DEFAULT_UC);
		3353	}
		3354
		3355	...
		3356	atexit (program_exits);
		3357
		3358
2543	=head2 C<ev_async> - how to wake up another event loop	3359	=head2 C<ev_async> - how to wake up an event loop
2544		3360
2545	In general, you cannot use an C<ev_loop> from multiple threads or other	3361	In general, you cannot use an C<ev_loop> from multiple threads or other
2546	asynchronous sources such as signal handlers (as opposed to multiple event	3362	asynchronous sources such as signal handlers (as opposed to multiple event
2547	loops - those are of course safe to use in different threads).	3363	loops - those are of course safe to use in different threads).
2548		3364
2549	Sometimes, however, you need to wake up another event loop you do not	3365	Sometimes, however, you need to wake up an event loop you do not control,
2550	control, for example because it belongs to another thread. This is what	3366	for example because it belongs to another thread. This is what C<ev_async>
2551	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3367	watchers do: as long as the C<ev_async> watcher is active, you can signal
2552	can signal it by calling C<ev_async_send>, which is thread- and signal	3368	it by calling C<ev_async_send>, which is thread- and signal safe.
2553	safe.
2554		3369
2555	This functionality is very similar to C<ev_signal> watchers, as signals,	3370	This functionality is very similar to C<ev_signal> watchers, as signals,
2556	too, are asynchronous in nature, and signals, too, will be compressed	3371	too, are asynchronous in nature, and signals, too, will be compressed
2557	(i.e. the number of callback invocations may be less than the number of	3372	(i.e. the number of callback invocations may be less than the number of
2558	C<ev_async_sent> calls).	3373	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2559		3374	of "global async watchers" by using a watcher on an otherwise unused
2560	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3375	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2561	just the default loop.	3376	even without knowing which loop owns the signal.
2562		3377
2563	=head3 Queueing	3378	=head3 Queueing
2564		3379
2565	C<ev_async> does not support queueing of data in any way. The reason	3380	C<ev_async> does not support queueing of data in any way. The reason
2566	is that the author does not know of a simple (or any) algorithm for a	3381	is that the author does not know of a simple (or any) algorithm for a
2567	multiple-writer-single-reader queue that works in all cases and doesn't	3382	multiple-writer-single-reader queue that works in all cases and doesn't
2568	need elaborate support such as pthreads.	3383	need elaborate support such as pthreads or unportable memory access
		3384	semantics.
2569		3385
2570	That means that if you want to queue data, you have to provide your own	3386	That means that if you want to queue data, you have to provide your own
2571	queue. But at least I can tell you how to implement locking around your	3387	queue. But at least I can tell you how to implement locking around your
2572	queue:	3388	queue:
2573		3389
…		…
2657	trust me.	3473	trust me.
2658		3474
2659	=item ev_async_send (loop, ev_async *)	3475	=item ev_async_send (loop, ev_async *)
2660		3476
2661	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3477	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2662	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3478	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3479	returns.
		3480
2663	C<ev_feed_event>, this call is safe to do from other threads, signal or	3481	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2664	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3482	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2665	section below on what exactly this means).	3483	embedding section below on what exactly this means).
2666		3484
2667	This call incurs the overhead of a system call only once per loop iteration,	3485	Note that, as with other watchers in libev, multiple events might get
2668	so while the overhead might be noticeable, it doesn't apply to repeated	3486	compressed into a single callback invocation (another way to look at
2669	calls to C<ev_async_send>.	3487	this is that C<ev_async> watchers are level-triggered: they are set on
		3488	C<ev_async_send>, reset when the event loop detects that).
		3489
		3490	This call incurs the overhead of at most one extra system call per event
		3491	loop iteration, if the event loop is blocked, and no syscall at all if
		3492	the event loop (or your program) is processing events. That means that
		3493	repeated calls are basically free (there is no need to avoid calls for
		3494	performance reasons) and that the overhead becomes smaller (typically
		3495	zero) under load.
2670		3496
2671	=item bool = ev_async_pending (ev_async *)	3497	=item bool = ev_async_pending (ev_async *)
2672		3498
2673	Returns a non-zero value when C<ev_async_send> has been called on the	3499	Returns a non-zero value when C<ev_async_send> has been called on the
2674	watcher but the event has not yet been processed (or even noted) by the	3500	watcher but the event has not yet been processed (or even noted) by the
…		…
2677	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3503	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2678	the loop iterates next and checks for the watcher to have become active,	3504	the loop iterates next and checks for the watcher to have become active,
2679	it will reset the flag again. C<ev_async_pending> can be used to very	3505	it will reset the flag again. C<ev_async_pending> can be used to very
2680	quickly check whether invoking the loop might be a good idea.	3506	quickly check whether invoking the loop might be a good idea.
2681		3507
2682	Not that this does I<not> check whether the watcher itself is pending, only	3508	Not that this does I<not> check whether the watcher itself is pending,
2683	whether it has been requested to make this watcher pending.	3509	only whether it has been requested to make this watcher pending: there
		3510	is a time window between the event loop checking and resetting the async
		3511	notification, and the callback being invoked.
2684		3512
2685	=back	3513	=back
2686		3514
2687		3515
2688	=head1 OTHER FUNCTIONS	3516	=head1 OTHER FUNCTIONS
…		…
2705		3533
2706	If C<timeout> is less than 0, then no timeout watcher will be	3534	If C<timeout> is less than 0, then no timeout watcher will be
2707	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3535	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2708	repeat = 0) will be started. C<0> is a valid timeout.	3536	repeat = 0) will be started. C<0> is a valid timeout.
2709		3537
2710	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3538	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2711	passed an C<revents> set like normal event callbacks (a combination of	3539	passed an C<revents> set like normal event callbacks (a combination of
2712	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3540	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2713	value passed to C<ev_once>. Note that it is possible to receive I<both>	3541	value passed to C<ev_once>. Note that it is possible to receive I<both>
2714	a timeout and an io event at the same time - you probably should give io	3542	a timeout and an io event at the same time - you probably should give io
2715	events precedence.	3543	events precedence.
2716		3544
2717	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3545	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2718		3546
2719	static void stdin_ready (int revents, void *arg)	3547	static void stdin_ready (int revents, void *arg)
2720	{	3548	{
2721	if (revents & EV_READ)	3549	if (revents & EV_READ)
2722	/* stdin might have data for us, joy! */;	3550	/* stdin might have data for us, joy! */;
2723	else if (revents & EV_TIMEOUT)	3551	else if (revents & EV_TIMER)
2724	/* doh, nothing entered */;	3552	/* doh, nothing entered */;
2725	}	3553	}
2726		3554
2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3555	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2728		3556
2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2730
2731	Feeds the given event set into the event loop, as if the specified event
2732	had happened for the specified watcher (which must be a pointer to an
2733	initialised but not necessarily started event watcher).
2734
2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3557	=item ev_feed_fd_event (loop, int fd, int revents)
2736		3558
2737	Feed an event on the given fd, as if a file descriptor backend detected	3559	Feed an event on the given fd, as if a file descriptor backend detected
2738	the given events it.	3560	the given events.
2739		3561
2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3562	=item ev_feed_signal_event (loop, int signum)
2741		3563
2742	Feed an event as if the given signal occurred (C<loop> must be the default	3564	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2743	loop!).	3565	which is async-safe.
2744		3566
2745	=back	3567	=back
		3568
		3569
		3570	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3571
		3572	This section explains some common idioms that are not immediately
		3573	obvious. Note that examples are sprinkled over the whole manual, and this
		3574	section only contains stuff that wouldn't fit anywhere else.
		3575
		3576	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3577
		3578	Each watcher has, by default, a C<void *data> member that you can read
		3579	or modify at any time: libev will completely ignore it. This can be used
		3580	to associate arbitrary data with your watcher. If you need more data and
		3581	don't want to allocate memory separately and store a pointer to it in that
		3582	data member, you can also "subclass" the watcher type and provide your own
		3583	data:
		3584
		3585	struct my_io
		3586	{
		3587	ev_io io;
		3588	int otherfd;
		3589	void *somedata;
		3590	struct whatever *mostinteresting;
		3591	};
		3592
		3593	...
		3594	struct my_io w;
		3595	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3596
		3597	And since your callback will be called with a pointer to the watcher, you
		3598	can cast it back to your own type:
		3599
		3600	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3601	{
		3602	struct my_io *w = (struct my_io *)w_;
		3603	...
		3604	}
		3605
		3606	More interesting and less C-conformant ways of casting your callback
		3607	function type instead have been omitted.
		3608
		3609	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3610
		3611	Another common scenario is to use some data structure with multiple
		3612	embedded watchers, in effect creating your own watcher that combines
		3613	multiple libev event sources into one "super-watcher":
		3614
		3615	struct my_biggy
		3616	{
		3617	int some_data;
		3618	ev_timer t1;
		3619	ev_timer t2;
		3620	}
		3621
		3622	In this case getting the pointer to C<my_biggy> is a bit more
		3623	complicated: Either you store the address of your C<my_biggy> struct in
		3624	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3625	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3626	real programmers):
		3627
		3628	#include <stddef.h>
		3629
		3630	static void
		3631	t1_cb (EV_P_ ev_timer *w, int revents)
		3632	{
		3633	struct my_biggy big = (struct my_biggy *)
		3634	(((char *)w) - offsetof (struct my_biggy, t1));
		3635	}
		3636
		3637	static void
		3638	t2_cb (EV_P_ ev_timer *w, int revents)
		3639	{
		3640	struct my_biggy big = (struct my_biggy *)
		3641	(((char *)w) - offsetof (struct my_biggy, t2));
		3642	}
		3643
		3644	=head2 AVOIDING FINISHING BEFORE RETURNING
		3645
		3646	Often you have structures like this in event-based programs:
		3647
		3648	callback ()
		3649	{
		3650	free (request);
		3651	}
		3652
		3653	request = start_new_request (..., callback);
		3654
		3655	The intent is to start some "lengthy" operation. The C<request> could be
		3656	used to cancel the operation, or do other things with it.
		3657
		3658	It's not uncommon to have code paths in C<start_new_request> that
		3659	immediately invoke the callback, for example, to report errors. Or you add
		3660	some caching layer that finds that it can skip the lengthy aspects of the
		3661	operation and simply invoke the callback with the result.
		3662
		3663	The problem here is that this will happen I<before> C<start_new_request>
		3664	has returned, so C<request> is not set.
		3665
		3666	Even if you pass the request by some safer means to the callback, you
		3667	might want to do something to the request after starting it, such as
		3668	canceling it, which probably isn't working so well when the callback has
		3669	already been invoked.
		3670
		3671	A common way around all these issues is to make sure that
		3672	C<start_new_request> I<always> returns before the callback is invoked. If
		3673	C<start_new_request> immediately knows the result, it can artificially
		3674	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3675	example, or more sneakily, by reusing an existing (stopped) watcher and
		3676	pushing it into the pending queue:
		3677
		3678	ev_set_cb (watcher, callback);
		3679	ev_feed_event (EV_A_ watcher, 0);
		3680
		3681	This way, C<start_new_request> can safely return before the callback is
		3682	invoked, while not delaying callback invocation too much.
		3683
		3684	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3685
		3686	Often (especially in GUI toolkits) there are places where you have
		3687	I<modal> interaction, which is most easily implemented by recursively
		3688	invoking C<ev_run>.
		3689
		3690	This brings the problem of exiting - a callback might want to finish the
		3691	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3692	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3693	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3694	other combination: In these cases, a simple C<ev_break> will not work.
		3695
		3696	The solution is to maintain "break this loop" variable for each C<ev_run>
		3697	invocation, and use a loop around C<ev_run> until the condition is
		3698	triggered, using C<EVRUN_ONCE>:
		3699
		3700	// main loop
		3701	int exit_main_loop = 0;
		3702
		3703	while (!exit_main_loop)
		3704	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3705
		3706	// in a modal watcher
		3707	int exit_nested_loop = 0;
		3708
		3709	while (!exit_nested_loop)
		3710	ev_run (EV_A_ EVRUN_ONCE);
		3711
		3712	To exit from any of these loops, just set the corresponding exit variable:
		3713
		3714	// exit modal loop
		3715	exit_nested_loop = 1;
		3716
		3717	// exit main program, after modal loop is finished
		3718	exit_main_loop = 1;
		3719
		3720	// exit both
		3721	exit_main_loop = exit_nested_loop = 1;
		3722
		3723	=head2 THREAD LOCKING EXAMPLE
		3724
		3725	Here is a fictitious example of how to run an event loop in a different
		3726	thread from where callbacks are being invoked and watchers are
		3727	created/added/removed.
		3728
		3729	For a real-world example, see the C<EV::Loop::Async> perl module,
		3730	which uses exactly this technique (which is suited for many high-level
		3731	languages).
		3732
		3733	The example uses a pthread mutex to protect the loop data, a condition
		3734	variable to wait for callback invocations, an async watcher to notify the
		3735	event loop thread and an unspecified mechanism to wake up the main thread.
		3736
		3737	First, you need to associate some data with the event loop:
		3738
		3739	typedef struct {
		3740	mutex_t lock; /* global loop lock */
		3741	ev_async async_w;
		3742	thread_t tid;
		3743	cond_t invoke_cv;
		3744	} userdata;
		3745
		3746	void prepare_loop (EV_P)
		3747	{
		3748	// for simplicity, we use a static userdata struct.
		3749	static userdata u;
		3750
		3751	ev_async_init (&u->async_w, async_cb);
		3752	ev_async_start (EV_A_ &u->async_w);
		3753
		3754	pthread_mutex_init (&u->lock, 0);
		3755	pthread_cond_init (&u->invoke_cv, 0);
		3756
		3757	// now associate this with the loop
		3758	ev_set_userdata (EV_A_ u);
		3759	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3760	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3761
		3762	// then create the thread running ev_run
		3763	pthread_create (&u->tid, 0, l_run, EV_A);
		3764	}
		3765
		3766	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3767	solely to wake up the event loop so it takes notice of any new watchers
		3768	that might have been added:
		3769
		3770	static void
		3771	async_cb (EV_P_ ev_async *w, int revents)
		3772	{
		3773	// just used for the side effects
		3774	}
		3775
		3776	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3777	protecting the loop data, respectively.
		3778
		3779	static void
		3780	l_release (EV_P)
		3781	{
		3782	userdata *u = ev_userdata (EV_A);
		3783	pthread_mutex_unlock (&u->lock);
		3784	}
		3785
		3786	static void
		3787	l_acquire (EV_P)
		3788	{
		3789	userdata *u = ev_userdata (EV_A);
		3790	pthread_mutex_lock (&u->lock);
		3791	}
		3792
		3793	The event loop thread first acquires the mutex, and then jumps straight
		3794	into C<ev_run>:
		3795
		3796	void *
		3797	l_run (void *thr_arg)
		3798	{
		3799	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3800
		3801	l_acquire (EV_A);
		3802	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3803	ev_run (EV_A_ 0);
		3804	l_release (EV_A);
		3805
		3806	return 0;
		3807	}
		3808
		3809	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3810	signal the main thread via some unspecified mechanism (signals? pipe
		3811	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3812	have been called (in a while loop because a) spurious wakeups are possible
		3813	and b) skipping inter-thread-communication when there are no pending
		3814	watchers is very beneficial):
		3815
		3816	static void
		3817	l_invoke (EV_P)
		3818	{
		3819	userdata *u = ev_userdata (EV_A);
		3820
		3821	while (ev_pending_count (EV_A))
		3822	{
		3823	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3824	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3825	}
		3826	}
		3827
		3828	Now, whenever the main thread gets told to invoke pending watchers, it
		3829	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3830	thread to continue:
		3831
		3832	static void
		3833	real_invoke_pending (EV_P)
		3834	{
		3835	userdata *u = ev_userdata (EV_A);
		3836
		3837	pthread_mutex_lock (&u->lock);
		3838	ev_invoke_pending (EV_A);
		3839	pthread_cond_signal (&u->invoke_cv);
		3840	pthread_mutex_unlock (&u->lock);
		3841	}
		3842
		3843	Whenever you want to start/stop a watcher or do other modifications to an
		3844	event loop, you will now have to lock:
		3845
		3846	ev_timer timeout_watcher;
		3847	userdata *u = ev_userdata (EV_A);
		3848
		3849	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3850
		3851	pthread_mutex_lock (&u->lock);
		3852	ev_timer_start (EV_A_ &timeout_watcher);
		3853	ev_async_send (EV_A_ &u->async_w);
		3854	pthread_mutex_unlock (&u->lock);
		3855
		3856	Note that sending the C<ev_async> watcher is required because otherwise
		3857	an event loop currently blocking in the kernel will have no knowledge
		3858	about the newly added timer. By waking up the loop it will pick up any new
		3859	watchers in the next event loop iteration.
		3860
		3861	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3862
		3863	While the overhead of a callback that e.g. schedules a thread is small, it
		3864	is still an overhead. If you embed libev, and your main usage is with some
		3865	kind of threads or coroutines, you might want to customise libev so that
		3866	doesn't need callbacks anymore.
		3867
		3868	Imagine you have coroutines that you can switch to using a function
		3869	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3870	and that due to some magic, the currently active coroutine is stored in a
		3871	global called C<current_coro>. Then you can build your own "wait for libev
		3872	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3873	the differing C<;> conventions):
		3874
		3875	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3876	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3877
		3878	That means instead of having a C callback function, you store the
		3879	coroutine to switch to in each watcher, and instead of having libev call
		3880	your callback, you instead have it switch to that coroutine.
		3881
		3882	A coroutine might now wait for an event with a function called
		3883	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3884	matter when, or whether the watcher is active or not when this function is
		3885	called):
		3886
		3887	void
		3888	wait_for_event (ev_watcher *w)
		3889	{
		3890	ev_set_cb (w, current_coro);
		3891	switch_to (libev_coro);
		3892	}
		3893
		3894	That basically suspends the coroutine inside C<wait_for_event> and
		3895	continues the libev coroutine, which, when appropriate, switches back to
		3896	this or any other coroutine.
		3897
		3898	You can do similar tricks if you have, say, threads with an event queue -
		3899	instead of storing a coroutine, you store the queue object and instead of
		3900	switching to a coroutine, you push the watcher onto the queue and notify
		3901	any waiters.
		3902
		3903	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3904	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3905
		3906	// my_ev.h
		3907	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3908	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3909	#include "../libev/ev.h"
		3910
		3911	// my_ev.c
		3912	#define EV_H "my_ev.h"
		3913	#include "../libev/ev.c"
		3914
		3915	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3916	F<my_ev.c> into your project. When properly specifying include paths, you
		3917	can even use F<ev.h> as header file name directly.
2746		3918
2747		3919
2748	=head1 LIBEVENT EMULATION	3920	=head1 LIBEVENT EMULATION
2749		3921
2750	Libev offers a compatibility emulation layer for libevent. It cannot	3922	Libev offers a compatibility emulation layer for libevent. It cannot
2751	emulate the internals of libevent, so here are some usage hints:	3923	emulate the internals of libevent, so here are some usage hints:
2752		3924
2753	=over 4	3925	=over 4
		3926
		3927	=item * Only the libevent-1.4.1-beta API is being emulated.
		3928
		3929	This was the newest libevent version available when libev was implemented,
		3930	and is still mostly unchanged in 2010.
2754		3931
2755	=item * Use it by including <event.h>, as usual.	3932	=item * Use it by including <event.h>, as usual.
2756		3933
2757	=item * The following members are fully supported: ev_base, ev_callback,	3934	=item * The following members are fully supported: ev_base, ev_callback,
2758	ev_arg, ev_fd, ev_res, ev_events.	3935	ev_arg, ev_fd, ev_res, ev_events.
…		…
2764	=item * Priorities are not currently supported. Initialising priorities	3941	=item * Priorities are not currently supported. Initialising priorities
2765	will fail and all watchers will have the same priority, even though there	3942	will fail and all watchers will have the same priority, even though there
2766	is an ev_pri field.	3943	is an ev_pri field.
2767		3944
2768	=item * In libevent, the last base created gets the signals, in libev, the	3945	=item * In libevent, the last base created gets the signals, in libev, the
2769	first base created (== the default loop) gets the signals.	3946	base that registered the signal gets the signals.
2770		3947
2771	=item * Other members are not supported.	3948	=item * Other members are not supported.
2772		3949
2773	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3950	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2774	to use the libev header file and library.	3951	to use the libev header file and library.
2775		3952
2776	=back	3953	=back
2777		3954
2778	=head1 C++ SUPPORT	3955	=head1 C++ SUPPORT
		3956
		3957	=head2 C API
		3958
		3959	The normal C API should work fine when used from C++: both ev.h and the
		3960	libev sources can be compiled as C++. Therefore, code that uses the C API
		3961	will work fine.
		3962
		3963	Proper exception specifications might have to be added to callbacks passed
		3964	to libev: exceptions may be thrown only from watcher callbacks, all
		3965	other callbacks (allocator, syserr, loop acquire/release and periodic
		3966	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3967	()> specification. If you have code that needs to be compiled as both C
		3968	and C++ you can use the C<EV_THROW> macro for this:
		3969
		3970	static void
		3971	fatal_error (const char *msg) EV_THROW
		3972	{
		3973	perror (msg);
		3974	abort ();
		3975	}
		3976
		3977	...
		3978	ev_set_syserr_cb (fatal_error);
		3979
		3980	The only API functions that can currently throw exceptions are C<ev_run>,
		3981	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3982	because it runs cleanup watchers).
		3983
		3984	Throwing exceptions in watcher callbacks is only supported if libev itself
		3985	is compiled with a C++ compiler or your C and C++ environments allow
		3986	throwing exceptions through C libraries (most do).
		3987
		3988	=head2 C++ API
2779		3989
2780	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3990	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2781	you to use some convenience methods to start/stop watchers and also change	3991	you to use some convenience methods to start/stop watchers and also change
2782	the callback model to a model using method callbacks on objects.	3992	the callback model to a model using method callbacks on objects.
2783		3993
2784	To use it,	3994	To use it,
2785		3995
2786	#include <ev++.h>	3996	#include <ev++.h>
2787		3997
2788	This automatically includes F<ev.h> and puts all of its definitions (many	3998	This automatically includes F<ev.h> and puts all of its definitions (many
2789	of them macros) into the global namespace. All C++ specific things are	3999	of them macros) into the global namespace. All C++ specific things are
2790	put into the C<ev> namespace. It should support all the same embedding	4000	put into the C<ev> namespace. It should support all the same embedding
…		…
2793	Care has been taken to keep the overhead low. The only data member the C++	4003	Care has been taken to keep the overhead low. The only data member the C++
2794	classes add (compared to plain C-style watchers) is the event loop pointer	4004	classes add (compared to plain C-style watchers) is the event loop pointer
2795	that the watcher is associated with (or no additional members at all if	4005	that the watcher is associated with (or no additional members at all if
2796	you disable C<EV_MULTIPLICITY> when embedding libev).	4006	you disable C<EV_MULTIPLICITY> when embedding libev).
2797		4007
2798	Currently, functions, and static and non-static member functions can be	4008	Currently, functions, static and non-static member functions and classes
2799	used as callbacks. Other types should be easy to add as long as they only	4009	with C<operator ()> can be used as callbacks. Other types should be easy
2800	need one additional pointer for context. If you need support for other	4010	to add as long as they only need one additional pointer for context. If
2801	types of functors please contact the author (preferably after implementing	4011	you need support for other types of functors please contact the author
2802	it).	4012	(preferably after implementing it).
		4013
		4014	For all this to work, your C++ compiler either has to use the same calling
		4015	conventions as your C compiler (for static member functions), or you have
		4016	to embed libev and compile libev itself as C++.
2803		4017
2804	Here is a list of things available in the C<ev> namespace:	4018	Here is a list of things available in the C<ev> namespace:
2805		4019
2806	=over 4	4020	=over 4
2807		4021
…		…
2817	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4031	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2818		4032
2819	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4033	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2820	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4034	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2821	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4035	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2822	defines by many implementations.	4036	defined by many implementations.
2823		4037
2824	All of those classes have these methods:	4038	All of those classes have these methods:
2825		4039
2826	=over 4	4040	=over 4
2827		4041
2828	=item ev::TYPE::TYPE ()	4042	=item ev::TYPE::TYPE ()
2829		4043
2830	=item ev::TYPE::TYPE (struct ev_loop *)	4044	=item ev::TYPE::TYPE (loop)
2831		4045
2832	=item ev::TYPE::~TYPE	4046	=item ev::TYPE::~TYPE
2833		4047
2834	The constructor (optionally) takes an event loop to associate the watcher	4048	The constructor (optionally) takes an event loop to associate the watcher
2835	with. If it is omitted, it will use C<EV_DEFAULT>.	4049	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2867		4081
2868	myclass obj;	4082	myclass obj;
2869	ev::io iow;	4083	ev::io iow;
2870	iow.set <myclass, &myclass::io_cb> (&obj);	4084	iow.set <myclass, &myclass::io_cb> (&obj);
2871		4085
		4086	=item w->set (object *)
		4087
		4088	This is a variation of a method callback - leaving out the method to call
		4089	will default the method to C<operator ()>, which makes it possible to use
		4090	functor objects without having to manually specify the C<operator ()> all
		4091	the time. Incidentally, you can then also leave out the template argument
		4092	list.
		4093
		4094	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4095	int revents)>.
		4096
		4097	See the method-C<set> above for more details.
		4098
		4099	Example: use a functor object as callback.
		4100
		4101	struct myfunctor
		4102	{
		4103	void operator() (ev::io &w, int revents)
		4104	{
		4105	...
		4106	}
		4107	}
		4108
		4109	myfunctor f;
		4110
		4111	ev::io w;
		4112	w.set (&f);
		4113
2872	=item w->set<function> (void *data = 0)	4114	=item w->set<function> (void *data = 0)
2873		4115
2874	Also sets a callback, but uses a static method or plain function as	4116	Also sets a callback, but uses a static method or plain function as
2875	callback. The optional C<data> argument will be stored in the watcher's	4117	callback. The optional C<data> argument will be stored in the watcher's
2876	C<data> member and is free for you to use.	4118	C<data> member and is free for you to use.
…		…
2882	Example: Use a plain function as callback.	4124	Example: Use a plain function as callback.
2883		4125
2884	static void io_cb (ev::io &w, int revents) { }	4126	static void io_cb (ev::io &w, int revents) { }
2885	iow.set <io_cb> ();	4127	iow.set <io_cb> ();
2886		4128
2887	=item w->set (struct ev_loop *)	4129	=item w->set (loop)
2888		4130
2889	Associates a different C<struct ev_loop> with this watcher. You can only	4131	Associates a different C<struct ev_loop> with this watcher. You can only
2890	do this when the watcher is inactive (and not pending either).	4132	do this when the watcher is inactive (and not pending either).
2891		4133
2892	=item w->set ([arguments])	4134	=item w->set ([arguments])
2893		4135
2894	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4136	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4137	with the same arguments. Either this method or a suitable start method
2895	called at least once. Unlike the C counterpart, an active watcher gets	4138	must be called at least once. Unlike the C counterpart, an active watcher
2896	automatically stopped and restarted when reconfiguring it with this	4139	gets automatically stopped and restarted when reconfiguring it with this
2897	method.	4140	method.
		4141
		4142	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4143	clashing with the C<set (loop)> method.
2898		4144
2899	=item w->start ()	4145	=item w->start ()
2900		4146
2901	Starts the watcher. Note that there is no C<loop> argument, as the	4147	Starts the watcher. Note that there is no C<loop> argument, as the
2902	constructor already stores the event loop.	4148	constructor already stores the event loop.
2903		4149
		4150	=item w->start ([arguments])
		4151
		4152	Instead of calling C<set> and C<start> methods separately, it is often
		4153	convenient to wrap them in one call. Uses the same type of arguments as
		4154	the configure C<set> method of the watcher.
		4155
2904	=item w->stop ()	4156	=item w->stop ()
2905		4157
2906	Stops the watcher if it is active. Again, no C<loop> argument.	4158	Stops the watcher if it is active. Again, no C<loop> argument.
2907		4159
2908	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4160	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2920		4172
2921	=back	4173	=back
2922		4174
2923	=back	4175	=back
2924		4176
2925	Example: Define a class with an IO and idle watcher, start one of them in	4177	Example: Define a class with two I/O and idle watchers, start the I/O
2926	the constructor.	4178	watchers in the constructor.
2927		4179
2928	class myclass	4180	class myclass
2929	{	4181	{
2930	ev::io io ; void io_cb (ev::io &w, int revents);	4182	ev::io io ; void io_cb (ev::io &w, int revents);
		4183	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2932		4185
2933	myclass (int fd)	4186	myclass (int fd)
2934	{	4187	{
2935	io .set <myclass, &myclass::io_cb > (this);	4188	io .set <myclass, &myclass::io_cb > (this);
		4189	io2 .set <myclass, &myclass::io2_cb > (this);
2936	idle.set <myclass, &myclass::idle_cb> (this);	4190	idle.set <myclass, &myclass::idle_cb> (this);
2937		4191
2938	io.start (fd, ev::READ);	4192	io.set (fd, ev::WRITE); // configure the watcher
		4193	io.start (); // start it whenever convenient
		4194
		4195	io2.start (fd, ev::READ); // set + start in one call
2939	}	4196	}
2940	};	4197	};
2941		4198
2942		4199
2943	=head1 OTHER LANGUAGE BINDINGS	4200	=head1 OTHER LANGUAGE BINDINGS
…		…
2962	L<http://software.schmorp.de/pkg/EV>.	4219	L<http://software.schmorp.de/pkg/EV>.
2963		4220
2964	=item Python	4221	=item Python
2965		4222
2966	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4223	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2967	seems to be quite complete and well-documented. Note, however, that the	4224	seems to be quite complete and well-documented.
2968	patch they require for libev is outright dangerous as it breaks the ABI
2969	for everybody else, and therefore, should never be applied in an installed
2970	libev (if python requires an incompatible ABI then it needs to embed
2971	libev).
2972		4225
2973	=item Ruby	4226	=item Ruby
2974		4227
2975	Tony Arcieri has written a ruby extension that offers access to a subset	4228	Tony Arcieri has written a ruby extension that offers access to a subset
2976	of the libev API and adds file handle abstractions, asynchronous DNS and	4229	of the libev API and adds file handle abstractions, asynchronous DNS and
2977	more on top of it. It can be found via gem servers. Its homepage is at	4230	more on top of it. It can be found via gem servers. Its homepage is at
2978	L<http://rev.rubyforge.org/>.	4231	L<http://rev.rubyforge.org/>.
2979		4232
		4233	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4234	makes rev work even on mingw.
		4235
		4236	=item Haskell
		4237
		4238	A haskell binding to libev is available at
		4239	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4240
2980	=item D	4241	=item D
2981		4242
2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4243	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4244	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
2984		4245
2985	=item Ocaml	4246	=item Ocaml
2986		4247
2987	Erkki Seppala has written Ocaml bindings for libev, to be found at	4248	Erkki Seppala has written Ocaml bindings for libev, to be found at
2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4249	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4250
		4251	=item Lua
		4252
		4253	Brian Maher has written a partial interface to libev for lua (at the
		4254	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4255	L<http://github.com/brimworks/lua-ev>.
		4256
		4257	=item Javascript
		4258
		4259	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4260
		4261	=item Others
		4262
		4263	There are others, and I stopped counting.
2989		4264
2990	=back	4265	=back
2991		4266
2992		4267
2993	=head1 MACRO MAGIC	4268	=head1 MACRO MAGIC
…		…
3007	loop argument"). The C<EV_A> form is used when this is the sole argument,	4282	loop argument"). The C<EV_A> form is used when this is the sole argument,
3008	C<EV_A_> is used when other arguments are following. Example:	4283	C<EV_A_> is used when other arguments are following. Example:
3009		4284
3010	ev_unref (EV_A);	4285	ev_unref (EV_A);
3011	ev_timer_add (EV_A_ watcher);	4286	ev_timer_add (EV_A_ watcher);
3012	ev_loop (EV_A_ 0);	4287	ev_run (EV_A_ 0);
3013		4288
3014	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4289	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3015	which is often provided by the following macro.	4290	which is often provided by the following macro.
3016		4291
3017	=item C<EV_P>, C<EV_P_>	4292	=item C<EV_P>, C<EV_P_>
…		…
3030	suitable for use with C<EV_A>.	4305	suitable for use with C<EV_A>.
3031		4306
3032	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4307	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3033		4308
3034	Similar to the other two macros, this gives you the value of the default	4309	Similar to the other two macros, this gives you the value of the default
3035	loop, if multiple loops are supported ("ev loop default").	4310	loop, if multiple loops are supported ("ev loop default"). The default loop
		4311	will be initialised if it isn't already initialised.
		4312
		4313	For non-multiplicity builds, these macros do nothing, so you always have
		4314	to initialise the loop somewhere.
3036		4315
3037	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4316	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3038		4317
3039	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4318	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3040	default loop has been initialised (C<UC> == unchecked). Their behaviour	4319	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3057	}	4336	}
3058		4337
3059	ev_check check;	4338	ev_check check;
3060	ev_check_init (&check, check_cb);	4339	ev_check_init (&check, check_cb);
3061	ev_check_start (EV_DEFAULT_ &check);	4340	ev_check_start (EV_DEFAULT_ &check);
3062	ev_loop (EV_DEFAULT_ 0);	4341	ev_run (EV_DEFAULT_ 0);
3063		4342
3064	=head1 EMBEDDING	4343	=head1 EMBEDDING
3065		4344
3066	Libev can (and often is) directly embedded into host	4345	Libev can (and often is) directly embedded into host
3067	applications. Examples of applications that embed it include the Deliantra	4346	applications. Examples of applications that embed it include the Deliantra
…		…
3147	libev.m4	4426	libev.m4
3148		4427
3149	=head2 PREPROCESSOR SYMBOLS/MACROS	4428	=head2 PREPROCESSOR SYMBOLS/MACROS
3150		4429
3151	Libev can be configured via a variety of preprocessor symbols you have to	4430	Libev can be configured via a variety of preprocessor symbols you have to
3152	define before including any of its files. The default in the absence of	4431	define before including (or compiling) any of its files. The default in
3153	autoconf is documented for every option.	4432	the absence of autoconf is documented for every option.
		4433
		4434	Symbols marked with "(h)" do not change the ABI, and can have different
		4435	values when compiling libev vs. including F<ev.h>, so it is permissible
		4436	to redefine them before including F<ev.h> without breaking compatibility
		4437	to a compiled library. All other symbols change the ABI, which means all
		4438	users of libev and the libev code itself must be compiled with compatible
		4439	settings.
3154		4440
3155	=over 4	4441	=over 4
3156		4442
		4443	=item EV_COMPAT3 (h)
		4444
		4445	Backwards compatibility is a major concern for libev. This is why this
		4446	release of libev comes with wrappers for the functions and symbols that
		4447	have been renamed between libev version 3 and 4.
		4448
		4449	You can disable these wrappers (to test compatibility with future
		4450	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4451	sources. This has the additional advantage that you can drop the C<struct>
		4452	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4453	typedef in that case.
		4454
		4455	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4456	and in some even more future version the compatibility code will be
		4457	removed completely.
		4458
3157	=item EV_STANDALONE	4459	=item EV_STANDALONE (h)
3158		4460
3159	Must always be C<1> if you do not use autoconf configuration, which	4461	Must always be C<1> if you do not use autoconf configuration, which
3160	keeps libev from including F<config.h>, and it also defines dummy	4462	keeps libev from including F<config.h>, and it also defines dummy
3161	implementations for some libevent functions (such as logging, which is not	4463	implementations for some libevent functions (such as logging, which is not
3162	supported). It will also not define any of the structs usually found in	4464	supported). It will also not define any of the structs usually found in
3163	F<event.h> that are not directly supported by the libev core alone.	4465	F<event.h> that are not directly supported by the libev core alone.
3164		4466
		4467	In standalone mode, libev will still try to automatically deduce the
		4468	configuration, but has to be more conservative.
		4469
		4470	=item EV_USE_FLOOR
		4471
		4472	If defined to be C<1>, libev will use the C<floor ()> function for its
		4473	periodic reschedule calculations, otherwise libev will fall back on a
		4474	portable (slower) implementation. If you enable this, you usually have to
		4475	link against libm or something equivalent. Enabling this when the C<floor>
		4476	function is not available will fail, so the safe default is to not enable
		4477	this.
		4478
3165	=item EV_USE_MONOTONIC	4479	=item EV_USE_MONOTONIC
3166		4480
3167	If defined to be C<1>, libev will try to detect the availability of the	4481	If defined to be C<1>, libev will try to detect the availability of the
3168	monotonic clock option at both compile time and runtime. Otherwise no use	4482	monotonic clock option at both compile time and runtime. Otherwise no
3169	of the monotonic clock option will be attempted. If you enable this, you	4483	use of the monotonic clock option will be attempted. If you enable this,
3170	usually have to link against librt or something similar. Enabling it when	4484	you usually have to link against librt or something similar. Enabling it
3171	the functionality isn't available is safe, though, although you have	4485	when the functionality isn't available is safe, though, although you have
3172	to make sure you link against any libraries where the C<clock_gettime>	4486	to make sure you link against any libraries where the C<clock_gettime>
3173	function is hiding in (often F<-lrt>).	4487	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3174		4488
3175	=item EV_USE_REALTIME	4489	=item EV_USE_REALTIME
3176		4490
3177	If defined to be C<1>, libev will try to detect the availability of the	4491	If defined to be C<1>, libev will try to detect the availability of the
3178	real-time clock option at compile time (and assume its availability at	4492	real-time clock option at compile time (and assume its availability
3179	runtime if successful). Otherwise no use of the real-time clock option will	4493	at runtime if successful). Otherwise no use of the real-time clock
3180	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4494	option will be attempted. This effectively replaces C<gettimeofday>
3181	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4495	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3182	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4496	correctness. See the note about libraries in the description of
		4497	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4498	C<EV_USE_CLOCK_SYSCALL>.
		4499
		4500	=item EV_USE_CLOCK_SYSCALL
		4501
		4502	If defined to be C<1>, libev will try to use a direct syscall instead
		4503	of calling the system-provided C<clock_gettime> function. This option
		4504	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4505	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4506	programs needlessly. Using a direct syscall is slightly slower (in
		4507	theory), because no optimised vdso implementation can be used, but avoids
		4508	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4509	higher, as it simplifies linking (no need for C<-lrt>).
3183		4510
3184	=item EV_USE_NANOSLEEP	4511	=item EV_USE_NANOSLEEP
3185		4512
3186	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4513	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3187	and will use it for delays. Otherwise it will use C<select ()>.	4514	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3203		4530
3204	=item EV_SELECT_USE_FD_SET	4531	=item EV_SELECT_USE_FD_SET
3205		4532
3206	If defined to C<1>, then the select backend will use the system C<fd_set>	4533	If defined to C<1>, then the select backend will use the system C<fd_set>
3207	structure. This is useful if libev doesn't compile due to a missing	4534	structure. This is useful if libev doesn't compile due to a missing
3208	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4535	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3209	exotic systems. This usually limits the range of file descriptors to some	4536	on exotic systems. This usually limits the range of file descriptors to
3210	low limit such as 1024 or might have other limitations (winsocket only	4537	some low limit such as 1024 or might have other limitations (winsocket
3211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4538	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3212	influence the size of the C<fd_set> used.	4539	configures the maximum size of the C<fd_set>.
3213		4540
3214	=item EV_SELECT_IS_WINSOCKET	4541	=item EV_SELECT_IS_WINSOCKET
3215		4542
3216	When defined to C<1>, the select backend will assume that	4543	When defined to C<1>, the select backend will assume that
3217	select/socket/connect etc. don't understand file descriptors but	4544	select/socket/connect etc. don't understand file descriptors but
…		…
3219	be used is the winsock select). This means that it will call	4546	be used is the winsock select). This means that it will call
3220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4547	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3221	it is assumed that all these functions actually work on fds, even	4548	it is assumed that all these functions actually work on fds, even
3222	on win32. Should not be defined on non-win32 platforms.	4549	on win32. Should not be defined on non-win32 platforms.
3223		4550
3224	=item EV_FD_TO_WIN32_HANDLE	4551	=item EV_FD_TO_WIN32_HANDLE(fd)
3225		4552
3226	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4553	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3227	file descriptors to socket handles. When not defining this symbol (the	4554	file descriptors to socket handles. When not defining this symbol (the
3228	default), then libev will call C<_get_osfhandle>, which is usually	4555	default), then libev will call C<_get_osfhandle>, which is usually
3229	correct. In some cases, programs use their own file descriptor management,	4556	correct. In some cases, programs use their own file descriptor management,
3230	in which case they can provide this function to map fds to socket handles.	4557	in which case they can provide this function to map fds to socket handles.
		4558
		4559	=item EV_WIN32_HANDLE_TO_FD(handle)
		4560
		4561	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4562	using the standard C<_open_osfhandle> function. For programs implementing
		4563	their own fd to handle mapping, overwriting this function makes it easier
		4564	to do so. This can be done by defining this macro to an appropriate value.
		4565
		4566	=item EV_WIN32_CLOSE_FD(fd)
		4567
		4568	If programs implement their own fd to handle mapping on win32, then this
		4569	macro can be used to override the C<close> function, useful to unregister
		4570	file descriptors again. Note that the replacement function has to close
		4571	the underlying OS handle.
		4572
		4573	=item EV_USE_WSASOCKET
		4574
		4575	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4576	communication socket, which works better in some environments. Otherwise,
		4577	the normal C<socket> function will be used, which works better in other
		4578	environments.
3231		4579
3232	=item EV_USE_POLL	4580	=item EV_USE_POLL
3233		4581
3234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4582	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3235	backend. Otherwise it will be enabled on non-win32 platforms. It	4583	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3271	If defined to be C<1>, libev will compile in support for the Linux inotify	4619	If defined to be C<1>, libev will compile in support for the Linux inotify
3272	interface to speed up C<ev_stat> watchers. Its actual availability will	4620	interface to speed up C<ev_stat> watchers. Its actual availability will
3273	be detected at runtime. If undefined, it will be enabled if the headers	4621	be detected at runtime. If undefined, it will be enabled if the headers
3274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4622	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3275		4623
		4624	=item EV_NO_SMP
		4625
		4626	If defined to be C<1>, libev will assume that memory is always coherent
		4627	between threads, that is, threads can be used, but threads never run on
		4628	different cpus (or different cpu cores). This reduces dependencies
		4629	and makes libev faster.
		4630
		4631	=item EV_NO_THREADS
		4632
		4633	If defined to be C<1>, libev will assume that it will never be called from
		4634	different threads (that includes signal handlers), which is a stronger
		4635	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4636	libev faster.
		4637
3276	=item EV_ATOMIC_T	4638	=item EV_ATOMIC_T
3277		4639
3278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4640	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3279	access is atomic with respect to other threads or signal contexts. No such	4641	access is atomic with respect to other threads or signal contexts. No
3280	type is easily found in the C language, so you can provide your own type	4642	such type is easily found in the C language, so you can provide your own
3281	that you know is safe for your purposes. It is used both for signal handler "locking"	4643	type that you know is safe for your purposes. It is used both for signal
3282	as well as for signal and thread safety in C<ev_async> watchers.	4644	handler "locking" as well as for signal and thread safety in C<ev_async>
		4645	watchers.
3283		4646
3284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4647	In the absence of this define, libev will use C<sig_atomic_t volatile>
3285	(from F<signal.h>), which is usually good enough on most platforms.	4648	(from F<signal.h>), which is usually good enough on most platforms.
3286		4649
3287	=item EV_H	4650	=item EV_H (h)
3288		4651
3289	The name of the F<ev.h> header file used to include it. The default if	4652	The name of the F<ev.h> header file used to include it. The default if
3290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4653	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3291	used to virtually rename the F<ev.h> header file in case of conflicts.	4654	used to virtually rename the F<ev.h> header file in case of conflicts.
3292		4655
3293	=item EV_CONFIG_H	4656	=item EV_CONFIG_H (h)
3294		4657
3295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4658	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4659	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3297	C<EV_H>, above.	4660	C<EV_H>, above.
3298		4661
3299	=item EV_EVENT_H	4662	=item EV_EVENT_H (h)
3300		4663
3301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4664	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3302	of how the F<event.h> header can be found, the default is C<"event.h">.	4665	of how the F<event.h> header can be found, the default is C<"event.h">.
3303		4666
3304	=item EV_PROTOTYPES	4667	=item EV_PROTOTYPES (h)
3305		4668
3306	If defined to be C<0>, then F<ev.h> will not define any function	4669	If defined to be C<0>, then F<ev.h> will not define any function
3307	prototypes, but still define all the structs and other symbols. This is	4670	prototypes, but still define all the structs and other symbols. This is
3308	occasionally useful if you want to provide your own wrapper functions	4671	occasionally useful if you want to provide your own wrapper functions
3309	around libev functions.	4672	around libev functions.
…		…
3314	will have the C<struct ev_loop *> as first argument, and you can create	4677	will have the C<struct ev_loop *> as first argument, and you can create
3315	additional independent event loops. Otherwise there will be no support	4678	additional independent event loops. Otherwise there will be no support
3316	for multiple event loops and there is no first event loop pointer	4679	for multiple event loops and there is no first event loop pointer
3317	argument. Instead, all functions act on the single default loop.	4680	argument. Instead, all functions act on the single default loop.
3318		4681
		4682	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4683	default loop when multiplicity is switched off - you always have to
		4684	initialise the loop manually in this case.
		4685
3319	=item EV_MINPRI	4686	=item EV_MINPRI
3320		4687
3321	=item EV_MAXPRI	4688	=item EV_MAXPRI
3322		4689
3323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4690	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3331	fine.	4698	fine.
3332		4699
3333	If your embedding application does not need any priorities, defining these	4700	If your embedding application does not need any priorities, defining these
3334	both to C<0> will save some memory and CPU.	4701	both to C<0> will save some memory and CPU.
3335		4702
3336	=item EV_PERIODIC_ENABLE	4703	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4704	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4705	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3337		4706
3338	If undefined or defined to be C<1>, then periodic timers are supported. If	4707	If undefined or defined to be C<1> (and the platform supports it), then
3339	defined to be C<0>, then they are not. Disabling them saves a few kB of	4708	the respective watcher type is supported. If defined to be C<0>, then it
3340	code.	4709	is not. Disabling watcher types mainly saves code size.
3341		4710
3342	=item EV_IDLE_ENABLE	4711	=item EV_FEATURES
3343
3344	If undefined or defined to be C<1>, then idle watchers are supported. If
3345	defined to be C<0>, then they are not. Disabling them saves a few kB of
3346	code.
3347
3348	=item EV_EMBED_ENABLE
3349
3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3351	defined to be C<0>, then they are not. Embed watchers rely on most other
3352	watcher types, which therefore must not be disabled.
3353
3354	=item EV_STAT_ENABLE
3355
3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3357	defined to be C<0>, then they are not.
3358
3359	=item EV_FORK_ENABLE
3360
3361	If undefined or defined to be C<1>, then fork watchers are supported. If
3362	defined to be C<0>, then they are not.
3363
3364	=item EV_ASYNC_ENABLE
3365
3366	If undefined or defined to be C<1>, then async watchers are supported. If
3367	defined to be C<0>, then they are not.
3368
3369	=item EV_MINIMAL
3370		4712
3371	If you need to shave off some kilobytes of code at the expense of some	4713	If you need to shave off some kilobytes of code at the expense of some
3372	speed, define this symbol to C<1>. Currently this is used to override some	4714	speed (but with the full API), you can define this symbol to request
3373	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4715	certain subsets of functionality. The default is to enable all features
3374	much smaller 2-heap for timer management over the default 4-heap.	4716	that can be enabled on the platform.
		4717
		4718	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4719	with some broad features you want) and then selectively re-enable
		4720	additional parts you want, for example if you want everything minimal,
		4721	but multiple event loop support, async and child watchers and the poll
		4722	backend, use this:
		4723
		4724	#define EV_FEATURES 0
		4725	#define EV_MULTIPLICITY 1
		4726	#define EV_USE_POLL 1
		4727	#define EV_CHILD_ENABLE 1
		4728	#define EV_ASYNC_ENABLE 1
		4729
		4730	The actual value is a bitset, it can be a combination of the following
		4731	values (by default, all of these are enabled):
		4732
		4733	=over 4
		4734
		4735	=item C<1> - faster/larger code
		4736
		4737	Use larger code to speed up some operations.
		4738
		4739	Currently this is used to override some inlining decisions (enlarging the
		4740	code size by roughly 30% on amd64).
		4741
		4742	When optimising for size, use of compiler flags such as C<-Os> with
		4743	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4744	assertions.
		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
		4748
		4749	=item C<2> - faster/larger data structures
		4750
		4751	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4752	hash table sizes and so on. This will usually further increase code size
		4753	and can additionally have an effect on the size of data structures at
		4754	runtime.
		4755
		4756	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4757	(e.g. gcc with C<-Os>).
		4758
		4759	=item C<4> - full API configuration
		4760
		4761	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4762	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4763
		4764	=item C<8> - full API
		4765
		4766	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4767	details on which parts of the API are still available without this
		4768	feature, and do not complain if this subset changes over time.
		4769
		4770	=item C<16> - enable all optional watcher types
		4771
		4772	Enables all optional watcher types. If you want to selectively enable
		4773	only some watcher types other than I/O and timers (e.g. prepare,
		4774	embed, async, child...) you can enable them manually by defining
		4775	C<EV_watchertype_ENABLE> to C<1> instead.
		4776
		4777	=item C<32> - enable all backends
		4778
		4779	This enables all backends - without this feature, you need to enable at
		4780	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4781
		4782	=item C<64> - enable OS-specific "helper" APIs
		4783
		4784	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4785	default.
		4786
		4787	=back
		4788
		4789	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4790	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4791	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4792	watchers, timers and monotonic clock support.
		4793
		4794	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4795	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4796	your program might be left out as well - a binary starting a timer and an
		4797	I/O watcher then might come out at only 5Kb.
		4798
		4799	=item EV_API_STATIC
		4800
		4801	If this symbol is defined (by default it is not), then all identifiers
		4802	will have static linkage. This means that libev will not export any
		4803	identifiers, and you cannot link against libev anymore. This can be useful
		4804	when you embed libev, only want to use libev functions in a single file,
		4805	and do not want its identifiers to be visible.
		4806
		4807	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4808	wants to use libev.
		4809
		4810	This option only works when libev is compiled with a C compiler, as C++
		4811	doesn't support the required declaration syntax.
		4812
		4813	=item EV_AVOID_STDIO
		4814
		4815	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4816	functions (printf, scanf, perror etc.). This will increase the code size
		4817	somewhat, but if your program doesn't otherwise depend on stdio and your
		4818	libc allows it, this avoids linking in the stdio library which is quite
		4819	big.
		4820
		4821	Note that error messages might become less precise when this option is
		4822	enabled.
		4823
		4824	=item EV_NSIG
		4825
		4826	The highest supported signal number, +1 (or, the number of
		4827	signals): Normally, libev tries to deduce the maximum number of signals
		4828	automatically, but sometimes this fails, in which case it can be
		4829	specified. Also, using a lower number than detected (C<32> should be
		4830	good for about any system in existence) can save some memory, as libev
		4831	statically allocates some 12-24 bytes per signal number.
3375		4832
3376	=item EV_PID_HASHSIZE	4833	=item EV_PID_HASHSIZE
3377		4834
3378	C<ev_child> watchers use a small hash table to distribute workload by	4835	C<ev_child> watchers use a small hash table to distribute workload by
3379	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4836	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3380	than enough. If you need to manage thousands of children you might want to	4837	usually more than enough. If you need to manage thousands of children you
3381	increase this value (I<must> be a power of two).	4838	might want to increase this value (I<must> be a power of two).
3382		4839
3383	=item EV_INOTIFY_HASHSIZE	4840	=item EV_INOTIFY_HASHSIZE
3384		4841
3385	C<ev_stat> watchers use a small hash table to distribute workload by	4842	C<ev_stat> watchers use a small hash table to distribute workload by
3386	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4843	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3387	usually more than enough. If you need to manage thousands of C<ev_stat>	4844	disabled), usually more than enough. If you need to manage thousands of
3388	watchers you might want to increase this value (I<must> be a power of	4845	C<ev_stat> watchers you might want to increase this value (I<must> be a
3389	two).	4846	power of two).
3390		4847
3391	=item EV_USE_4HEAP	4848	=item EV_USE_4HEAP
3392		4849
3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4850	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4851	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4852	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3396	faster performance with many (thousands) of watchers.	4853	faster performance with many (thousands) of watchers.
3397		4854
3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4855	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3399	(disabled).	4856	will be C<0>.
3400		4857
3401	=item EV_HEAP_CACHE_AT	4858	=item EV_HEAP_CACHE_AT
3402		4859
3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4860	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4861	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4862	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4863	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3407	but avoids random read accesses on heap changes. This improves performance	4864	but avoids random read accesses on heap changes. This improves performance
3408	noticeably with many (hundreds) of watchers.	4865	noticeably with many (hundreds) of watchers.
3409		4866
3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4867	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3411	(disabled).	4868	will be C<0>.
3412		4869
3413	=item EV_VERIFY	4870	=item EV_VERIFY
3414		4871
3415	Controls how much internal verification (see C<ev_loop_verify ()>) will	4872	Controls how much internal verification (see C<ev_verify ()>) will
3416	be done: If set to C<0>, no internal verification code will be compiled	4873	be done: If set to C<0>, no internal verification code will be compiled
3417	in. If set to C<1>, then verification code will be compiled in, but not	4874	in. If set to C<1>, then verification code will be compiled in, but not
3418	called. If set to C<2>, then the internal verification code will be	4875	called. If set to C<2>, then the internal verification code will be
3419	called once per loop, which can slow down libev. If set to C<3>, then the	4876	called once per loop, which can slow down libev. If set to C<3>, then the
3420	verification code will be called very frequently, which will slow down	4877	verification code will be called very frequently, which will slow down
3421	libev considerably.	4878	libev considerably.
3422		4879
3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4880	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3424	C<0>.	4881	will be C<0>.
3425		4882
3426	=item EV_COMMON	4883	=item EV_COMMON
3427		4884
3428	By default, all watchers have a C<void *data> member. By redefining	4885	By default, all watchers have a C<void *data> member. By redefining
3429	this macro to a something else you can include more and other types of	4886	this macro to something else you can include more and other types of
3430	members. You have to define it each time you include one of the files,	4887	members. You have to define it each time you include one of the files,
3431	though, and it must be identical each time.	4888	though, and it must be identical each time.
3432		4889
3433	For example, the perl EV module uses something like this:	4890	For example, the perl EV module uses something like this:
3434		4891
…		…
3487	file.	4944	file.
3488		4945
3489	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4946	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3490	that everybody includes and which overrides some configure choices:	4947	that everybody includes and which overrides some configure choices:
3491		4948
3492	#define EV_MINIMAL 1	4949	#define EV_FEATURES 8
3493	#define EV_USE_POLL 0	4950	#define EV_USE_SELECT 1
3494	#define EV_MULTIPLICITY 0
3495	#define EV_PERIODIC_ENABLE 0	4951	#define EV_PREPARE_ENABLE 1
		4952	#define EV_IDLE_ENABLE 1
3496	#define EV_STAT_ENABLE 0	4953	#define EV_SIGNAL_ENABLE 1
3497	#define EV_FORK_ENABLE 0	4954	#define EV_CHILD_ENABLE 1
		4955	#define EV_USE_STDEXCEPT 0
3498	#define EV_CONFIG_H <config.h>	4956	#define EV_CONFIG_H <config.h>
3499	#define EV_MINPRI 0
3500	#define EV_MAXPRI 0
3501		4957
3502	#include "ev++.h"	4958	#include "ev++.h"
3503		4959
3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3505		4961
3506	#include "ev_cpp.h"	4962	#include "ev_cpp.h"
3507	#include "ev.c"	4963	#include "ev.c"
3508		4964
3509	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4965	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3510		4966
3511	=head2 THREADS AND COROUTINES	4967	=head2 THREADS AND COROUTINES
3512		4968
3513	=head3 THREADS	4969	=head3 THREADS
3514		4970
…		…
3565	default loop and triggering an C<ev_async> watcher from the default loop	5021	default loop and triggering an C<ev_async> watcher from the default loop
3566	watcher callback into the event loop interested in the signal.	5022	watcher callback into the event loop interested in the signal.
3567		5023
3568	=back	5024	=back
3569		5025
		5026	See also L</THREAD LOCKING EXAMPLE>.
		5027
3570	=head3 COROUTINES	5028	=head3 COROUTINES
3571		5029
3572	Libev is very accommodating to coroutines ("cooperative threads"):	5030	Libev is very accommodating to coroutines ("cooperative threads"):
3573	libev fully supports nesting calls to its functions from different	5031	libev fully supports nesting calls to its functions from different
3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5032	coroutines (e.g. you can call C<ev_run> on the same loop from two
3575	different coroutines, and switch freely between both coroutines running the	5033	different coroutines, and switch freely between both coroutines running
3576	loop, as long as you don't confuse yourself). The only exception is that	5034	the loop, as long as you don't confuse yourself). The only exception is
3577	you must not do this from C<ev_periodic> reschedule callbacks.	5035	that you must not do this from C<ev_periodic> reschedule callbacks.
3578		5036
3579	Care has been taken to ensure that libev does not keep local state inside	5037	Care has been taken to ensure that libev does not keep local state inside
3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5038	C<ev_run>, and other calls do not usually allow for coroutine switches as
3581	they do not call any callbacks.	5039	they do not call any callbacks.
3582		5040
3583	=head2 COMPILER WARNINGS	5041	=head2 COMPILER WARNINGS
3584		5042
3585	Depending on your compiler and compiler settings, you might get no or a	5043	Depending on your compiler and compiler settings, you might get no or a
…		…
3596	maintainable.	5054	maintainable.
3597		5055
3598	And of course, some compiler warnings are just plain stupid, or simply	5056	And of course, some compiler warnings are just plain stupid, or simply
3599	wrong (because they don't actually warn about the condition their message	5057	wrong (because they don't actually warn about the condition their message
3600	seems to warn about). For example, certain older gcc versions had some	5058	seems to warn about). For example, certain older gcc versions had some
3601	warnings that resulted an extreme number of false positives. These have	5059	warnings that resulted in an extreme number of false positives. These have
3602	been fixed, but some people still insist on making code warn-free with	5060	been fixed, but some people still insist on making code warn-free with
3603	such buggy versions.	5061	such buggy versions.
3604		5062
3605	While libev is written to generate as few warnings as possible,	5063	While libev is written to generate as few warnings as possible,
3606	"warn-free" code is not a goal, and it is recommended not to build libev	5064	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3642	I suggest using suppression lists.	5100	I suggest using suppression lists.
3643		5101
3644		5102
3645	=head1 PORTABILITY NOTES	5103	=head1 PORTABILITY NOTES
3646		5104
		5105	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5106
		5107	GNU/Linux is the only common platform that supports 64 bit file/large file
		5108	interfaces but I<disables> them by default.
		5109
		5110	That means that libev compiled in the default environment doesn't support
		5111	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5112
		5113	Unfortunately, many programs try to work around this GNU/Linux issue
		5114	by enabling the large file API, which makes them incompatible with the
		5115	standard libev compiled for their system.
		5116
		5117	Likewise, libev cannot enable the large file API itself as this would
		5118	suddenly make it incompatible to the default compile time environment,
		5119	i.e. all programs not using special compile switches.
		5120
		5121	=head2 OS/X AND DARWIN BUGS
		5122
		5123	The whole thing is a bug if you ask me - basically any system interface
		5124	you touch is broken, whether it is locales, poll, kqueue or even the
		5125	OpenGL drivers.
		5126
		5127	=head3 C<kqueue> is buggy
		5128
		5129	The kqueue syscall is broken in all known versions - most versions support
		5130	only sockets, many support pipes.
		5131
		5132	Libev tries to work around this by not using C<kqueue> by default on this
		5133	rotten platform, but of course you can still ask for it when creating a
		5134	loop - embedding a socket-only kqueue loop into a select-based one is
		5135	probably going to work well.
		5136
		5137	=head3 C<poll> is buggy
		5138
		5139	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5140	implementation by something calling C<kqueue> internally around the 10.5.6
		5141	release, so now C<kqueue> I<and> C<poll> are broken.
		5142
		5143	Libev tries to work around this by not using C<poll> by default on
		5144	this rotten platform, but of course you can still ask for it when creating
		5145	a loop.
		5146
		5147	=head3 C<select> is buggy
		5148
		5149	All that's left is C<select>, and of course Apple found a way to fuck this
		5150	one up as well: On OS/X, C<select> actively limits the number of file
		5151	descriptors you can pass in to 1024 - your program suddenly crashes when
		5152	you use more.
		5153
		5154	There is an undocumented "workaround" for this - defining
		5155	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5156	work on OS/X.
		5157
		5158	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5159
		5160	=head3 C<errno> reentrancy
		5161
		5162	The default compile environment on Solaris is unfortunately so
		5163	thread-unsafe that you can't even use components/libraries compiled
		5164	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5165	defined by default. A valid, if stupid, implementation choice.
		5166
		5167	If you want to use libev in threaded environments you have to make sure
		5168	it's compiled with C<_REENTRANT> defined.
		5169
		5170	=head3 Event port backend
		5171
		5172	The scalable event interface for Solaris is called "event
		5173	ports". Unfortunately, this mechanism is very buggy in all major
		5174	releases. If you run into high CPU usage, your program freezes or you get
		5175	a large number of spurious wakeups, make sure you have all the relevant
		5176	and latest kernel patches applied. No, I don't know which ones, but there
		5177	are multiple ones to apply, and afterwards, event ports actually work
		5178	great.
		5179
		5180	If you can't get it to work, you can try running the program by setting
		5181	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5182	C<select> backends.
		5183
		5184	=head2 AIX POLL BUG
		5185
		5186	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5187	this by trying to avoid the poll backend altogether (i.e. it's not even
		5188	compiled in), which normally isn't a big problem as C<select> works fine
		5189	with large bitsets on AIX, and AIX is dead anyway.
		5190
3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5191	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5192
		5193	=head3 General issues
3648		5194
3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5195	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3650	requires, and its I/O model is fundamentally incompatible with the POSIX	5196	requires, and its I/O model is fundamentally incompatible with the POSIX
3651	model. Libev still offers limited functionality on this platform in	5197	model. Libev still offers limited functionality on this platform in
3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5198	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3653	descriptors. This only applies when using Win32 natively, not when using	5199	descriptors. This only applies when using Win32 natively, not when using
3654	e.g. cygwin.	5200	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5201	as every compiler comes with a slightly differently broken/incompatible
		5202	environment.
3655		5203
3656	Lifting these limitations would basically require the full	5204	Lifting these limitations would basically require the full
3657	re-implementation of the I/O system. If you are into these kinds of	5205	re-implementation of the I/O system. If you are into this kind of thing,
3658	things, then note that glib does exactly that for you in a very portable	5206	then note that glib does exactly that for you in a very portable way (note
3659	way (note also that glib is the slowest event library known to man).	5207	also that glib is the slowest event library known to man).
3660		5208
3661	There is no supported compilation method available on windows except	5209	There is no supported compilation method available on windows except
3662	embedding it into other applications.	5210	embedding it into other applications.
		5211
		5212	Sensible signal handling is officially unsupported by Microsoft - libev
		5213	tries its best, but under most conditions, signals will simply not work.
3663		5214
3664	Not a libev limitation but worth mentioning: windows apparently doesn't	5215	Not a libev limitation but worth mentioning: windows apparently doesn't
3665	accept large writes: instead of resulting in a partial write, windows will	5216	accept large writes: instead of resulting in a partial write, windows will
3666	either accept everything or return C<ENOBUFS> if the buffer is too large,	5217	either accept everything or return C<ENOBUFS> if the buffer is too large,
3667	so make sure you only write small amounts into your sockets (less than a	5218	so make sure you only write small amounts into your sockets (less than a
…		…
3672	the abysmal performance of winsockets, using a large number of sockets	5223	the abysmal performance of winsockets, using a large number of sockets
3673	is not recommended (and not reasonable). If your program needs to use	5224	is not recommended (and not reasonable). If your program needs to use
3674	more than a hundred or so sockets, then likely it needs to use a totally	5225	more than a hundred or so sockets, then likely it needs to use a totally
3675	different implementation for windows, as libev offers the POSIX readiness	5226	different implementation for windows, as libev offers the POSIX readiness
3676	notification model, which cannot be implemented efficiently on windows	5227	notification model, which cannot be implemented efficiently on windows
3677	(Microsoft monopoly games).	5228	(due to Microsoft monopoly games).
3678		5229
3679	A typical way to use libev under windows is to embed it (see the embedding	5230	A typical way to use libev under windows is to embed it (see the embedding
3680	section for details) and use the following F<evwrap.h> header file instead	5231	section for details) and use the following F<evwrap.h> header file instead
3681	of F<ev.h>:	5232	of F<ev.h>:
3682		5233
…		…
3689	you do I<not> compile the F<ev.c> or any other embedded source files!):	5240	you do I<not> compile the F<ev.c> or any other embedded source files!):
3690		5241
3691	#include "evwrap.h"	5242	#include "evwrap.h"
3692	#include "ev.c"	5243	#include "ev.c"
3693		5244
3694	=over 4
3695
3696	=item The winsocket select function	5245	=head3 The winsocket C<select> function
3697		5246
3698	The winsocket C<select> function doesn't follow POSIX in that it	5247	The winsocket C<select> function doesn't follow POSIX in that it
3699	requires socket I<handles> and not socket I<file descriptors> (it is	5248	requires socket I<handles> and not socket I<file descriptors> (it is
3700	also extremely buggy). This makes select very inefficient, and also	5249	also extremely buggy). This makes select very inefficient, and also
3701	requires a mapping from file descriptors to socket handles (the Microsoft	5250	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3710	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5259	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3711		5260
3712	Note that winsockets handling of fd sets is O(n), so you can easily get a	5261	Note that winsockets handling of fd sets is O(n), so you can easily get a
3713	complexity in the O(n²) range when using win32.	5262	complexity in the O(n²) range when using win32.
3714		5263
3715	=item Limited number of file descriptors	5264	=head3 Limited number of file descriptors
3716		5265
3717	Windows has numerous arbitrary (and low) limits on things.	5266	Windows has numerous arbitrary (and low) limits on things.
3718		5267
3719	Early versions of winsocket's select only supported waiting for a maximum	5268	Early versions of winsocket's select only supported waiting for a maximum
3720	of C<64> handles (probably owning to the fact that all windows kernels	5269	of C<64> handles (probably owning to the fact that all windows kernels
3721	can only wait for C<64> things at the same time internally; Microsoft	5270	can only wait for C<64> things at the same time internally; Microsoft
3722	recommends spawning a chain of threads and wait for 63 handles and the	5271	recommends spawning a chain of threads and wait for 63 handles and the
3723	previous thread in each. Great).	5272	previous thread in each. Sounds great!).
3724		5273
3725	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5274	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3726	to some high number (e.g. C<2048>) before compiling the winsocket select	5275	to some high number (e.g. C<2048>) before compiling the winsocket select
3727	call (which might be in libev or elsewhere, for example, perl does its own	5276	call (which might be in libev or elsewhere, for example, perl and many
3728	select emulation on windows).	5277	other interpreters do their own select emulation on windows).
3729		5278
3730	Another limit is the number of file descriptors in the Microsoft runtime	5279	Another limit is the number of file descriptors in the Microsoft runtime
3731	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5280	libraries, which by default is C<64> (there must be a hidden I<64>
3732	or something like this inside Microsoft). You can increase this by calling	5281	fetish or something like this inside Microsoft). You can increase this
3733	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5282	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3734	arbitrary limit), but is broken in many versions of the Microsoft runtime	5283	(another arbitrary limit), but is broken in many versions of the Microsoft
3735	libraries.
3736
3737	This might get you to about C<512> or C<2048> sockets (depending on	5284	runtime libraries. This might get you to about C<512> or C<2048> sockets
3738	windows version and/or the phase of the moon). To get more, you need to	5285	(depending on windows version and/or the phase of the moon). To get more,
3739	wrap all I/O functions and provide your own fd management, but the cost of	5286	you need to wrap all I/O functions and provide your own fd management, but
3740	calling select (O(n²)) will likely make this unworkable.	5287	the cost of calling select (O(n²)) will likely make this unworkable.
3741
3742	=back
3743		5288
3744	=head2 PORTABILITY REQUIREMENTS	5289	=head2 PORTABILITY REQUIREMENTS
3745		5290
3746	In addition to a working ISO-C implementation and of course the	5291	In addition to a working ISO-C implementation and of course the
3747	backend-specific APIs, libev relies on a few additional extensions:	5292	backend-specific APIs, libev relies on a few additional extensions:
…		…
3754	Libev assumes not only that all watcher pointers have the same internal	5299	Libev assumes not only that all watcher pointers have the same internal
3755	structure (guaranteed by POSIX but not by ISO C for example), but it also	5300	structure (guaranteed by POSIX but not by ISO C for example), but it also
3756	assumes that the same (machine) code can be used to call any watcher	5301	assumes that the same (machine) code can be used to call any watcher
3757	callback: The watcher callbacks have different type signatures, but libev	5302	callback: The watcher callbacks have different type signatures, but libev
3758	calls them using an C<ev_watcher *> internally.	5303	calls them using an C<ev_watcher *> internally.
		5304
		5305	=item pointer accesses must be thread-atomic
		5306
		5307	Accessing a pointer value must be atomic, it must both be readable and
		5308	writable in one piece - this is the case on all current architectures.
3759		5309
3760	=item C<sig_atomic_t volatile> must be thread-atomic as well	5310	=item C<sig_atomic_t volatile> must be thread-atomic as well
3761		5311
3762	The type C<sig_atomic_t volatile> (or whatever is defined as	5312	The type C<sig_atomic_t volatile> (or whatever is defined as
3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5313	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3772	thread" or will block signals process-wide, both behaviours would	5322	thread" or will block signals process-wide, both behaviours would
3773	be compatible with libev. Interaction between C<sigprocmask> and	5323	be compatible with libev. Interaction between C<sigprocmask> and
3774	C<pthread_sigmask> could complicate things, however.	5324	C<pthread_sigmask> could complicate things, however.
3775		5325
3776	The most portable way to handle signals is to block signals in all threads	5326	The most portable way to handle signals is to block signals in all threads
3777	except the initial one, and run the default loop in the initial thread as	5327	except the initial one, and run the signal handling loop in the initial
3778	well.	5328	thread as well.
3779		5329
3780	=item C<long> must be large enough for common memory allocation sizes	5330	=item C<long> must be large enough for common memory allocation sizes
3781		5331
3782	To improve portability and simplify its API, libev uses C<long> internally	5332	To improve portability and simplify its API, libev uses C<long> internally
3783	instead of C<size_t> when allocating its data structures. On non-POSIX	5333	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3786	watchers.	5336	watchers.
3787		5337
3788	=item C<double> must hold a time value in seconds with enough accuracy	5338	=item C<double> must hold a time value in seconds with enough accuracy
3789		5339
3790	The type C<double> is used to represent timestamps. It is required to	5340	The type C<double> is used to represent timestamps. It is required to
3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5341	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3792	enough for at least into the year 4000. This requirement is fulfilled by	5342	good enough for at least into the year 4000 with millisecond accuracy
		5343	(the design goal for libev). This requirement is overfulfilled by
3793	implementations implementing IEEE 754 (basically all existing ones).	5344	implementations using IEEE 754, which is basically all existing ones.
		5345
		5346	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5347	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5348	is either obsolete or somebody patched it to use C<long double> or
		5349	something like that, just kidding).
3794		5350
3795	=back	5351	=back
3796		5352
3797	If you know of other additional requirements drop me a note.	5353	If you know of other additional requirements drop me a note.
3798		5354
…		…
3860	=item Processing ev_async_send: O(number_of_async_watchers)	5416	=item Processing ev_async_send: O(number_of_async_watchers)
3861		5417
3862	=item Processing signals: O(max_signal_number)	5418	=item Processing signals: O(max_signal_number)
3863		5419
3864	Sending involves a system call I<iff> there were no other C<ev_async_send>	5420	Sending involves a system call I<iff> there were no other C<ev_async_send>
3865	calls in the current loop iteration. Checking for async and signal events	5421	calls in the current loop iteration and the loop is currently
		5422	blocked. Checking for async and signal events involves iterating over all
3866	involves iterating over all running async watchers or all signal numbers.	5423	running async watchers or all signal numbers.
3867		5424
3868	=back	5425	=back
3869		5426
3870		5427
		5428	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5429
		5430	The major version 4 introduced some incompatible changes to the API.
		5431
		5432	At the moment, the C<ev.h> header file provides compatibility definitions
		5433	for all changes, so most programs should still compile. The compatibility
		5434	layer might be removed in later versions of libev, so better update to the
		5435	new API early than late.
		5436
		5437	=over 4
		5438
		5439	=item C<EV_COMPAT3> backwards compatibility mechanism
		5440
		5441	The backward compatibility mechanism can be controlled by
		5442	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5443	section.
		5444
		5445	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5446
		5447	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5448
		5449	ev_loop_destroy (EV_DEFAULT_UC);
		5450	ev_loop_fork (EV_DEFAULT);
		5451
		5452	=item function/symbol renames
		5453
		5454	A number of functions and symbols have been renamed:
		5455
		5456	ev_loop => ev_run
		5457	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5458	EVLOOP_ONESHOT => EVRUN_ONCE
		5459
		5460	ev_unloop => ev_break
		5461	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5462	EVUNLOOP_ONE => EVBREAK_ONE
		5463	EVUNLOOP_ALL => EVBREAK_ALL
		5464
		5465	EV_TIMEOUT => EV_TIMER
		5466
		5467	ev_loop_count => ev_iteration
		5468	ev_loop_depth => ev_depth
		5469	ev_loop_verify => ev_verify
		5470
		5471	Most functions working on C<struct ev_loop> objects don't have an
		5472	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5473	associated constants have been renamed to not collide with the C<struct
		5474	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5475	as all other watcher types. Note that C<ev_loop_fork> is still called
		5476	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5477	typedef.
		5478
		5479	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5480
		5481	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5482	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5483	and work, but the library code will of course be larger.
		5484
		5485	=back
		5486
		5487
		5488	=head1 GLOSSARY
		5489
		5490	=over 4
		5491
		5492	=item active
		5493
		5494	A watcher is active as long as it has been started and not yet stopped.
		5495	See L</WATCHER STATES> for details.
		5496
		5497	=item application
		5498
		5499	In this document, an application is whatever is using libev.
		5500
		5501	=item backend
		5502
		5503	The part of the code dealing with the operating system interfaces.
		5504
		5505	=item callback
		5506
		5507	The address of a function that is called when some event has been
		5508	detected. Callbacks are being passed the event loop, the watcher that
		5509	received the event, and the actual event bitset.
		5510
		5511	=item callback/watcher invocation
		5512
		5513	The act of calling the callback associated with a watcher.
		5514
		5515	=item event
		5516
		5517	A change of state of some external event, such as data now being available
		5518	for reading on a file descriptor, time having passed or simply not having
		5519	any other events happening anymore.
		5520
		5521	In libev, events are represented as single bits (such as C<EV_READ> or
		5522	C<EV_TIMER>).
		5523
		5524	=item event library
		5525
		5526	A software package implementing an event model and loop.
		5527
		5528	=item event loop
		5529
		5530	An entity that handles and processes external events and converts them
		5531	into callback invocations.
		5532
		5533	=item event model
		5534
		5535	The model used to describe how an event loop handles and processes
		5536	watchers and events.
		5537
		5538	=item pending
		5539
		5540	A watcher is pending as soon as the corresponding event has been
		5541	detected. See L</WATCHER STATES> for details.
		5542
		5543	=item real time
		5544
		5545	The physical time that is observed. It is apparently strictly monotonic :)
		5546
		5547	=item wall-clock time
		5548
		5549	The time and date as shown on clocks. Unlike real time, it can actually
		5550	be wrong and jump forwards and backwards, e.g. when you adjust your
		5551	clock.
		5552
		5553	=item watcher
		5554
		5555	A data structure that describes interest in certain events. Watchers need
		5556	to be started (attached to an event loop) before they can receive events.
		5557
		5558	=back
		5559
3871	=head1 AUTHOR	5560	=head1 AUTHOR
3872		5561
3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5562	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5563	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3874		5564

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines