ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.253 by root, Tue Jul 14 18:33:48 2009 UTC vs.
Revision 1.444 by root, Mon Oct 29 00:00:22 2018 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
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	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);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	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>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	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
86	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
…		…
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	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
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	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
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	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
108	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
109	(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>).
110		121
111	It also is quite fast (see this	122	It also is quite fast (see this
112	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
113	for example).	124	for example).
114		125
…		…
117	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)
118	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
120	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
121	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
122	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
123	this argument.	134	this argument.
124		135
125	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
126		137
127	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
132	on 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
133	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
134	throughout libev.	146	time differences (e.g. delays) throughout libev.
135		147
136	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
137		149
138	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	151	and internal errors (bugs).
…		…
163		175
164	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
165		177
166	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
167	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
168	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>.
169		182
170	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
171		184
172	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
173	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
174	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 >>).
175		194
176	=item int ev_version_major ()	195	=item int ev_version_major ()
177		196
178	=item int ev_version_minor ()	197	=item int ev_version_minor ()
179		198
…		…
190	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
191	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
192	not a problem.	211	not a problem.
193		212
194	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
195	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
196		216
197	assert (("libev version mismatch",	217	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
200		220
…		…
211	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
213		233
214	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
215		235
216	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
217	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
218	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
219	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
220	(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
221	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
222		243
223	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
224		245
225	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
226	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
227	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
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
230		251
231	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
232		253
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		255
235	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
236	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
237	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
238	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
…		…
264	}	285	}
265		286
266	...	287	...
267	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
268		289
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		291
271	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
272	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
273	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
274	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
…		…
286	}	307	}
287		308
288	...	309	...
289	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
290		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
291	=back	325	=back
292		326
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		328
295	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
296	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
297	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
298		332
299	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
300	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
301	not.	335	do not.
302		336
303	=over 4	337	=over 4
304		338
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		340
307	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
308	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
309	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
310	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".
311		351
312	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
313	function.	353	function (or via the C<EV_DEFAULT> macro).
314		354
315	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
316	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
317	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).
318		359
319	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,
320	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
321	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
322	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
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	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.
325		384
326	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
327	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>).
328		387
329	The following flags are supported:	388	The following flags are supported:
…		…
339		398
340	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
341	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
342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
343	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
344	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
345	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).
346		407
347	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
348		409
349	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
350	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.
351	enabling this flag.
352		412
353	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,
354	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
355	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
356	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
357	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
358	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
359		420
360	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
361	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
362	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
363		424
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	426	environment variable.
		427
		428	=item C<EVFLAG_NOINOTIFY>
		429
		430	When this flag is specified, then libev will not attempt to use the
		431	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		432	testing, this flag can be useful to conserve inotify file descriptors, as
		433	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		434
		435	=item C<EVFLAG_SIGNALFD>
		436
		437	When this flag is specified, then libev will attempt to use the
		438	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		439	delivers signals synchronously, which makes it both faster and might make
		440	it possible to get the queued signal data. It can also simplify signal
		441	handling with threads, as long as you properly block signals in your
		442	threads that are not interested in handling them.
		443
		444	Signalfd will not be used by default as this changes your signal mask, and
		445	there are a lot of shoddy libraries and programs (glib's threadpool for
		446	example) that can't properly initialise their signal masks.
		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
366		462
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		464
369	This is your standard select(2) backend. Not I<completely> standard, as	465	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	466	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	491	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	492	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		493
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		495
		496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		497	kernels).
		498
400	For few fds, this backend is a bit little slower than poll and select,	499	For few fds, this backend is a bit little slower than poll and select, but
401	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
402	like O(total_fds) where n is the total number of fds (or the highest fd),	501	O(total_fds) where total_fds is the total number of fds (or the highest
403	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
404		503
405	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	507	descriptor (and unnecessary guessing of parameters), problems with dup,
		508	returning before the timeout value, resulting in additional iterations
		509	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	510	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	511	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	513	and is of course hard to detect.
413		514
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
415	of course I<doesn't>, and epoll just loves to report events for totally	516	but of course I<doesn't>, and epoll just loves to report events for
416	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
417	even remove them from the set) than registered in the set (especially	518	one cannot even remove them from the set) than registered in the set
418	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
420	events to filter out spurious ones, recreating the set when required.	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
		525	not least, it also refuses to work with some file descriptors which work
		526	perfectly fine with C<select> (files, many character devices...).
		527
		528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
421		531
422	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
462		572
463	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
464	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
465	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
467	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
469	cases	579	drops fds silently in similarly hard-to-detect cases.
470		580
471	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
472		582
473	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
474	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		602
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	604	it's really slow, but it still scales very well (O(active_fds)).
495		605
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	606	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	607	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	609	might perform better.
504		610
505	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	612	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
509		625
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
512		628
513	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
514		630
515	Try all backends (even potentially broken ones that wouldn't be tried	631	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		634
519	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		644
521	=back	645	=back
522		646
523	If one or more of these are or'ed into the flags value, then only these	647	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	648	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	649	here). If none are specified, all backends in C<ev_recommended_backends
526		650	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		651
555	Example: Try to create a event loop that uses epoll and nothing else.	652	Example: Try to create a event loop that uses epoll and nothing else.
556		653
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	655	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
560		657
		658	Example: Use whatever libev has to offer, but make sure that kqueue is
		659	used if available.
		660
		661	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		662
561	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
562		664
563	Destroys the default loop again (frees all memory and kernel state	665	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	666	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	667	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	668	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	669	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	670	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		672
571	Note that certain global state, such as signal state (and installed signal	673	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	674	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
574		676
575	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	678	C<ev_loop_new>, but it can also be used on the default loop returned by
		679	C<ev_default_loop>, in which case it is not thread-safe.
		680
		681	Note that it is not advisable to call this function on the default loop
		682	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	684	and C<ev_loop_destroy>.
579		685
580	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
581		687
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	688	This function sets a flag that causes subsequent C<ev_run> iterations
588	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
589	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
590	the child process (or both child and parent, but that again makes little	691	watchers (except inside an C<ev_prepare> callback), but it makes most
591	sense). You I<must> call it in the child before using any of the libev	692	sense after forking, in the child process. You I<must> call it (or use
592	functions, and it will only take effect at the next C<ev_loop> iteration.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
		698	Again, you I<have> to call it on I<any> loop that you want to re-use after
		699	a fork, I<even if you do not plan to use the loop in the parent>. This is
		700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		701	during fork.
593		702
594	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	704	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	705	you just fork+exec or create a new loop in the child, you don't have to
		706	call it at all (in fact, C<epoll> is so badly broken that it makes a
		707	difference, but libev will usually detect this case on its own and do a
		708	costly reset of the backend).
597		709
598	The function itself is quite fast and it's usually not a problem to call	710	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		712
		713	Example: Automate calling C<ev_loop_fork> on the default loop when
		714	using pthreads.
		715
		716	static void
		717	post_fork_child (void)
		718	{
		719	ev_loop_fork (EV_DEFAULT);
		720	}
		721
		722	...
602	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		724
611	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
612		726
613	Returns true when the given loop is, in fact, the default loop, and false	727	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	728	otherwise.
615		729
616	=item unsigned int ev_loop_count (loop)	730	=item unsigned int ev_iteration (loop)
617		731
618	Returns the count of loop iterations for the loop, which is identical to	732	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	733	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	734	and happily wraps around with enough iterations.
621		735
622	This value can sometimes be useful as a generation counter of sorts (it	736	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	737	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	738	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		739	prepare and check phases.
625		740
626	=item unsigned int ev_loop_depth (loop)	741	=item unsigned int ev_depth (loop)
627		742
628	Returns the number of times C<ev_loop> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
630		745
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	748	in which case it is higher.
634		749
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	751	throwing an exception etc.), doesn't count as "exit" - consider this
		752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
637		754
638	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
639		756
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	758	use.
…		…
650		767
651	=item ev_now_update (loop)	768	=item ev_now_update (loop)
652		769
653	Establishes the current time by querying the kernel, updating the time	770	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	771	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	772	is usually done automatically within C<ev_run ()>.
656		773
657	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	776	the current time is a good idea.
660		777
661	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
662		779
663	=item ev_suspend (loop)	780	=item ev_suspend (loop)
664		781
665	=item ev_resume (loop)	782	=item ev_resume (loop)
666		783
667	These two functions suspend and resume a loop, for use when the loop is	784	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	785	loop is not used for a while and timeouts should not be processed.
669		786
670	A typical use case would be an interactive program such as a game: When	787	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	788	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	789	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	790	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	792	C<ev_resume> directly afterwards to resume timer processing.
676		793
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	794	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	795	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	796	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	797	occurred while suspended).
681		798
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	799	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	800	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
685		802
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
688		805
689	=item ev_loop (loop, int flags)	806	=item bool ev_run (loop, int flags)
690		807
691	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	809	after you have initialised all your watchers and you want to start
693	events.	810	handling events. It will ask the operating system for any new events, call
		811	the watcher callbacks, and then repeat the whole process indefinitely: This
		812	is why event loops are called I<loops>.
694		813
695	If the flags argument is specified as C<0>, it will not return until	814	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	815	until either no event watchers are active anymore or C<ev_break> was
		816	called.
697		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
		821
698	Please note that an explicit C<ev_unloop> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
699	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
700	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
701	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
702	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
703	beauty.	827	beauty.
704		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
706	those events and any already outstanding ones, but will not block your	835	those events and any already outstanding ones, but will not wait and
707	process in case there are no events and will return after one iteration of	836	block your process in case there are no events and will return after one
708	the loop.	837	iteration of the loop. This is sometimes useful to poll and handle new
		838	events while doing lengthy calculations, to keep the program responsive.
709		839
710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	840	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
711	necessary) and will handle those and any already outstanding ones. It	841	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	842	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	843	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	844	user-registered callback will be called), and will return after one
715	iteration of the loop.	845	iteration of the loop.
716		846
717	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
718	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
720	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
721		851
722	Here are the gory details of what C<ev_loop> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
723		855
		856	- Increment loop depth.
		857	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
		859	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	860	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- If a fork was detected (by any means), queue and call all fork watchers.	861	- If a fork was detected (by any means), queue and call all fork watchers.
727	- Queue and call all prepare watchers.	862	- Queue and call all prepare watchers.
		863	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	864	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	865	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	866	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	867	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	868	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	869	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	870	any active watchers at all will result in not sleeping).
735	- Sleep if the I/O and timer collect interval say so.	871	- Sleep if the I/O and timer collect interval say so.
		872	- Increment loop iteration counter.
736	- Block the process, waiting for any events.	873	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	874	- Queue all outstanding I/O (fd) events.
738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	875	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
739	- Queue all expired timers.	876	- Queue all expired timers.
740	- Queue all expired periodics.	877	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	878	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	879	- Queue all check watchers.
743	- Call all queued watchers in reverse order (i.e. check watchers first).	880	- Call all queued watchers in reverse order (i.e. check watchers first).
744	Signals and child watchers are implemented as I/O watchers, and will	881	Signals and child watchers are implemented as I/O watchers, and will
745	be handled here by queueing them when their watcher gets executed.	882	be handled here by queueing them when their watcher gets executed.
746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	883	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
747	were used, or there are no active watchers, return, otherwise	884	were used, or there are no active watchers, goto FINISH, otherwise
748	continue with step *.	885	continue with step LOOP.
		886	FINISH:
		887	- Reset the ev_break status iff it was EVBREAK_ONE.
		888	- Decrement the loop depth.
		889	- Return.
749		890
750	Example: Queue some jobs and then loop until no events are outstanding	891	Example: Queue some jobs and then loop until no events are outstanding
751	anymore.	892	anymore.
752		893
753	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	896	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
757		898
758	=item ev_unloop (loop, how)	899	=item ev_break (loop, how)
759		900
760	Can be used to make a call to C<ev_loop> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
761	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
764		905
765	This "unloop state" will be cleared when entering C<ev_loop> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
766		907
767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
768		910
769	=item ev_ref (loop)	911	=item ev_ref (loop)
770		912
771	=item ev_unref (loop)	913	=item ev_unref (loop)
772		914
773	Ref/unref can be used to add or remove a reference count on the event	915	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	916	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	917	count is nonzero, C<ev_run> will not return on its own.
776		918
777	If you have a watcher you never unregister that should not keep C<ev_loop>	919	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	920	unregister, but that nevertheless should not keep C<ev_run> from
		921	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	922	before stopping it.
780		923
781	As an example, libev itself uses this for its internal signal pipe: It	924	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	925	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	926	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	927	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	928	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	929	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	930	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	931	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	932	in the callback).
790		933
791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	934	Example: Create a signal watcher, but keep it from keeping C<ev_run>
792	running when nothing else is active.	935	running when nothing else is active.
793		936
794	ev_signal exitsig;	937	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	940	ev_unref (loop);
798		941
799	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
800		943
801	ev_ref (loop);	944	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
822	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
823		966
824	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
825	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
827	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
828	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
829	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
830	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
831		975
832	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
833	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
834	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
835	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	985	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	986	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	987	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	988	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	989	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	990	then you can't do more than 100 transactions per second).
847		991
848	Setting the I<timeout collect interval> can improve the opportunity for	992	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	993	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	994	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	995	times the process sleeps and wakes up again. Another useful technique to
…		…
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1003	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		1004
861	=item ev_invoke_pending (loop)	1005	=item ev_invoke_pending (loop)
862		1006
863	This call will simply invoke all pending watchers while resetting their	1007	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	1008	pending state. Normally, C<ev_run> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	1009	but when overriding the invoke callback this call comes handy. This
		1010	function can be invoked from a watcher - this can be useful for example
		1011	when you want to do some lengthy calculation and want to pass further
		1012	event handling to another thread (you still have to make sure only one
		1013	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1014
		1015	=item int ev_pending_count (loop)
		1016
		1017	Returns the number of pending watchers - zero indicates that no watchers
		1018	are pending.
866		1019
867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1020	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868		1021
869	This overrides the invoke pending functionality of the loop: Instead of	1022	This overrides the invoke pending functionality of the loop: Instead of
870	invoking all pending watchers when there are any, C<ev_loop> will call	1023	invoking all pending watchers when there are any, C<ev_run> will call
871	this callback instead. This is useful, for example, when you want to	1024	this callback instead. This is useful, for example, when you want to
872	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
873		1026
874	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
875	callback.	1028	callback.
876		1029
877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
878		1031
879	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
880	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
881	each call to a libev function.	1034	each call to a libev function.
882		1035
883	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
884	wait for it to return. One way around this is to wake up the loop via	1037	to wait for it to return. One way around this is to wake up the event
885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
886	and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
887		1040
888	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
889	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
890	afterwards.	1043	afterwards.
891		1044
892	Ideally, C<release> will just call your mutex_unlock function, and	1045	Ideally, C<release> will just call your mutex_unlock function, and
893	C<acquire> will just call the mutex_lock function again.	1046	C<acquire> will just call the mutex_lock function again.
894		1047
		1048	While event loop modifications are allowed between invocations of
		1049	C<release> and C<acquire> (that's their only purpose after all), no
		1050	modifications done will affect the event loop, i.e. adding watchers will
		1051	have no effect on the set of file descriptors being watched, or the time
		1052	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1053	to take note of any changes you made.
		1054
		1055	In theory, threads executing C<ev_run> will be async-cancel safe between
		1056	invocations of C<release> and C<acquire>.
		1057
		1058	See also the locking example in the C<THREADS> section later in this
		1059	document.
		1060
895	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
896		1062
897	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
898		1064
899	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
901	C<0.>	1067	C<0>.
902		1068
903	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
904	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
905	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
906	any other purpose as well.	1072	any other purpose as well.
907		1073
908	=item ev_loop_verify (loop)	1074	=item ev_verify (loop)
909		1075
910	This function only does something when C<EV_VERIFY> support has been	1076	This function only does something when C<EV_VERIFY> support has been
911	compiled in, which is the default for non-minimal builds. It tries to go	1077	compiled in, which is the default for non-minimal builds. It tries to go
912	through all internal structures and checks them for validity. If anything	1078	through all internal structures and checks them for validity. If anything
913	is found to be inconsistent, it will print an error message to standard	1079	is found to be inconsistent, it will print an error message to standard
…		…
924		1090
925	In the following description, uppercase C<TYPE> in names stands for the	1091	In the following description, uppercase C<TYPE> in names stands for the
926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1092	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
927	watchers and C<ev_io_start> for I/O watchers.	1093	watchers and C<ev_io_start> for I/O watchers.
928		1094
929	A watcher is a structure that you create and register to record your	1095	A watcher is an opaque structure that you allocate and register to record
930	interest in some event. For instance, if you want to wait for STDIN to	1096	your interest in some event. To make a concrete example, imagine you want
931	become readable, you would create an C<ev_io> watcher for that:	1097	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1098	for that:
932		1099
933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1100	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
934	{	1101	{
935	ev_io_stop (w);	1102	ev_io_stop (w);
936	ev_unloop (loop, EVUNLOOP_ALL);	1103	ev_break (loop, EVBREAK_ALL);
937	}	1104	}
938		1105
939	struct ev_loop *loop = ev_default_loop (0);	1106	struct ev_loop *loop = ev_default_loop (0);
940		1107
941	ev_io stdin_watcher;	1108	ev_io stdin_watcher;
942		1109
943	ev_init (&stdin_watcher, my_cb);	1110	ev_init (&stdin_watcher, my_cb);
944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1111	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
945	ev_io_start (loop, &stdin_watcher);	1112	ev_io_start (loop, &stdin_watcher);
946		1113
947	ev_loop (loop, 0);	1114	ev_run (loop, 0);
948		1115
949	As you can see, you are responsible for allocating the memory for your	1116	As you can see, you are responsible for allocating the memory for your
950	watcher structures (and it is I<usually> a bad idea to do this on the	1117	watcher structures (and it is I<usually> a bad idea to do this on the
951	stack).	1118	stack).
952		1119
953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1120	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1121	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
955		1122
956	Each watcher structure must be initialised by a call to C<ev_init	1123	Each watcher structure must be initialised by a call to C<ev_init (watcher
957	(watcher *, callback)>, which expects a callback to be provided. This	1124	*, callback)>, which expects a callback to be provided. This callback is
958	callback gets invoked each time the event occurs (or, in the case of I/O	1125	invoked each time the event occurs (or, in the case of I/O watchers, each
959	watchers, each time the event loop detects that the file descriptor given	1126	time the event loop detects that the file descriptor given is readable
960	is readable and/or writable).	1127	and/or writable).
961		1128
962	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1129	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
963	macro to configure it, with arguments specific to the watcher type. There	1130	macro to configure it, with arguments specific to the watcher type. There
964	is also a macro to combine initialisation and setting in one call: C<<	1131	is also a macro to combine initialisation and setting in one call: C<<
965	ev_TYPE_init (watcher *, callback, ...) >>.	1132	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
988	=item C<EV_WRITE>	1155	=item C<EV_WRITE>
989		1156
990	The file descriptor in the C<ev_io> watcher has become readable and/or	1157	The file descriptor in the C<ev_io> watcher has become readable and/or
991	writable.	1158	writable.
992		1159
993	=item C<EV_TIMEOUT>	1160	=item C<EV_TIMER>
994		1161
995	The C<ev_timer> watcher has timed out.	1162	The C<ev_timer> watcher has timed out.
996		1163
997	=item C<EV_PERIODIC>	1164	=item C<EV_PERIODIC>
998		1165
…		…
1016		1183
1017	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1018		1185
1019	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1020		1187
1021	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1022	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1023	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1024	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1025	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1026	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1027	C<ev_loop> from blocking).	1199	blocking).
1028		1200
1029	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1030		1202
1031	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1032		1204
1033	=item C<EV_FORK>	1205	=item C<EV_FORK>
1034		1206
1035	The event loop has been resumed in the child process after fork (see	1207	The event loop has been resumed in the child process after fork (see
1036	C<ev_fork>).	1208	C<ev_fork>).
		1209
		1210	=item C<EV_CLEANUP>
		1211
		1212	The event loop is about to be destroyed (see C<ev_cleanup>).
1037		1213
1038	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1039		1215
1040	The given async watcher has been asynchronously notified (see C<ev_async>).	1216	The given async watcher has been asynchronously notified (see C<ev_async>).
1041		1217
…		…
1088		1264
1089	ev_io w;	1265	ev_io w;
1090	ev_init (&w, my_cb);	1266	ev_init (&w, my_cb);
1091	ev_io_set (&w, STDIN_FILENO, EV_READ);	1267	ev_io_set (&w, STDIN_FILENO, EV_READ);
1092		1268
1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1269	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1094		1270
1095	This macro initialises the type-specific parts of a watcher. You need to	1271	This macro initialises the type-specific parts of a watcher. You need to
1096	call C<ev_init> at least once before you call this macro, but you can	1272	call C<ev_init> at least once before you call this macro, but you can
1097	call C<ev_TYPE_set> any number of times. You must not, however, call this	1273	call C<ev_TYPE_set> any number of times. You must not, however, call this
1098	macro on a watcher that is active (it can be pending, however, which is a	1274	macro on a watcher that is active (it can be pending, however, which is a
…		…
1111		1287
1112	Example: Initialise and set an C<ev_io> watcher in one step.	1288	Example: Initialise and set an C<ev_io> watcher in one step.
1113		1289
1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1290	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1115		1291
1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1292	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1117		1293
1118	Starts (activates) the given watcher. Only active watchers will receive	1294	Starts (activates) the given watcher. Only active watchers will receive
1119	events. If the watcher is already active nothing will happen.	1295	events. If the watcher is already active nothing will happen.
1120		1296
1121	Example: Start the C<ev_io> watcher that is being abused as example in this	1297	Example: Start the C<ev_io> watcher that is being abused as example in this
1122	whole section.	1298	whole section.
1123		1299
1124	ev_io_start (EV_DEFAULT_UC, &w);	1300	ev_io_start (EV_DEFAULT_UC, &w);
1125		1301
1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1302	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1127		1303
1128	Stops the given watcher if active, and clears the pending status (whether	1304	Stops the given watcher if active, and clears the pending status (whether
1129	the watcher was active or not).	1305	the watcher was active or not).
1130		1306
1131	It is possible that stopped watchers are pending - for example,	1307	It is possible that stopped watchers are pending - for example,
…		…
1151		1327
1152	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1153		1329
1154	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1155		1331
1156	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1157		1333
1158	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1159	(modulo threads).	1335	(modulo threads).
1160		1336
1161	=item ev_set_priority (ev_TYPE *watcher, priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
1162		1338
1163	=item int ev_priority (ev_TYPE *watcher)	1339	=item int ev_priority (ev_TYPE *watcher)
1164		1340
1165	Set and query the priority of the watcher. The priority is a small	1341	Set and query the priority of the watcher. The priority is a small
1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1342	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1179	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1180		1356
1181	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1182	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1183		1359
1184	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1185	priorities.	1361	priorities.
1186		1362
1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1188		1364
1189	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1198	watcher isn't pending it does nothing and returns C<0>.	1374	watcher isn't pending it does nothing and returns C<0>.
1199		1375
1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1376	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1201	callback to be invoked, which can be accomplished with this function.	1377	callback to be invoked, which can be accomplished with this function.
1202		1378
		1379	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1380
		1381	Feeds the given event set into the event loop, as if the specified event
		1382	had happened for the specified watcher (which must be a pointer to an
		1383	initialised but not necessarily started event watcher). Obviously you must
		1384	not free the watcher as long as it has pending events.
		1385
		1386	Stopping the watcher, letting libev invoke it, or calling
		1387	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1388	not started in the first place.
		1389
		1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1391	functions that do not need a watcher.
		1392
1203	=back	1393	=back
1204		1394
		1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1396	OWN COMPOSITE WATCHERS> idioms.
1205		1397
1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1398	=head2 WATCHER STATES
1207		1399
1208	Each watcher has, by default, a member C<void *data> that you can change	1400	There are various watcher states mentioned throughout this manual -
1209	and read at any time: libev will completely ignore it. This can be used	1401	active, pending and so on. In this section these states and the rules to
1210	to associate arbitrary data with your watcher. If you need more data and	1402	transition between them will be described in more detail - and while these
1211	don't want to allocate memory and store a pointer to it in that data	1403	rules might look complicated, they usually do "the right thing".
1212	member, you can also "subclass" the watcher type and provide your own
1213	data:
1214		1404
1215	struct my_io	1405	=over 4
1216	{
1217	ev_io io;
1218	int otherfd;
1219	void *somedata;
1220	struct whatever *mostinteresting;
1221	};
1222		1406
1223	...	1407	=item initialised
1224	struct my_io w;
1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1226		1408
1227	And since your callback will be called with a pointer to the watcher, you	1409	Before a watcher can be registered with the event loop it has to be
1228	can cast it back to your own type:	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1229		1412
1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1413	In this state it is simply some block of memory that is suitable for
1231	{	1414	use in an event loop. It can be moved around, freed, reused etc. at
1232	struct my_io *w = (struct my_io *)w_;	1415	will - as long as you either keep the memory contents intact, or call
1233	...	1416	C<ev_TYPE_init> again.
1234	}
1235		1417
1236	More interesting and less C-conformant ways of casting your callback type	1418	=item started/running/active
1237	instead have been omitted.
1238		1419
1239	Another common scenario is to use some data structure with multiple	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1240	embedded watchers:	1421	property of the event loop, and is actively waiting for events. While in
		1422	this state it cannot be accessed (except in a few documented ways), moved,
		1423	freed or anything else - the only legal thing is to keep a pointer to it,
		1424	and call libev functions on it that are documented to work on active watchers.
1241		1425
1242	struct my_biggy	1426	=item pending
1243	{
1244	int some_data;
1245	ev_timer t1;
1246	ev_timer t2;
1247	}
1248		1427
1249	In this case getting the pointer to C<my_biggy> is a bit more	1428	If a watcher is active and libev determines that an event it is interested
1250	complicated: Either you store the address of your C<my_biggy> struct	1429	in has occurred (such as a timer expiring), it will become pending. It will
1251	in the C<data> member of the watcher (for woozies), or you need to use	1430	stay in this pending state until either it is stopped or its callback is
1252	some pointer arithmetic using C<offsetof> inside your watchers (for real	1431	about to be invoked, so it is not normally pending inside the watcher
1253	programmers):	1432	callback.
1254		1433
1255	#include <stddef.h>	1434	The watcher might or might not be active while it is pending (for example,
		1435	an expired non-repeating timer can be pending but no longer active). If it
		1436	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1437	but it is still property of the event loop at this time, so cannot be
		1438	moved, freed or reused. And if it is active the rules described in the
		1439	previous item still apply.
1256		1440
1257	static void	1441	It is also possible to feed an event on a watcher that is not active (e.g.
1258	t1_cb (EV_P_ ev_timer *w, int revents)	1442	via C<ev_feed_event>), in which case it becomes pending without being
1259	{	1443	active.
1260	struct my_biggy big = (struct my_biggy *)
1261	(((char *)w) - offsetof (struct my_biggy, t1));
1262	}
1263		1444
1264	static void	1445	=item stopped
1265	t2_cb (EV_P_ ev_timer *w, int revents)	1446
1266	{	1447	A watcher can be stopped implicitly by libev (in which case it might still
1267	struct my_biggy big = (struct my_biggy *)	1448	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1268	(((char *)w) - offsetof (struct my_biggy, t2));	1449	latter will clear any pending state the watcher might be in, regardless
1269	}	1450	of whether it was active or not, so stopping a watcher explicitly before
		1451	freeing it is often a good idea.
		1452
		1453	While stopped (and not pending) the watcher is essentially in the
		1454	initialised state, that is, it can be reused, moved, modified in any way
		1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
		1457
		1458	=back
1270		1459
1271	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1272		1461
1273	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1274	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1317		1506
1318	For example, to emulate how many other event libraries handle priorities,	1507	For example, to emulate how many other event libraries handle priorities,
1319	you can associate an C<ev_idle> watcher to each such watcher, and in	1508	you can associate an C<ev_idle> watcher to each such watcher, and in
1320	the normal watcher callback, you just start the idle watcher. The real	1509	the normal watcher callback, you just start the idle watcher. The real
1321	processing is done in the idle watcher callback. This causes libev to	1510	processing is done in the idle watcher callback. This causes libev to
1322	continously poll and process kernel event data for the watcher, but when	1511	continuously poll and process kernel event data for the watcher, but when
1323	the lock-out case is known to be rare (which in turn is rare :), this is	1512	the lock-out case is known to be rare (which in turn is rare :), this is
1324	workable.	1513	workable.
1325		1514
1326	Usually, however, the lock-out model implemented that way will perform	1515	Usually, however, the lock-out model implemented that way will perform
1327	miserably under the type of load it was designed to handle. In that case,	1516	miserably under the type of load it was designed to handle. In that case,
…		…
1341	{	1530	{
1342	// stop the I/O watcher, we received the event, but	1531	// stop the I/O watcher, we received the event, but
1343	// are not yet ready to handle it.	1532	// are not yet ready to handle it.
1344	ev_io_stop (EV_A_ w);	1533	ev_io_stop (EV_A_ w);
1345		1534
1346	// start the idle watcher to ahndle the actual event.	1535	// start the idle watcher to handle the actual event.
1347	// it will not be executed as long as other watchers	1536	// it will not be executed as long as other watchers
1348	// with the default priority are receiving events.	1537	// with the default priority are receiving events.
1349	ev_idle_start (EV_A_ &idle);	1538	ev_idle_start (EV_A_ &idle);
1350	}	1539	}
1351		1540
…		…
1401	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1402	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1403	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1404	required if you know what you are doing).	1593	required if you know what you are doing).
1405		1594
1406	If you cannot use non-blocking mode, then force the use of a
1407	known-to-be-good backend (at the time of this writing, this includes only
1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1409	descriptors for which non-blocking operation makes no sense (such as
1410	files) - libev doesn't guarentee any specific behaviour in that case.
1411
1412	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1413	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1415	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1416	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1417	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1418	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1420		1602
1421	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1422	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1423	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1424	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1425	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1426	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1427	indefinitely.	1609	indefinitely.
1428		1610
1429	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1430		1612
…		…
1458		1640
1459	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1460	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1461	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1462		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1463	=head3 The special problem of fork	1678	=head3 The special problem of fork
1464		1679
1465	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1466	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1467	it in the child.	1682	it in the child if you want to continue to use it in the child.
1468		1683
1469	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1470	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1472	C<EVBACKEND_POLL>.
1473		1687
1474	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1475		1689
1476	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1477	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1480		1694
1481	So when you encounter spurious, unexplained daemon exits, make sure you	1695	So when you encounter spurious, unexplained daemon exits, make sure you
1482	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1696	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1483	somewhere, as that would have given you a big clue).	1697	somewhere, as that would have given you a big clue).
1484		1698
		1699	=head3 The special problem of accept()ing when you can't
		1700
		1701	Many implementations of the POSIX C<accept> function (for example,
		1702	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1703	connection from the pending queue in all error cases.
		1704
		1705	For example, larger servers often run out of file descriptors (because
		1706	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1707	rejecting the connection, leading to libev signalling readiness on
		1708	the next iteration again (the connection still exists after all), and
		1709	typically causing the program to loop at 100% CPU usage.
		1710
		1711	Unfortunately, the set of errors that cause this issue differs between
		1712	operating systems, there is usually little the app can do to remedy the
		1713	situation, and no known thread-safe method of removing the connection to
		1714	cope with overload is known (to me).
		1715
		1716	One of the easiest ways to handle this situation is to just ignore it
		1717	- when the program encounters an overload, it will just loop until the
		1718	situation is over. While this is a form of busy waiting, no OS offers an
		1719	event-based way to handle this situation, so it's the best one can do.
		1720
		1721	A better way to handle the situation is to log any errors other than
		1722	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1723	messages, and continue as usual, which at least gives the user an idea of
		1724	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1725	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1726	usage.
		1727
		1728	If your program is single-threaded, then you could also keep a dummy file
		1729	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1730	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1731	close that fd, and create a new dummy fd. This will gracefully refuse
		1732	clients under typical overload conditions.
		1733
		1734	The last way to handle it is to simply log the error and C<exit>, as
		1735	is often done with C<malloc> failures, but this results in an easy
		1736	opportunity for a DoS attack.
1485		1737
1486	=head3 Watcher-Specific Functions	1738	=head3 Watcher-Specific Functions
1487		1739
1488	=over 4	1740	=over 4
1489		1741
…		…
1521	...	1773	...
1522	struct ev_loop *loop = ev_default_init (0);	1774	struct ev_loop *loop = ev_default_init (0);
1523	ev_io stdin_readable;	1775	ev_io stdin_readable;
1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1776	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1525	ev_io_start (loop, &stdin_readable);	1777	ev_io_start (loop, &stdin_readable);
1526	ev_loop (loop, 0);	1778	ev_run (loop, 0);
1527		1779
1528		1780
1529	=head2 C<ev_timer> - relative and optionally repeating timeouts	1781	=head2 C<ev_timer> - relative and optionally repeating timeouts
1530		1782
1531	Timer watchers are simple relative timers that generate an event after a	1783	Timer watchers are simple relative timers that generate an event after a
…		…
1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1538	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1539		1791
1540	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1541	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1542	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1543	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1544	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1545	no longer true when a callback calls C<ev_loop> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1546		1799
1547	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1548		1801
1549	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1550	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1625		1878
1626	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1627	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1628	within the callback:	1881	within the callback:
1629		1882
		1883	ev_tstamp timeout = 60.;
1630	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1631		1886
1632	static void	1887	static void
1633	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1634	{	1889	{
1635	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1636	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1637		1892
1638	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1639	if (timeout < now)	1894	if (after < 0.)
1640	{	1895	{
1641	// timeout occured, take action	1896	// timeout occurred, take action
1642	}	1897	}
1643	else	1898	else
1644	{	1899	{
1645	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1646	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1647	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1648	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1649	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1650	}	1906	}
1651	}	1907	}
1652		1908
1653	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1654	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1655	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1656	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1657	re-schedule the timer to fire at that future time, to see if maybe we have
1658	a timeout then.
1659		1913
1660	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1661	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1662		1923
1663	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1664	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1665	libev to change the timeout.	1926	libev to change the timeout.
1666		1927
1667	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1668	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1669	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1670		1932
		1933	last_activity = ev_now (EV_A);
1671	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1672	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1673	callback (loop, timer, EV_TIMEOUT);
1674		1936
1675	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1676	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1677		1939
		1940	if (activity detected)
1678	last_actiivty = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1679		1950
1680	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1681	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1682
1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
1684	callback :) - just change the timeout and invoke the callback, which will
1685	fix things for you.
1686		1953
1687	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1688		1955
1689	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1690	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1718	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1719	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1720	overkill :)	1987	overkill :)
1721		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1722	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1723		2027
1724	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1725	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1726	time only before and after C<ev_loop> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1728	lots of events in one iteration.	2032	lots of events in one iteration.
1729		2033
1730	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1731	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1732	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1733	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1734	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1735		2040
1736	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1737		2042
1738	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1740	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
		2080
		2081	=head3 The special problems of suspended animation
		2082
		2083	When you leave the server world it is quite customary to hit machines that
		2084	can suspend/hibernate - what happens to the clocks during such a suspend?
		2085
		2086	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2087	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2088	to run until the system is suspended, but they will not advance while the
		2089	system is suspended. That means, on resume, it will be as if the program
		2090	was frozen for a few seconds, but the suspend time will not be counted
		2091	towards C<ev_timer> when a monotonic clock source is used. The real time
		2092	clock advanced as expected, but if it is used as sole clocksource, then a
		2093	long suspend would be detected as a time jump by libev, and timers would
		2094	be adjusted accordingly.
		2095
		2096	I would not be surprised to see different behaviour in different between
		2097	operating systems, OS versions or even different hardware.
		2098
		2099	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2100	time jump in the monotonic clocks and the realtime clock. If the program
		2101	is suspended for a very long time, and monotonic clock sources are in use,
		2102	then you can expect C<ev_timer>s to expire as the full suspension time
		2103	will be counted towards the timers. When no monotonic clock source is in
		2104	use, then libev will again assume a timejump and adjust accordingly.
		2105
		2106	It might be beneficial for this latter case to call C<ev_suspend>
		2107	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2108	deterministic behaviour in this case (you can do nothing against
		2109	C<SIGSTOP>).
1741		2110
1742	=head3 Watcher-Specific Functions and Data Members	2111	=head3 Watcher-Specific Functions and Data Members
1743		2112
1744	=over 4	2113	=over 4
1745		2114
1746	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2115	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1747		2116
1748	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2117	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1749		2118
1750	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1751	is C<0.>, then it will automatically be stopped once the timeout is	2120	negative values are supported). If C<repeat> is C<0.>, then it will
1752	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1753	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1754	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1755		2124
1756	The timer itself will do a best-effort at avoiding drift, that is, if	2125	The timer itself will do a best-effort at avoiding drift, that is, if
1757	you configure a timer to trigger every 10 seconds, then it will normally	2126	you configure a timer to trigger every 10 seconds, then it will normally
1758	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1759	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1760	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1761		2130
1762	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1763		2132
1764	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
1765	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
1766		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
1767	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1768		2143
1769	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
1770		2146
1771	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
1772	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1773		2149
		2150	=back
		2151
1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1775	usage example.	2153	usage example.
		2154
		2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2156
		2157	Returns the remaining time until a timer fires. If the timer is active,
		2158	then this time is relative to the current event loop time, otherwise it's
		2159	the timeout value currently configured.
		2160
		2161	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2162	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2163	will return C<4>. When the timer expires and is restarted, it will return
		2164	roughly C<7> (likely slightly less as callback invocation takes some time,
		2165	too), and so on.
1776		2166
1777	=item ev_tstamp repeat [read-write]	2167	=item ev_tstamp repeat [read-write]
1778		2168
1779	The current C<repeat> value. Will be used each time the watcher times out	2169	The current C<repeat> value. Will be used each time the watcher times out
1780	or C<ev_timer_again> is called, and determines the next timeout (if any),	2170	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1806	}	2196	}
1807		2197
1808	ev_timer mytimer;	2198	ev_timer mytimer;
1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2199	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1810	ev_timer_again (&mytimer); /* start timer */	2200	ev_timer_again (&mytimer); /* start timer */
1811	ev_loop (loop, 0);	2201	ev_run (loop, 0);
1812		2202
1813	// and in some piece of code that gets executed on any "activity":	2203	// and in some piece of code that gets executed on any "activity":
1814	// reset the timeout to start ticking again at 10 seconds	2204	// reset the timeout to start ticking again at 10 seconds
1815	ev_timer_again (&mytimer);	2205	ev_timer_again (&mytimer);
1816		2206
…		…
1820	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
1821	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
1822		2212
1823	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1824	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
1825	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
1826	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
1827	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
1828	wrist-watch).	2218	wrist-watch).
1829		2219
1830	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
1835	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2225	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1836	it, as it uses a relative timeout).	2226	it, as it uses a relative timeout).
1837		2227
1838	C<ev_periodic> watchers can also be used to implement vastly more complex	2228	C<ev_periodic> watchers can also be used to implement vastly more complex
1839	timers, such as triggering an event on each "midnight, local time", or	2229	timers, such as triggering an event on each "midnight, local time", or
1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2230	other complicated rules. This cannot easily be done with C<ev_timer>
1841	those cannot react to time jumps.	2231	watchers, as those cannot react to time jumps.
1842		2232
1843	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
1844	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
1845	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
1846	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
1847	(but this is no longer true when a callback calls C<ev_loop> recursively).	2237	(but this is no longer true when a callback calls C<ev_run> recursively).
1848		2238
1849	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1850		2240
1851	=over 4	2241	=over 4
1852		2242
…		…
1887		2277
1888	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
1889	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
1890	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
1891		2281
1892	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
1893	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
1894	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
1895		2288
1896	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
1897	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
1898	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
1899	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
1929		2322
1930	NOTE: I<< This callback must always return a time that is higher than or	2323	NOTE: I<< This callback must always return a time that is higher than or
1931	equal to the passed C<now> value >>.	2324	equal to the passed C<now> value >>.
1932		2325
1933	This can be used to create very complex timers, such as a timer that	2326	This can be used to create very complex timers, such as a timer that
1934	triggers on "next midnight, local time". To do this, you would calculate the	2327	triggers on "next midnight, local time". To do this, you would calculate
1935	next midnight after C<now> and return the timestamp value for this. How	2328	the next midnight after C<now> and return the timestamp value for
1936	you do this is, again, up to you (but it is not trivial, which is the main	2329	this. Here is a (completely untested, no error checking) example on how to
1937	reason I omitted it as an example).	2330	do this:
		2331
		2332	#include <time.h>
		2333
		2334	static ev_tstamp
		2335	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2336	{
		2337	time_t tnow = (time_t)now;
		2338	struct tm tm;
		2339	localtime_r (&tnow, &tm);
		2340
		2341	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2342	++tm.tm_mday; // midnight next day
		2343
		2344	return mktime (&tm);
		2345	}
		2346
		2347	Note: this code might run into trouble on days that have more then two
		2348	midnights (beginning and end).
1938		2349
1939	=back	2350	=back
1940		2351
1941	=item ev_periodic_again (loop, ev_periodic *)	2352	=item ev_periodic_again (loop, ev_periodic *)
1942		2353
…		…
1980	Example: Call a callback every hour, or, more precisely, whenever the	2391	Example: Call a callback every hour, or, more precisely, whenever the
1981	system time is divisible by 3600. The callback invocation times have	2392	system time is divisible by 3600. The callback invocation times have
1982	potentially a lot of jitter, but good long-term stability.	2393	potentially a lot of jitter, but good long-term stability.
1983		2394
1984	static void	2395	static void
1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2396	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1986	{	2397	{
1987	... its now a full hour (UTC, or TAI or whatever your clock follows)	2398	... its now a full hour (UTC, or TAI or whatever your clock follows)
1988	}	2399	}
1989		2400
1990	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
…		…
2007		2418
2008	ev_periodic hourly_tick;	2419	ev_periodic hourly_tick;
2009	ev_periodic_init (&hourly_tick, clock_cb,	2420	ev_periodic_init (&hourly_tick, clock_cb,
2010	fmod (ev_now (loop), 3600.), 3600., 0);	2421	fmod (ev_now (loop), 3600.), 3600., 0);
2011	ev_periodic_start (loop, &hourly_tick);	2422	ev_periodic_start (loop, &hourly_tick);
2012		2423
2013		2424
2014	=head2 C<ev_signal> - signal me when a signal gets signalled!	2425	=head2 C<ev_signal> - signal me when a signal gets signalled!
2015		2426
2016	Signal watchers will trigger an event when the process receives a specific	2427	Signal watchers will trigger an event when the process receives a specific
2017	signal one or more times. Even though signals are very asynchronous, libev	2428	signal one or more times. Even though signals are very asynchronous, libev
2018	will try it's best to deliver signals synchronously, i.e. as part of the	2429	will try its best to deliver signals synchronously, i.e. as part of the
2019	normal event processing, like any other event.	2430	normal event processing, like any other event.
2020		2431
2021	If you want signals asynchronously, just use C<sigaction> as you would	2432	If you want signals to be delivered truly asynchronously, just use
2022	do without libev and forget about sharing the signal. You can even use	2433	C<sigaction> as you would do without libev and forget about sharing
2023	C<ev_async> from a signal handler to synchronously wake up an event loop.	2434	the signal. You can even use C<ev_async> from a signal handler to
		2435	synchronously wake up an event loop.
2024		2436
2025	You can configure as many watchers as you like per signal. Only when the	2437	You can configure as many watchers as you like for the same signal, but
2026	first watcher gets started will libev actually register a signal handler	2438	only within the same loop, i.e. you can watch for C<SIGINT> in your
2027	with the kernel (thus it coexists with your own signal handlers as long as	2439	default loop and for C<SIGIO> in another loop, but you cannot watch for
2028	you don't register any with libev for the same signal). Similarly, when	2440	C<SIGINT> in both the default loop and another loop at the same time. At
2029	the last signal watcher for a signal is stopped, libev will reset the	2441	the moment, C<SIGCHLD> is permanently tied to the default loop.
2030	signal handler to SIG_DFL (regardless of what it was set to before).	2442
		2443	Only after the first watcher for a signal is started will libev actually
		2444	register something with the kernel. It thus coexists with your own signal
		2445	handlers as long as you don't register any with libev for the same signal.
2031		2446
2032	If possible and supported, libev will install its handlers with	2447	If possible and supported, libev will install its handlers with
2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2448	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2034	interrupted. If you have a problem with system calls getting interrupted by	2449	not be unduly interrupted. If you have a problem with system calls getting
2035	signals you can block all signals in an C<ev_check> watcher and unblock	2450	interrupted by signals you can block all signals in an C<ev_check> watcher
2036	them in an C<ev_prepare> watcher.	2451	and unblock them in an C<ev_prepare> watcher.
		2452
		2453	=head3 The special problem of inheritance over fork/execve/pthread_create
		2454
		2455	Both the signal mask (C<sigprocmask>) and the signal disposition
		2456	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2457	stopping it again), that is, libev might or might not block the signal,
		2458	and might or might not set or restore the installed signal handler (but
		2459	see C<EVFLAG_NOSIGMASK>).
		2460
		2461	While this does not matter for the signal disposition (libev never
		2462	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2463	C<execve>), this matters for the signal mask: many programs do not expect
		2464	certain signals to be blocked.
		2465
		2466	This means that before calling C<exec> (from the child) you should reset
		2467	the signal mask to whatever "default" you expect (all clear is a good
		2468	choice usually).
		2469
		2470	The simplest way to ensure that the signal mask is reset in the child is
		2471	to install a fork handler with C<pthread_atfork> that resets it. That will
		2472	catch fork calls done by libraries (such as the libc) as well.
		2473
		2474	In current versions of libev, the signal will not be blocked indefinitely
		2475	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2476	the window of opportunity for problems, it will not go away, as libev
		2477	I<has> to modify the signal mask, at least temporarily.
		2478
		2479	So I can't stress this enough: I<If you do not reset your signal mask when
		2480	you expect it to be empty, you have a race condition in your code>. This
		2481	is not a libev-specific thing, this is true for most event libraries.
		2482
		2483	=head3 The special problem of threads signal handling
		2484
		2485	POSIX threads has problematic signal handling semantics, specifically,
		2486	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2487	threads in a process block signals, which is hard to achieve.
		2488
		2489	When you want to use sigwait (or mix libev signal handling with your own
		2490	for the same signals), you can tackle this problem by globally blocking
		2491	all signals before creating any threads (or creating them with a fully set
		2492	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2493	loops. Then designate one thread as "signal receiver thread" which handles
		2494	these signals. You can pass on any signals that libev might be interested
		2495	in by calling C<ev_feed_signal>.
2037		2496
2038	=head3 Watcher-Specific Functions and Data Members	2497	=head3 Watcher-Specific Functions and Data Members
2039		2498
2040	=over 4	2499	=over 4
2041		2500
…		…
2057	Example: Try to exit cleanly on SIGINT.	2516	Example: Try to exit cleanly on SIGINT.
2058		2517
2059	static void	2518	static void
2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2519	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2061	{	2520	{
2062	ev_unloop (loop, EVUNLOOP_ALL);	2521	ev_break (loop, EVBREAK_ALL);
2063	}	2522	}
2064		2523
2065	ev_signal signal_watcher;	2524	ev_signal signal_watcher;
2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2525	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2067	ev_signal_start (loop, &signal_watcher);	2526	ev_signal_start (loop, &signal_watcher);
…		…
2086	libev)	2545	libev)
2087		2546
2088	=head3 Process Interaction	2547	=head3 Process Interaction
2089		2548
2090	Libev grabs C<SIGCHLD> as soon as the default event loop is	2549	Libev grabs C<SIGCHLD> as soon as the default event loop is
2091	initialised. This is necessary to guarantee proper behaviour even if	2550	initialised. This is necessary to guarantee proper behaviour even if the
2092	the first child watcher is started after the child exits. The occurrence	2551	first child watcher is started after the child exits. The occurrence
2093	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2552	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2094	synchronously as part of the event loop processing. Libev always reaps all	2553	synchronously as part of the event loop processing. Libev always reaps all
2095	children, even ones not watched.	2554	children, even ones not watched.
2096		2555
2097	=head3 Overriding the Built-In Processing	2556	=head3 Overriding the Built-In Processing
…		…
2107	=head3 Stopping the Child Watcher	2566	=head3 Stopping the Child Watcher
2108		2567
2109	Currently, the child watcher never gets stopped, even when the	2568	Currently, the child watcher never gets stopped, even when the
2110	child terminates, so normally one needs to stop the watcher in the	2569	child terminates, so normally one needs to stop the watcher in the
2111	callback. Future versions of libev might stop the watcher automatically	2570	callback. Future versions of libev might stop the watcher automatically
2112	when a child exit is detected.	2571	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2572	problem).
2113		2573
2114	=head3 Watcher-Specific Functions and Data Members	2574	=head3 Watcher-Specific Functions and Data Members
2115		2575
2116	=over 4	2576	=over 4
2117		2577
…		…
2175		2635
2176	=head2 C<ev_stat> - did the file attributes just change?	2636	=head2 C<ev_stat> - did the file attributes just change?
2177		2637
2178	This watches a file system path for attribute changes. That is, it calls	2638	This watches a file system path for attribute changes. That is, it calls
2179	C<stat> on that path in regular intervals (or when the OS says it changed)	2639	C<stat> on that path in regular intervals (or when the OS says it changed)
2180	and sees if it changed compared to the last time, invoking the callback if	2640	and sees if it changed compared to the last time, invoking the callback
2181	it did.	2641	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2642	happen after the watcher has been started will be reported.
2182		2643
2183	The path does not need to exist: changing from "path exists" to "path does	2644	The path does not need to exist: changing from "path exists" to "path does
2184	not exist" is a status change like any other. The condition "path does not	2645	not exist" is a status change like any other. The condition "path does not
2185	exist" (or more correctly "path cannot be stat'ed") is signified by the	2646	exist" (or more correctly "path cannot be stat'ed") is signified by the
2186	C<st_nlink> field being zero (which is otherwise always forced to be at	2647	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2416	Apart from keeping your process non-blocking (which is a useful	2877	Apart from keeping your process non-blocking (which is a useful
2417	effect on its own sometimes), idle watchers are a good place to do	2878	effect on its own sometimes), idle watchers are a good place to do
2418	"pseudo-background processing", or delay processing stuff to after the	2879	"pseudo-background processing", or delay processing stuff to after the
2419	event loop has handled all outstanding events.	2880	event loop has handled all outstanding events.
2420		2881
		2882	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2883
		2884	As long as there is at least one active idle watcher, libev will never
		2885	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2886	For this to work, the idle watcher doesn't need to be invoked at all - the
		2887	lowest priority will do.
		2888
		2889	This mode of operation can be useful together with an C<ev_check> watcher,
		2890	to do something on each event loop iteration - for example to balance load
		2891	between different connections.
		2892
		2893	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2894	example.
		2895
2421	=head3 Watcher-Specific Functions and Data Members	2896	=head3 Watcher-Specific Functions and Data Members
2422		2897
2423	=over 4	2898	=over 4
2424		2899
2425	=item ev_idle_init (ev_idle *, callback)	2900	=item ev_idle_init (ev_idle *, callback)
…		…
2436	callback, free it. Also, use no error checking, as usual.	2911	callback, free it. Also, use no error checking, as usual.
2437		2912
2438	static void	2913	static void
2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2914	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2440	{	2915	{
		2916	// stop the watcher
		2917	ev_idle_stop (loop, w);
		2918
		2919	// now we can free it
2441	free (w);	2920	free (w);
		2921
2442	// now do something you wanted to do when the program has	2922	// now do something you wanted to do when the program has
2443	// no longer anything immediate to do.	2923	// no longer anything immediate to do.
2444	}	2924	}
2445		2925
2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2926	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2448	ev_idle_start (loop, idle_watcher);	2928	ev_idle_start (loop, idle_watcher);
2449		2929
2450		2930
2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2931	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2452		2932
2453	Prepare and check watchers are usually (but not always) used in pairs:	2933	Prepare and check watchers are often (but not always) used in pairs:
2454	prepare watchers get invoked before the process blocks and check watchers	2934	prepare watchers get invoked before the process blocks and check watchers
2455	afterwards.	2935	afterwards.
2456		2936
2457	You I<must not> call C<ev_loop> or similar functions that enter	2937	You I<must not> call C<ev_run> (or similar functions that enter the
2458	the current event loop from either C<ev_prepare> or C<ev_check>	2938	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2459	watchers. Other loops than the current one are fine, however. The	2939	C<ev_check> watchers. Other loops than the current one are fine,
2460	rationale behind this is that you do not need to check for recursion in	2940	however. The rationale behind this is that you do not need to check
2461	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2941	for recursion in those watchers, i.e. the sequence will always be
2462	C<ev_check> so if you have one watcher of each kind they will always be	2942	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2463	called in pairs bracketing the blocking call.	2943	kind they will always be called in pairs bracketing the blocking call.
2464		2944
2465	Their main purpose is to integrate other event mechanisms into libev and	2945	Their main purpose is to integrate other event mechanisms into libev and
2466	their use is somewhat advanced. They could be used, for example, to track	2946	their use is somewhat advanced. They could be used, for example, to track
2467	variable changes, implement your own watchers, integrate net-snmp or a	2947	variable changes, implement your own watchers, integrate net-snmp or a
2468	coroutine library and lots more. They are also occasionally useful if	2948	coroutine library and lots more. They are also occasionally useful if
…		…
2486	with priority higher than or equal to the event loop and one coroutine	2966	with priority higher than or equal to the event loop and one coroutine
2487	of lower priority, but only once, using idle watchers to keep the event	2967	of lower priority, but only once, using idle watchers to keep the event
2488	loop from blocking if lower-priority coroutines are active, thus mapping	2968	loop from blocking if lower-priority coroutines are active, thus mapping
2489	low-priority coroutines to idle/background tasks).	2969	low-priority coroutines to idle/background tasks).
2490		2970
2491	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2971	When used for this purpose, it is recommended to give C<ev_check> watchers
2492	priority, to ensure that they are being run before any other watchers	2972	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2493	after the poll (this doesn't matter for C<ev_prepare> watchers).	2973	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2974	watchers).
2494		2975
2495	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2976	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2496	activate ("feed") events into libev. While libev fully supports this, they	2977	activate ("feed") events into libev. While libev fully supports this, they
2497	might get executed before other C<ev_check> watchers did their job. As	2978	might get executed before other C<ev_check> watchers did their job. As
2498	C<ev_check> watchers are often used to embed other (non-libev) event	2979	C<ev_check> watchers are often used to embed other (non-libev) event
2499	loops those other event loops might be in an unusable state until their	2980	loops those other event loops might be in an unusable state until their
2500	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2981	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2501	others).	2982	others).
		2983
		2984	=head3 Abusing an C<ev_check> watcher for its side-effect
		2985
		2986	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2987	useful because they are called once per event loop iteration. For
		2988	example, if you want to handle a large number of connections fairly, you
		2989	normally only do a bit of work for each active connection, and if there
		2990	is more work to do, you wait for the next event loop iteration, so other
		2991	connections have a chance of making progress.
		2992
		2993	Using an C<ev_check> watcher is almost enough: it will be called on the
		2994	next event loop iteration. However, that isn't as soon as possible -
		2995	without external events, your C<ev_check> watcher will not be invoked.
		2996
		2997	This is where C<ev_idle> watchers come in handy - all you need is a
		2998	single global idle watcher that is active as long as you have one active
		2999	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3000	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3001	invoked. Neither watcher alone can do that.
2502		3002
2503	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2504		3004
2505	=over 4	3005	=over 4
2506		3006
…		…
2630		3130
2631	if (timeout >= 0)	3131	if (timeout >= 0)
2632	// create/start timer	3132	// create/start timer
2633		3133
2634	// poll	3134	// poll
2635	ev_loop (EV_A_ 0);	3135	ev_run (EV_A_ 0);
2636		3136
2637	// stop timer again	3137	// stop timer again
2638	if (timeout >= 0)	3138	if (timeout >= 0)
2639	ev_timer_stop (EV_A_ &to);	3139	ev_timer_stop (EV_A_ &to);
2640		3140
…		…
2707		3207
2708	=over 4	3208	=over 4
2709		3209
2710	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2711		3211
2712	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3212	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2713		3213
2714	Configures the watcher to embed the given loop, which must be	3214	Configures the watcher to embed the given loop, which must be
2715	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2716	invoked automatically, otherwise it is the responsibility of the callback	3216	invoked automatically, otherwise it is the responsibility of the callback
2717	to invoke it (it will continue to be called until the sweep has been done,	3217	to invoke it (it will continue to be called until the sweep has been done,
2718	if you do not want that, you need to temporarily stop the embed watcher).	3218	if you do not want that, you need to temporarily stop the embed watcher).
2719		3219
2720	=item ev_embed_sweep (loop, ev_embed *)	3220	=item ev_embed_sweep (loop, ev_embed *)
2721		3221
2722	Make a single, non-blocking sweep over the embedded loop. This works	3222	Make a single, non-blocking sweep over the embedded loop. This works
2723	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3223	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2724	appropriate way for embedded loops.	3224	appropriate way for embedded loops.
2725		3225
2726	=item struct ev_loop *other [read-only]	3226	=item struct ev_loop *other [read-only]
2727		3227
2728	The embedded event loop.	3228	The embedded event loop.
…		…
2738	used).	3238	used).
2739		3239
2740	struct ev_loop *loop_hi = ev_default_init (0);	3240	struct ev_loop *loop_hi = ev_default_init (0);
2741	struct ev_loop *loop_lo = 0;	3241	struct ev_loop *loop_lo = 0;
2742	ev_embed embed;	3242	ev_embed embed;
2743		3243
2744	// see if there is a chance of getting one that works	3244	// see if there is a chance of getting one that works
2745	// (remember that a flags value of 0 means autodetection)	3245	// (remember that a flags value of 0 means autodetection)
2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3246	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3247	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2748	: 0;	3248	: 0;
…		…
2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3262	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2763		3263
2764	struct ev_loop *loop = ev_default_init (0);	3264	struct ev_loop *loop = ev_default_init (0);
2765	struct ev_loop *loop_socket = 0;	3265	struct ev_loop *loop_socket = 0;
2766	ev_embed embed;	3266	ev_embed embed;
2767		3267
2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3268	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3269	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2770	{	3270	{
2771	ev_embed_init (&embed, 0, loop_socket);	3271	ev_embed_init (&embed, 0, loop_socket);
2772	ev_embed_start (loop, &embed);	3272	ev_embed_start (loop, &embed);
…		…
2780		3280
2781	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3281	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2782		3282
2783	Fork watchers are called when a C<fork ()> was detected (usually because	3283	Fork watchers are called when a C<fork ()> was detected (usually because
2784	whoever is a good citizen cared to tell libev about it by calling	3284	whoever is a good citizen cared to tell libev about it by calling
2785	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3285	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2786	event loop blocks next and before C<ev_check> watchers are being called,	3286	and before C<ev_check> watchers are being called, and only in the child
2787	and only in the child after the fork. If whoever good citizen calling	3287	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3288	and calls it in the wrong process, the fork handlers will be invoked, too,
2789	handlers will be invoked, too, of course.	3289	of course.
2790		3290
2791	=head3 The special problem of life after fork - how is it possible?	3291	=head3 The special problem of life after fork - how is it possible?
2792		3292
2793	Most uses of C<fork()> consist of forking, then some simple calls to ste	3293	Most uses of C<fork ()> consist of forking, then some simple calls to set
2794	up/change the process environment, followed by a call to C<exec()>. This	3294	up/change the process environment, followed by a call to C<exec()>. This
2795	sequence should be handled by libev without any problems.	3295	sequence should be handled by libev without any problems.
2796		3296
2797	This changes when the application actually wants to do event handling	3297	This changes when the application actually wants to do event handling
2798	in the child, or both parent in child, in effect "continuing" after the	3298	in the child, or both parent in child, in effect "continuing" after the
…		…
2814	disadvantage of having to use multiple event loops (which do not support	3314	disadvantage of having to use multiple event loops (which do not support
2815	signal watchers).	3315	signal watchers).
2816		3316
2817	When this is not possible, or you want to use the default loop for	3317	When this is not possible, or you want to use the default loop for
2818	other reasons, then in the process that wants to start "fresh", call	3318	other reasons, then in the process that wants to start "fresh", call
2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3319	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2820	the default loop will "orphan" (not stop) all registered watchers, so you	3320	Destroying the default loop will "orphan" (not stop) all registered
2821	have to be careful not to execute code that modifies those watchers. Note	3321	watchers, so you have to be careful not to execute code that modifies
2822	also that in that case, you have to re-register any signal watchers.	3322	those watchers. Note also that in that case, you have to re-register any
		3323	signal watchers.
2823		3324
2824	=head3 Watcher-Specific Functions and Data Members	3325	=head3 Watcher-Specific Functions and Data Members
2825		3326
2826	=over 4	3327	=over 4
2827		3328
2828	=item ev_fork_init (ev_signal *, callback)	3329	=item ev_fork_init (ev_fork *, callback)
2829		3330
2830	Initialises and configures the fork watcher - it has no parameters of any	3331	Initialises and configures the fork watcher - it has no parameters of any
2831	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3332	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2832	believe me.	3333	really.
2833		3334
2834	=back	3335	=back
2835		3336
2836		3337
		3338	=head2 C<ev_cleanup> - even the best things end
		3339
		3340	Cleanup watchers are called just before the event loop is being destroyed
		3341	by a call to C<ev_loop_destroy>.
		3342
		3343	While there is no guarantee that the event loop gets destroyed, cleanup
		3344	watchers provide a convenient method to install cleanup hooks for your
		3345	program, worker threads and so on - you just to make sure to destroy the
		3346	loop when you want them to be invoked.
		3347
		3348	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3349	all other watchers, they do not keep a reference to the event loop (which
		3350	makes a lot of sense if you think about it). Like all other watchers, you
		3351	can call libev functions in the callback, except C<ev_cleanup_start>.
		3352
		3353	=head3 Watcher-Specific Functions and Data Members
		3354
		3355	=over 4
		3356
		3357	=item ev_cleanup_init (ev_cleanup *, callback)
		3358
		3359	Initialises and configures the cleanup watcher - it has no parameters of
		3360	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3361	pointless, I assure you.
		3362
		3363	=back
		3364
		3365	Example: Register an atexit handler to destroy the default loop, so any
		3366	cleanup functions are called.
		3367
		3368	static void
		3369	program_exits (void)
		3370	{
		3371	ev_loop_destroy (EV_DEFAULT_UC);
		3372	}
		3373
		3374	...
		3375	atexit (program_exits);
		3376
		3377
2837	=head2 C<ev_async> - how to wake up another event loop	3378	=head2 C<ev_async> - how to wake up an event loop
2838		3379
2839	In general, you cannot use an C<ev_loop> from multiple threads or other	3380	In general, you cannot use an C<ev_loop> from multiple threads or other
2840	asynchronous sources such as signal handlers (as opposed to multiple event	3381	asynchronous sources such as signal handlers (as opposed to multiple event
2841	loops - those are of course safe to use in different threads).	3382	loops - those are of course safe to use in different threads).
2842		3383
2843	Sometimes, however, you need to wake up another event loop you do not	3384	Sometimes, however, you need to wake up an event loop you do not control,
2844	control, for example because it belongs to another thread. This is what	3385	for example because it belongs to another thread. This is what C<ev_async>
2845	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3386	watchers do: as long as the C<ev_async> watcher is active, you can signal
2846	can signal it by calling C<ev_async_send>, which is thread- and signal	3387	it by calling C<ev_async_send>, which is thread- and signal safe.
2847	safe.
2848		3388
2849	This functionality is very similar to C<ev_signal> watchers, as signals,	3389	This functionality is very similar to C<ev_signal> watchers, as signals,
2850	too, are asynchronous in nature, and signals, too, will be compressed	3390	too, are asynchronous in nature, and signals, too, will be compressed
2851	(i.e. the number of callback invocations may be less than the number of	3391	(i.e. the number of callback invocations may be less than the number of
2852	C<ev_async_sent> calls).	3392	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2853		3393	of "global async watchers" by using a watcher on an otherwise unused
2854	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3394	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2855	just the default loop.	3395	even without knowing which loop owns the signal.
2856		3396
2857	=head3 Queueing	3397	=head3 Queueing
2858		3398
2859	C<ev_async> does not support queueing of data in any way. The reason	3399	C<ev_async> does not support queueing of data in any way. The reason
2860	is that the author does not know of a simple (or any) algorithm for a	3400	is that the author does not know of a simple (or any) algorithm for a
2861	multiple-writer-single-reader queue that works in all cases and doesn't	3401	multiple-writer-single-reader queue that works in all cases and doesn't
2862	need elaborate support such as pthreads.	3402	need elaborate support such as pthreads or unportable memory access
		3403	semantics.
2863		3404
2864	That means that if you want to queue data, you have to provide your own	3405	That means that if you want to queue data, you have to provide your own
2865	queue. But at least I can tell you how to implement locking around your	3406	queue. But at least I can tell you how to implement locking around your
2866	queue:	3407	queue:
2867		3408
…		…
2951	trust me.	3492	trust me.
2952		3493
2953	=item ev_async_send (loop, ev_async *)	3494	=item ev_async_send (loop, ev_async *)
2954		3495
2955	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3496	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2956	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3497	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3498	returns.
		3499
2957	C<ev_feed_event>, this call is safe to do from other threads, signal or	3500	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3501	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2959	section below on what exactly this means).	3502	embedding section below on what exactly this means).
2960		3503
2961	Note that, as with other watchers in libev, multiple events might get	3504	Note that, as with other watchers in libev, multiple events might get
2962	compressed into a single callback invocation (another way to look at this	3505	compressed into a single callback invocation (another way to look at
2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3506	this is that C<ev_async> watchers are level-triggered: they are set on
2964	reset when the event loop detects that).	3507	C<ev_async_send>, reset when the event loop detects that).
2965		3508
2966	This call incurs the overhead of a system call only once per event loop	3509	This call incurs the overhead of at most one extra system call per event
2967	iteration, so while the overhead might be noticeable, it doesn't apply to	3510	loop iteration, if the event loop is blocked, and no syscall at all if
2968	repeated calls to C<ev_async_send> for the same event loop.	3511	the event loop (or your program) is processing events. That means that
		3512	repeated calls are basically free (there is no need to avoid calls for
		3513	performance reasons) and that the overhead becomes smaller (typically
		3514	zero) under load.
2969		3515
2970	=item bool = ev_async_pending (ev_async *)	3516	=item bool = ev_async_pending (ev_async *)
2971		3517
2972	Returns a non-zero value when C<ev_async_send> has been called on the	3518	Returns a non-zero value when C<ev_async_send> has been called on the
2973	watcher but the event has not yet been processed (or even noted) by the	3519	watcher but the event has not yet been processed (or even noted) by the
…		…
2990		3536
2991	There are some other functions of possible interest. Described. Here. Now.	3537	There are some other functions of possible interest. Described. Here. Now.
2992		3538
2993	=over 4	3539	=over 4
2994		3540
2995	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3541	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2996		3542
2997	This function combines a simple timer and an I/O watcher, calls your	3543	This function combines a simple timer and an I/O watcher, calls your
2998	callback on whichever event happens first and automatically stops both	3544	callback on whichever event happens first and automatically stops both
2999	watchers. This is useful if you want to wait for a single event on an fd	3545	watchers. This is useful if you want to wait for a single event on an fd
3000	or timeout without having to allocate/configure/start/stop/free one or	3546	or timeout without having to allocate/configure/start/stop/free one or
…		…
3006		3552
3007	If C<timeout> is less than 0, then no timeout watcher will be	3553	If C<timeout> is less than 0, then no timeout watcher will be
3008	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3554	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3009	repeat = 0) will be started. C<0> is a valid timeout.	3555	repeat = 0) will be started. C<0> is a valid timeout.
3010		3556
3011	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3557	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3012	passed an C<revents> set like normal event callbacks (a combination of	3558	passed an C<revents> set like normal event callbacks (a combination of
3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3559	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3014	value passed to C<ev_once>. Note that it is possible to receive I<both>	3560	value passed to C<ev_once>. Note that it is possible to receive I<both>
3015	a timeout and an io event at the same time - you probably should give io	3561	a timeout and an io event at the same time - you probably should give io
3016	events precedence.	3562	events precedence.
3017		3563
3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3564	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3019		3565
3020	static void stdin_ready (int revents, void *arg)	3566	static void stdin_ready (int revents, void *arg)
3021	{	3567	{
3022	if (revents & EV_READ)	3568	if (revents & EV_READ)
3023	/* stdin might have data for us, joy! */;	3569	/* stdin might have data for us, joy! */;
3024	else if (revents & EV_TIMEOUT)	3570	else if (revents & EV_TIMER)
3025	/* doh, nothing entered */;	3571	/* doh, nothing entered */;
3026	}	3572	}
3027		3573
3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3574	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3029		3575
3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3031
3032	Feeds the given event set into the event loop, as if the specified event
3033	had happened for the specified watcher (which must be a pointer to an
3034	initialised but not necessarily started event watcher).
3035
3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3576	=item ev_feed_fd_event (loop, int fd, int revents)
3037		3577
3038	Feed an event on the given fd, as if a file descriptor backend detected	3578	Feed an event on the given fd, as if a file descriptor backend detected
3039	the given events it.	3579	the given events.
3040		3580
3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3581	=item ev_feed_signal_event (loop, int signum)
3042		3582
3043	Feed an event as if the given signal occurred (C<loop> must be the default	3583	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3044	loop!).	3584	which is async-safe.
3045		3585
3046	=back	3586	=back
		3587
		3588
		3589	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3590
		3591	This section explains some common idioms that are not immediately
		3592	obvious. Note that examples are sprinkled over the whole manual, and this
		3593	section only contains stuff that wouldn't fit anywhere else.
		3594
		3595	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3596
		3597	Each watcher has, by default, a C<void *data> member that you can read
		3598	or modify at any time: libev will completely ignore it. This can be used
		3599	to associate arbitrary data with your watcher. If you need more data and
		3600	don't want to allocate memory separately and store a pointer to it in that
		3601	data member, you can also "subclass" the watcher type and provide your own
		3602	data:
		3603
		3604	struct my_io
		3605	{
		3606	ev_io io;
		3607	int otherfd;
		3608	void *somedata;
		3609	struct whatever *mostinteresting;
		3610	};
		3611
		3612	...
		3613	struct my_io w;
		3614	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3615
		3616	And since your callback will be called with a pointer to the watcher, you
		3617	can cast it back to your own type:
		3618
		3619	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3620	{
		3621	struct my_io *w = (struct my_io *)w_;
		3622	...
		3623	}
		3624
		3625	More interesting and less C-conformant ways of casting your callback
		3626	function type instead have been omitted.
		3627
		3628	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3629
		3630	Another common scenario is to use some data structure with multiple
		3631	embedded watchers, in effect creating your own watcher that combines
		3632	multiple libev event sources into one "super-watcher":
		3633
		3634	struct my_biggy
		3635	{
		3636	int some_data;
		3637	ev_timer t1;
		3638	ev_timer t2;
		3639	}
		3640
		3641	In this case getting the pointer to C<my_biggy> is a bit more
		3642	complicated: Either you store the address of your C<my_biggy> struct in
		3643	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3644	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3645	real programmers):
		3646
		3647	#include <stddef.h>
		3648
		3649	static void
		3650	t1_cb (EV_P_ ev_timer *w, int revents)
		3651	{
		3652	struct my_biggy big = (struct my_biggy *)
		3653	(((char *)w) - offsetof (struct my_biggy, t1));
		3654	}
		3655
		3656	static void
		3657	t2_cb (EV_P_ ev_timer *w, int revents)
		3658	{
		3659	struct my_biggy big = (struct my_biggy *)
		3660	(((char *)w) - offsetof (struct my_biggy, t2));
		3661	}
		3662
		3663	=head2 AVOIDING FINISHING BEFORE RETURNING
		3664
		3665	Often you have structures like this in event-based programs:
		3666
		3667	callback ()
		3668	{
		3669	free (request);
		3670	}
		3671
		3672	request = start_new_request (..., callback);
		3673
		3674	The intent is to start some "lengthy" operation. The C<request> could be
		3675	used to cancel the operation, or do other things with it.
		3676
		3677	It's not uncommon to have code paths in C<start_new_request> that
		3678	immediately invoke the callback, for example, to report errors. Or you add
		3679	some caching layer that finds that it can skip the lengthy aspects of the
		3680	operation and simply invoke the callback with the result.
		3681
		3682	The problem here is that this will happen I<before> C<start_new_request>
		3683	has returned, so C<request> is not set.
		3684
		3685	Even if you pass the request by some safer means to the callback, you
		3686	might want to do something to the request after starting it, such as
		3687	canceling it, which probably isn't working so well when the callback has
		3688	already been invoked.
		3689
		3690	A common way around all these issues is to make sure that
		3691	C<start_new_request> I<always> returns before the callback is invoked. If
		3692	C<start_new_request> immediately knows the result, it can artificially
		3693	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3694	example, or more sneakily, by reusing an existing (stopped) watcher and
		3695	pushing it into the pending queue:
		3696
		3697	ev_set_cb (watcher, callback);
		3698	ev_feed_event (EV_A_ watcher, 0);
		3699
		3700	This way, C<start_new_request> can safely return before the callback is
		3701	invoked, while not delaying callback invocation too much.
		3702
		3703	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3704
		3705	Often (especially in GUI toolkits) there are places where you have
		3706	I<modal> interaction, which is most easily implemented by recursively
		3707	invoking C<ev_run>.
		3708
		3709	This brings the problem of exiting - a callback might want to finish the
		3710	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3711	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3712	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3713	other combination: In these cases, a simple C<ev_break> will not work.
		3714
		3715	The solution is to maintain "break this loop" variable for each C<ev_run>
		3716	invocation, and use a loop around C<ev_run> until the condition is
		3717	triggered, using C<EVRUN_ONCE>:
		3718
		3719	// main loop
		3720	int exit_main_loop = 0;
		3721
		3722	while (!exit_main_loop)
		3723	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3724
		3725	// in a modal watcher
		3726	int exit_nested_loop = 0;
		3727
		3728	while (!exit_nested_loop)
		3729	ev_run (EV_A_ EVRUN_ONCE);
		3730
		3731	To exit from any of these loops, just set the corresponding exit variable:
		3732
		3733	// exit modal loop
		3734	exit_nested_loop = 1;
		3735
		3736	// exit main program, after modal loop is finished
		3737	exit_main_loop = 1;
		3738
		3739	// exit both
		3740	exit_main_loop = exit_nested_loop = 1;
		3741
		3742	=head2 THREAD LOCKING EXAMPLE
		3743
		3744	Here is a fictitious example of how to run an event loop in a different
		3745	thread from where callbacks are being invoked and watchers are
		3746	created/added/removed.
		3747
		3748	For a real-world example, see the C<EV::Loop::Async> perl module,
		3749	which uses exactly this technique (which is suited for many high-level
		3750	languages).
		3751
		3752	The example uses a pthread mutex to protect the loop data, a condition
		3753	variable to wait for callback invocations, an async watcher to notify the
		3754	event loop thread and an unspecified mechanism to wake up the main thread.
		3755
		3756	First, you need to associate some data with the event loop:
		3757
		3758	typedef struct {
		3759	mutex_t lock; /* global loop lock */
		3760	ev_async async_w;
		3761	thread_t tid;
		3762	cond_t invoke_cv;
		3763	} userdata;
		3764
		3765	void prepare_loop (EV_P)
		3766	{
		3767	// for simplicity, we use a static userdata struct.
		3768	static userdata u;
		3769
		3770	ev_async_init (&u->async_w, async_cb);
		3771	ev_async_start (EV_A_ &u->async_w);
		3772
		3773	pthread_mutex_init (&u->lock, 0);
		3774	pthread_cond_init (&u->invoke_cv, 0);
		3775
		3776	// now associate this with the loop
		3777	ev_set_userdata (EV_A_ u);
		3778	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3779	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3780
		3781	// then create the thread running ev_run
		3782	pthread_create (&u->tid, 0, l_run, EV_A);
		3783	}
		3784
		3785	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3786	solely to wake up the event loop so it takes notice of any new watchers
		3787	that might have been added:
		3788
		3789	static void
		3790	async_cb (EV_P_ ev_async *w, int revents)
		3791	{
		3792	// just used for the side effects
		3793	}
		3794
		3795	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3796	protecting the loop data, respectively.
		3797
		3798	static void
		3799	l_release (EV_P)
		3800	{
		3801	userdata *u = ev_userdata (EV_A);
		3802	pthread_mutex_unlock (&u->lock);
		3803	}
		3804
		3805	static void
		3806	l_acquire (EV_P)
		3807	{
		3808	userdata *u = ev_userdata (EV_A);
		3809	pthread_mutex_lock (&u->lock);
		3810	}
		3811
		3812	The event loop thread first acquires the mutex, and then jumps straight
		3813	into C<ev_run>:
		3814
		3815	void *
		3816	l_run (void *thr_arg)
		3817	{
		3818	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3819
		3820	l_acquire (EV_A);
		3821	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3822	ev_run (EV_A_ 0);
		3823	l_release (EV_A);
		3824
		3825	return 0;
		3826	}
		3827
		3828	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3829	signal the main thread via some unspecified mechanism (signals? pipe
		3830	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3831	have been called (in a while loop because a) spurious wakeups are possible
		3832	and b) skipping inter-thread-communication when there are no pending
		3833	watchers is very beneficial):
		3834
		3835	static void
		3836	l_invoke (EV_P)
		3837	{
		3838	userdata *u = ev_userdata (EV_A);
		3839
		3840	while (ev_pending_count (EV_A))
		3841	{
		3842	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3843	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3844	}
		3845	}
		3846
		3847	Now, whenever the main thread gets told to invoke pending watchers, it
		3848	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3849	thread to continue:
		3850
		3851	static void
		3852	real_invoke_pending (EV_P)
		3853	{
		3854	userdata *u = ev_userdata (EV_A);
		3855
		3856	pthread_mutex_lock (&u->lock);
		3857	ev_invoke_pending (EV_A);
		3858	pthread_cond_signal (&u->invoke_cv);
		3859	pthread_mutex_unlock (&u->lock);
		3860	}
		3861
		3862	Whenever you want to start/stop a watcher or do other modifications to an
		3863	event loop, you will now have to lock:
		3864
		3865	ev_timer timeout_watcher;
		3866	userdata *u = ev_userdata (EV_A);
		3867
		3868	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3869
		3870	pthread_mutex_lock (&u->lock);
		3871	ev_timer_start (EV_A_ &timeout_watcher);
		3872	ev_async_send (EV_A_ &u->async_w);
		3873	pthread_mutex_unlock (&u->lock);
		3874
		3875	Note that sending the C<ev_async> watcher is required because otherwise
		3876	an event loop currently blocking in the kernel will have no knowledge
		3877	about the newly added timer. By waking up the loop it will pick up any new
		3878	watchers in the next event loop iteration.
		3879
		3880	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3881
		3882	While the overhead of a callback that e.g. schedules a thread is small, it
		3883	is still an overhead. If you embed libev, and your main usage is with some
		3884	kind of threads or coroutines, you might want to customise libev so that
		3885	doesn't need callbacks anymore.
		3886
		3887	Imagine you have coroutines that you can switch to using a function
		3888	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3889	and that due to some magic, the currently active coroutine is stored in a
		3890	global called C<current_coro>. Then you can build your own "wait for libev
		3891	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3892	the differing C<;> conventions):
		3893
		3894	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3895	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3896
		3897	That means instead of having a C callback function, you store the
		3898	coroutine to switch to in each watcher, and instead of having libev call
		3899	your callback, you instead have it switch to that coroutine.
		3900
		3901	A coroutine might now wait for an event with a function called
		3902	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3903	matter when, or whether the watcher is active or not when this function is
		3904	called):
		3905
		3906	void
		3907	wait_for_event (ev_watcher *w)
		3908	{
		3909	ev_set_cb (w, current_coro);
		3910	switch_to (libev_coro);
		3911	}
		3912
		3913	That basically suspends the coroutine inside C<wait_for_event> and
		3914	continues the libev coroutine, which, when appropriate, switches back to
		3915	this or any other coroutine.
		3916
		3917	You can do similar tricks if you have, say, threads with an event queue -
		3918	instead of storing a coroutine, you store the queue object and instead of
		3919	switching to a coroutine, you push the watcher onto the queue and notify
		3920	any waiters.
		3921
		3922	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3923	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3924
		3925	// my_ev.h
		3926	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3927	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3928	#include "../libev/ev.h"
		3929
		3930	// my_ev.c
		3931	#define EV_H "my_ev.h"
		3932	#include "../libev/ev.c"
		3933
		3934	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3935	F<my_ev.c> into your project. When properly specifying include paths, you
		3936	can even use F<ev.h> as header file name directly.
3047		3937
3048		3938
3049	=head1 LIBEVENT EMULATION	3939	=head1 LIBEVENT EMULATION
3050		3940
3051	Libev offers a compatibility emulation layer for libevent. It cannot	3941	Libev offers a compatibility emulation layer for libevent. It cannot
3052	emulate the internals of libevent, so here are some usage hints:	3942	emulate the internals of libevent, so here are some usage hints:
3053		3943
3054	=over 4	3944	=over 4
		3945
		3946	=item * Only the libevent-1.4.1-beta API is being emulated.
		3947
		3948	This was the newest libevent version available when libev was implemented,
		3949	and is still mostly unchanged in 2010.
3055		3950
3056	=item * Use it by including <event.h>, as usual.	3951	=item * Use it by including <event.h>, as usual.
3057		3952
3058	=item * The following members are fully supported: ev_base, ev_callback,	3953	=item * The following members are fully supported: ev_base, ev_callback,
3059	ev_arg, ev_fd, ev_res, ev_events.	3954	ev_arg, ev_fd, ev_res, ev_events.
…		…
3065	=item * Priorities are not currently supported. Initialising priorities	3960	=item * Priorities are not currently supported. Initialising priorities
3066	will fail and all watchers will have the same priority, even though there	3961	will fail and all watchers will have the same priority, even though there
3067	is an ev_pri field.	3962	is an ev_pri field.
3068		3963
3069	=item * In libevent, the last base created gets the signals, in libev, the	3964	=item * In libevent, the last base created gets the signals, in libev, the
3070	first base created (== the default loop) gets the signals.	3965	base that registered the signal gets the signals.
3071		3966
3072	=item * Other members are not supported.	3967	=item * Other members are not supported.
3073		3968
3074	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3969	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3075	to use the libev header file and library.	3970	to use the libev header file and library.
3076		3971
3077	=back	3972	=back
3078		3973
3079	=head1 C++ SUPPORT	3974	=head1 C++ SUPPORT
		3975
		3976	=head2 C API
		3977
		3978	The normal C API should work fine when used from C++: both ev.h and the
		3979	libev sources can be compiled as C++. Therefore, code that uses the C API
		3980	will work fine.
		3981
		3982	Proper exception specifications might have to be added to callbacks passed
		3983	to libev: exceptions may be thrown only from watcher callbacks, all
		3984	other callbacks (allocator, syserr, loop acquire/release and periodic
		3985	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3986	()> specification. If you have code that needs to be compiled as both C
		3987	and C++ you can use the C<EV_THROW> macro for this:
		3988
		3989	static void
		3990	fatal_error (const char *msg) EV_THROW
		3991	{
		3992	perror (msg);
		3993	abort ();
		3994	}
		3995
		3996	...
		3997	ev_set_syserr_cb (fatal_error);
		3998
		3999	The only API functions that can currently throw exceptions are C<ev_run>,
		4000	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4001	because it runs cleanup watchers).
		4002
		4003	Throwing exceptions in watcher callbacks is only supported if libev itself
		4004	is compiled with a C++ compiler or your C and C++ environments allow
		4005	throwing exceptions through C libraries (most do).
		4006
		4007	=head2 C++ API
3080		4008
3081	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4009	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3082	you to use some convenience methods to start/stop watchers and also change	4010	you to use some convenience methods to start/stop watchers and also change
3083	the callback model to a model using method callbacks on objects.	4011	the callback model to a model using method callbacks on objects.
3084		4012
3085	To use it,	4013	To use it,
3086		4014
3087	#include <ev++.h>	4015	#include <ev++.h>
3088		4016
3089	This automatically includes F<ev.h> and puts all of its definitions (many	4017	This automatically includes F<ev.h> and puts all of its definitions (many
3090	of them macros) into the global namespace. All C++ specific things are	4018	of them macros) into the global namespace. All C++ specific things are
3091	put into the C<ev> namespace. It should support all the same embedding	4019	put into the C<ev> namespace. It should support all the same embedding
…		…
3094	Care has been taken to keep the overhead low. The only data member the C++	4022	Care has been taken to keep the overhead low. The only data member the C++
3095	classes add (compared to plain C-style watchers) is the event loop pointer	4023	classes add (compared to plain C-style watchers) is the event loop pointer
3096	that the watcher is associated with (or no additional members at all if	4024	that the watcher is associated with (or no additional members at all if
3097	you disable C<EV_MULTIPLICITY> when embedding libev).	4025	you disable C<EV_MULTIPLICITY> when embedding libev).
3098		4026
3099	Currently, functions, and static and non-static member functions can be	4027	Currently, functions, static and non-static member functions and classes
3100	used as callbacks. Other types should be easy to add as long as they only	4028	with C<operator ()> can be used as callbacks. Other types should be easy
3101	need one additional pointer for context. If you need support for other	4029	to add as long as they only need one additional pointer for context. If
3102	types of functors please contact the author (preferably after implementing	4030	you need support for other types of functors please contact the author
3103	it).	4031	(preferably after implementing it).
		4032
		4033	For all this to work, your C++ compiler either has to use the same calling
		4034	conventions as your C compiler (for static member functions), or you have
		4035	to embed libev and compile libev itself as C++.
3104		4036
3105	Here is a list of things available in the C<ev> namespace:	4037	Here is a list of things available in the C<ev> namespace:
3106		4038
3107	=over 4	4039	=over 4
3108		4040
…		…
3118	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4050	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3119		4051
3120	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4052	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3121	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4053	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3122	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4054	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3123	defines by many implementations.	4055	defined by many implementations.
3124		4056
3125	All of those classes have these methods:	4057	All of those classes have these methods:
3126		4058
3127	=over 4	4059	=over 4
3128		4060
3129	=item ev::TYPE::TYPE ()	4061	=item ev::TYPE::TYPE ()
3130		4062
3131	=item ev::TYPE::TYPE (struct ev_loop *)	4063	=item ev::TYPE::TYPE (loop)
3132		4064
3133	=item ev::TYPE::~TYPE	4065	=item ev::TYPE::~TYPE
3134		4066
3135	The constructor (optionally) takes an event loop to associate the watcher	4067	The constructor (optionally) takes an event loop to associate the watcher
3136	with. If it is omitted, it will use C<EV_DEFAULT>.	4068	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3169	myclass obj;	4101	myclass obj;
3170	ev::io iow;	4102	ev::io iow;
3171	iow.set <myclass, &myclass::io_cb> (&obj);	4103	iow.set <myclass, &myclass::io_cb> (&obj);
3172		4104
3173	=item w->set (object *)	4105	=item w->set (object *)
3174
3175	This is an B<experimental> feature that might go away in a future version.
3176		4106
3177	This is a variation of a method callback - leaving out the method to call	4107	This is a variation of a method callback - leaving out the method to call
3178	will default the method to C<operator ()>, which makes it possible to use	4108	will default the method to C<operator ()>, which makes it possible to use
3179	functor objects without having to manually specify the C<operator ()> all	4109	functor objects without having to manually specify the C<operator ()> all
3180	the time. Incidentally, you can then also leave out the template argument	4110	the time. Incidentally, you can then also leave out the template argument
…		…
3192	void operator() (ev::io &w, int revents)	4122	void operator() (ev::io &w, int revents)
3193	{	4123	{
3194	...	4124	...
3195	}	4125	}
3196	}	4126	}
3197		4127
3198	myfunctor f;	4128	myfunctor f;
3199		4129
3200	ev::io w;	4130	ev::io w;
3201	w.set (&f);	4131	w.set (&f);
3202		4132
…		…
3213	Example: Use a plain function as callback.	4143	Example: Use a plain function as callback.
3214		4144
3215	static void io_cb (ev::io &w, int revents) { }	4145	static void io_cb (ev::io &w, int revents) { }
3216	iow.set <io_cb> ();	4146	iow.set <io_cb> ();
3217		4147
3218	=item w->set (struct ev_loop *)	4148	=item w->set (loop)
3219		4149
3220	Associates a different C<struct ev_loop> with this watcher. You can only	4150	Associates a different C<struct ev_loop> with this watcher. You can only
3221	do this when the watcher is inactive (and not pending either).	4151	do this when the watcher is inactive (and not pending either).
3222		4152
3223	=item w->set ([arguments])	4153	=item w->set ([arguments])
3224		4154
3225	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4155	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4156	with the same arguments. Either this method or a suitable start method
3226	called at least once. Unlike the C counterpart, an active watcher gets	4157	must be called at least once. Unlike the C counterpart, an active watcher
3227	automatically stopped and restarted when reconfiguring it with this	4158	gets automatically stopped and restarted when reconfiguring it with this
3228	method.	4159	method.
		4160
		4161	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4162	clashing with the C<set (loop)> method.
3229		4163
3230	=item w->start ()	4164	=item w->start ()
3231		4165
3232	Starts the watcher. Note that there is no C<loop> argument, as the	4166	Starts the watcher. Note that there is no C<loop> argument, as the
3233	constructor already stores the event loop.	4167	constructor already stores the event loop.
3234		4168
		4169	=item w->start ([arguments])
		4170
		4171	Instead of calling C<set> and C<start> methods separately, it is often
		4172	convenient to wrap them in one call. Uses the same type of arguments as
		4173	the configure C<set> method of the watcher.
		4174
3235	=item w->stop ()	4175	=item w->stop ()
3236		4176
3237	Stops the watcher if it is active. Again, no C<loop> argument.	4177	Stops the watcher if it is active. Again, no C<loop> argument.
3238		4178
3239	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4179	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3251		4191
3252	=back	4192	=back
3253		4193
3254	=back	4194	=back
3255		4195
3256	Example: Define a class with an IO and idle watcher, start one of them in	4196	Example: Define a class with two I/O and idle watchers, start the I/O
3257	the constructor.	4197	watchers in the constructor.
3258		4198
3259	class myclass	4199	class myclass
3260	{	4200	{
3261	ev::io io ; void io_cb (ev::io &w, int revents);	4201	ev::io io ; void io_cb (ev::io &w, int revents);
		4202	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4203	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3263		4204
3264	myclass (int fd)	4205	myclass (int fd)
3265	{	4206	{
3266	io .set <myclass, &myclass::io_cb > (this);	4207	io .set <myclass, &myclass::io_cb > (this);
		4208	io2 .set <myclass, &myclass::io2_cb > (this);
3267	idle.set <myclass, &myclass::idle_cb> (this);	4209	idle.set <myclass, &myclass::idle_cb> (this);
3268		4210
3269	io.start (fd, ev::READ);	4211	io.set (fd, ev::WRITE); // configure the watcher
		4212	io.start (); // start it whenever convenient
		4213
		4214	io2.start (fd, ev::READ); // set + start in one call
3270	}	4215	}
3271	};	4216	};
3272		4217
3273		4218
3274	=head1 OTHER LANGUAGE BINDINGS	4219	=head1 OTHER LANGUAGE BINDINGS
…		…
3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4258	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3314		4259
3315	=item D	4260	=item D
3316		4261
3317	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4262	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4263	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3319		4264
3320	=item Ocaml	4265	=item Ocaml
3321		4266
3322	Erkki Seppala has written Ocaml bindings for libev, to be found at	4267	Erkki Seppala has written Ocaml bindings for libev, to be found at
3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4268	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4269
		4270	=item Lua
		4271
		4272	Brian Maher has written a partial interface to libev for lua (at the
		4273	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4274	L<http://github.com/brimworks/lua-ev>.
		4275
		4276	=item Javascript
		4277
		4278	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4279
		4280	=item Others
		4281
		4282	There are others, and I stopped counting.
3324		4283
3325	=back	4284	=back
3326		4285
3327		4286
3328	=head1 MACRO MAGIC	4287	=head1 MACRO MAGIC
…		…
3342	loop argument"). The C<EV_A> form is used when this is the sole argument,	4301	loop argument"). The C<EV_A> form is used when this is the sole argument,
3343	C<EV_A_> is used when other arguments are following. Example:	4302	C<EV_A_> is used when other arguments are following. Example:
3344		4303
3345	ev_unref (EV_A);	4304	ev_unref (EV_A);
3346	ev_timer_add (EV_A_ watcher);	4305	ev_timer_add (EV_A_ watcher);
3347	ev_loop (EV_A_ 0);	4306	ev_run (EV_A_ 0);
3348		4307
3349	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4308	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3350	which is often provided by the following macro.	4309	which is often provided by the following macro.
3351		4310
3352	=item C<EV_P>, C<EV_P_>	4311	=item C<EV_P>, C<EV_P_>
…		…
3365	suitable for use with C<EV_A>.	4324	suitable for use with C<EV_A>.
3366		4325
3367	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4326	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3368		4327
3369	Similar to the other two macros, this gives you the value of the default	4328	Similar to the other two macros, this gives you the value of the default
3370	loop, if multiple loops are supported ("ev loop default").	4329	loop, if multiple loops are supported ("ev loop default"). The default loop
		4330	will be initialised if it isn't already initialised.
		4331
		4332	For non-multiplicity builds, these macros do nothing, so you always have
		4333	to initialise the loop somewhere.
3371		4334
3372	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4335	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3373		4336
3374	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4337	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3375	default loop has been initialised (C<UC> == unchecked). Their behaviour	4338	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3392	}	4355	}
3393		4356
3394	ev_check check;	4357	ev_check check;
3395	ev_check_init (&check, check_cb);	4358	ev_check_init (&check, check_cb);
3396	ev_check_start (EV_DEFAULT_ &check);	4359	ev_check_start (EV_DEFAULT_ &check);
3397	ev_loop (EV_DEFAULT_ 0);	4360	ev_run (EV_DEFAULT_ 0);
3398		4361
3399	=head1 EMBEDDING	4362	=head1 EMBEDDING
3400		4363
3401	Libev can (and often is) directly embedded into host	4364	Libev can (and often is) directly embedded into host
3402	applications. Examples of applications that embed it include the Deliantra	4365	applications. Examples of applications that embed it include the Deliantra
…		…
3442	ev_vars.h	4405	ev_vars.h
3443	ev_wrap.h	4406	ev_wrap.h
3444		4407
3445	ev_win32.c required on win32 platforms only	4408	ev_win32.c required on win32 platforms only
3446		4409
3447	ev_select.c only when select backend is enabled (which is enabled by default)	4410	ev_select.c only when select backend is enabled
3448	ev_poll.c only when poll backend is enabled (disabled by default)	4411	ev_poll.c only when poll backend is enabled
3449	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4412	ev_epoll.c only when the epoll backend is enabled
3450	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4413	ev_kqueue.c only when the kqueue backend is enabled
3451	ev_port.c only when the solaris port backend is enabled (disabled by default)	4414	ev_port.c only when the solaris port backend is enabled
3452		4415
3453	F<ev.c> includes the backend files directly when enabled, so you only need	4416	F<ev.c> includes the backend files directly when enabled, so you only need
3454	to compile this single file.	4417	to compile this single file.
3455		4418
3456	=head3 LIBEVENT COMPATIBILITY API	4419	=head3 LIBEVENT COMPATIBILITY API
…		…
3482	libev.m4	4445	libev.m4
3483		4446
3484	=head2 PREPROCESSOR SYMBOLS/MACROS	4447	=head2 PREPROCESSOR SYMBOLS/MACROS
3485		4448
3486	Libev can be configured via a variety of preprocessor symbols you have to	4449	Libev can be configured via a variety of preprocessor symbols you have to
3487	define before including any of its files. The default in the absence of	4450	define before including (or compiling) any of its files. The default in
3488	autoconf is documented for every option.	4451	the absence of autoconf is documented for every option.
		4452
		4453	Symbols marked with "(h)" do not change the ABI, and can have different
		4454	values when compiling libev vs. including F<ev.h>, so it is permissible
		4455	to redefine them before including F<ev.h> without breaking compatibility
		4456	to a compiled library. All other symbols change the ABI, which means all
		4457	users of libev and the libev code itself must be compiled with compatible
		4458	settings.
3489		4459
3490	=over 4	4460	=over 4
3491		4461
		4462	=item EV_COMPAT3 (h)
		4463
		4464	Backwards compatibility is a major concern for libev. This is why this
		4465	release of libev comes with wrappers for the functions and symbols that
		4466	have been renamed between libev version 3 and 4.
		4467
		4468	You can disable these wrappers (to test compatibility with future
		4469	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4470	sources. This has the additional advantage that you can drop the C<struct>
		4471	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4472	typedef in that case.
		4473
		4474	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4475	and in some even more future version the compatibility code will be
		4476	removed completely.
		4477
3492	=item EV_STANDALONE	4478	=item EV_STANDALONE (h)
3493		4479
3494	Must always be C<1> if you do not use autoconf configuration, which	4480	Must always be C<1> if you do not use autoconf configuration, which
3495	keeps libev from including F<config.h>, and it also defines dummy	4481	keeps libev from including F<config.h>, and it also defines dummy
3496	implementations for some libevent functions (such as logging, which is not	4482	implementations for some libevent functions (such as logging, which is not
3497	supported). It will also not define any of the structs usually found in	4483	supported). It will also not define any of the structs usually found in
3498	F<event.h> that are not directly supported by the libev core alone.	4484	F<event.h> that are not directly supported by the libev core alone.
3499		4485
3500	In stanbdalone mode, libev will still try to automatically deduce the	4486	In standalone mode, libev will still try to automatically deduce the
3501	configuration, but has to be more conservative.	4487	configuration, but has to be more conservative.
		4488
		4489	=item EV_USE_FLOOR
		4490
		4491	If defined to be C<1>, libev will use the C<floor ()> function for its
		4492	periodic reschedule calculations, otherwise libev will fall back on a
		4493	portable (slower) implementation. If you enable this, you usually have to
		4494	link against libm or something equivalent. Enabling this when the C<floor>
		4495	function is not available will fail, so the safe default is to not enable
		4496	this.
3502		4497
3503	=item EV_USE_MONOTONIC	4498	=item EV_USE_MONOTONIC
3504		4499
3505	If defined to be C<1>, libev will try to detect the availability of the	4500	If defined to be C<1>, libev will try to detect the availability of the
3506	monotonic clock option at both compile time and runtime. Otherwise no	4501	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3570	be used is the winsock select). This means that it will call	4565	be used is the winsock select). This means that it will call
3571	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4566	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3572	it is assumed that all these functions actually work on fds, even	4567	it is assumed that all these functions actually work on fds, even
3573	on win32. Should not be defined on non-win32 platforms.	4568	on win32. Should not be defined on non-win32 platforms.
3574		4569
3575	=item EV_FD_TO_WIN32_HANDLE	4570	=item EV_FD_TO_WIN32_HANDLE(fd)
3576		4571
3577	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4572	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3578	file descriptors to socket handles. When not defining this symbol (the	4573	file descriptors to socket handles. When not defining this symbol (the
3579	default), then libev will call C<_get_osfhandle>, which is usually	4574	default), then libev will call C<_get_osfhandle>, which is usually
3580	correct. In some cases, programs use their own file descriptor management,	4575	correct. In some cases, programs use their own file descriptor management,
3581	in which case they can provide this function to map fds to socket handles.	4576	in which case they can provide this function to map fds to socket handles.
		4577
		4578	=item EV_WIN32_HANDLE_TO_FD(handle)
		4579
		4580	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4581	using the standard C<_open_osfhandle> function. For programs implementing
		4582	their own fd to handle mapping, overwriting this function makes it easier
		4583	to do so. This can be done by defining this macro to an appropriate value.
		4584
		4585	=item EV_WIN32_CLOSE_FD(fd)
		4586
		4587	If programs implement their own fd to handle mapping on win32, then this
		4588	macro can be used to override the C<close> function, useful to unregister
		4589	file descriptors again. Note that the replacement function has to close
		4590	the underlying OS handle.
		4591
		4592	=item EV_USE_WSASOCKET
		4593
		4594	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4595	communication socket, which works better in some environments. Otherwise,
		4596	the normal C<socket> function will be used, which works better in other
		4597	environments.
3582		4598
3583	=item EV_USE_POLL	4599	=item EV_USE_POLL
3584		4600
3585	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4601	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3586	backend. Otherwise it will be enabled on non-win32 platforms. It	4602	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3622	If defined to be C<1>, libev will compile in support for the Linux inotify	4638	If defined to be C<1>, libev will compile in support for the Linux inotify
3623	interface to speed up C<ev_stat> watchers. Its actual availability will	4639	interface to speed up C<ev_stat> watchers. Its actual availability will
3624	be detected at runtime. If undefined, it will be enabled if the headers	4640	be detected at runtime. If undefined, it will be enabled if the headers
3625	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4641	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3626		4642
		4643	=item EV_NO_SMP
		4644
		4645	If defined to be C<1>, libev will assume that memory is always coherent
		4646	between threads, that is, threads can be used, but threads never run on
		4647	different cpus (or different cpu cores). This reduces dependencies
		4648	and makes libev faster.
		4649
		4650	=item EV_NO_THREADS
		4651
		4652	If defined to be C<1>, libev will assume that it will never be called from
		4653	different threads (that includes signal handlers), which is a stronger
		4654	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4655	libev faster.
		4656
3627	=item EV_ATOMIC_T	4657	=item EV_ATOMIC_T
3628		4658
3629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4659	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3630	access is atomic with respect to other threads or signal contexts. No such	4660	access is atomic with respect to other threads or signal contexts. No
3631	type is easily found in the C language, so you can provide your own type	4661	such type is easily found in the C language, so you can provide your own
3632	that you know is safe for your purposes. It is used both for signal handler "locking"	4662	type that you know is safe for your purposes. It is used both for signal
3633	as well as for signal and thread safety in C<ev_async> watchers.	4663	handler "locking" as well as for signal and thread safety in C<ev_async>
		4664	watchers.
3634		4665
3635	In the absence of this define, libev will use C<sig_atomic_t volatile>	4666	In the absence of this define, libev will use C<sig_atomic_t volatile>
3636	(from F<signal.h>), which is usually good enough on most platforms.	4667	(from F<signal.h>), which is usually good enough on most platforms.
3637		4668
3638	=item EV_H	4669	=item EV_H (h)
3639		4670
3640	The name of the F<ev.h> header file used to include it. The default if	4671	The name of the F<ev.h> header file used to include it. The default if
3641	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4672	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3642	used to virtually rename the F<ev.h> header file in case of conflicts.	4673	used to virtually rename the F<ev.h> header file in case of conflicts.
3643		4674
3644	=item EV_CONFIG_H	4675	=item EV_CONFIG_H (h)
3645		4676
3646	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4677	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3647	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4678	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3648	C<EV_H>, above.	4679	C<EV_H>, above.
3649		4680
3650	=item EV_EVENT_H	4681	=item EV_EVENT_H (h)
3651		4682
3652	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4683	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3653	of how the F<event.h> header can be found, the default is C<"event.h">.	4684	of how the F<event.h> header can be found, the default is C<"event.h">.
3654		4685
3655	=item EV_PROTOTYPES	4686	=item EV_PROTOTYPES (h)
3656		4687
3657	If defined to be C<0>, then F<ev.h> will not define any function	4688	If defined to be C<0>, then F<ev.h> will not define any function
3658	prototypes, but still define all the structs and other symbols. This is	4689	prototypes, but still define all the structs and other symbols. This is
3659	occasionally useful if you want to provide your own wrapper functions	4690	occasionally useful if you want to provide your own wrapper functions
3660	around libev functions.	4691	around libev functions.
…		…
3665	will have the C<struct ev_loop *> as first argument, and you can create	4696	will have the C<struct ev_loop *> as first argument, and you can create
3666	additional independent event loops. Otherwise there will be no support	4697	additional independent event loops. Otherwise there will be no support
3667	for multiple event loops and there is no first event loop pointer	4698	for multiple event loops and there is no first event loop pointer
3668	argument. Instead, all functions act on the single default loop.	4699	argument. Instead, all functions act on the single default loop.
3669		4700
		4701	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4702	default loop when multiplicity is switched off - you always have to
		4703	initialise the loop manually in this case.
		4704
3670	=item EV_MINPRI	4705	=item EV_MINPRI
3671		4706
3672	=item EV_MAXPRI	4707	=item EV_MAXPRI
3673		4708
3674	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4709	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3682	fine.	4717	fine.
3683		4718
3684	If your embedding application does not need any priorities, defining these	4719	If your embedding application does not need any priorities, defining these
3685	both to C<0> will save some memory and CPU.	4720	both to C<0> will save some memory and CPU.
3686		4721
3687	=item EV_PERIODIC_ENABLE	4722	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4723	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4724	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3688		4725
3689	If undefined or defined to be C<1>, then periodic timers are supported. If	4726	If undefined or defined to be C<1> (and the platform supports it), then
3690	defined to be C<0>, then they are not. Disabling them saves a few kB of	4727	the respective watcher type is supported. If defined to be C<0>, then it
3691	code.	4728	is not. Disabling watcher types mainly saves code size.
3692		4729
3693	=item EV_IDLE_ENABLE	4730	=item EV_FEATURES
3694
3695	If undefined or defined to be C<1>, then idle watchers are supported. If
3696	defined to be C<0>, then they are not. Disabling them saves a few kB of
3697	code.
3698
3699	=item EV_EMBED_ENABLE
3700
3701	If undefined or defined to be C<1>, then embed watchers are supported. If
3702	defined to be C<0>, then they are not. Embed watchers rely on most other
3703	watcher types, which therefore must not be disabled.
3704
3705	=item EV_STAT_ENABLE
3706
3707	If undefined or defined to be C<1>, then stat watchers are supported. If
3708	defined to be C<0>, then they are not.
3709
3710	=item EV_FORK_ENABLE
3711
3712	If undefined or defined to be C<1>, then fork watchers are supported. If
3713	defined to be C<0>, then they are not.
3714
3715	=item EV_ASYNC_ENABLE
3716
3717	If undefined or defined to be C<1>, then async watchers are supported. If
3718	defined to be C<0>, then they are not.
3719
3720	=item EV_MINIMAL
3721		4731
3722	If you need to shave off some kilobytes of code at the expense of some	4732	If you need to shave off some kilobytes of code at the expense of some
3723	speed (but with the full API), define this symbol to C<1>. Currently this	4733	speed (but with the full API), you can define this symbol to request
3724	is used to override some inlining decisions, saves roughly 30% code size	4734	certain subsets of functionality. The default is to enable all features
3725	on amd64. It also selects a much smaller 2-heap for timer management over	4735	that can be enabled on the platform.
3726	the default 4-heap.
3727		4736
3728	You can save even more by disabling watcher types you do not need	4737	A typical way to use this symbol is to define it to C<0> (or to a bitset
3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4738	with some broad features you want) and then selectively re-enable
3730	(C<-DNDEBUG>) will usually reduce code size a lot.	4739	additional parts you want, for example if you want everything minimal,
		4740	but multiple event loop support, async and child watchers and the poll
		4741	backend, use this:
3731		4742
3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4743	#define EV_FEATURES 0
3733	provide a bare-bones event library. See C<ev.h> for details on what parts	4744	#define EV_MULTIPLICITY 1
3734	of the API are still available, and do not complain if this subset changes	4745	#define EV_USE_POLL 1
3735	over time.	4746	#define EV_CHILD_ENABLE 1
		4747	#define EV_ASYNC_ENABLE 1
		4748
		4749	The actual value is a bitset, it can be a combination of the following
		4750	values (by default, all of these are enabled):
		4751
		4752	=over 4
		4753
		4754	=item C<1> - faster/larger code
		4755
		4756	Use larger code to speed up some operations.
		4757
		4758	Currently this is used to override some inlining decisions (enlarging the
		4759	code size by roughly 30% on amd64).
		4760
		4761	When optimising for size, use of compiler flags such as C<-Os> with
		4762	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4763	assertions.
		4764
		4765	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4766	(e.g. gcc with C<-Os>).
		4767
		4768	=item C<2> - faster/larger data structures
		4769
		4770	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4771	hash table sizes and so on. This will usually further increase code size
		4772	and can additionally have an effect on the size of data structures at
		4773	runtime.
		4774
		4775	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4776	(e.g. gcc with C<-Os>).
		4777
		4778	=item C<4> - full API configuration
		4779
		4780	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4781	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4782
		4783	=item C<8> - full API
		4784
		4785	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4786	details on which parts of the API are still available without this
		4787	feature, and do not complain if this subset changes over time.
		4788
		4789	=item C<16> - enable all optional watcher types
		4790
		4791	Enables all optional watcher types. If you want to selectively enable
		4792	only some watcher types other than I/O and timers (e.g. prepare,
		4793	embed, async, child...) you can enable them manually by defining
		4794	C<EV_watchertype_ENABLE> to C<1> instead.
		4795
		4796	=item C<32> - enable all backends
		4797
		4798	This enables all backends - without this feature, you need to enable at
		4799	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4800
		4801	=item C<64> - enable OS-specific "helper" APIs
		4802
		4803	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4804	default.
		4805
		4806	=back
		4807
		4808	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4809	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4810	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4811	watchers, timers and monotonic clock support.
		4812
		4813	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4814	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4815	your program might be left out as well - a binary starting a timer and an
		4816	I/O watcher then might come out at only 5Kb.
		4817
		4818	=item EV_API_STATIC
		4819
		4820	If this symbol is defined (by default it is not), then all identifiers
		4821	will have static linkage. This means that libev will not export any
		4822	identifiers, and you cannot link against libev anymore. This can be useful
		4823	when you embed libev, only want to use libev functions in a single file,
		4824	and do not want its identifiers to be visible.
		4825
		4826	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4827	wants to use libev.
		4828
		4829	This option only works when libev is compiled with a C compiler, as C++
		4830	doesn't support the required declaration syntax.
		4831
		4832	=item EV_AVOID_STDIO
		4833
		4834	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4835	functions (printf, scanf, perror etc.). This will increase the code size
		4836	somewhat, but if your program doesn't otherwise depend on stdio and your
		4837	libc allows it, this avoids linking in the stdio library which is quite
		4838	big.
		4839
		4840	Note that error messages might become less precise when this option is
		4841	enabled.
		4842
		4843	=item EV_NSIG
		4844
		4845	The highest supported signal number, +1 (or, the number of
		4846	signals): Normally, libev tries to deduce the maximum number of signals
		4847	automatically, but sometimes this fails, in which case it can be
		4848	specified. Also, using a lower number than detected (C<32> should be
		4849	good for about any system in existence) can save some memory, as libev
		4850	statically allocates some 12-24 bytes per signal number.
3736		4851
3737	=item EV_PID_HASHSIZE	4852	=item EV_PID_HASHSIZE
3738		4853
3739	C<ev_child> watchers use a small hash table to distribute workload by	4854	C<ev_child> watchers use a small hash table to distribute workload by
3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4855	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3741	than enough. If you need to manage thousands of children you might want to	4856	usually more than enough. If you need to manage thousands of children you
3742	increase this value (I<must> be a power of two).	4857	might want to increase this value (I<must> be a power of two).
3743		4858
3744	=item EV_INOTIFY_HASHSIZE	4859	=item EV_INOTIFY_HASHSIZE
3745		4860
3746	C<ev_stat> watchers use a small hash table to distribute workload by	4861	C<ev_stat> watchers use a small hash table to distribute workload by
3747	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4862	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3748	usually more than enough. If you need to manage thousands of C<ev_stat>	4863	disabled), usually more than enough. If you need to manage thousands of
3749	watchers you might want to increase this value (I<must> be a power of	4864	C<ev_stat> watchers you might want to increase this value (I<must> be a
3750	two).	4865	power of two).
3751		4866
3752	=item EV_USE_4HEAP	4867	=item EV_USE_4HEAP
3753		4868
3754	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4869	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3755	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4870	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4871	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3757	faster performance with many (thousands) of watchers.	4872	faster performance with many (thousands) of watchers.
3758		4873
3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4874	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3760	(disabled).	4875	will be C<0>.
3761		4876
3762	=item EV_HEAP_CACHE_AT	4877	=item EV_HEAP_CACHE_AT
3763		4878
3764	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4879	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3765	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4880	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3766	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4881	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3767	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4882	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3768	but avoids random read accesses on heap changes. This improves performance	4883	but avoids random read accesses on heap changes. This improves performance
3769	noticeably with many (hundreds) of watchers.	4884	noticeably with many (hundreds) of watchers.
3770		4885
3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4886	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3772	(disabled).	4887	will be C<0>.
3773		4888
3774	=item EV_VERIFY	4889	=item EV_VERIFY
3775		4890
3776	Controls how much internal verification (see C<ev_loop_verify ()>) will	4891	Controls how much internal verification (see C<ev_verify ()>) will
3777	be done: If set to C<0>, no internal verification code will be compiled	4892	be done: If set to C<0>, no internal verification code will be compiled
3778	in. If set to C<1>, then verification code will be compiled in, but not	4893	in. If set to C<1>, then verification code will be compiled in, but not
3779	called. If set to C<2>, then the internal verification code will be	4894	called. If set to C<2>, then the internal verification code will be
3780	called once per loop, which can slow down libev. If set to C<3>, then the	4895	called once per loop, which can slow down libev. If set to C<3>, then the
3781	verification code will be called very frequently, which will slow down	4896	verification code will be called very frequently, which will slow down
3782	libev considerably.	4897	libev considerably.
3783		4898
3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4899	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3785	C<0>.	4900	will be C<0>.
3786		4901
3787	=item EV_COMMON	4902	=item EV_COMMON
3788		4903
3789	By default, all watchers have a C<void *data> member. By redefining	4904	By default, all watchers have a C<void *data> member. By redefining
3790	this macro to a something else you can include more and other types of	4905	this macro to something else you can include more and other types of
3791	members. You have to define it each time you include one of the files,	4906	members. You have to define it each time you include one of the files,
3792	though, and it must be identical each time.	4907	though, and it must be identical each time.
3793		4908
3794	For example, the perl EV module uses something like this:	4909	For example, the perl EV module uses something like this:
3795		4910
…		…
3848	file.	4963	file.
3849		4964
3850	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4965	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3851	that everybody includes and which overrides some configure choices:	4966	that everybody includes and which overrides some configure choices:
3852		4967
3853	#define EV_MINIMAL 1	4968	#define EV_FEATURES 8
3854	#define EV_USE_POLL 0	4969	#define EV_USE_SELECT 1
3855	#define EV_MULTIPLICITY 0
3856	#define EV_PERIODIC_ENABLE 0	4970	#define EV_PREPARE_ENABLE 1
		4971	#define EV_IDLE_ENABLE 1
3857	#define EV_STAT_ENABLE 0	4972	#define EV_SIGNAL_ENABLE 1
3858	#define EV_FORK_ENABLE 0	4973	#define EV_CHILD_ENABLE 1
		4974	#define EV_USE_STDEXCEPT 0
3859	#define EV_CONFIG_H <config.h>	4975	#define EV_CONFIG_H <config.h>
3860	#define EV_MINPRI 0
3861	#define EV_MAXPRI 0
3862		4976
3863	#include "ev++.h"	4977	#include "ev++.h"
3864		4978
3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4979	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3866		4980
3867	#include "ev_cpp.h"	4981	#include "ev_cpp.h"
3868	#include "ev.c"	4982	#include "ev.c"
3869		4983
3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4984	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3871		4985
3872	=head2 THREADS AND COROUTINES	4986	=head2 THREADS AND COROUTINES
3873		4987
3874	=head3 THREADS	4988	=head3 THREADS
3875		4989
…		…
3926	default loop and triggering an C<ev_async> watcher from the default loop	5040	default loop and triggering an C<ev_async> watcher from the default loop
3927	watcher callback into the event loop interested in the signal.	5041	watcher callback into the event loop interested in the signal.
3928		5042
3929	=back	5043	=back
3930		5044
3931	=head4 THREAD LOCKING EXAMPLE	5045	See also L</THREAD LOCKING EXAMPLE>.
3932		5046
3933	=head3 COROUTINES	5047	=head3 COROUTINES
3934		5048
3935	Libev is very accommodating to coroutines ("cooperative threads"):	5049	Libev is very accommodating to coroutines ("cooperative threads"):
3936	libev fully supports nesting calls to its functions from different	5050	libev fully supports nesting calls to its functions from different
3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5051	coroutines (e.g. you can call C<ev_run> on the same loop from two
3938	different coroutines, and switch freely between both coroutines running the	5052	different coroutines, and switch freely between both coroutines running
3939	loop, as long as you don't confuse yourself). The only exception is that	5053	the loop, as long as you don't confuse yourself). The only exception is
3940	you must not do this from C<ev_periodic> reschedule callbacks.	5054	that you must not do this from C<ev_periodic> reschedule callbacks.
3941		5055
3942	Care has been taken to ensure that libev does not keep local state inside	5056	Care has been taken to ensure that libev does not keep local state inside
3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5057	C<ev_run>, and other calls do not usually allow for coroutine switches as
3944	they do not call any callbacks.	5058	they do not call any callbacks.
3945		5059
3946	=head2 COMPILER WARNINGS	5060	=head2 COMPILER WARNINGS
3947		5061
3948	Depending on your compiler and compiler settings, you might get no or a	5062	Depending on your compiler and compiler settings, you might get no or a
…		…
3959	maintainable.	5073	maintainable.
3960		5074
3961	And of course, some compiler warnings are just plain stupid, or simply	5075	And of course, some compiler warnings are just plain stupid, or simply
3962	wrong (because they don't actually warn about the condition their message	5076	wrong (because they don't actually warn about the condition their message
3963	seems to warn about). For example, certain older gcc versions had some	5077	seems to warn about). For example, certain older gcc versions had some
3964	warnings that resulted an extreme number of false positives. These have	5078	warnings that resulted in an extreme number of false positives. These have
3965	been fixed, but some people still insist on making code warn-free with	5079	been fixed, but some people still insist on making code warn-free with
3966	such buggy versions.	5080	such buggy versions.
3967		5081
3968	While libev is written to generate as few warnings as possible,	5082	While libev is written to generate as few warnings as possible,
3969	"warn-free" code is not a goal, and it is recommended not to build libev	5083	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4005	I suggest using suppression lists.	5119	I suggest using suppression lists.
4006		5120
4007		5121
4008	=head1 PORTABILITY NOTES	5122	=head1 PORTABILITY NOTES
4009		5123
		5124	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5125
		5126	GNU/Linux is the only common platform that supports 64 bit file/large file
		5127	interfaces but I<disables> them by default.
		5128
		5129	That means that libev compiled in the default environment doesn't support
		5130	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5131
		5132	Unfortunately, many programs try to work around this GNU/Linux issue
		5133	by enabling the large file API, which makes them incompatible with the
		5134	standard libev compiled for their system.
		5135
		5136	Likewise, libev cannot enable the large file API itself as this would
		5137	suddenly make it incompatible to the default compile time environment,
		5138	i.e. all programs not using special compile switches.
		5139
		5140	=head2 OS/X AND DARWIN BUGS
		5141
		5142	The whole thing is a bug if you ask me - basically any system interface
		5143	you touch is broken, whether it is locales, poll, kqueue or even the
		5144	OpenGL drivers.
		5145
		5146	=head3 C<kqueue> is buggy
		5147
		5148	The kqueue syscall is broken in all known versions - most versions support
		5149	only sockets, many support pipes.
		5150
		5151	Libev tries to work around this by not using C<kqueue> by default on this
		5152	rotten platform, but of course you can still ask for it when creating a
		5153	loop - embedding a socket-only kqueue loop into a select-based one is
		5154	probably going to work well.
		5155
		5156	=head3 C<poll> is buggy
		5157
		5158	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5159	implementation by something calling C<kqueue> internally around the 10.5.6
		5160	release, so now C<kqueue> I<and> C<poll> are broken.
		5161
		5162	Libev tries to work around this by not using C<poll> by default on
		5163	this rotten platform, but of course you can still ask for it when creating
		5164	a loop.
		5165
		5166	=head3 C<select> is buggy
		5167
		5168	All that's left is C<select>, and of course Apple found a way to fuck this
		5169	one up as well: On OS/X, C<select> actively limits the number of file
		5170	descriptors you can pass in to 1024 - your program suddenly crashes when
		5171	you use more.
		5172
		5173	There is an undocumented "workaround" for this - defining
		5174	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5175	work on OS/X.
		5176
		5177	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5178
		5179	=head3 C<errno> reentrancy
		5180
		5181	The default compile environment on Solaris is unfortunately so
		5182	thread-unsafe that you can't even use components/libraries compiled
		5183	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5184	defined by default. A valid, if stupid, implementation choice.
		5185
		5186	If you want to use libev in threaded environments you have to make sure
		5187	it's compiled with C<_REENTRANT> defined.
		5188
		5189	=head3 Event port backend
		5190
		5191	The scalable event interface for Solaris is called "event
		5192	ports". Unfortunately, this mechanism is very buggy in all major
		5193	releases. If you run into high CPU usage, your program freezes or you get
		5194	a large number of spurious wakeups, make sure you have all the relevant
		5195	and latest kernel patches applied. No, I don't know which ones, but there
		5196	are multiple ones to apply, and afterwards, event ports actually work
		5197	great.
		5198
		5199	If you can't get it to work, you can try running the program by setting
		5200	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5201	C<select> backends.
		5202
		5203	=head2 AIX POLL BUG
		5204
		5205	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5206	this by trying to avoid the poll backend altogether (i.e. it's not even
		5207	compiled in), which normally isn't a big problem as C<select> works fine
		5208	with large bitsets on AIX, and AIX is dead anyway.
		5209
4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5210	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5211
		5212	=head3 General issues
4011		5213
4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5214	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4013	requires, and its I/O model is fundamentally incompatible with the POSIX	5215	requires, and its I/O model is fundamentally incompatible with the POSIX
4014	model. Libev still offers limited functionality on this platform in	5216	model. Libev still offers limited functionality on this platform in
4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5217	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4016	descriptors. This only applies when using Win32 natively, not when using	5218	descriptors. This only applies when using Win32 natively, not when using
4017	e.g. cygwin.	5219	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5220	as every compiler comes with a slightly differently broken/incompatible
		5221	environment.
4018		5222
4019	Lifting these limitations would basically require the full	5223	Lifting these limitations would basically require the full
4020	re-implementation of the I/O system. If you are into these kinds of	5224	re-implementation of the I/O system. If you are into this kind of thing,
4021	things, then note that glib does exactly that for you in a very portable	5225	then note that glib does exactly that for you in a very portable way (note
4022	way (note also that glib is the slowest event library known to man).	5226	also that glib is the slowest event library known to man).
4023		5227
4024	There is no supported compilation method available on windows except	5228	There is no supported compilation method available on windows except
4025	embedding it into other applications.	5229	embedding it into other applications.
4026		5230
4027	Sensible signal handling is officially unsupported by Microsoft - libev	5231	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4055	you do I<not> compile the F<ev.c> or any other embedded source files!):	5259	you do I<not> compile the F<ev.c> or any other embedded source files!):
4056		5260
4057	#include "evwrap.h"	5261	#include "evwrap.h"
4058	#include "ev.c"	5262	#include "ev.c"
4059		5263
4060	=over 4
4061
4062	=item The winsocket select function	5264	=head3 The winsocket C<select> function
4063		5265
4064	The winsocket C<select> function doesn't follow POSIX in that it	5266	The winsocket C<select> function doesn't follow POSIX in that it
4065	requires socket I<handles> and not socket I<file descriptors> (it is	5267	requires socket I<handles> and not socket I<file descriptors> (it is
4066	also extremely buggy). This makes select very inefficient, and also	5268	also extremely buggy). This makes select very inefficient, and also
4067	requires a mapping from file descriptors to socket handles (the Microsoft	5269	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4076	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5278	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4077		5279
4078	Note that winsockets handling of fd sets is O(n), so you can easily get a	5280	Note that winsockets handling of fd sets is O(n), so you can easily get a
4079	complexity in the O(n²) range when using win32.	5281	complexity in the O(n²) range when using win32.
4080		5282
4081	=item Limited number of file descriptors	5283	=head3 Limited number of file descriptors
4082		5284
4083	Windows has numerous arbitrary (and low) limits on things.	5285	Windows has numerous arbitrary (and low) limits on things.
4084		5286
4085	Early versions of winsocket's select only supported waiting for a maximum	5287	Early versions of winsocket's select only supported waiting for a maximum
4086	of C<64> handles (probably owning to the fact that all windows kernels	5288	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4101	runtime libraries. This might get you to about C<512> or C<2048> sockets	5303	runtime libraries. This might get you to about C<512> or C<2048> sockets
4102	(depending on windows version and/or the phase of the moon). To get more,	5304	(depending on windows version and/or the phase of the moon). To get more,
4103	you need to wrap all I/O functions and provide your own fd management, but	5305	you need to wrap all I/O functions and provide your own fd management, but
4104	the cost of calling select (O(n²)) will likely make this unworkable.	5306	the cost of calling select (O(n²)) will likely make this unworkable.
4105		5307
4106	=back
4107
4108	=head2 PORTABILITY REQUIREMENTS	5308	=head2 PORTABILITY REQUIREMENTS
4109		5309
4110	In addition to a working ISO-C implementation and of course the	5310	In addition to a working ISO-C implementation and of course the
4111	backend-specific APIs, libev relies on a few additional extensions:	5311	backend-specific APIs, libev relies on a few additional extensions:
4112		5312
…		…
4118	Libev assumes not only that all watcher pointers have the same internal	5318	Libev assumes not only that all watcher pointers have the same internal
4119	structure (guaranteed by POSIX but not by ISO C for example), but it also	5319	structure (guaranteed by POSIX but not by ISO C for example), but it also
4120	assumes that the same (machine) code can be used to call any watcher	5320	assumes that the same (machine) code can be used to call any watcher
4121	callback: The watcher callbacks have different type signatures, but libev	5321	callback: The watcher callbacks have different type signatures, but libev
4122	calls them using an C<ev_watcher *> internally.	5322	calls them using an C<ev_watcher *> internally.
		5323
		5324	=item null pointers and integer zero are represented by 0 bytes
		5325
		5326	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5327	relies on this setting pointers and integers to null.
		5328
		5329	=item pointer accesses must be thread-atomic
		5330
		5331	Accessing a pointer value must be atomic, it must both be readable and
		5332	writable in one piece - this is the case on all current architectures.
4123		5333
4124	=item C<sig_atomic_t volatile> must be thread-atomic as well	5334	=item C<sig_atomic_t volatile> must be thread-atomic as well
4125		5335
4126	The type C<sig_atomic_t volatile> (or whatever is defined as	5336	The type C<sig_atomic_t volatile> (or whatever is defined as
4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5337	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4136	thread" or will block signals process-wide, both behaviours would	5346	thread" or will block signals process-wide, both behaviours would
4137	be compatible with libev. Interaction between C<sigprocmask> and	5347	be compatible with libev. Interaction between C<sigprocmask> and
4138	C<pthread_sigmask> could complicate things, however.	5348	C<pthread_sigmask> could complicate things, however.
4139		5349
4140	The most portable way to handle signals is to block signals in all threads	5350	The most portable way to handle signals is to block signals in all threads
4141	except the initial one, and run the default loop in the initial thread as	5351	except the initial one, and run the signal handling loop in the initial
4142	well.	5352	thread as well.
4143		5353
4144	=item C<long> must be large enough for common memory allocation sizes	5354	=item C<long> must be large enough for common memory allocation sizes
4145		5355
4146	To improve portability and simplify its API, libev uses C<long> internally	5356	To improve portability and simplify its API, libev uses C<long> internally
4147	instead of C<size_t> when allocating its data structures. On non-POSIX	5357	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4150	watchers.	5360	watchers.
4151		5361
4152	=item C<double> must hold a time value in seconds with enough accuracy	5362	=item C<double> must hold a time value in seconds with enough accuracy
4153		5363
4154	The type C<double> is used to represent timestamps. It is required to	5364	The type C<double> is used to represent timestamps. It is required to
4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5365	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4156	enough for at least into the year 4000. This requirement is fulfilled by	5366	good enough for at least into the year 4000 with millisecond accuracy
		5367	(the design goal for libev). This requirement is overfulfilled by
4157	implementations implementing IEEE 754, which is basically all existing	5368	implementations using IEEE 754, which is basically all existing ones.
		5369
4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5370	With IEEE 754 doubles, you get microsecond accuracy until at least the
4159	2200.	5371	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5372	is either obsolete or somebody patched it to use C<long double> or
		5373	something like that, just kidding).
4160		5374
4161	=back	5375	=back
4162		5376
4163	If you know of other additional requirements drop me a note.	5377	If you know of other additional requirements drop me a note.
4164		5378
…		…
4226	=item Processing ev_async_send: O(number_of_async_watchers)	5440	=item Processing ev_async_send: O(number_of_async_watchers)
4227		5441
4228	=item Processing signals: O(max_signal_number)	5442	=item Processing signals: O(max_signal_number)
4229		5443
4230	Sending involves a system call I<iff> there were no other C<ev_async_send>	5444	Sending involves a system call I<iff> there were no other C<ev_async_send>
4231	calls in the current loop iteration. Checking for async and signal events	5445	calls in the current loop iteration and the loop is currently
		5446	blocked. Checking for async and signal events involves iterating over all
4232	involves iterating over all running async watchers or all signal numbers.	5447	running async watchers or all signal numbers.
4233		5448
4234	=back	5449	=back
4235		5450
4236		5451
		5452	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5453
		5454	The major version 4 introduced some incompatible changes to the API.
		5455
		5456	At the moment, the C<ev.h> header file provides compatibility definitions
		5457	for all changes, so most programs should still compile. The compatibility
		5458	layer might be removed in later versions of libev, so better update to the
		5459	new API early than late.
		5460
		5461	=over 4
		5462
		5463	=item C<EV_COMPAT3> backwards compatibility mechanism
		5464
		5465	The backward compatibility mechanism can be controlled by
		5466	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5467	section.
		5468
		5469	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5470
		5471	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5472
		5473	ev_loop_destroy (EV_DEFAULT_UC);
		5474	ev_loop_fork (EV_DEFAULT);
		5475
		5476	=item function/symbol renames
		5477
		5478	A number of functions and symbols have been renamed:
		5479
		5480	ev_loop => ev_run
		5481	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5482	EVLOOP_ONESHOT => EVRUN_ONCE
		5483
		5484	ev_unloop => ev_break
		5485	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5486	EVUNLOOP_ONE => EVBREAK_ONE
		5487	EVUNLOOP_ALL => EVBREAK_ALL
		5488
		5489	EV_TIMEOUT => EV_TIMER
		5490
		5491	ev_loop_count => ev_iteration
		5492	ev_loop_depth => ev_depth
		5493	ev_loop_verify => ev_verify
		5494
		5495	Most functions working on C<struct ev_loop> objects don't have an
		5496	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5497	associated constants have been renamed to not collide with the C<struct
		5498	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5499	as all other watcher types. Note that C<ev_loop_fork> is still called
		5500	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5501	typedef.
		5502
		5503	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5504
		5505	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5506	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5507	and work, but the library code will of course be larger.
		5508
		5509	=back
		5510
		5511
4237	=head1 GLOSSARY	5512	=head1 GLOSSARY
4238		5513
4239	=over 4	5514	=over 4
4240		5515
4241	=item active	5516	=item active
4242		5517
4243	A watcher is active as long as it has been started (has been attached to	5518	A watcher is active as long as it has been started and not yet stopped.
4244	an event loop) but not yet stopped (disassociated from the event loop).	5519	See L</WATCHER STATES> for details.
4245		5520
4246	=item application	5521	=item application
4247		5522
4248	In this document, an application is whatever is using libev.	5523	In this document, an application is whatever is using libev.
		5524
		5525	=item backend
		5526
		5527	The part of the code dealing with the operating system interfaces.
4249		5528
4250	=item callback	5529	=item callback
4251		5530
4252	The address of a function that is called when some event has been	5531	The address of a function that is called when some event has been
4253	detected. Callbacks are being passed the event loop, the watcher that	5532	detected. Callbacks are being passed the event loop, the watcher that
4254	received the event, and the actual event bitset.	5533	received the event, and the actual event bitset.
4255		5534
4256	=item callback invocation	5535	=item callback/watcher invocation
4257		5536
4258	The act of calling the callback associated with a watcher.	5537	The act of calling the callback associated with a watcher.
4259		5538
4260	=item event	5539	=item event
4261		5540
4262	A change of state of some external event, such as data now being available	5541	A change of state of some external event, such as data now being available
4263	for reading on a file descriptor, time having passed or simply not having	5542	for reading on a file descriptor, time having passed or simply not having
4264	any other events happening anymore.	5543	any other events happening anymore.
4265		5544
4266	In libev, events are represented as single bits (such as C<EV_READ> or	5545	In libev, events are represented as single bits (such as C<EV_READ> or
4267	C<EV_TIMEOUT>).	5546	C<EV_TIMER>).
4268		5547
4269	=item event library	5548	=item event library
4270		5549
4271	A software package implementing an event model and loop.	5550	A software package implementing an event model and loop.
4272		5551
…		…
4280	The model used to describe how an event loop handles and processes	5559	The model used to describe how an event loop handles and processes
4281	watchers and events.	5560	watchers and events.
4282		5561
4283	=item pending	5562	=item pending
4284		5563
4285	A watcher is pending as soon as the corresponding event has been detected,	5564	A watcher is pending as soon as the corresponding event has been
4286	and stops being pending as soon as the watcher will be invoked or its	5565	detected. See L</WATCHER STATES> for details.
4287	pending status is explicitly cleared by the application.
4288
4289	A watcher can be pending, but not active. Stopping a watcher also clears
4290	its pending status.
4291		5566
4292	=item real time	5567	=item real time
4293		5568
4294	The physical time that is observed. It is apparently strictly monotonic :)	5569	The physical time that is observed. It is apparently strictly monotonic :)
4295		5570
4296	=item wall-clock time	5571	=item wall-clock time
4297		5572
4298	The time and date as shown on clocks. Unlike real time, it can actually	5573	The time and date as shown on clocks. Unlike real time, it can actually
4299	be wrong and jump forwards and backwards, e.g. when the you adjust your	5574	be wrong and jump forwards and backwards, e.g. when you adjust your
4300	clock.	5575	clock.
4301		5576
4302	=item watcher	5577	=item watcher
4303		5578
4304	A data structure that describes interest in certain events. Watchers need	5579	A data structure that describes interest in certain events. Watchers need
4305	to be started (attached to an event loop) before they can receive events.	5580	to be started (attached to an event loop) before they can receive events.
4306		5581
4307	=item watcher invocation
4308
4309	The act of calling the callback associated with a watcher.
4310
4311	=back	5582	=back
4312		5583
4313	=head1 AUTHOR	5584	=head1 AUTHOR
4314		5585
4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5586	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5587	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4316		5588

Diff Legend

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