ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.431 by root, Fri Nov 22 16:42:10 2013 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 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
68		72
69	The newest version of this document is also available as an html-formatted	73	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	74	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	75	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		76
		77	While this document tries to be as complete as possible in documenting
		78	libev, its usage and the rationale behind its design, it is not a tutorial
		79	on event-based programming, nor will it introduce event-based programming
		80	with libev.
		81
		82	Familiarity with event based programming techniques in general is assumed
		83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
		93	=head1 ABOUT LIBEV
72		94
73	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
74	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
75	these event sources and provide your program with events.	97	these event sources and provide your program with events.
76		98
…		…
86	=head2 FEATURES	108	=head2 FEATURES
87		109
88	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
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	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
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	117	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(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>).
98		121
99	It also is quite fast (see this	122	It also is quite fast (see this
100	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
101	for example).	124	for example).
102		125
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	134	this argument.
112		135
113	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
114		137
115	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
121	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
122	throughout libev.	146	time differences (e.g. delays) throughout libev.
123		147
124	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
125		149
126	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	151	and internal errors (bugs).
…		…
151		175
152	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
153		177
154	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
155	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
156	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>.
157		182
158	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
159		184
160	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
161	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
162	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 >>).
163		194
164	=item int ev_version_major ()	195	=item int ev_version_major ()
165		196
166	=item int ev_version_minor ()	197	=item int ev_version_minor ()
167		198
…		…
178	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
179	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
180	not a problem.	211	not a problem.
181		212
182	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
183	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
184		216
185	assert (("libev version mismatch",	217	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
188		220
…		…
199	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
201		233
202	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
203		235
204	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
205	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
206	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
207	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
208	(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
209	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
210		243
211	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
212		245
213	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
214	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
218		251
219	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
220		253
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
222		255
223	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
252	}	285	}
253		286
254	...	287	...
255	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
256		289
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
258		291
259	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
260	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
261	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	307	}
275		308
276	...	309	...
277	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
278		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
279	=back	325	=back
280		326
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		328
283	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
284	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
285	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
286		332
287	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
288	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
289	not.	335	do not.
290		336
291	=over 4	337	=over 4
292		338
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		340
295	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
296	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
297	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
298	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".
299		351
300	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
301	function.	353	function (or via the C<EV_DEFAULT> macro).
302		354
303	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
304	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
305	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).
306		359
307	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,
308	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
309	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
310	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
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	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.
313		384
314	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
315	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>).
316		387
317	The following flags are supported:	388	The following flags are supported:
…		…
327		398
328	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
329	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
330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
331	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
332	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
333	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).
334		407
335	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
336		409
337	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
338	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.
339	enabling this flag.
340		412
341	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,
342	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
343	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
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	422	flag.
351		423
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	424	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	425	environment variable.
354		426
		427	=item C<EVFLAG_NOINOTIFY>
		428
		429	When this flag is specified, then libev will not attempt to use the
		430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		431	testing, this flag can be useful to conserve inotify file descriptors, as
		432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		433
		434	=item C<EVFLAG_SIGNALFD>
		435
		436	When this flag is specified, then libev will attempt to use the
		437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		438	delivers signals synchronously, which makes it both faster and might make
		439	it possible to get the queued signal data. It can also simplify signal
		440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
		442
		443	Signalfd will not be used by default as this changes your signal mask, and
		444	there are a lot of shoddy libraries and programs (glib's threadpool for
		445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
		461
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		463
357	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	466	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	490	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	491	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		492
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		494
		495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		496	kernels).
		497
388	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
389	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
390	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
391	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
392		502
393	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	512	and is of course hard to detect.
401		513
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
403	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
404	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
405	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
406	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
		524	not least, it also refuses to work with some file descriptors which work
		525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
409		530
410	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
450		571
451	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
452	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
453	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
455	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
457	cases	578	drops fds silently in similarly hard-to-detect cases.
458		579
459	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
460		581
461	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
462	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		601
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
483		604
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	608	might perform better.
492		609
493	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
497		624
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
500		627
501	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
502		629
503	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		633
507	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		643
509	=back	644	=back
510		645
511	If one or more of these are or'ed into the flags value, then only these	646	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	647	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	648	here). If none are specified, all backends in C<ev_recommended_backends
514		649	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		650
543	Example: Try to create a event loop that uses epoll and nothing else.	651	Example: Try to create a event loop that uses epoll and nothing else.
544		652
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	654	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
548		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
549	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
550		663
551	Destroys the default loop again (frees all memory and kernel state	664	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	665	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	666	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	667	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	668	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		671
559	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
562		675
563	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	683	and C<ev_loop_destroy>.
567		684
568	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
569		686
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	688	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	689	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	690	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	691	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	692
		693	Again, you I<have> to call it on I<any> loop that you want to re-use after
		694	a fork, I<even if you do not plan to use the loop in the parent>. This is
		695	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		696	during fork.
581		697
582	On the other hand, you only need to call this function in the child	698	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	699	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	700	you just fork+exec or create a new loop in the child, you don't have to
		701	call it at all (in fact, C<epoll> is so badly broken that it makes a
		702	difference, but libev will usually detect this case on its own and do a
		703	costly reset of the backend).
585		704
586	The function itself is quite fast and it's usually not a problem to call	705	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	706	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		707
		708	Example: Automate calling C<ev_loop_fork> on the default loop when
		709	using pthreads.
		710
		711	static void
		712	post_fork_child (void)
		713	{
		714	ev_loop_fork (EV_DEFAULT);
		715	}
		716
		717	...
590	pthread_atfork (0, 0, ev_default_fork);	718	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		719
599	=item int ev_is_default_loop (loop)	720	=item int ev_is_default_loop (loop)
600		721
601	Returns true when the given loop is, in fact, the default loop, and false	722	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	723	otherwise.
603		724
604	=item unsigned int ev_loop_count (loop)	725	=item unsigned int ev_iteration (loop)
605		726
606	Returns the count of loop iterations for the loop, which is identical to	727	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	728	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	729	and happily wraps around with enough iterations.
609		730
610	This value can sometimes be useful as a generation counter of sorts (it	731	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	732	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	733	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		734	prepare and check phases.
		735
		736	=item unsigned int ev_depth (loop)
		737
		738	Returns the number of times C<ev_run> was entered minus the number of
		739	times C<ev_run> was exited normally, in other words, the recursion depth.
		740
		741	Outside C<ev_run>, this number is zero. In a callback, this number is
		742	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		743	in which case it is higher.
		744
		745	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		746	throwing an exception etc.), doesn't count as "exit" - consider this
		747	as a hint to avoid such ungentleman-like behaviour unless it's really
		748	convenient, in which case it is fully supported.
613		749
614	=item unsigned int ev_backend (loop)	750	=item unsigned int ev_backend (loop)
615		751
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	752	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	753	use.
…		…
626		762
627	=item ev_now_update (loop)	763	=item ev_now_update (loop)
628		764
629	Establishes the current time by querying the kernel, updating the time	765	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	766	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	767	is usually done automatically within C<ev_run ()>.
632		768
633	This function is rarely useful, but when some event callback runs for a	769	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	770	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	771	the current time is a good idea.
636		772
637	See also "The special problem of time updates" in the C<ev_timer> section.	773	See also L</The special problem of time updates> in the C<ev_timer> section.
638		774
639	=item ev_suspend (loop)	775	=item ev_suspend (loop)
640		776
641	=item ev_resume (loop)	777	=item ev_resume (loop)
642		778
643	These two functions suspend and resume a loop, for use when the loop is	779	These two functions suspend and resume an event loop, for use when the
644	not used for a while and timeouts should not be processed.	780	loop is not used for a while and timeouts should not be processed.
645		781
646	A typical use case would be an interactive program such as a game: When	782	A typical use case would be an interactive program such as a game: When
647	the user presses C<^Z> to suspend the game and resumes it an hour later it	783	the user presses C<^Z> to suspend the game and resumes it an hour later it
648	would be best to handle timeouts as if no time had actually passed while	784	would be best to handle timeouts as if no time had actually passed while
649	the program was suspended. This can be achieved by calling C<ev_suspend>	785	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
651	C<ev_resume> directly afterwards to resume timer processing.	787	C<ev_resume> directly afterwards to resume timer processing.
652		788
653	Effectively, all C<ev_timer> watchers will be delayed by the time spend	789	Effectively, all C<ev_timer> watchers will be delayed by the time spend
654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	790	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
655	will be rescheduled (that is, they will lose any events that would have	791	will be rescheduled (that is, they will lose any events that would have
656	occured while suspended).	792	occurred while suspended).
657		793
658	After calling C<ev_suspend> you B<must not> call I<any> function on the	794	After calling C<ev_suspend> you B<must not> call I<any> function on the
659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	795	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
660	without a previous call to C<ev_suspend>.	796	without a previous call to C<ev_suspend>.
661		797
662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	798	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
663	event loop time (see C<ev_now_update>).	799	event loop time (see C<ev_now_update>).
664		800
665	=item ev_loop (loop, int flags)	801	=item bool ev_run (loop, int flags)
666		802
667	Finally, this is it, the event handler. This function usually is called	803	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	804	after you have initialised all your watchers and you want to start
669	events.	805	handling events. It will ask the operating system for any new events, call
		806	the watcher callbacks, and then repeat the whole process indefinitely: This
		807	is why event loops are called I<loops>.
670		808
671	If the flags argument is specified as C<0>, it will not return until	809	If the flags argument is specified as C<0>, it will keep handling events
672	either no event watchers are active anymore or C<ev_unloop> was called.	810	until either no event watchers are active anymore or C<ev_break> was
		811	called.
673		812
		813	The return value is false if there are no more active watchers (which
		814	usually means "all jobs done" or "deadlock"), and true in all other cases
		815	(which usually means " you should call C<ev_run> again").
		816
674	Please note that an explicit C<ev_unloop> is usually better than	817	Please note that an explicit C<ev_break> is usually better than
675	relying on all watchers to be stopped when deciding when a program has	818	relying on all watchers to be stopped when deciding when a program has
676	finished (especially in interactive programs), but having a program	819	finished (especially in interactive programs), but having a program
677	that automatically loops as long as it has to and no longer by virtue	820	that automatically loops as long as it has to and no longer by virtue
678	of relying on its watchers stopping correctly, that is truly a thing of	821	of relying on its watchers stopping correctly, that is truly a thing of
679	beauty.	822	beauty.
680		823
		824	This function is I<mostly> exception-safe - you can break out of a
		825	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		826	exception and so on. This does not decrement the C<ev_depth> value, nor
		827	will it clear any outstanding C<EVBREAK_ONE> breaks.
		828
681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	829	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
682	those events and any already outstanding ones, but will not block your	830	those events and any already outstanding ones, but will not wait and
683	process in case there are no events and will return after one iteration of	831	block your process in case there are no events and will return after one
684	the loop.	832	iteration of the loop. This is sometimes useful to poll and handle new
		833	events while doing lengthy calculations, to keep the program responsive.
685		834
686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	835	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
687	necessary) and will handle those and any already outstanding ones. It	836	necessary) and will handle those and any already outstanding ones. It
688	will block your process until at least one new event arrives (which could	837	will block your process until at least one new event arrives (which could
689	be an event internal to libev itself, so there is no guarantee that a	838	be an event internal to libev itself, so there is no guarantee that a
690	user-registered callback will be called), and will return after one	839	user-registered callback will be called), and will return after one
691	iteration of the loop.	840	iteration of the loop.
692		841
693	This is useful if you are waiting for some external event in conjunction	842	This is useful if you are waiting for some external event in conjunction
694	with something not expressible using other libev watchers (i.e. "roll your	843	with something not expressible using other libev watchers (i.e. "roll your
695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	844	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
696	usually a better approach for this kind of thing.	845	usually a better approach for this kind of thing.
697		846
698	Here are the gory details of what C<ev_loop> does:	847	Here are the gory details of what C<ev_run> does (this is for your
		848	understanding, not a guarantee that things will work exactly like this in
		849	future versions):
699		850
		851	- Increment loop depth.
		852	- Reset the ev_break status.
700	- Before the first iteration, call any pending watchers.	853	- Before the first iteration, call any pending watchers.
		854	LOOP:
701	* If EVFLAG_FORKCHECK was used, check for a fork.	855	- If EVFLAG_FORKCHECK was used, check for a fork.
702	- If a fork was detected (by any means), queue and call all fork watchers.	856	- If a fork was detected (by any means), queue and call all fork watchers.
703	- Queue and call all prepare watchers.	857	- Queue and call all prepare watchers.
		858	- If ev_break was called, goto FINISH.
704	- If we have been forked, detach and recreate the kernel state	859	- If we have been forked, detach and recreate the kernel state
705	as to not disturb the other process.	860	as to not disturb the other process.
706	- Update the kernel state with all outstanding changes.	861	- Update the kernel state with all outstanding changes.
707	- Update the "event loop time" (ev_now ()).	862	- Update the "event loop time" (ev_now ()).
708	- Calculate for how long to sleep or block, if at all	863	- Calculate for how long to sleep or block, if at all
709	(active idle watchers, EVLOOP_NONBLOCK or not having	864	(active idle watchers, EVRUN_NOWAIT or not having
710	any active watchers at all will result in not sleeping).	865	any active watchers at all will result in not sleeping).
711	- Sleep if the I/O and timer collect interval say so.	866	- Sleep if the I/O and timer collect interval say so.
		867	- Increment loop iteration counter.
712	- Block the process, waiting for any events.	868	- Block the process, waiting for any events.
713	- Queue all outstanding I/O (fd) events.	869	- Queue all outstanding I/O (fd) events.
714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	870	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
715	- Queue all expired timers.	871	- Queue all expired timers.
716	- Queue all expired periodics.	872	- Queue all expired periodics.
717	- Unless any events are pending now, queue all idle watchers.	873	- Queue all idle watchers with priority higher than that of pending events.
718	- Queue all check watchers.	874	- Queue all check watchers.
719	- Call all queued watchers in reverse order (i.e. check watchers first).	875	- Call all queued watchers in reverse order (i.e. check watchers first).
720	Signals and child watchers are implemented as I/O watchers, and will	876	Signals and child watchers are implemented as I/O watchers, and will
721	be handled here by queueing them when their watcher gets executed.	877	be handled here by queueing them when their watcher gets executed.
722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	878	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
723	were used, or there are no active watchers, return, otherwise	879	were used, or there are no active watchers, goto FINISH, otherwise
724	continue with step *.	880	continue with step LOOP.
		881	FINISH:
		882	- Reset the ev_break status iff it was EVBREAK_ONE.
		883	- Decrement the loop depth.
		884	- Return.
725		885
726	Example: Queue some jobs and then loop until no events are outstanding	886	Example: Queue some jobs and then loop until no events are outstanding
727	anymore.	887	anymore.
728		888
729	... queue jobs here, make sure they register event watchers as long	889	... queue jobs here, make sure they register event watchers as long
730	... as they still have work to do (even an idle watcher will do..)	890	... as they still have work to do (even an idle watcher will do..)
731	ev_loop (my_loop, 0);	891	ev_run (my_loop, 0);
732	... jobs done or somebody called unloop. yeah!	892	... jobs done or somebody called break. yeah!
733		893
734	=item ev_unloop (loop, how)	894	=item ev_break (loop, how)
735		895
736	Can be used to make a call to C<ev_loop> return early (but only after it	896	Can be used to make a call to C<ev_run> return early (but only after it
737	has processed all outstanding events). The C<how> argument must be either	897	has processed all outstanding events). The C<how> argument must be either
738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	898	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	899	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
740		900
741	This "unloop state" will be cleared when entering C<ev_loop> again.	901	This "break state" will be cleared on the next call to C<ev_run>.
742		902
743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	903	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		904	which case it will have no effect.
744		905
745	=item ev_ref (loop)	906	=item ev_ref (loop)
746		907
747	=item ev_unref (loop)	908	=item ev_unref (loop)
748		909
749	Ref/unref can be used to add or remove a reference count on the event	910	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	911	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	912	count is nonzero, C<ev_run> will not return on its own.
752		913
753	If you have a watcher you never unregister that should not keep C<ev_loop>	914	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	915	unregister, but that nevertheless should not keep C<ev_run> from
		916	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	917	before stopping it.
756		918
757	As an example, libev itself uses this for its internal signal pipe: It	919	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	920	is not visible to the libev user and should not keep C<ev_run> from
759	exiting if no event watchers registered by it are active. It is also an	921	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	922	excellent way to do this for generic recurring timers or from within
761	third-party libraries. Just remember to I<unref after start> and I<ref	923	third-party libraries. Just remember to I<unref after start> and I<ref
762	before stop> (but only if the watcher wasn't active before, or was active	924	before stop> (but only if the watcher wasn't active before, or was active
763	before, respectively. Note also that libev might stop watchers itself	925	before, respectively. Note also that libev might stop watchers itself
764	(e.g. non-repeating timers) in which case you have to C<ev_ref>	926	(e.g. non-repeating timers) in which case you have to C<ev_ref>
765	in the callback).	927	in the callback).
766		928
767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	929	Example: Create a signal watcher, but keep it from keeping C<ev_run>
768	running when nothing else is active.	930	running when nothing else is active.
769		931
770	ev_signal exitsig;	932	ev_signal exitsig;
771	ev_signal_init (&exitsig, sig_cb, SIGINT);	933	ev_signal_init (&exitsig, sig_cb, SIGINT);
772	ev_signal_start (loop, &exitsig);	934	ev_signal_start (loop, &exitsig);
773	evf_unref (loop);	935	ev_unref (loop);
774		936
775	Example: For some weird reason, unregister the above signal handler again.	937	Example: For some weird reason, unregister the above signal handler again.
776		938
777	ev_ref (loop);	939	ev_ref (loop);
778	ev_signal_stop (loop, &exitsig);	940	ev_signal_stop (loop, &exitsig);
…		…
798	overhead for the actual polling but can deliver many events at once.	960	overhead for the actual polling but can deliver many events at once.
799		961
800	By setting a higher I<io collect interval> you allow libev to spend more	962	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	963	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	964	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	965	C<ev_timer>) will not be affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	966	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		967	sleep time ensures that libev will not poll for I/O events more often then
		968	once per this interval, on average (as long as the host time resolution is
		969	good enough).
805		970
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	971	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	972	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	973	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	974	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		976
812	Many (busy) programs can usually benefit by setting the I/O collect	977	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	978	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	979	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	980	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	981	as this approaches the timing granularity of most systems. Note that if
		982	you do transactions with the outside world and you can't increase the
		983	parallelity, then this setting will limit your transaction rate (if you
		984	need to poll once per transaction and the I/O collect interval is 0.01,
		985	then you can't do more than 100 transactions per second).
817		986
818	Setting the I<timeout collect interval> can improve the opportunity for	987	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	988	saving power, as the program will "bundle" timer callback invocations that
820	are "near" in time together, by delaying some, thus reducing the number of	989	are "near" in time together, by delaying some, thus reducing the number of
821	times the process sleeps and wakes up again. Another useful technique to	990	times the process sleeps and wakes up again. Another useful technique to
822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	991	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	992	they fire on, say, one-second boundaries only.
824		993
		994	Example: we only need 0.1s timeout granularity, and we wish not to poll
		995	more often than 100 times per second:
		996
		997	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		998	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		999
		1000	=item ev_invoke_pending (loop)
		1001
		1002	This call will simply invoke all pending watchers while resetting their
		1003	pending state. Normally, C<ev_run> does this automatically when required,
		1004	but when overriding the invoke callback this call comes handy. This
		1005	function can be invoked from a watcher - this can be useful for example
		1006	when you want to do some lengthy calculation and want to pass further
		1007	event handling to another thread (you still have to make sure only one
		1008	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1009
		1010	=item int ev_pending_count (loop)
		1011
		1012	Returns the number of pending watchers - zero indicates that no watchers
		1013	are pending.
		1014
		1015	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1016
		1017	This overrides the invoke pending functionality of the loop: Instead of
		1018	invoking all pending watchers when there are any, C<ev_run> will call
		1019	this callback instead. This is useful, for example, when you want to
		1020	invoke the actual watchers inside another context (another thread etc.).
		1021
		1022	If you want to reset the callback, use C<ev_invoke_pending> as new
		1023	callback.
		1024
		1025	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1026
		1027	Sometimes you want to share the same loop between multiple threads. This
		1028	can be done relatively simply by putting mutex_lock/unlock calls around
		1029	each call to a libev function.
		1030
		1031	However, C<ev_run> can run an indefinite time, so it is not feasible
		1032	to wait for it to return. One way around this is to wake up the event
		1033	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1034	I<release> and I<acquire> callbacks on the loop.
		1035
		1036	When set, then C<release> will be called just before the thread is
		1037	suspended waiting for new events, and C<acquire> is called just
		1038	afterwards.
		1039
		1040	Ideally, C<release> will just call your mutex_unlock function, and
		1041	C<acquire> will just call the mutex_lock function again.
		1042
		1043	While event loop modifications are allowed between invocations of
		1044	C<release> and C<acquire> (that's their only purpose after all), no
		1045	modifications done will affect the event loop, i.e. adding watchers will
		1046	have no effect on the set of file descriptors being watched, or the time
		1047	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1048	to take note of any changes you made.
		1049
		1050	In theory, threads executing C<ev_run> will be async-cancel safe between
		1051	invocations of C<release> and C<acquire>.
		1052
		1053	See also the locking example in the C<THREADS> section later in this
		1054	document.
		1055
		1056	=item ev_set_userdata (loop, void *data)
		1057
		1058	=item void *ev_userdata (loop)
		1059
		1060	Set and retrieve a single C<void *> associated with a loop. When
		1061	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1062	C<0>.
		1063
		1064	These two functions can be used to associate arbitrary data with a loop,
		1065	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1066	C<acquire> callbacks described above, but of course can be (ab-)used for
		1067	any other purpose as well.
		1068
825	=item ev_loop_verify (loop)	1069	=item ev_verify (loop)
826		1070
827	This function only does something when C<EV_VERIFY> support has been	1071	This function only does something when C<EV_VERIFY> support has been
828	compiled in, which is the default for non-minimal builds. It tries to go	1072	compiled in, which is the default for non-minimal builds. It tries to go
829	through all internal structures and checks them for validity. If anything	1073	through all internal structures and checks them for validity. If anything
830	is found to be inconsistent, it will print an error message to standard	1074	is found to be inconsistent, it will print an error message to standard
…		…
841		1085
842	In the following description, uppercase C<TYPE> in names stands for the	1086	In the following description, uppercase C<TYPE> in names stands for the
843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1087	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
844	watchers and C<ev_io_start> for I/O watchers.	1088	watchers and C<ev_io_start> for I/O watchers.
845		1089
846	A watcher is a structure that you create and register to record your	1090	A watcher is an opaque structure that you allocate and register to record
847	interest in some event. For instance, if you want to wait for STDIN to	1091	your interest in some event. To make a concrete example, imagine you want
848	become readable, you would create an C<ev_io> watcher for that:	1092	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1093	for that:
849		1094
850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1095	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
851	{	1096	{
852	ev_io_stop (w);	1097	ev_io_stop (w);
853	ev_unloop (loop, EVUNLOOP_ALL);	1098	ev_break (loop, EVBREAK_ALL);
854	}	1099	}
855		1100
856	struct ev_loop *loop = ev_default_loop (0);	1101	struct ev_loop *loop = ev_default_loop (0);
857		1102
858	ev_io stdin_watcher;	1103	ev_io stdin_watcher;
859		1104
860	ev_init (&stdin_watcher, my_cb);	1105	ev_init (&stdin_watcher, my_cb);
861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1106	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
862	ev_io_start (loop, &stdin_watcher);	1107	ev_io_start (loop, &stdin_watcher);
863		1108
864	ev_loop (loop, 0);	1109	ev_run (loop, 0);
865		1110
866	As you can see, you are responsible for allocating the memory for your	1111	As you can see, you are responsible for allocating the memory for your
867	watcher structures (and it is I<usually> a bad idea to do this on the	1112	watcher structures (and it is I<usually> a bad idea to do this on the
868	stack).	1113	stack).
869		1114
870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1115	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1116	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
872		1117
873	Each watcher structure must be initialised by a call to C<ev_init	1118	Each watcher structure must be initialised by a call to C<ev_init (watcher
874	(watcher *, callback)>, which expects a callback to be provided. This	1119	*, callback)>, which expects a callback to be provided. This callback is
875	callback gets invoked each time the event occurs (or, in the case of I/O	1120	invoked each time the event occurs (or, in the case of I/O watchers, each
876	watchers, each time the event loop detects that the file descriptor given	1121	time the event loop detects that the file descriptor given is readable
877	is readable and/or writable).	1122	and/or writable).
878		1123
879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1124	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
880	macro to configure it, with arguments specific to the watcher type. There	1125	macro to configure it, with arguments specific to the watcher type. There
881	is also a macro to combine initialisation and setting in one call: C<<	1126	is also a macro to combine initialisation and setting in one call: C<<
882	ev_TYPE_init (watcher *, callback, ...) >>.	1127	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
905	=item C<EV_WRITE>	1150	=item C<EV_WRITE>
906		1151
907	The file descriptor in the C<ev_io> watcher has become readable and/or	1152	The file descriptor in the C<ev_io> watcher has become readable and/or
908	writable.	1153	writable.
909		1154
910	=item C<EV_TIMEOUT>	1155	=item C<EV_TIMER>
911		1156
912	The C<ev_timer> watcher has timed out.	1157	The C<ev_timer> watcher has timed out.
913		1158
914	=item C<EV_PERIODIC>	1159	=item C<EV_PERIODIC>
915		1160
…		…
933		1178
934	=item C<EV_PREPARE>	1179	=item C<EV_PREPARE>
935		1180
936	=item C<EV_CHECK>	1181	=item C<EV_CHECK>
937		1182
938	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1183	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
939	to gather new events, and all C<ev_check> watchers are invoked just after	1184	gather new events, and all C<ev_check> watchers are queued (not invoked)
940	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1185	just after C<ev_run> has gathered them, but before it queues any callbacks
		1186	for any received events. That means C<ev_prepare> watchers are the last
		1187	watchers invoked before the event loop sleeps or polls for new events, and
		1188	C<ev_check> watchers will be invoked before any other watchers of the same
		1189	or lower priority within an event loop iteration.
		1190
941	received events. Callbacks of both watcher types can start and stop as	1191	Callbacks of both watcher types can start and stop as many watchers as
942	many watchers as they want, and all of them will be taken into account	1192	they want, and all of them will be taken into account (for example, a
943	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1193	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
944	C<ev_loop> from blocking).	1194	blocking).
945		1195
946	=item C<EV_EMBED>	1196	=item C<EV_EMBED>
947		1197
948	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1198	The embedded event loop specified in the C<ev_embed> watcher needs attention.
949		1199
950	=item C<EV_FORK>	1200	=item C<EV_FORK>
951		1201
952	The event loop has been resumed in the child process after fork (see	1202	The event loop has been resumed in the child process after fork (see
953	C<ev_fork>).	1203	C<ev_fork>).
		1204
		1205	=item C<EV_CLEANUP>
		1206
		1207	The event loop is about to be destroyed (see C<ev_cleanup>).
954		1208
955	=item C<EV_ASYNC>	1209	=item C<EV_ASYNC>
956		1210
957	The given async watcher has been asynchronously notified (see C<ev_async>).	1211	The given async watcher has been asynchronously notified (see C<ev_async>).
958		1212
…		…
1005		1259
1006	ev_io w;	1260	ev_io w;
1007	ev_init (&w, my_cb);	1261	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1262	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1263
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1264	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1265
1012	This macro initialises the type-specific parts of a watcher. You need to	1266	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1267	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1268	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1269	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1282
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1283	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1284
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1286
1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1287	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1288
1035	Starts (activates) the given watcher. Only active watchers will receive	1289	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1290	events. If the watcher is already active nothing will happen.
1037		1291
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1292	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1293	whole section.
1040		1294
1041	ev_io_start (EV_DEFAULT_UC, &w);	1295	ev_io_start (EV_DEFAULT_UC, &w);
1042		1296
1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1297	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1298
1045	Stops the given watcher if active, and clears the pending status (whether	1299	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1300	the watcher was active or not).
1047		1301
1048	It is possible that stopped watchers are pending - for example,	1302	It is possible that stopped watchers are pending - for example,
…		…
1068		1322
1069	=item callback ev_cb (ev_TYPE *watcher)	1323	=item callback ev_cb (ev_TYPE *watcher)
1070		1324
1071	Returns the callback currently set on the watcher.	1325	Returns the callback currently set on the watcher.
1072		1326
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1327	=item ev_set_cb (ev_TYPE *watcher, callback)
1074		1328
1075	Change the callback. You can change the callback at virtually any time	1329	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1330	(modulo threads).
1077		1331
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1332	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1333
1080	=item int ev_priority (ev_TYPE *watcher)	1334	=item int ev_priority (ev_TYPE *watcher)
1081		1335
1082	Set and query the priority of the watcher. The priority is a small	1336	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1337	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1338	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1339	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1340	from being executed (except for C<ev_idle> watchers).
1087		1341
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1342	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1343	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1344
1096	You I<must not> change the priority of a watcher as long as it is active or	1345	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1346	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1347
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1348	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1349	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1350	or might not have been clamped to the valid range.
		1351
		1352	The default priority used by watchers when no priority has been set is
		1353	always C<0>, which is supposed to not be too high and not be too low :).
		1354
		1355	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1356	priorities.
1105		1357
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1358	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1359
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1360	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1361	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1117	watcher isn't pending it does nothing and returns C<0>.	1369	watcher isn't pending it does nothing and returns C<0>.
1118		1370
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1371	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1372	callback to be invoked, which can be accomplished with this function.
1121		1373
		1374	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1375
		1376	Feeds the given event set into the event loop, as if the specified event
		1377	had happened for the specified watcher (which must be a pointer to an
		1378	initialised but not necessarily started event watcher). Obviously you must
		1379	not free the watcher as long as it has pending events.
		1380
		1381	Stopping the watcher, letting libev invoke it, or calling
		1382	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1383	not started in the first place.
		1384
		1385	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1386	functions that do not need a watcher.
		1387
1122	=back	1388	=back
1123		1389
		1390	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1391	OWN COMPOSITE WATCHERS> idioms.
1124		1392
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1393	=head2 WATCHER STATES
1126		1394
1127	Each watcher has, by default, a member C<void *data> that you can change	1395	There are various watcher states mentioned throughout this manual -
1128	and read at any time: libev will completely ignore it. This can be used	1396	active, pending and so on. In this section these states and the rules to
1129	to associate arbitrary data with your watcher. If you need more data and	1397	transition between them will be described in more detail - and while these
1130	don't want to allocate memory and store a pointer to it in that data	1398	rules might look complicated, they usually do "the right thing".
1131	member, you can also "subclass" the watcher type and provide your own
1132	data:
1133		1399
1134	struct my_io	1400	=over 4
		1401
		1402	=item initialised
		1403
		1404	Before a watcher can be registered with the event loop it has to be
		1405	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1406	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1407
		1408	In this state it is simply some block of memory that is suitable for
		1409	use in an event loop. It can be moved around, freed, reused etc. at
		1410	will - as long as you either keep the memory contents intact, or call
		1411	C<ev_TYPE_init> again.
		1412
		1413	=item started/running/active
		1414
		1415	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1416	property of the event loop, and is actively waiting for events. While in
		1417	this state it cannot be accessed (except in a few documented ways), moved,
		1418	freed or anything else - the only legal thing is to keep a pointer to it,
		1419	and call libev functions on it that are documented to work on active watchers.
		1420
		1421	=item pending
		1422
		1423	If a watcher is active and libev determines that an event it is interested
		1424	in has occurred (such as a timer expiring), it will become pending. It will
		1425	stay in this pending state until either it is stopped or its callback is
		1426	about to be invoked, so it is not normally pending inside the watcher
		1427	callback.
		1428
		1429	The watcher might or might not be active while it is pending (for example,
		1430	an expired non-repeating timer can be pending but no longer active). If it
		1431	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1432	but it is still property of the event loop at this time, so cannot be
		1433	moved, freed or reused. And if it is active the rules described in the
		1434	previous item still apply.
		1435
		1436	It is also possible to feed an event on a watcher that is not active (e.g.
		1437	via C<ev_feed_event>), in which case it becomes pending without being
		1438	active.
		1439
		1440	=item stopped
		1441
		1442	A watcher can be stopped implicitly by libev (in which case it might still
		1443	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1444	latter will clear any pending state the watcher might be in, regardless
		1445	of whether it was active or not, so stopping a watcher explicitly before
		1446	freeing it is often a good idea.
		1447
		1448	While stopped (and not pending) the watcher is essentially in the
		1449	initialised state, that is, it can be reused, moved, modified in any way
		1450	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1451	it again).
		1452
		1453	=back
		1454
		1455	=head2 WATCHER PRIORITY MODELS
		1456
		1457	Many event loops support I<watcher priorities>, which are usually small
		1458	integers that influence the ordering of event callback invocation
		1459	between watchers in some way, all else being equal.
		1460
		1461	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1462	description for the more technical details such as the actual priority
		1463	range.
		1464
		1465	There are two common ways how these these priorities are being interpreted
		1466	by event loops:
		1467
		1468	In the more common lock-out model, higher priorities "lock out" invocation
		1469	of lower priority watchers, which means as long as higher priority
		1470	watchers receive events, lower priority watchers are not being invoked.
		1471
		1472	The less common only-for-ordering model uses priorities solely to order
		1473	callback invocation within a single event loop iteration: Higher priority
		1474	watchers are invoked before lower priority ones, but they all get invoked
		1475	before polling for new events.
		1476
		1477	Libev uses the second (only-for-ordering) model for all its watchers
		1478	except for idle watchers (which use the lock-out model).
		1479
		1480	The rationale behind this is that implementing the lock-out model for
		1481	watchers is not well supported by most kernel interfaces, and most event
		1482	libraries will just poll for the same events again and again as long as
		1483	their callbacks have not been executed, which is very inefficient in the
		1484	common case of one high-priority watcher locking out a mass of lower
		1485	priority ones.
		1486
		1487	Static (ordering) priorities are most useful when you have two or more
		1488	watchers handling the same resource: a typical usage example is having an
		1489	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1490	timeouts. Under load, data might be received while the program handles
		1491	other jobs, but since timers normally get invoked first, the timeout
		1492	handler will be executed before checking for data. In that case, giving
		1493	the timer a lower priority than the I/O watcher ensures that I/O will be
		1494	handled first even under adverse conditions (which is usually, but not
		1495	always, what you want).
		1496
		1497	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1498	will only be executed when no same or higher priority watchers have
		1499	received events, they can be used to implement the "lock-out" model when
		1500	required.
		1501
		1502	For example, to emulate how many other event libraries handle priorities,
		1503	you can associate an C<ev_idle> watcher to each such watcher, and in
		1504	the normal watcher callback, you just start the idle watcher. The real
		1505	processing is done in the idle watcher callback. This causes libev to
		1506	continuously poll and process kernel event data for the watcher, but when
		1507	the lock-out case is known to be rare (which in turn is rare :), this is
		1508	workable.
		1509
		1510	Usually, however, the lock-out model implemented that way will perform
		1511	miserably under the type of load it was designed to handle. In that case,
		1512	it might be preferable to stop the real watcher before starting the
		1513	idle watcher, so the kernel will not have to process the event in case
		1514	the actual processing will be delayed for considerable time.
		1515
		1516	Here is an example of an I/O watcher that should run at a strictly lower
		1517	priority than the default, and which should only process data when no
		1518	other events are pending:
		1519
		1520	ev_idle idle; // actual processing watcher
		1521	ev_io io; // actual event watcher
		1522
		1523	static void
		1524	io_cb (EV_P_ ev_io *w, int revents)
1135	{	1525	{
1136	ev_io io;	1526	// stop the I/O watcher, we received the event, but
1137	int otherfd;	1527	// are not yet ready to handle it.
1138	void *somedata;	1528	ev_io_stop (EV_A_ w);
1139	struct whatever *mostinteresting;	1529
		1530	// start the idle watcher to handle the actual event.
		1531	// it will not be executed as long as other watchers
		1532	// with the default priority are receiving events.
		1533	ev_idle_start (EV_A_ &idle);
1140	};	1534	}
1141		1535
1142	...	1536	static void
1143	struct my_io w;	1537	idle_cb (EV_P_ ev_idle *w, int revents)
1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1145
1146	And since your callback will be called with a pointer to the watcher, you
1147	can cast it back to your own type:
1148
1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1150	{	1538	{
1151	struct my_io *w = (struct my_io *)w_;	1539	// actual processing
1152	...	1540	read (STDIN_FILENO, ...);
		1541
		1542	// have to start the I/O watcher again, as
		1543	// we have handled the event
		1544	ev_io_start (EV_P_ &io);
1153	}	1545	}
1154		1546
1155	More interesting and less C-conformant ways of casting your callback type	1547	// initialisation
1156	instead have been omitted.	1548	ev_idle_init (&idle, idle_cb);
		1549	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1550	ev_io_start (EV_DEFAULT_ &io);
1157		1551
1158	Another common scenario is to use some data structure with multiple	1552	In the "real" world, it might also be beneficial to start a timer, so that
1159	embedded watchers:	1553	low-priority connections can not be locked out forever under load. This
1160		1554	enables your program to keep a lower latency for important connections
1161	struct my_biggy	1555	during short periods of high load, while not completely locking out less
1162	{	1556	important ones.
1163	int some_data;
1164	ev_timer t1;
1165	ev_timer t2;
1166	}
1167
1168	In this case getting the pointer to C<my_biggy> is a bit more
1169	complicated: Either you store the address of your C<my_biggy> struct
1170	in the C<data> member of the watcher (for woozies), or you need to use
1171	some pointer arithmetic using C<offsetof> inside your watchers (for real
1172	programmers):
1173
1174	#include <stddef.h>
1175
1176	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{
1179	struct my_biggy big = (struct my_biggy *
1180	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}
1182
1183	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{
1186	struct my_biggy big = (struct my_biggy *
1187	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}
1189		1557
1190		1558
1191	=head1 WATCHER TYPES	1559	=head1 WATCHER TYPES
1192		1560
1193	This section describes each watcher in detail, but will not repeat	1561	This section describes each watcher in detail, but will not repeat
…		…
1217	In general you can register as many read and/or write event watchers per	1585	In general you can register as many read and/or write event watchers per
1218	fd as you want (as long as you don't confuse yourself). Setting all file	1586	fd as you want (as long as you don't confuse yourself). Setting all file
1219	descriptors to non-blocking mode is also usually a good idea (but not	1587	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1588	required if you know what you are doing).
1221		1589
1222	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1225
1226	Another thing you have to watch out for is that it is quite easy to	1590	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1591	receive "spurious" readiness notifications, that is, your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1592	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1593	because there is no data. It is very easy to get into this situation even
1230	lot of those (for example Solaris ports), it is very easy to get into	1594	with a relatively standard program structure. Thus it is best to always
1231	this situation even with a relatively standard program structure. Thus	1595	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1232	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1233	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1596	preferable to a program hanging until some data arrives.
1234		1597
1235	If you cannot run the fd in non-blocking mode (for example you should	1598	If you cannot run the fd in non-blocking mode (for example you should
1236	not play around with an Xlib connection), then you have to separately	1599	not play around with an Xlib connection), then you have to separately
1237	re-test whether a file descriptor is really ready with a known-to-be good	1600	re-test whether a file descriptor is really ready with a known-to-be good
1238	interface such as poll (fortunately in our Xlib example, Xlib already	1601	interface such as poll (fortunately in the case of Xlib, it already does
1239	does this on its own, so its quite safe to use). Some people additionally	1602	this on its own, so its quite safe to use). Some people additionally
1240	use C<SIGALRM> and an interval timer, just to be sure you won't block	1603	use C<SIGALRM> and an interval timer, just to be sure you won't block
1241	indefinitely.	1604	indefinitely.
1242		1605
1243	But really, best use non-blocking mode.	1606	But really, best use non-blocking mode.
1244		1607
…		…
1272		1635
1273	There is no workaround possible except not registering events	1636	There is no workaround possible except not registering events
1274	for potentially C<dup ()>'ed file descriptors, or to resort to	1637	for potentially C<dup ()>'ed file descriptors, or to resort to
1275	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1638	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1276		1639
		1640	=head3 The special problem of files
		1641
		1642	Many people try to use C<select> (or libev) on file descriptors
		1643	representing files, and expect it to become ready when their program
		1644	doesn't block on disk accesses (which can take a long time on their own).
		1645
		1646	However, this cannot ever work in the "expected" way - you get a readiness
		1647	notification as soon as the kernel knows whether and how much data is
		1648	there, and in the case of open files, that's always the case, so you
		1649	always get a readiness notification instantly, and your read (or possibly
		1650	write) will still block on the disk I/O.
		1651
		1652	Another way to view it is that in the case of sockets, pipes, character
		1653	devices and so on, there is another party (the sender) that delivers data
		1654	on its own, but in the case of files, there is no such thing: the disk
		1655	will not send data on its own, simply because it doesn't know what you
		1656	wish to read - you would first have to request some data.
		1657
		1658	Since files are typically not-so-well supported by advanced notification
		1659	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1660	to files, even though you should not use it. The reason for this is
		1661	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1662	usually a tty, often a pipe, but also sometimes files or special devices
		1663	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1664	F</dev/urandom>), and even though the file might better be served with
		1665	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1666	it "just works" instead of freezing.
		1667
		1668	So avoid file descriptors pointing to files when you know it (e.g. use
		1669	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1670	when you rarely read from a file instead of from a socket, and want to
		1671	reuse the same code path.
		1672
1277	=head3 The special problem of fork	1673	=head3 The special problem of fork
1278		1674
1279	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1675	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1280	useless behaviour. Libev fully supports fork, but needs to be told about	1676	useless behaviour. Libev fully supports fork, but needs to be told about
1281	it in the child.	1677	it in the child if you want to continue to use it in the child.
1282		1678
1283	To support fork in your programs, you either have to call	1679	To support fork in your child processes, you have to call C<ev_loop_fork
1284	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1680	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1681	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1286	C<EVBACKEND_POLL>.
1287		1682
1288	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1289		1684
1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1291	when writing to a pipe whose other end has been closed, your program gets	1686	when writing to a pipe whose other end has been closed, your program gets
…		…
1294		1689
1295	So when you encounter spurious, unexplained daemon exits, make sure you	1690	So when you encounter spurious, unexplained daemon exits, make sure you
1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1691	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1297	somewhere, as that would have given you a big clue).	1692	somewhere, as that would have given you a big clue).
1298		1693
		1694	=head3 The special problem of accept()ing when you can't
		1695
		1696	Many implementations of the POSIX C<accept> function (for example,
		1697	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1698	connection from the pending queue in all error cases.
		1699
		1700	For example, larger servers often run out of file descriptors (because
		1701	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1702	rejecting the connection, leading to libev signalling readiness on
		1703	the next iteration again (the connection still exists after all), and
		1704	typically causing the program to loop at 100% CPU usage.
		1705
		1706	Unfortunately, the set of errors that cause this issue differs between
		1707	operating systems, there is usually little the app can do to remedy the
		1708	situation, and no known thread-safe method of removing the connection to
		1709	cope with overload is known (to me).
		1710
		1711	One of the easiest ways to handle this situation is to just ignore it
		1712	- when the program encounters an overload, it will just loop until the
		1713	situation is over. While this is a form of busy waiting, no OS offers an
		1714	event-based way to handle this situation, so it's the best one can do.
		1715
		1716	A better way to handle the situation is to log any errors other than
		1717	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1718	messages, and continue as usual, which at least gives the user an idea of
		1719	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1720	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1721	usage.
		1722
		1723	If your program is single-threaded, then you could also keep a dummy file
		1724	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1725	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1726	close that fd, and create a new dummy fd. This will gracefully refuse
		1727	clients under typical overload conditions.
		1728
		1729	The last way to handle it is to simply log the error and C<exit>, as
		1730	is often done with C<malloc> failures, but this results in an easy
		1731	opportunity for a DoS attack.
1299		1732
1300	=head3 Watcher-Specific Functions	1733	=head3 Watcher-Specific Functions
1301		1734
1302	=over 4	1735	=over 4
1303		1736
…		…
1335	...	1768	...
1336	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1337	ev_io stdin_readable;	1770	ev_io stdin_readable;
1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1339	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1340	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1341		1774
1342		1775
1343	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1344		1777
1345	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1783	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1353		1786
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
		1788	passed (not I<at>, so on systems with very low-resolution clocks this
		1789	might introduce a small delay, see "the special problem of being too
1355	passed. If multiple timers become ready during the same loop iteration	1790	early", below). If multiple timers become ready during the same loop
1356	then the ones with earlier time-out values are invoked before ones with	1791	iteration then the ones with earlier time-out values are invoked before
1357	later time-out values (but this is no longer true when a callback calls	1792	ones of the same priority with later time-out values (but this is no
1358	C<ev_loop> recursively).	1793	longer true when a callback calls C<ev_run> recursively).
1359		1794
1360	=head3 Be smart about timeouts	1795	=head3 Be smart about timeouts
1361		1796
1362	Many real-world problems involve some kind of timeout, usually for error	1797	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1798	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1842	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1843	member and C<ev_timer_again>.
1409		1844
1410	At start:	1845	At start:
1411		1846
1412	ev_timer_init (timer, callback);	1847	ev_init (timer, callback);
1413	timer->repeat = 60.;	1848	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1849	ev_timer_again (loop, timer);
1415		1850
1416	Each time there is some activity:	1851	Each time there is some activity:
1417		1852
…		…
1438		1873
1439	In this case, it would be more efficient to leave the C<ev_timer> alone,	1874	In this case, it would be more efficient to leave the C<ev_timer> alone,
1440	but remember the time of last activity, and check for a real timeout only	1875	but remember the time of last activity, and check for a real timeout only
1441	within the callback:	1876	within the callback:
1442		1877
		1878	ev_tstamp timeout = 60.;
1443	ev_tstamp last_activity; // time of last activity	1879	ev_tstamp last_activity; // time of last activity
		1880	ev_timer timer;
1444		1881
1445	static void	1882	static void
1446	callback (EV_P_ ev_timer *w, int revents)	1883	callback (EV_P_ ev_timer *w, int revents)
1447	{	1884	{
1448	ev_tstamp now = ev_now (EV_A);	1885	// calculate when the timeout would happen
1449	ev_tstamp timeout = last_activity + 60.;	1886	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1450		1887
1451	// if last_activity + 60. is older than now, we did time out	1888	// if negative, it means we the timeout already occurred
1452	if (timeout < now)	1889	if (after < 0.)
1453	{	1890	{
1454	// timeout occured, take action	1891	// timeout occurred, take action
1455	}	1892	}
1456	else	1893	else
1457	{	1894	{
1458	// callback was invoked, but there was some activity, re-arm	1895	// callback was invoked, but there was some recent
1459	// the watcher to fire in last_activity + 60, which is	1896	// activity. simply restart the timer to time out
1460	// guaranteed to be in the future, so "again" is positive:	1897	// after "after" seconds, which is the earliest time
1461	w->repeat = timeout - now;	1898	// the timeout can occur.
		1899	ev_timer_set (w, after, 0.);
1462	ev_timer_again (EV_A_ w);	1900	ev_timer_start (EV_A_ w);
1463	}	1901	}
1464	}	1902	}
1465		1903
1466	To summarise the callback: first calculate the real timeout (defined	1904	To summarise the callback: first calculate in how many seconds the
1467	as "60 seconds after the last activity"), then check if that time has	1905	timeout will occur (by calculating the absolute time when it would occur,
1468	been reached, which means something I<did>, in fact, time out. Otherwise	1906	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1469	the callback was invoked too early (C<timeout> is in the future), so	1907	(EV_A)> from that).
1470	re-schedule the timer to fire at that future time, to see if maybe we have
1471	a timeout then.
1472		1908
1473	Note how C<ev_timer_again> is used, taking advantage of the	1909	If this value is negative, then we are already past the timeout, i.e. we
1474	C<ev_timer_again> optimisation when the timer is already running.	1910	timed out, and need to do whatever is needed in this case.
		1911
		1912	Otherwise, we now the earliest time at which the timeout would trigger,
		1913	and simply start the timer with this timeout value.
		1914
		1915	In other words, each time the callback is invoked it will check whether
		1916	the timeout occurred. If not, it will simply reschedule itself to check
		1917	again at the earliest time it could time out. Rinse. Repeat.
1475		1918
1476	This scheme causes more callback invocations (about one every 60 seconds	1919	This scheme causes more callback invocations (about one every 60 seconds
1477	minus half the average time between activity), but virtually no calls to	1920	minus half the average time between activity), but virtually no calls to
1478	libev to change the timeout.	1921	libev to change the timeout.
1479		1922
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1923	To start the machinery, simply initialise the watcher and set
1481	to the current time (meaning we just have some activity :), then call the	1924	C<last_activity> to the current time (meaning there was some activity just
1482	callback, which will "do the right thing" and start the timer:	1925	now), then call the callback, which will "do the right thing" and start
		1926	the timer:
1483		1927
		1928	last_activity = ev_now (EV_A);
1484	ev_timer_init (timer, callback);	1929	ev_init (&timer, callback);
1485	last_activity = ev_now (loop);	1930	callback (EV_A_ &timer, 0);
1486	callback (loop, timer, EV_TIMEOUT);
1487		1931
1488	And when there is some activity, simply store the current time in	1932	When there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1933	C<last_activity>, no libev calls at all:
1490		1934
		1935	if (activity detected)
1491	last_actiivty = ev_now (loop);	1936	last_activity = ev_now (EV_A);
		1937
		1938	When your timeout value changes, then the timeout can be changed by simply
		1939	providing a new value, stopping the timer and calling the callback, which
		1940	will again do the right thing (for example, time out immediately :).
		1941
		1942	timeout = new_value;
		1943	ev_timer_stop (EV_A_ &timer);
		1944	callback (EV_A_ &timer, 0);
1492		1945
1493	This technique is slightly more complex, but in most cases where the	1946	This technique is slightly more complex, but in most cases where the
1494	time-out is unlikely to be triggered, much more efficient.	1947	time-out is unlikely to be triggered, much more efficient.
1495
1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
1497	callback :) - just change the timeout and invoke the callback, which will
1498	fix things for you.
1499		1948
1500	=item 4. Wee, just use a double-linked list for your timeouts.	1949	=item 4. Wee, just use a double-linked list for your timeouts.
1501		1950
1502	If there is not one request, but many thousands (millions...), all	1951	If there is not one request, but many thousands (millions...), all
1503	employing some kind of timeout with the same timeout value, then one can	1952	employing some kind of timeout with the same timeout value, then one can
…		…
1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1979	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1531	rather complicated, but extremely efficient, something that really pays	1980	rather complicated, but extremely efficient, something that really pays
1532	off after the first million or so of active timers, i.e. it's usually	1981	off after the first million or so of active timers, i.e. it's usually
1533	overkill :)	1982	overkill :)
1534		1983
		1984	=head3 The special problem of being too early
		1985
		1986	If you ask a timer to call your callback after three seconds, then
		1987	you expect it to be invoked after three seconds - but of course, this
		1988	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1989	guaranteed to any precision by libev - imagine somebody suspending the
		1990	process with a STOP signal for a few hours for example.
		1991
		1992	So, libev tries to invoke your callback as soon as possible I<after> the
		1993	delay has occurred, but cannot guarantee this.
		1994
		1995	A less obvious failure mode is calling your callback too early: many event
		1996	loops compare timestamps with a "elapsed delay >= requested delay", but
		1997	this can cause your callback to be invoked much earlier than you would
		1998	expect.
		1999
		2000	To see why, imagine a system with a clock that only offers full second
		2001	resolution (think windows if you can't come up with a broken enough OS
		2002	yourself). If you schedule a one-second timer at the time 500.9, then the
		2003	event loop will schedule your timeout to elapse at a system time of 500
		2004	(500.9 truncated to the resolution) + 1, or 501.
		2005
		2006	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2007	501" and invoke the callback 0.1s after it was started, even though a
		2008	one-second delay was requested - this is being "too early", despite best
		2009	intentions.
		2010
		2011	This is the reason why libev will never invoke the callback if the elapsed
		2012	delay equals the requested delay, but only when the elapsed delay is
		2013	larger than the requested delay. In the example above, libev would only invoke
		2014	the callback at system time 502, or 1.1s after the timer was started.
		2015
		2016	So, while libev cannot guarantee that your callback will be invoked
		2017	exactly when requested, it I<can> and I<does> guarantee that the requested
		2018	delay has actually elapsed, or in other words, it always errs on the "too
		2019	late" side of things.
		2020
1535	=head3 The special problem of time updates	2021	=head3 The special problem of time updates
1536		2022
1537	Establishing the current time is a costly operation (it usually takes at	2023	Establishing the current time is a costly operation (it usually takes
1538	least two system calls): EV therefore updates its idea of the current	2024	at least one system call): EV therefore updates its idea of the current
1539	time only before and after C<ev_loop> collects new events, which causes a	2025	time only before and after C<ev_run> collects new events, which causes a
1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2026	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1541	lots of events in one iteration.	2027	lots of events in one iteration.
1542		2028
1543	The relative timeouts are calculated relative to the C<ev_now ()>	2029	The relative timeouts are calculated relative to the C<ev_now ()>
1544	time. This is usually the right thing as this timestamp refers to the time	2030	time. This is usually the right thing as this timestamp refers to the time
…		…
1550		2036
1551	If the event loop is suspended for a long time, you can also force an	2037	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2038	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	2039	()>.
1554		2040
		2041	=head3 The special problem of unsynchronised clocks
		2042
		2043	Modern systems have a variety of clocks - libev itself uses the normal
		2044	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2045	jumps).
		2046
		2047	Neither of these clocks is synchronised with each other or any other clock
		2048	on the system, so C<ev_time ()> might return a considerably different time
		2049	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2050	a call to C<gettimeofday> might return a second count that is one higher
		2051	than a directly following call to C<time>.
		2052
		2053	The moral of this is to only compare libev-related timestamps with
		2054	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2055	a second or so.
		2056
		2057	One more problem arises due to this lack of synchronisation: if libev uses
		2058	the system monotonic clock and you compare timestamps from C<ev_time>
		2059	or C<ev_now> from when you started your timer and when your callback is
		2060	invoked, you will find that sometimes the callback is a bit "early".
		2061
		2062	This is because C<ev_timer>s work in real time, not wall clock time, so
		2063	libev makes sure your callback is not invoked before the delay happened,
		2064	I<measured according to the real time>, not the system clock.
		2065
		2066	If your timeouts are based on a physical timescale (e.g. "time out this
		2067	connection after 100 seconds") then this shouldn't bother you as it is
		2068	exactly the right behaviour.
		2069
		2070	If you want to compare wall clock/system timestamps to your timers, then
		2071	you need to use C<ev_periodic>s, as these are based on the wall clock
		2072	time, where your comparisons will always generate correct results.
		2073
		2074	=head3 The special problems of suspended animation
		2075
		2076	When you leave the server world it is quite customary to hit machines that
		2077	can suspend/hibernate - what happens to the clocks during such a suspend?
		2078
		2079	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2080	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2081	to run until the system is suspended, but they will not advance while the
		2082	system is suspended. That means, on resume, it will be as if the program
		2083	was frozen for a few seconds, but the suspend time will not be counted
		2084	towards C<ev_timer> when a monotonic clock source is used. The real time
		2085	clock advanced as expected, but if it is used as sole clocksource, then a
		2086	long suspend would be detected as a time jump by libev, and timers would
		2087	be adjusted accordingly.
		2088
		2089	I would not be surprised to see different behaviour in different between
		2090	operating systems, OS versions or even different hardware.
		2091
		2092	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2093	time jump in the monotonic clocks and the realtime clock. If the program
		2094	is suspended for a very long time, and monotonic clock sources are in use,
		2095	then you can expect C<ev_timer>s to expire as the full suspension time
		2096	will be counted towards the timers. When no monotonic clock source is in
		2097	use, then libev will again assume a timejump and adjust accordingly.
		2098
		2099	It might be beneficial for this latter case to call C<ev_suspend>
		2100	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2101	deterministic behaviour in this case (you can do nothing against
		2102	C<SIGSTOP>).
		2103
1555	=head3 Watcher-Specific Functions and Data Members	2104	=head3 Watcher-Specific Functions and Data Members
1556		2105
1557	=over 4	2106	=over 4
1558		2107
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2108	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1572	keep up with the timer (because it takes longer than those 10 seconds to	2121	keep up with the timer (because it takes longer than those 10 seconds to
1573	do stuff) the timer will not fire more than once per event loop iteration.	2122	do stuff) the timer will not fire more than once per event loop iteration.
1574		2123
1575	=item ev_timer_again (loop, ev_timer *)	2124	=item ev_timer_again (loop, ev_timer *)
1576		2125
1577	This will act as if the timer timed out and restart it again if it is	2126	This will act as if the timer timed out, and restarts it again if it is
1578	repeating. The exact semantics are:	2127	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2128	timeout to the C<repeat> value and calling C<ev_timer_start>.
1579		2129
		2130	The exact semantics are as in the following rules, all of which will be
		2131	applied to the watcher:
		2132
		2133	=over 4
		2134
1580	If the timer is pending, its pending status is cleared.	2135	=item If the timer is pending, the pending status is always cleared.
1581		2136
1582	If the timer is started but non-repeating, stop it (as if it timed out).	2137	=item If the timer is started but non-repeating, stop it (as if it timed
		2138	out, without invoking it).
1583		2139
1584	If the timer is repeating, either start it if necessary (with the	2140	=item If the timer is repeating, make the C<repeat> value the new timeout
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	2141	and start the timer, if necessary.
1586		2142
		2143	=back
		2144
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2145	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1588	usage example.	2146	usage example.
		2147
		2148	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2149
		2150	Returns the remaining time until a timer fires. If the timer is active,
		2151	then this time is relative to the current event loop time, otherwise it's
		2152	the timeout value currently configured.
		2153
		2154	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2155	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2156	will return C<4>. When the timer expires and is restarted, it will return
		2157	roughly C<7> (likely slightly less as callback invocation takes some time,
		2158	too), and so on.
1589		2159
1590	=item ev_tstamp repeat [read-write]	2160	=item ev_tstamp repeat [read-write]
1591		2161
1592	The current C<repeat> value. Will be used each time the watcher times out	2162	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	2163	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1619	}	2189	}
1620		2190
1621	ev_timer mytimer;	2191	ev_timer mytimer;
1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2192	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1623	ev_timer_again (&mytimer); /* start timer */	2193	ev_timer_again (&mytimer); /* start timer */
1624	ev_loop (loop, 0);	2194	ev_run (loop, 0);
1625		2195
1626	// and in some piece of code that gets executed on any "activity":	2196	// and in some piece of code that gets executed on any "activity":
1627	// reset the timeout to start ticking again at 10 seconds	2197	// reset the timeout to start ticking again at 10 seconds
1628	ev_timer_again (&mytimer);	2198	ev_timer_again (&mytimer);
1629		2199
…		…
1655		2225
1656	As with timers, the callback is guaranteed to be invoked only when the	2226	As with timers, the callback is guaranteed to be invoked only when the
1657	point in time where it is supposed to trigger has passed. If multiple	2227	point in time where it is supposed to trigger has passed. If multiple
1658	timers become ready during the same loop iteration then the ones with	2228	timers become ready during the same loop iteration then the ones with
1659	earlier time-out values are invoked before ones with later time-out values	2229	earlier time-out values are invoked before ones with later time-out values
1660	(but this is no longer true when a callback calls C<ev_loop> recursively).	2230	(but this is no longer true when a callback calls C<ev_run> recursively).
1661		2231
1662	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1663		2233
1664	=over 4	2234	=over 4
1665		2235
…		…
1700		2270
1701	Another way to think about it (for the mathematically inclined) is that	2271	Another way to think about it (for the mathematically inclined) is that
1702	C<ev_periodic> will try to run the callback in this mode at the next possible	2272	C<ev_periodic> will try to run the callback in this mode at the next possible
1703	time where C<time = offset (mod interval)>, regardless of any time jumps.	2273	time where C<time = offset (mod interval)>, regardless of any time jumps.
1704		2274
1705	For numerical stability it is preferable that the C<offset> value is near	2275	The C<interval> I<MUST> be positive, and for numerical stability, the
1706	C<ev_now ()> (the current time), but there is no range requirement for	2276	interval value should be higher than C<1/8192> (which is around 100
1707	this value, and in fact is often specified as zero.	2277	microseconds) and C<offset> should be higher than C<0> and should have
		2278	at most a similar magnitude as the current time (say, within a factor of
		2279	ten). Typical values for offset are, in fact, C<0> or something between
		2280	C<0> and C<interval>, which is also the recommended range.
1708		2281
1709	Note also that there is an upper limit to how often a timer can fire (CPU	2282	Note also that there is an upper limit to how often a timer can fire (CPU
1710	speed for example), so if C<interval> is very small then timing stability	2283	speed for example), so if C<interval> is very small then timing stability
1711	will of course deteriorate. Libev itself tries to be exact to be about one	2284	will of course deteriorate. Libev itself tries to be exact to be about one
1712	millisecond (if the OS supports it and the machine is fast enough).	2285	millisecond (if the OS supports it and the machine is fast enough).
…		…
1793	Example: Call a callback every hour, or, more precisely, whenever the	2366	Example: Call a callback every hour, or, more precisely, whenever the
1794	system time is divisible by 3600. The callback invocation times have	2367	system time is divisible by 3600. The callback invocation times have
1795	potentially a lot of jitter, but good long-term stability.	2368	potentially a lot of jitter, but good long-term stability.
1796		2369
1797	static void	2370	static void
1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2371	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1799	{	2372	{
1800	... its now a full hour (UTC, or TAI or whatever your clock follows)	2373	... its now a full hour (UTC, or TAI or whatever your clock follows)
1801	}	2374	}
1802		2375
1803	ev_periodic hourly_tick;	2376	ev_periodic hourly_tick;
…		…
1826		2399
1827	=head2 C<ev_signal> - signal me when a signal gets signalled!	2400	=head2 C<ev_signal> - signal me when a signal gets signalled!
1828		2401
1829	Signal watchers will trigger an event when the process receives a specific	2402	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2403	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2404	will try its best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2405	normal event processing, like any other event.
1833		2406
1834	If you want signals asynchronously, just use C<sigaction> as you would	2407	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2408	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2409	the signal. You can even use C<ev_async> from a signal handler to
		2410	synchronously wake up an event loop.
1837		2411
1838	You can configure as many watchers as you like per signal. Only when the	2412	You can configure as many watchers as you like for the same signal, but
1839	first watcher gets started will libev actually register a signal handler	2413	only within the same loop, i.e. you can watch for C<SIGINT> in your
1840	with the kernel (thus it coexists with your own signal handlers as long as	2414	default loop and for C<SIGIO> in another loop, but you cannot watch for
1841	you don't register any with libev for the same signal). Similarly, when	2415	C<SIGINT> in both the default loop and another loop at the same time. At
1842	the last signal watcher for a signal is stopped, libev will reset the	2416	the moment, C<SIGCHLD> is permanently tied to the default loop.
1843	signal handler to SIG_DFL (regardless of what it was set to before).	2417
		2418	Only after the first watcher for a signal is started will libev actually
		2419	register something with the kernel. It thus coexists with your own signal
		2420	handlers as long as you don't register any with libev for the same signal.
1844		2421
1845	If possible and supported, libev will install its handlers with	2422	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2423	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2424	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2425	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2426	and unblock them in an C<ev_prepare> watcher.
		2427
		2428	=head3 The special problem of inheritance over fork/execve/pthread_create
		2429
		2430	Both the signal mask (C<sigprocmask>) and the signal disposition
		2431	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2432	stopping it again), that is, libev might or might not block the signal,
		2433	and might or might not set or restore the installed signal handler (but
		2434	see C<EVFLAG_NOSIGMASK>).
		2435
		2436	While this does not matter for the signal disposition (libev never
		2437	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2438	C<execve>), this matters for the signal mask: many programs do not expect
		2439	certain signals to be blocked.
		2440
		2441	This means that before calling C<exec> (from the child) you should reset
		2442	the signal mask to whatever "default" you expect (all clear is a good
		2443	choice usually).
		2444
		2445	The simplest way to ensure that the signal mask is reset in the child is
		2446	to install a fork handler with C<pthread_atfork> that resets it. That will
		2447	catch fork calls done by libraries (such as the libc) as well.
		2448
		2449	In current versions of libev, the signal will not be blocked indefinitely
		2450	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2451	the window of opportunity for problems, it will not go away, as libev
		2452	I<has> to modify the signal mask, at least temporarily.
		2453
		2454	So I can't stress this enough: I<If you do not reset your signal mask when
		2455	you expect it to be empty, you have a race condition in your code>. This
		2456	is not a libev-specific thing, this is true for most event libraries.
		2457
		2458	=head3 The special problem of threads signal handling
		2459
		2460	POSIX threads has problematic signal handling semantics, specifically,
		2461	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2462	threads in a process block signals, which is hard to achieve.
		2463
		2464	When you want to use sigwait (or mix libev signal handling with your own
		2465	for the same signals), you can tackle this problem by globally blocking
		2466	all signals before creating any threads (or creating them with a fully set
		2467	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2468	loops. Then designate one thread as "signal receiver thread" which handles
		2469	these signals. You can pass on any signals that libev might be interested
		2470	in by calling C<ev_feed_signal>.
1850		2471
1851	=head3 Watcher-Specific Functions and Data Members	2472	=head3 Watcher-Specific Functions and Data Members
1852		2473
1853	=over 4	2474	=over 4
1854		2475
…		…
1870	Example: Try to exit cleanly on SIGINT.	2491	Example: Try to exit cleanly on SIGINT.
1871		2492
1872	static void	2493	static void
1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2494	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1874	{	2495	{
1875	ev_unloop (loop, EVUNLOOP_ALL);	2496	ev_break (loop, EVBREAK_ALL);
1876	}	2497	}
1877		2498
1878	ev_signal signal_watcher;	2499	ev_signal signal_watcher;
1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2500	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1880	ev_signal_start (loop, &signal_watcher);	2501	ev_signal_start (loop, &signal_watcher);
…		…
1886	some child status changes (most typically when a child of yours dies or	2507	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2508	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2509	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2510	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2511	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2512	but forking and registering a watcher a few event loop iterations later or
1892	not.	2513	in the next callback invocation is not.
1893		2514
1894	Only the default event loop is capable of handling signals, and therefore	2515	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2516	you can only register child watchers in the default event loop.
1896		2517
		2518	Due to some design glitches inside libev, child watchers will always be
		2519	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2520	libev)
		2521
1897	=head3 Process Interaction	2522	=head3 Process Interaction
1898		2523
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2524	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2525	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2526	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2527	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2528	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2529	children, even ones not watched.
1905		2530
1906	=head3 Overriding the Built-In Processing	2531	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2541	=head3 Stopping the Child Watcher
1917		2542
1918	Currently, the child watcher never gets stopped, even when the	2543	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2544	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2545	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2546	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2547	problem).
1922		2548
1923	=head3 Watcher-Specific Functions and Data Members	2549	=head3 Watcher-Specific Functions and Data Members
1924		2550
1925	=over 4	2551	=over 4
1926		2552
…		…
1984		2610
1985	=head2 C<ev_stat> - did the file attributes just change?	2611	=head2 C<ev_stat> - did the file attributes just change?
1986		2612
1987	This watches a file system path for attribute changes. That is, it calls	2613	This watches a file system path for attribute changes. That is, it calls
1988	C<stat> on that path in regular intervals (or when the OS says it changed)	2614	C<stat> on that path in regular intervals (or when the OS says it changed)
1989	and sees if it changed compared to the last time, invoking the callback if	2615	and sees if it changed compared to the last time, invoking the callback
1990	it did.	2616	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2617	happen after the watcher has been started will be reported.
1991		2618
1992	The path does not need to exist: changing from "path exists" to "path does	2619	The path does not need to exist: changing from "path exists" to "path does
1993	not exist" is a status change like any other. The condition "path does not	2620	not exist" is a status change like any other. The condition "path does not
1994	exist" (or more correctly "path cannot be stat'ed") is signified by the	2621	exist" (or more correctly "path cannot be stat'ed") is signified by the
1995	C<st_nlink> field being zero (which is otherwise always forced to be at	2622	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2225	Apart from keeping your process non-blocking (which is a useful	2852	Apart from keeping your process non-blocking (which is a useful
2226	effect on its own sometimes), idle watchers are a good place to do	2853	effect on its own sometimes), idle watchers are a good place to do
2227	"pseudo-background processing", or delay processing stuff to after the	2854	"pseudo-background processing", or delay processing stuff to after the
2228	event loop has handled all outstanding events.	2855	event loop has handled all outstanding events.
2229		2856
		2857	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2858
		2859	As long as there is at least one active idle watcher, libev will never
		2860	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2861	For this to work, the idle watcher doesn't need to be invoked at all - the
		2862	lowest priority will do.
		2863
		2864	This mode of operation can be useful together with an C<ev_check> watcher,
		2865	to do something on each event loop iteration - for example to balance load
		2866	between different connections.
		2867
		2868	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2869	example.
		2870
2230	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
2231		2872
2232	=over 4	2873	=over 4
2233		2874
2234	=item ev_idle_init (ev_idle *, callback)	2875	=item ev_idle_init (ev_idle *, callback)
…		…
2245	callback, free it. Also, use no error checking, as usual.	2886	callback, free it. Also, use no error checking, as usual.
2246		2887
2247	static void	2888	static void
2248	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2889	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2249	{	2890	{
		2891	// stop the watcher
		2892	ev_idle_stop (loop, w);
		2893
		2894	// now we can free it
2250	free (w);	2895	free (w);
		2896
2251	// now do something you wanted to do when the program has	2897	// now do something you wanted to do when the program has
2252	// no longer anything immediate to do.	2898	// no longer anything immediate to do.
2253	}	2899	}
2254		2900
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2901	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2902	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2903	ev_idle_start (loop, idle_watcher);
2258		2904
2259		2905
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2906	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2907
2262	Prepare and check watchers are usually (but not always) used in pairs:	2908	Prepare and check watchers are often (but not always) used in pairs:
2263	prepare watchers get invoked before the process blocks and check watchers	2909	prepare watchers get invoked before the process blocks and check watchers
2264	afterwards.	2910	afterwards.
2265		2911
2266	You I<must not> call C<ev_loop> or similar functions that enter	2912	You I<must not> call C<ev_run> or similar functions that enter
2267	the current event loop from either C<ev_prepare> or C<ev_check>	2913	the current event loop from either C<ev_prepare> or C<ev_check>
2268	watchers. Other loops than the current one are fine, however. The	2914	watchers. Other loops than the current one are fine, however. The
2269	rationale behind this is that you do not need to check for recursion in	2915	rationale behind this is that you do not need to check for recursion in
2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2916	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2271	C<ev_check> so if you have one watcher of each kind they will always be	2917	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2295	with priority higher than or equal to the event loop and one coroutine	2941	with priority higher than or equal to the event loop and one coroutine
2296	of lower priority, but only once, using idle watchers to keep the event	2942	of lower priority, but only once, using idle watchers to keep the event
2297	loop from blocking if lower-priority coroutines are active, thus mapping	2943	loop from blocking if lower-priority coroutines are active, thus mapping
2298	low-priority coroutines to idle/background tasks).	2944	low-priority coroutines to idle/background tasks).
2299		2945
2300	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2946	When used for this purpose, it is recommended to give C<ev_check> watchers
2301	priority, to ensure that they are being run before any other watchers	2947	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2302	after the poll (this doesn't matter for C<ev_prepare> watchers).	2948	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2949	watchers).
2303		2950
2304	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2951	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2305	activate ("feed") events into libev. While libev fully supports this, they	2952	activate ("feed") events into libev. While libev fully supports this, they
2306	might get executed before other C<ev_check> watchers did their job. As	2953	might get executed before other C<ev_check> watchers did their job. As
2307	C<ev_check> watchers are often used to embed other (non-libev) event	2954	C<ev_check> watchers are often used to embed other (non-libev) event
2308	loops those other event loops might be in an unusable state until their	2955	loops those other event loops might be in an unusable state until their
2309	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2956	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2310	others).	2957	others).
		2958
		2959	=head3 Abusing an C<ev_check> watcher for its side-effect
		2960
		2961	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2962	useful because they are called once per event loop iteration. For
		2963	example, if you want to handle a large number of connections fairly, you
		2964	normally only do a bit of work for each active connection, and if there
		2965	is more work to do, you wait for the next event loop iteration, so other
		2966	connections have a chance of making progress.
		2967
		2968	Using an C<ev_check> watcher is almost enough: it will be called on the
		2969	next event loop iteration. However, that isn't as soon as possible -
		2970	without external events, your C<ev_check> watcher will not be invoked.
		2971
		2972	This is where C<ev_idle> watchers come in handy - all you need is a
		2973	single global idle watcher that is active as long as you have one active
		2974	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2975	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2976	invoked. Neither watcher alone can do that.
2311		2977
2312	=head3 Watcher-Specific Functions and Data Members	2978	=head3 Watcher-Specific Functions and Data Members
2313		2979
2314	=over 4	2980	=over 4
2315		2981
…		…
2355	struct pollfd fds [nfd];	3021	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	3022	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3023	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		3024
2359	/* the callback is illegal, but won't be called as we stop during check */	3025	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	3026	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	3027	ev_timer_start (loop, &tw);
2362		3028
2363	// create one ev_io per pollfd	3029	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	3030	for (int i = 0; i < nfd; ++i)
2365	{	3031	{
…		…
2439		3105
2440	if (timeout >= 0)	3106	if (timeout >= 0)
2441	// create/start timer	3107	// create/start timer
2442		3108
2443	// poll	3109	// poll
2444	ev_loop (EV_A_ 0);	3110	ev_run (EV_A_ 0);
2445		3111
2446	// stop timer again	3112	// stop timer again
2447	if (timeout >= 0)	3113	if (timeout >= 0)
2448	ev_timer_stop (EV_A_ &to);	3114	ev_timer_stop (EV_A_ &to);
2449		3115
…		…
2516		3182
2517	=over 4	3183	=over 4
2518		3184
2519	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2520		3186
2521	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3187	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2522		3188
2523	Configures the watcher to embed the given loop, which must be	3189	Configures the watcher to embed the given loop, which must be
2524	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3190	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2525	invoked automatically, otherwise it is the responsibility of the callback	3191	invoked automatically, otherwise it is the responsibility of the callback
2526	to invoke it (it will continue to be called until the sweep has been done,	3192	to invoke it (it will continue to be called until the sweep has been done,
2527	if you do not want that, you need to temporarily stop the embed watcher).	3193	if you do not want that, you need to temporarily stop the embed watcher).
2528		3194
2529	=item ev_embed_sweep (loop, ev_embed *)	3195	=item ev_embed_sweep (loop, ev_embed *)
2530		3196
2531	Make a single, non-blocking sweep over the embedded loop. This works	3197	Make a single, non-blocking sweep over the embedded loop. This works
2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3198	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2533	appropriate way for embedded loops.	3199	appropriate way for embedded loops.
2534		3200
2535	=item struct ev_loop *other [read-only]	3201	=item struct ev_loop *other [read-only]
2536		3202
2537	The embedded event loop.	3203	The embedded event loop.
…		…
2589		3255
2590	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3256	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2591		3257
2592	Fork watchers are called when a C<fork ()> was detected (usually because	3258	Fork watchers are called when a C<fork ()> was detected (usually because
2593	whoever is a good citizen cared to tell libev about it by calling	3259	whoever is a good citizen cared to tell libev about it by calling
2594	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3260	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2595	event loop blocks next and before C<ev_check> watchers are being called,	3261	and before C<ev_check> watchers are being called, and only in the child
2596	and only in the child after the fork. If whoever good citizen calling	3262	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3263	and calls it in the wrong process, the fork handlers will be invoked, too,
2598	handlers will be invoked, too, of course.	3264	of course.
		3265
		3266	=head3 The special problem of life after fork - how is it possible?
		3267
		3268	Most uses of C<fork()> consist of forking, then some simple calls to set
		3269	up/change the process environment, followed by a call to C<exec()>. This
		3270	sequence should be handled by libev without any problems.
		3271
		3272	This changes when the application actually wants to do event handling
		3273	in the child, or both parent in child, in effect "continuing" after the
		3274	fork.
		3275
		3276	The default mode of operation (for libev, with application help to detect
		3277	forks) is to duplicate all the state in the child, as would be expected
		3278	when I<either> the parent I<or> the child process continues.
		3279
		3280	When both processes want to continue using libev, then this is usually the
		3281	wrong result. In that case, usually one process (typically the parent) is
		3282	supposed to continue with all watchers in place as before, while the other
		3283	process typically wants to start fresh, i.e. without any active watchers.
		3284
		3285	The cleanest and most efficient way to achieve that with libev is to
		3286	simply create a new event loop, which of course will be "empty", and
		3287	use that for new watchers. This has the advantage of not touching more
		3288	memory than necessary, and thus avoiding the copy-on-write, and the
		3289	disadvantage of having to use multiple event loops (which do not support
		3290	signal watchers).
		3291
		3292	When this is not possible, or you want to use the default loop for
		3293	other reasons, then in the process that wants to start "fresh", call
		3294	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3295	Destroying the default loop will "orphan" (not stop) all registered
		3296	watchers, so you have to be careful not to execute code that modifies
		3297	those watchers. Note also that in that case, you have to re-register any
		3298	signal watchers.
2599		3299
2600	=head3 Watcher-Specific Functions and Data Members	3300	=head3 Watcher-Specific Functions and Data Members
2601		3301
2602	=over 4	3302	=over 4
2603		3303
2604	=item ev_fork_init (ev_signal *, callback)	3304	=item ev_fork_init (ev_fork *, callback)
2605		3305
2606	Initialises and configures the fork watcher - it has no parameters of any	3306	Initialises and configures the fork watcher - it has no parameters of any
2607	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3307	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2608	believe me.	3308	really.
2609		3309
2610	=back	3310	=back
2611		3311
2612		3312
		3313	=head2 C<ev_cleanup> - even the best things end
		3314
		3315	Cleanup watchers are called just before the event loop is being destroyed
		3316	by a call to C<ev_loop_destroy>.
		3317
		3318	While there is no guarantee that the event loop gets destroyed, cleanup
		3319	watchers provide a convenient method to install cleanup hooks for your
		3320	program, worker threads and so on - you just to make sure to destroy the
		3321	loop when you want them to be invoked.
		3322
		3323	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3324	all other watchers, they do not keep a reference to the event loop (which
		3325	makes a lot of sense if you think about it). Like all other watchers, you
		3326	can call libev functions in the callback, except C<ev_cleanup_start>.
		3327
		3328	=head3 Watcher-Specific Functions and Data Members
		3329
		3330	=over 4
		3331
		3332	=item ev_cleanup_init (ev_cleanup *, callback)
		3333
		3334	Initialises and configures the cleanup watcher - it has no parameters of
		3335	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3336	pointless, I assure you.
		3337
		3338	=back
		3339
		3340	Example: Register an atexit handler to destroy the default loop, so any
		3341	cleanup functions are called.
		3342
		3343	static void
		3344	program_exits (void)
		3345	{
		3346	ev_loop_destroy (EV_DEFAULT_UC);
		3347	}
		3348
		3349	...
		3350	atexit (program_exits);
		3351
		3352
2613	=head2 C<ev_async> - how to wake up another event loop	3353	=head2 C<ev_async> - how to wake up an event loop
2614		3354
2615	In general, you cannot use an C<ev_loop> from multiple threads or other	3355	In general, you cannot use an C<ev_loop> from multiple threads or other
2616	asynchronous sources such as signal handlers (as opposed to multiple event	3356	asynchronous sources such as signal handlers (as opposed to multiple event
2617	loops - those are of course safe to use in different threads).	3357	loops - those are of course safe to use in different threads).
2618		3358
2619	Sometimes, however, you need to wake up another event loop you do not	3359	Sometimes, however, you need to wake up an event loop you do not control,
2620	control, for example because it belongs to another thread. This is what	3360	for example because it belongs to another thread. This is what C<ev_async>
2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3361	watchers do: as long as the C<ev_async> watcher is active, you can signal
2622	can signal it by calling C<ev_async_send>, which is thread- and signal	3362	it by calling C<ev_async_send>, which is thread- and signal safe.
2623	safe.
2624		3363
2625	This functionality is very similar to C<ev_signal> watchers, as signals,	3364	This functionality is very similar to C<ev_signal> watchers, as signals,
2626	too, are asynchronous in nature, and signals, too, will be compressed	3365	too, are asynchronous in nature, and signals, too, will be compressed
2627	(i.e. the number of callback invocations may be less than the number of	3366	(i.e. the number of callback invocations may be less than the number of
2628	C<ev_async_sent> calls).	3367	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2629		3368	of "global async watchers" by using a watcher on an otherwise unused
2630	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3369	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2631	just the default loop.	3370	even without knowing which loop owns the signal.
2632		3371
2633	=head3 Queueing	3372	=head3 Queueing
2634		3373
2635	C<ev_async> does not support queueing of data in any way. The reason	3374	C<ev_async> does not support queueing of data in any way. The reason
2636	is that the author does not know of a simple (or any) algorithm for a	3375	is that the author does not know of a simple (or any) algorithm for a
2637	multiple-writer-single-reader queue that works in all cases and doesn't	3376	multiple-writer-single-reader queue that works in all cases and doesn't
2638	need elaborate support such as pthreads.	3377	need elaborate support such as pthreads or unportable memory access
		3378	semantics.
2639		3379
2640	That means that if you want to queue data, you have to provide your own	3380	That means that if you want to queue data, you have to provide your own
2641	queue. But at least I can tell you how to implement locking around your	3381	queue. But at least I can tell you how to implement locking around your
2642	queue:	3382	queue:
2643		3383
…		…
2727	trust me.	3467	trust me.
2728		3468
2729	=item ev_async_send (loop, ev_async *)	3469	=item ev_async_send (loop, ev_async *)
2730		3470
2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3472	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3473	returns.
		3474
2733	C<ev_feed_event>, this call is safe to do from other threads, signal or	3475	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3476	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2735	section below on what exactly this means).	3477	embedding section below on what exactly this means).
2736		3478
2737	Note that, as with other watchers in libev, multiple events might get	3479	Note that, as with other watchers in libev, multiple events might get
2738	compressed into a single callback invocation (another way to look at this	3480	compressed into a single callback invocation (another way to look at
2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3481	this is that C<ev_async> watchers are level-triggered: they are set on
2740	reset when the event loop detects that).	3482	C<ev_async_send>, reset when the event loop detects that).
2741		3483
2742	This call incurs the overhead of a system call only once per event loop	3484	This call incurs the overhead of at most one extra system call per event
2743	iteration, so while the overhead might be noticeable, it doesn't apply to	3485	loop iteration, if the event loop is blocked, and no syscall at all if
2744	repeated calls to C<ev_async_send> for the same event loop.	3486	the event loop (or your program) is processing events. That means that
		3487	repeated calls are basically free (there is no need to avoid calls for
		3488	performance reasons) and that the overhead becomes smaller (typically
		3489	zero) under load.
2745		3490
2746	=item bool = ev_async_pending (ev_async *)	3491	=item bool = ev_async_pending (ev_async *)
2747		3492
2748	Returns a non-zero value when C<ev_async_send> has been called on the	3493	Returns a non-zero value when C<ev_async_send> has been called on the
2749	watcher but the event has not yet been processed (or even noted) by the	3494	watcher but the event has not yet been processed (or even noted) by the
…		…
2782		3527
2783	If C<timeout> is less than 0, then no timeout watcher will be	3528	If C<timeout> is less than 0, then no timeout watcher will be
2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3529	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2785	repeat = 0) will be started. C<0> is a valid timeout.	3530	repeat = 0) will be started. C<0> is a valid timeout.
2786		3531
2787	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3532	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2788	passed an C<revents> set like normal event callbacks (a combination of	3533	passed an C<revents> set like normal event callbacks (a combination of
2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3534	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2790	value passed to C<ev_once>. Note that it is possible to receive I<both>	3535	value passed to C<ev_once>. Note that it is possible to receive I<both>
2791	a timeout and an io event at the same time - you probably should give io	3536	a timeout and an io event at the same time - you probably should give io
2792	events precedence.	3537	events precedence.
2793		3538
2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3539	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2795		3540
2796	static void stdin_ready (int revents, void *arg)	3541	static void stdin_ready (int revents, void *arg)
2797	{	3542	{
2798	if (revents & EV_READ)	3543	if (revents & EV_READ)
2799	/* stdin might have data for us, joy! */;	3544	/* stdin might have data for us, joy! */;
2800	else if (revents & EV_TIMEOUT)	3545	else if (revents & EV_TIMER)
2801	/* doh, nothing entered */;	3546	/* doh, nothing entered */;
2802	}	3547	}
2803		3548
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3549	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805		3550
2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3551	=item ev_feed_fd_event (loop, int fd, int revents)
2813		3552
2814	Feed an event on the given fd, as if a file descriptor backend detected	3553	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3554	the given events.
2816		3555
2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3556	=item ev_feed_signal_event (loop, int signum)
2818		3557
2819	Feed an event as if the given signal occurred (C<loop> must be the default	3558	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2820	loop!).	3559	which is async-safe.
2821		3560
2822	=back	3561	=back
		3562
		3563
		3564	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3565
		3566	This section explains some common idioms that are not immediately
		3567	obvious. Note that examples are sprinkled over the whole manual, and this
		3568	section only contains stuff that wouldn't fit anywhere else.
		3569
		3570	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3571
		3572	Each watcher has, by default, a C<void *data> member that you can read
		3573	or modify at any time: libev will completely ignore it. This can be used
		3574	to associate arbitrary data with your watcher. If you need more data and
		3575	don't want to allocate memory separately and store a pointer to it in that
		3576	data member, you can also "subclass" the watcher type and provide your own
		3577	data:
		3578
		3579	struct my_io
		3580	{
		3581	ev_io io;
		3582	int otherfd;
		3583	void *somedata;
		3584	struct whatever *mostinteresting;
		3585	};
		3586
		3587	...
		3588	struct my_io w;
		3589	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3590
		3591	And since your callback will be called with a pointer to the watcher, you
		3592	can cast it back to your own type:
		3593
		3594	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3595	{
		3596	struct my_io *w = (struct my_io *)w_;
		3597	...
		3598	}
		3599
		3600	More interesting and less C-conformant ways of casting your callback
		3601	function type instead have been omitted.
		3602
		3603	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3604
		3605	Another common scenario is to use some data structure with multiple
		3606	embedded watchers, in effect creating your own watcher that combines
		3607	multiple libev event sources into one "super-watcher":
		3608
		3609	struct my_biggy
		3610	{
		3611	int some_data;
		3612	ev_timer t1;
		3613	ev_timer t2;
		3614	}
		3615
		3616	In this case getting the pointer to C<my_biggy> is a bit more
		3617	complicated: Either you store the address of your C<my_biggy> struct in
		3618	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3619	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3620	real programmers):
		3621
		3622	#include <stddef.h>
		3623
		3624	static void
		3625	t1_cb (EV_P_ ev_timer *w, int revents)
		3626	{
		3627	struct my_biggy big = (struct my_biggy *)
		3628	(((char *)w) - offsetof (struct my_biggy, t1));
		3629	}
		3630
		3631	static void
		3632	t2_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t2));
		3636	}
		3637
		3638	=head2 AVOIDING FINISHING BEFORE RETURNING
		3639
		3640	Often you have structures like this in event-based programs:
		3641
		3642	callback ()
		3643	{
		3644	free (request);
		3645	}
		3646
		3647	request = start_new_request (..., callback);
		3648
		3649	The intent is to start some "lengthy" operation. The C<request> could be
		3650	used to cancel the operation, or do other things with it.
		3651
		3652	It's not uncommon to have code paths in C<start_new_request> that
		3653	immediately invoke the callback, for example, to report errors. Or you add
		3654	some caching layer that finds that it can skip the lengthy aspects of the
		3655	operation and simply invoke the callback with the result.
		3656
		3657	The problem here is that this will happen I<before> C<start_new_request>
		3658	has returned, so C<request> is not set.
		3659
		3660	Even if you pass the request by some safer means to the callback, you
		3661	might want to do something to the request after starting it, such as
		3662	canceling it, which probably isn't working so well when the callback has
		3663	already been invoked.
		3664
		3665	A common way around all these issues is to make sure that
		3666	C<start_new_request> I<always> returns before the callback is invoked. If
		3667	C<start_new_request> immediately knows the result, it can artificially
		3668	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3669	example, or more sneakily, by reusing an existing (stopped) watcher and
		3670	pushing it into the pending queue:
		3671
		3672	ev_set_cb (watcher, callback);
		3673	ev_feed_event (EV_A_ watcher, 0);
		3674
		3675	This way, C<start_new_request> can safely return before the callback is
		3676	invoked, while not delaying callback invocation too much.
		3677
		3678	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3679
		3680	Often (especially in GUI toolkits) there are places where you have
		3681	I<modal> interaction, which is most easily implemented by recursively
		3682	invoking C<ev_run>.
		3683
		3684	This brings the problem of exiting - a callback might want to finish the
		3685	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3686	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3687	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3688	other combination: In these cases, a simple C<ev_break> will not work.
		3689
		3690	The solution is to maintain "break this loop" variable for each C<ev_run>
		3691	invocation, and use a loop around C<ev_run> until the condition is
		3692	triggered, using C<EVRUN_ONCE>:
		3693
		3694	// main loop
		3695	int exit_main_loop = 0;
		3696
		3697	while (!exit_main_loop)
		3698	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3699
		3700	// in a modal watcher
		3701	int exit_nested_loop = 0;
		3702
		3703	while (!exit_nested_loop)
		3704	ev_run (EV_A_ EVRUN_ONCE);
		3705
		3706	To exit from any of these loops, just set the corresponding exit variable:
		3707
		3708	// exit modal loop
		3709	exit_nested_loop = 1;
		3710
		3711	// exit main program, after modal loop is finished
		3712	exit_main_loop = 1;
		3713
		3714	// exit both
		3715	exit_main_loop = exit_nested_loop = 1;
		3716
		3717	=head2 THREAD LOCKING EXAMPLE
		3718
		3719	Here is a fictitious example of how to run an event loop in a different
		3720	thread from where callbacks are being invoked and watchers are
		3721	created/added/removed.
		3722
		3723	For a real-world example, see the C<EV::Loop::Async> perl module,
		3724	which uses exactly this technique (which is suited for many high-level
		3725	languages).
		3726
		3727	The example uses a pthread mutex to protect the loop data, a condition
		3728	variable to wait for callback invocations, an async watcher to notify the
		3729	event loop thread and an unspecified mechanism to wake up the main thread.
		3730
		3731	First, you need to associate some data with the event loop:
		3732
		3733	typedef struct {
		3734	mutex_t lock; /* global loop lock */
		3735	ev_async async_w;
		3736	thread_t tid;
		3737	cond_t invoke_cv;
		3738	} userdata;
		3739
		3740	void prepare_loop (EV_P)
		3741	{
		3742	// for simplicity, we use a static userdata struct.
		3743	static userdata u;
		3744
		3745	ev_async_init (&u->async_w, async_cb);
		3746	ev_async_start (EV_A_ &u->async_w);
		3747
		3748	pthread_mutex_init (&u->lock, 0);
		3749	pthread_cond_init (&u->invoke_cv, 0);
		3750
		3751	// now associate this with the loop
		3752	ev_set_userdata (EV_A_ u);
		3753	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3754	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3755
		3756	// then create the thread running ev_run
		3757	pthread_create (&u->tid, 0, l_run, EV_A);
		3758	}
		3759
		3760	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3761	solely to wake up the event loop so it takes notice of any new watchers
		3762	that might have been added:
		3763
		3764	static void
		3765	async_cb (EV_P_ ev_async *w, int revents)
		3766	{
		3767	// just used for the side effects
		3768	}
		3769
		3770	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3771	protecting the loop data, respectively.
		3772
		3773	static void
		3774	l_release (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777	pthread_mutex_unlock (&u->lock);
		3778	}
		3779
		3780	static void
		3781	l_acquire (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_lock (&u->lock);
		3785	}
		3786
		3787	The event loop thread first acquires the mutex, and then jumps straight
		3788	into C<ev_run>:
		3789
		3790	void *
		3791	l_run (void *thr_arg)
		3792	{
		3793	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3794
		3795	l_acquire (EV_A);
		3796	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3797	ev_run (EV_A_ 0);
		3798	l_release (EV_A);
		3799
		3800	return 0;
		3801	}
		3802
		3803	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3804	signal the main thread via some unspecified mechanism (signals? pipe
		3805	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3806	have been called (in a while loop because a) spurious wakeups are possible
		3807	and b) skipping inter-thread-communication when there are no pending
		3808	watchers is very beneficial):
		3809
		3810	static void
		3811	l_invoke (EV_P)
		3812	{
		3813	userdata *u = ev_userdata (EV_A);
		3814
		3815	while (ev_pending_count (EV_A))
		3816	{
		3817	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3818	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3819	}
		3820	}
		3821
		3822	Now, whenever the main thread gets told to invoke pending watchers, it
		3823	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3824	thread to continue:
		3825
		3826	static void
		3827	real_invoke_pending (EV_P)
		3828	{
		3829	userdata *u = ev_userdata (EV_A);
		3830
		3831	pthread_mutex_lock (&u->lock);
		3832	ev_invoke_pending (EV_A);
		3833	pthread_cond_signal (&u->invoke_cv);
		3834	pthread_mutex_unlock (&u->lock);
		3835	}
		3836
		3837	Whenever you want to start/stop a watcher or do other modifications to an
		3838	event loop, you will now have to lock:
		3839
		3840	ev_timer timeout_watcher;
		3841	userdata *u = ev_userdata (EV_A);
		3842
		3843	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3844
		3845	pthread_mutex_lock (&u->lock);
		3846	ev_timer_start (EV_A_ &timeout_watcher);
		3847	ev_async_send (EV_A_ &u->async_w);
		3848	pthread_mutex_unlock (&u->lock);
		3849
		3850	Note that sending the C<ev_async> watcher is required because otherwise
		3851	an event loop currently blocking in the kernel will have no knowledge
		3852	about the newly added timer. By waking up the loop it will pick up any new
		3853	watchers in the next event loop iteration.
		3854
		3855	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3856
		3857	While the overhead of a callback that e.g. schedules a thread is small, it
		3858	is still an overhead. If you embed libev, and your main usage is with some
		3859	kind of threads or coroutines, you might want to customise libev so that
		3860	doesn't need callbacks anymore.
		3861
		3862	Imagine you have coroutines that you can switch to using a function
		3863	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3864	and that due to some magic, the currently active coroutine is stored in a
		3865	global called C<current_coro>. Then you can build your own "wait for libev
		3866	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3867	the differing C<;> conventions):
		3868
		3869	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3870	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3871
		3872	That means instead of having a C callback function, you store the
		3873	coroutine to switch to in each watcher, and instead of having libev call
		3874	your callback, you instead have it switch to that coroutine.
		3875
		3876	A coroutine might now wait for an event with a function called
		3877	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3878	matter when, or whether the watcher is active or not when this function is
		3879	called):
		3880
		3881	void
		3882	wait_for_event (ev_watcher *w)
		3883	{
		3884	ev_set_cb (w, current_coro);
		3885	switch_to (libev_coro);
		3886	}
		3887
		3888	That basically suspends the coroutine inside C<wait_for_event> and
		3889	continues the libev coroutine, which, when appropriate, switches back to
		3890	this or any other coroutine.
		3891
		3892	You can do similar tricks if you have, say, threads with an event queue -
		3893	instead of storing a coroutine, you store the queue object and instead of
		3894	switching to a coroutine, you push the watcher onto the queue and notify
		3895	any waiters.
		3896
		3897	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3898	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3899
		3900	// my_ev.h
		3901	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3902	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3903	#include "../libev/ev.h"
		3904
		3905	// my_ev.c
		3906	#define EV_H "my_ev.h"
		3907	#include "../libev/ev.c"
		3908
		3909	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3910	F<my_ev.c> into your project. When properly specifying include paths, you
		3911	can even use F<ev.h> as header file name directly.
2823		3912
2824		3913
2825	=head1 LIBEVENT EMULATION	3914	=head1 LIBEVENT EMULATION
2826		3915
2827	Libev offers a compatibility emulation layer for libevent. It cannot	3916	Libev offers a compatibility emulation layer for libevent. It cannot
2828	emulate the internals of libevent, so here are some usage hints:	3917	emulate the internals of libevent, so here are some usage hints:
2829		3918
2830	=over 4	3919	=over 4
		3920
		3921	=item * Only the libevent-1.4.1-beta API is being emulated.
		3922
		3923	This was the newest libevent version available when libev was implemented,
		3924	and is still mostly unchanged in 2010.
2831		3925
2832	=item * Use it by including <event.h>, as usual.	3926	=item * Use it by including <event.h>, as usual.
2833		3927
2834	=item * The following members are fully supported: ev_base, ev_callback,	3928	=item * The following members are fully supported: ev_base, ev_callback,
2835	ev_arg, ev_fd, ev_res, ev_events.	3929	ev_arg, ev_fd, ev_res, ev_events.
…		…
2841	=item * Priorities are not currently supported. Initialising priorities	3935	=item * Priorities are not currently supported. Initialising priorities
2842	will fail and all watchers will have the same priority, even though there	3936	will fail and all watchers will have the same priority, even though there
2843	is an ev_pri field.	3937	is an ev_pri field.
2844		3938
2845	=item * In libevent, the last base created gets the signals, in libev, the	3939	=item * In libevent, the last base created gets the signals, in libev, the
2846	first base created (== the default loop) gets the signals.	3940	base that registered the signal gets the signals.
2847		3941
2848	=item * Other members are not supported.	3942	=item * Other members are not supported.
2849		3943
2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3944	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2851	to use the libev header file and library.	3945	to use the libev header file and library.
2852		3946
2853	=back	3947	=back
2854		3948
2855	=head1 C++ SUPPORT	3949	=head1 C++ SUPPORT
		3950
		3951	=head2 C API
		3952
		3953	The normal C API should work fine when used from C++: both ev.h and the
		3954	libev sources can be compiled as C++. Therefore, code that uses the C API
		3955	will work fine.
		3956
		3957	Proper exception specifications might have to be added to callbacks passed
		3958	to libev: exceptions may be thrown only from watcher callbacks, all
		3959	other callbacks (allocator, syserr, loop acquire/release and periodic
		3960	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3961	()> specification. If you have code that needs to be compiled as both C
		3962	and C++ you can use the C<EV_THROW> macro for this:
		3963
		3964	static void
		3965	fatal_error (const char *msg) EV_THROW
		3966	{
		3967	perror (msg);
		3968	abort ();
		3969	}
		3970
		3971	...
		3972	ev_set_syserr_cb (fatal_error);
		3973
		3974	The only API functions that can currently throw exceptions are C<ev_run>,
		3975	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3976	because it runs cleanup watchers).
		3977
		3978	Throwing exceptions in watcher callbacks is only supported if libev itself
		3979	is compiled with a C++ compiler or your C and C++ environments allow
		3980	throwing exceptions through C libraries (most do).
		3981
		3982	=head2 C++ API
2856		3983
2857	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3984	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2858	you to use some convenience methods to start/stop watchers and also change	3985	you to use some convenience methods to start/stop watchers and also change
2859	the callback model to a model using method callbacks on objects.	3986	the callback model to a model using method callbacks on objects.
2860		3987
2861	To use it,	3988	To use it,
2862		3989
2863	#include <ev++.h>	3990	#include <ev++.h>
2864		3991
2865	This automatically includes F<ev.h> and puts all of its definitions (many	3992	This automatically includes F<ev.h> and puts all of its definitions (many
2866	of them macros) into the global namespace. All C++ specific things are	3993	of them macros) into the global namespace. All C++ specific things are
2867	put into the C<ev> namespace. It should support all the same embedding	3994	put into the C<ev> namespace. It should support all the same embedding
…		…
2870	Care has been taken to keep the overhead low. The only data member the C++	3997	Care has been taken to keep the overhead low. The only data member the C++
2871	classes add (compared to plain C-style watchers) is the event loop pointer	3998	classes add (compared to plain C-style watchers) is the event loop pointer
2872	that the watcher is associated with (or no additional members at all if	3999	that the watcher is associated with (or no additional members at all if
2873	you disable C<EV_MULTIPLICITY> when embedding libev).	4000	you disable C<EV_MULTIPLICITY> when embedding libev).
2874		4001
2875	Currently, functions, and static and non-static member functions can be	4002	Currently, functions, static and non-static member functions and classes
2876	used as callbacks. Other types should be easy to add as long as they only	4003	with C<operator ()> can be used as callbacks. Other types should be easy
2877	need one additional pointer for context. If you need support for other	4004	to add as long as they only need one additional pointer for context. If
2878	types of functors please contact the author (preferably after implementing	4005	you need support for other types of functors please contact the author
2879	it).	4006	(preferably after implementing it).
		4007
		4008	For all this to work, your C++ compiler either has to use the same calling
		4009	conventions as your C compiler (for static member functions), or you have
		4010	to embed libev and compile libev itself as C++.
2880		4011
2881	Here is a list of things available in the C<ev> namespace:	4012	Here is a list of things available in the C<ev> namespace:
2882		4013
2883	=over 4	4014	=over 4
2884		4015
…		…
2894	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4025	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2895		4026
2896	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4027	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2897	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4028	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2898	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4029	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2899	defines by many implementations.	4030	defined by many implementations.
2900		4031
2901	All of those classes have these methods:	4032	All of those classes have these methods:
2902		4033
2903	=over 4	4034	=over 4
2904		4035
2905	=item ev::TYPE::TYPE ()	4036	=item ev::TYPE::TYPE ()
2906		4037
2907	=item ev::TYPE::TYPE (struct ev_loop *)	4038	=item ev::TYPE::TYPE (loop)
2908		4039
2909	=item ev::TYPE::~TYPE	4040	=item ev::TYPE::~TYPE
2910		4041
2911	The constructor (optionally) takes an event loop to associate the watcher	4042	The constructor (optionally) takes an event loop to associate the watcher
2912	with. If it is omitted, it will use C<EV_DEFAULT>.	4043	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2945	myclass obj;	4076	myclass obj;
2946	ev::io iow;	4077	ev::io iow;
2947	iow.set <myclass, &myclass::io_cb> (&obj);	4078	iow.set <myclass, &myclass::io_cb> (&obj);
2948		4079
2949	=item w->set (object *)	4080	=item w->set (object *)
2950
2951	This is an B<experimental> feature that might go away in a future version.
2952		4081
2953	This is a variation of a method callback - leaving out the method to call	4082	This is a variation of a method callback - leaving out the method to call
2954	will default the method to C<operator ()>, which makes it possible to use	4083	will default the method to C<operator ()>, which makes it possible to use
2955	functor objects without having to manually specify the C<operator ()> all	4084	functor objects without having to manually specify the C<operator ()> all
2956	the time. Incidentally, you can then also leave out the template argument	4085	the time. Incidentally, you can then also leave out the template argument
…		…
2989	Example: Use a plain function as callback.	4118	Example: Use a plain function as callback.
2990		4119
2991	static void io_cb (ev::io &w, int revents) { }	4120	static void io_cb (ev::io &w, int revents) { }
2992	iow.set <io_cb> ();	4121	iow.set <io_cb> ();
2993		4122
2994	=item w->set (struct ev_loop *)	4123	=item w->set (loop)
2995		4124
2996	Associates a different C<struct ev_loop> with this watcher. You can only	4125	Associates a different C<struct ev_loop> with this watcher. You can only
2997	do this when the watcher is inactive (and not pending either).	4126	do this when the watcher is inactive (and not pending either).
2998		4127
2999	=item w->set ([arguments])	4128	=item w->set ([arguments])
3000		4129
3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4130	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4131	with the same arguments. Either this method or a suitable start method
3002	called at least once. Unlike the C counterpart, an active watcher gets	4132	must be called at least once. Unlike the C counterpart, an active watcher
3003	automatically stopped and restarted when reconfiguring it with this	4133	gets automatically stopped and restarted when reconfiguring it with this
3004	method.	4134	method.
		4135
		4136	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4137	clashing with the C<set (loop)> method.
3005		4138
3006	=item w->start ()	4139	=item w->start ()
3007		4140
3008	Starts the watcher. Note that there is no C<loop> argument, as the	4141	Starts the watcher. Note that there is no C<loop> argument, as the
3009	constructor already stores the event loop.	4142	constructor already stores the event loop.
3010		4143
		4144	=item w->start ([arguments])
		4145
		4146	Instead of calling C<set> and C<start> methods separately, it is often
		4147	convenient to wrap them in one call. Uses the same type of arguments as
		4148	the configure C<set> method of the watcher.
		4149
3011	=item w->stop ()	4150	=item w->stop ()
3012		4151
3013	Stops the watcher if it is active. Again, no C<loop> argument.	4152	Stops the watcher if it is active. Again, no C<loop> argument.
3014		4153
3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4154	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3027		4166
3028	=back	4167	=back
3029		4168
3030	=back	4169	=back
3031		4170
3032	Example: Define a class with an IO and idle watcher, start one of them in	4171	Example: Define a class with two I/O and idle watchers, start the I/O
3033	the constructor.	4172	watchers in the constructor.
3034		4173
3035	class myclass	4174	class myclass
3036	{	4175	{
3037	ev::io io ; void io_cb (ev::io &w, int revents);	4176	ev::io io ; void io_cb (ev::io &w, int revents);
		4177	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4178	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3039		4179
3040	myclass (int fd)	4180	myclass (int fd)
3041	{	4181	{
3042	io .set <myclass, &myclass::io_cb > (this);	4182	io .set <myclass, &myclass::io_cb > (this);
		4183	io2 .set <myclass, &myclass::io2_cb > (this);
3043	idle.set <myclass, &myclass::idle_cb> (this);	4184	idle.set <myclass, &myclass::idle_cb> (this);
3044		4185
3045	io.start (fd, ev::READ);	4186	io.set (fd, ev::WRITE); // configure the watcher
		4187	io.start (); // start it whenever convenient
		4188
		4189	io2.start (fd, ev::READ); // set + start in one call
3046	}	4190	}
3047	};	4191	};
3048		4192
3049		4193
3050	=head1 OTHER LANGUAGE BINDINGS	4194	=head1 OTHER LANGUAGE BINDINGS
…		…
3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4233	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3090		4234
3091	=item D	4235	=item D
3092		4236
3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4237	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4238	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3095		4239
3096	=item Ocaml	4240	=item Ocaml
3097		4241
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	4242	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4243	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4244
		4245	=item Lua
		4246
		4247	Brian Maher has written a partial interface to libev for lua (at the
		4248	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4249	L<http://github.com/brimworks/lua-ev>.
		4250
		4251	=item Javascript
		4252
		4253	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4254
		4255	=item Others
		4256
		4257	There are others, and I stopped counting.
3100		4258
3101	=back	4259	=back
3102		4260
3103		4261
3104	=head1 MACRO MAGIC	4262	=head1 MACRO MAGIC
…		…
3118	loop argument"). The C<EV_A> form is used when this is the sole argument,	4276	loop argument"). The C<EV_A> form is used when this is the sole argument,
3119	C<EV_A_> is used when other arguments are following. Example:	4277	C<EV_A_> is used when other arguments are following. Example:
3120		4278
3121	ev_unref (EV_A);	4279	ev_unref (EV_A);
3122	ev_timer_add (EV_A_ watcher);	4280	ev_timer_add (EV_A_ watcher);
3123	ev_loop (EV_A_ 0);	4281	ev_run (EV_A_ 0);
3124		4282
3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4283	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3126	which is often provided by the following macro.	4284	which is often provided by the following macro.
3127		4285
3128	=item C<EV_P>, C<EV_P_>	4286	=item C<EV_P>, C<EV_P_>
…		…
3141	suitable for use with C<EV_A>.	4299	suitable for use with C<EV_A>.
3142		4300
3143	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4301	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3144		4302
3145	Similar to the other two macros, this gives you the value of the default	4303	Similar to the other two macros, this gives you the value of the default
3146	loop, if multiple loops are supported ("ev loop default").	4304	loop, if multiple loops are supported ("ev loop default"). The default loop
		4305	will be initialised if it isn't already initialised.
		4306
		4307	For non-multiplicity builds, these macros do nothing, so you always have
		4308	to initialise the loop somewhere.
3147		4309
3148	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4310	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3149		4311
3150	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4312	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3151	default loop has been initialised (C<UC> == unchecked). Their behaviour	4313	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3168	}	4330	}
3169		4331
3170	ev_check check;	4332	ev_check check;
3171	ev_check_init (&check, check_cb);	4333	ev_check_init (&check, check_cb);
3172	ev_check_start (EV_DEFAULT_ &check);	4334	ev_check_start (EV_DEFAULT_ &check);
3173	ev_loop (EV_DEFAULT_ 0);	4335	ev_run (EV_DEFAULT_ 0);
3174		4336
3175	=head1 EMBEDDING	4337	=head1 EMBEDDING
3176		4338
3177	Libev can (and often is) directly embedded into host	4339	Libev can (and often is) directly embedded into host
3178	applications. Examples of applications that embed it include the Deliantra	4340	applications. Examples of applications that embed it include the Deliantra
…		…
3258	libev.m4	4420	libev.m4
3259		4421
3260	=head2 PREPROCESSOR SYMBOLS/MACROS	4422	=head2 PREPROCESSOR SYMBOLS/MACROS
3261		4423
3262	Libev can be configured via a variety of preprocessor symbols you have to	4424	Libev can be configured via a variety of preprocessor symbols you have to
3263	define before including any of its files. The default in the absence of	4425	define before including (or compiling) any of its files. The default in
3264	autoconf is documented for every option.	4426	the absence of autoconf is documented for every option.
		4427
		4428	Symbols marked with "(h)" do not change the ABI, and can have different
		4429	values when compiling libev vs. including F<ev.h>, so it is permissible
		4430	to redefine them before including F<ev.h> without breaking compatibility
		4431	to a compiled library. All other symbols change the ABI, which means all
		4432	users of libev and the libev code itself must be compiled with compatible
		4433	settings.
3265		4434
3266	=over 4	4435	=over 4
3267		4436
		4437	=item EV_COMPAT3 (h)
		4438
		4439	Backwards compatibility is a major concern for libev. This is why this
		4440	release of libev comes with wrappers for the functions and symbols that
		4441	have been renamed between libev version 3 and 4.
		4442
		4443	You can disable these wrappers (to test compatibility with future
		4444	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4445	sources. This has the additional advantage that you can drop the C<struct>
		4446	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4447	typedef in that case.
		4448
		4449	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4450	and in some even more future version the compatibility code will be
		4451	removed completely.
		4452
3268	=item EV_STANDALONE	4453	=item EV_STANDALONE (h)
3269		4454
3270	Must always be C<1> if you do not use autoconf configuration, which	4455	Must always be C<1> if you do not use autoconf configuration, which
3271	keeps libev from including F<config.h>, and it also defines dummy	4456	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	4457	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	4458	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	4459	F<event.h> that are not directly supported by the libev core alone.
3275		4460
3276	In stanbdalone mode, libev will still try to automatically deduce the	4461	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	4462	configuration, but has to be more conservative.
		4463
		4464	=item EV_USE_FLOOR
		4465
		4466	If defined to be C<1>, libev will use the C<floor ()> function for its
		4467	periodic reschedule calculations, otherwise libev will fall back on a
		4468	portable (slower) implementation. If you enable this, you usually have to
		4469	link against libm or something equivalent. Enabling this when the C<floor>
		4470	function is not available will fail, so the safe default is to not enable
		4471	this.
3278		4472
3279	=item EV_USE_MONOTONIC	4473	=item EV_USE_MONOTONIC
3280		4474
3281	If defined to be C<1>, libev will try to detect the availability of the	4475	If defined to be C<1>, libev will try to detect the availability of the
3282	monotonic clock option at both compile time and runtime. Otherwise no	4476	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3346	be used is the winsock select). This means that it will call	4540	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4541	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	4542	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	4543	on win32. Should not be defined on non-win32 platforms.
3350		4544
3351	=item EV_FD_TO_WIN32_HANDLE	4545	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		4546
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4547	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	4548	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	4549	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	4550	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	4551	in which case they can provide this function to map fds to socket handles.
		4552
		4553	=item EV_WIN32_HANDLE_TO_FD(handle)
		4554
		4555	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4556	using the standard C<_open_osfhandle> function. For programs implementing
		4557	their own fd to handle mapping, overwriting this function makes it easier
		4558	to do so. This can be done by defining this macro to an appropriate value.
		4559
		4560	=item EV_WIN32_CLOSE_FD(fd)
		4561
		4562	If programs implement their own fd to handle mapping on win32, then this
		4563	macro can be used to override the C<close> function, useful to unregister
		4564	file descriptors again. Note that the replacement function has to close
		4565	the underlying OS handle.
		4566
		4567	=item EV_USE_WSASOCKET
		4568
		4569	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4570	communication socket, which works better in some environments. Otherwise,
		4571	the normal C<socket> function will be used, which works better in other
		4572	environments.
3358		4573
3359	=item EV_USE_POLL	4574	=item EV_USE_POLL
3360		4575
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4576	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	4577	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3398	If defined to be C<1>, libev will compile in support for the Linux inotify	4613	If defined to be C<1>, libev will compile in support for the Linux inotify
3399	interface to speed up C<ev_stat> watchers. Its actual availability will	4614	interface to speed up C<ev_stat> watchers. Its actual availability will
3400	be detected at runtime. If undefined, it will be enabled if the headers	4615	be detected at runtime. If undefined, it will be enabled if the headers
3401	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4616	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3402		4617
		4618	=item EV_NO_SMP
		4619
		4620	If defined to be C<1>, libev will assume that memory is always coherent
		4621	between threads, that is, threads can be used, but threads never run on
		4622	different cpus (or different cpu cores). This reduces dependencies
		4623	and makes libev faster.
		4624
		4625	=item EV_NO_THREADS
		4626
		4627	If defined to be C<1>, libev will assume that it will never be called from
		4628	different threads (that includes signal handlers), which is a stronger
		4629	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4630	libev faster.
		4631
3403	=item EV_ATOMIC_T	4632	=item EV_ATOMIC_T
3404		4633
3405	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4634	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3406	access is atomic with respect to other threads or signal contexts. No such	4635	access is atomic with respect to other threads or signal contexts. No
3407	type is easily found in the C language, so you can provide your own type	4636	such type is easily found in the C language, so you can provide your own
3408	that you know is safe for your purposes. It is used both for signal handler "locking"	4637	type that you know is safe for your purposes. It is used both for signal
3409	as well as for signal and thread safety in C<ev_async> watchers.	4638	handler "locking" as well as for signal and thread safety in C<ev_async>
		4639	watchers.
3410		4640
3411	In the absence of this define, libev will use C<sig_atomic_t volatile>	4641	In the absence of this define, libev will use C<sig_atomic_t volatile>
3412	(from F<signal.h>), which is usually good enough on most platforms.	4642	(from F<signal.h>), which is usually good enough on most platforms.
3413		4643
3414	=item EV_H	4644	=item EV_H (h)
3415		4645
3416	The name of the F<ev.h> header file used to include it. The default if	4646	The name of the F<ev.h> header file used to include it. The default if
3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4647	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3418	used to virtually rename the F<ev.h> header file in case of conflicts.	4648	used to virtually rename the F<ev.h> header file in case of conflicts.
3419		4649
3420	=item EV_CONFIG_H	4650	=item EV_CONFIG_H (h)
3421		4651
3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4652	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4653	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3424	C<EV_H>, above.	4654	C<EV_H>, above.
3425		4655
3426	=item EV_EVENT_H	4656	=item EV_EVENT_H (h)
3427		4657
3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4658	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3429	of how the F<event.h> header can be found, the default is C<"event.h">.	4659	of how the F<event.h> header can be found, the default is C<"event.h">.
3430		4660
3431	=item EV_PROTOTYPES	4661	=item EV_PROTOTYPES (h)
3432		4662
3433	If defined to be C<0>, then F<ev.h> will not define any function	4663	If defined to be C<0>, then F<ev.h> will not define any function
3434	prototypes, but still define all the structs and other symbols. This is	4664	prototypes, but still define all the structs and other symbols. This is
3435	occasionally useful if you want to provide your own wrapper functions	4665	occasionally useful if you want to provide your own wrapper functions
3436	around libev functions.	4666	around libev functions.
…		…
3441	will have the C<struct ev_loop *> as first argument, and you can create	4671	will have the C<struct ev_loop *> as first argument, and you can create
3442	additional independent event loops. Otherwise there will be no support	4672	additional independent event loops. Otherwise there will be no support
3443	for multiple event loops and there is no first event loop pointer	4673	for multiple event loops and there is no first event loop pointer
3444	argument. Instead, all functions act on the single default loop.	4674	argument. Instead, all functions act on the single default loop.
3445		4675
		4676	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4677	default loop when multiplicity is switched off - you always have to
		4678	initialise the loop manually in this case.
		4679
3446	=item EV_MINPRI	4680	=item EV_MINPRI
3447		4681
3448	=item EV_MAXPRI	4682	=item EV_MAXPRI
3449		4683
3450	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4684	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3458	fine.	4692	fine.
3459		4693
3460	If your embedding application does not need any priorities, defining these	4694	If your embedding application does not need any priorities, defining these
3461	both to C<0> will save some memory and CPU.	4695	both to C<0> will save some memory and CPU.
3462		4696
3463	=item EV_PERIODIC_ENABLE	4697	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4698	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4699	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3464		4700
3465	If undefined or defined to be C<1>, then periodic timers are supported. If	4701	If undefined or defined to be C<1> (and the platform supports it), then
3466	defined to be C<0>, then they are not. Disabling them saves a few kB of	4702	the respective watcher type is supported. If defined to be C<0>, then it
3467	code.	4703	is not. Disabling watcher types mainly saves code size.
3468		4704
3469	=item EV_IDLE_ENABLE	4705	=item EV_FEATURES
3470
3471	If undefined or defined to be C<1>, then idle watchers are supported. If
3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
3473	code.
3474
3475	=item EV_EMBED_ENABLE
3476
3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3478	defined to be C<0>, then they are not. Embed watchers rely on most other
3479	watcher types, which therefore must not be disabled.
3480
3481	=item EV_STAT_ENABLE
3482
3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3484	defined to be C<0>, then they are not.
3485
3486	=item EV_FORK_ENABLE
3487
3488	If undefined or defined to be C<1>, then fork watchers are supported. If
3489	defined to be C<0>, then they are not.
3490
3491	=item EV_ASYNC_ENABLE
3492
3493	If undefined or defined to be C<1>, then async watchers are supported. If
3494	defined to be C<0>, then they are not.
3495
3496	=item EV_MINIMAL
3497		4706
3498	If you need to shave off some kilobytes of code at the expense of some	4707	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	4708	speed (but with the full API), you can define this symbol to request
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4709	certain subsets of functionality. The default is to enable all features
3501	much smaller 2-heap for timer management over the default 4-heap.	4710	that can be enabled on the platform.
		4711
		4712	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4713	with some broad features you want) and then selectively re-enable
		4714	additional parts you want, for example if you want everything minimal,
		4715	but multiple event loop support, async and child watchers and the poll
		4716	backend, use this:
		4717
		4718	#define EV_FEATURES 0
		4719	#define EV_MULTIPLICITY 1
		4720	#define EV_USE_POLL 1
		4721	#define EV_CHILD_ENABLE 1
		4722	#define EV_ASYNC_ENABLE 1
		4723
		4724	The actual value is a bitset, it can be a combination of the following
		4725	values (by default, all of these are enabled):
		4726
		4727	=over 4
		4728
		4729	=item C<1> - faster/larger code
		4730
		4731	Use larger code to speed up some operations.
		4732
		4733	Currently this is used to override some inlining decisions (enlarging the
		4734	code size by roughly 30% on amd64).
		4735
		4736	When optimising for size, use of compiler flags such as C<-Os> with
		4737	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4738	assertions.
		4739
		4740	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4741	(e.g. gcc with C<-Os>).
		4742
		4743	=item C<2> - faster/larger data structures
		4744
		4745	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4746	hash table sizes and so on. This will usually further increase code size
		4747	and can additionally have an effect on the size of data structures at
		4748	runtime.
		4749
		4750	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4751	(e.g. gcc with C<-Os>).
		4752
		4753	=item C<4> - full API configuration
		4754
		4755	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4756	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4757
		4758	=item C<8> - full API
		4759
		4760	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4761	details on which parts of the API are still available without this
		4762	feature, and do not complain if this subset changes over time.
		4763
		4764	=item C<16> - enable all optional watcher types
		4765
		4766	Enables all optional watcher types. If you want to selectively enable
		4767	only some watcher types other than I/O and timers (e.g. prepare,
		4768	embed, async, child...) you can enable them manually by defining
		4769	C<EV_watchertype_ENABLE> to C<1> instead.
		4770
		4771	=item C<32> - enable all backends
		4772
		4773	This enables all backends - without this feature, you need to enable at
		4774	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4775
		4776	=item C<64> - enable OS-specific "helper" APIs
		4777
		4778	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4779	default.
		4780
		4781	=back
		4782
		4783	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4784	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4785	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4786	watchers, timers and monotonic clock support.
		4787
		4788	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4789	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4790	your program might be left out as well - a binary starting a timer and an
		4791	I/O watcher then might come out at only 5Kb.
		4792
		4793	=item EV_API_STATIC
		4794
		4795	If this symbol is defined (by default it is not), then all identifiers
		4796	will have static linkage. This means that libev will not export any
		4797	identifiers, and you cannot link against libev anymore. This can be useful
		4798	when you embed libev, only want to use libev functions in a single file,
		4799	and do not want its identifiers to be visible.
		4800
		4801	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4802	wants to use libev.
		4803
		4804	This option only works when libev is compiled with a C compiler, as C++
		4805	doesn't support the required declaration syntax.
		4806
		4807	=item EV_AVOID_STDIO
		4808
		4809	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4810	functions (printf, scanf, perror etc.). This will increase the code size
		4811	somewhat, but if your program doesn't otherwise depend on stdio and your
		4812	libc allows it, this avoids linking in the stdio library which is quite
		4813	big.
		4814
		4815	Note that error messages might become less precise when this option is
		4816	enabled.
		4817
		4818	=item EV_NSIG
		4819
		4820	The highest supported signal number, +1 (or, the number of
		4821	signals): Normally, libev tries to deduce the maximum number of signals
		4822	automatically, but sometimes this fails, in which case it can be
		4823	specified. Also, using a lower number than detected (C<32> should be
		4824	good for about any system in existence) can save some memory, as libev
		4825	statically allocates some 12-24 bytes per signal number.
3502		4826
3503	=item EV_PID_HASHSIZE	4827	=item EV_PID_HASHSIZE
3504		4828
3505	C<ev_child> watchers use a small hash table to distribute workload by	4829	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4830	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3507	than enough. If you need to manage thousands of children you might want to	4831	usually more than enough. If you need to manage thousands of children you
3508	increase this value (I<must> be a power of two).	4832	might want to increase this value (I<must> be a power of two).
3509		4833
3510	=item EV_INOTIFY_HASHSIZE	4834	=item EV_INOTIFY_HASHSIZE
3511		4835
3512	C<ev_stat> watchers use a small hash table to distribute workload by	4836	C<ev_stat> watchers use a small hash table to distribute workload by
3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4837	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3514	usually more than enough. If you need to manage thousands of C<ev_stat>	4838	disabled), usually more than enough. If you need to manage thousands of
3515	watchers you might want to increase this value (I<must> be a power of	4839	C<ev_stat> watchers you might want to increase this value (I<must> be a
3516	two).	4840	power of two).
3517		4841
3518	=item EV_USE_4HEAP	4842	=item EV_USE_4HEAP
3519		4843
3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4844	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4845	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4846	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3523	faster performance with many (thousands) of watchers.	4847	faster performance with many (thousands) of watchers.
3524		4848
3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4849	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3526	(disabled).	4850	will be C<0>.
3527		4851
3528	=item EV_HEAP_CACHE_AT	4852	=item EV_HEAP_CACHE_AT
3529		4853
3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4854	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4855	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4856	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4857	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3534	but avoids random read accesses on heap changes. This improves performance	4858	but avoids random read accesses on heap changes. This improves performance
3535	noticeably with many (hundreds) of watchers.	4859	noticeably with many (hundreds) of watchers.
3536		4860
3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4861	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3538	(disabled).	4862	will be C<0>.
3539		4863
3540	=item EV_VERIFY	4864	=item EV_VERIFY
3541		4865
3542	Controls how much internal verification (see C<ev_loop_verify ()>) will	4866	Controls how much internal verification (see C<ev_verify ()>) will
3543	be done: If set to C<0>, no internal verification code will be compiled	4867	be done: If set to C<0>, no internal verification code will be compiled
3544	in. If set to C<1>, then verification code will be compiled in, but not	4868	in. If set to C<1>, then verification code will be compiled in, but not
3545	called. If set to C<2>, then the internal verification code will be	4869	called. If set to C<2>, then the internal verification code will be
3546	called once per loop, which can slow down libev. If set to C<3>, then the	4870	called once per loop, which can slow down libev. If set to C<3>, then the
3547	verification code will be called very frequently, which will slow down	4871	verification code will be called very frequently, which will slow down
3548	libev considerably.	4872	libev considerably.
3549		4873
3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4874	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3551	C<0>.	4875	will be C<0>.
3552		4876
3553	=item EV_COMMON	4877	=item EV_COMMON
3554		4878
3555	By default, all watchers have a C<void *data> member. By redefining	4879	By default, all watchers have a C<void *data> member. By redefining
3556	this macro to a something else you can include more and other types of	4880	this macro to something else you can include more and other types of
3557	members. You have to define it each time you include one of the files,	4881	members. You have to define it each time you include one of the files,
3558	though, and it must be identical each time.	4882	though, and it must be identical each time.
3559		4883
3560	For example, the perl EV module uses something like this:	4884	For example, the perl EV module uses something like this:
3561		4885
…		…
3614	file.	4938	file.
3615		4939
3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4940	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3617	that everybody includes and which overrides some configure choices:	4941	that everybody includes and which overrides some configure choices:
3618		4942
3619	#define EV_MINIMAL 1	4943	#define EV_FEATURES 8
3620	#define EV_USE_POLL 0	4944	#define EV_USE_SELECT 1
3621	#define EV_MULTIPLICITY 0
3622	#define EV_PERIODIC_ENABLE 0	4945	#define EV_PREPARE_ENABLE 1
		4946	#define EV_IDLE_ENABLE 1
3623	#define EV_STAT_ENABLE 0	4947	#define EV_SIGNAL_ENABLE 1
3624	#define EV_FORK_ENABLE 0	4948	#define EV_CHILD_ENABLE 1
		4949	#define EV_USE_STDEXCEPT 0
3625	#define EV_CONFIG_H <config.h>	4950	#define EV_CONFIG_H <config.h>
3626	#define EV_MINPRI 0
3627	#define EV_MAXPRI 0
3628		4951
3629	#include "ev++.h"	4952	#include "ev++.h"
3630		4953
3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4954	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3632		4955
3633	#include "ev_cpp.h"	4956	#include "ev_cpp.h"
3634	#include "ev.c"	4957	#include "ev.c"
3635		4958
3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4959	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3637		4960
3638	=head2 THREADS AND COROUTINES	4961	=head2 THREADS AND COROUTINES
3639		4962
3640	=head3 THREADS	4963	=head3 THREADS
3641		4964
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	5015	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	5016	watcher callback into the event loop interested in the signal.
3694		5017
3695	=back	5018	=back
3696		5019
		5020	See also L</THREAD LOCKING EXAMPLE>.
		5021
3697	=head3 COROUTINES	5022	=head3 COROUTINES
3698		5023
3699	Libev is very accommodating to coroutines ("cooperative threads"):	5024	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	5025	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5026	coroutines (e.g. you can call C<ev_run> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	5027	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	5028	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	5029	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		5030
3706	Care has been taken to ensure that libev does not keep local state inside	5031	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5032	C<ev_run>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	5033	they do not call any callbacks.
3709		5034
3710	=head2 COMPILER WARNINGS	5035	=head2 COMPILER WARNINGS
3711		5036
3712	Depending on your compiler and compiler settings, you might get no or a	5037	Depending on your compiler and compiler settings, you might get no or a
…		…
3723	maintainable.	5048	maintainable.
3724		5049
3725	And of course, some compiler warnings are just plain stupid, or simply	5050	And of course, some compiler warnings are just plain stupid, or simply
3726	wrong (because they don't actually warn about the condition their message	5051	wrong (because they don't actually warn about the condition their message
3727	seems to warn about). For example, certain older gcc versions had some	5052	seems to warn about). For example, certain older gcc versions had some
3728	warnings that resulted an extreme number of false positives. These have	5053	warnings that resulted in an extreme number of false positives. These have
3729	been fixed, but some people still insist on making code warn-free with	5054	been fixed, but some people still insist on making code warn-free with
3730	such buggy versions.	5055	such buggy versions.
3731		5056
3732	While libev is written to generate as few warnings as possible,	5057	While libev is written to generate as few warnings as possible,
3733	"warn-free" code is not a goal, and it is recommended not to build libev	5058	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3769	I suggest using suppression lists.	5094	I suggest using suppression lists.
3770		5095
3771		5096
3772	=head1 PORTABILITY NOTES	5097	=head1 PORTABILITY NOTES
3773		5098
		5099	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5100
		5101	GNU/Linux is the only common platform that supports 64 bit file/large file
		5102	interfaces but I<disables> them by default.
		5103
		5104	That means that libev compiled in the default environment doesn't support
		5105	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5106
		5107	Unfortunately, many programs try to work around this GNU/Linux issue
		5108	by enabling the large file API, which makes them incompatible with the
		5109	standard libev compiled for their system.
		5110
		5111	Likewise, libev cannot enable the large file API itself as this would
		5112	suddenly make it incompatible to the default compile time environment,
		5113	i.e. all programs not using special compile switches.
		5114
		5115	=head2 OS/X AND DARWIN BUGS
		5116
		5117	The whole thing is a bug if you ask me - basically any system interface
		5118	you touch is broken, whether it is locales, poll, kqueue or even the
		5119	OpenGL drivers.
		5120
		5121	=head3 C<kqueue> is buggy
		5122
		5123	The kqueue syscall is broken in all known versions - most versions support
		5124	only sockets, many support pipes.
		5125
		5126	Libev tries to work around this by not using C<kqueue> by default on this
		5127	rotten platform, but of course you can still ask for it when creating a
		5128	loop - embedding a socket-only kqueue loop into a select-based one is
		5129	probably going to work well.
		5130
		5131	=head3 C<poll> is buggy
		5132
		5133	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5134	implementation by something calling C<kqueue> internally around the 10.5.6
		5135	release, so now C<kqueue> I<and> C<poll> are broken.
		5136
		5137	Libev tries to work around this by not using C<poll> by default on
		5138	this rotten platform, but of course you can still ask for it when creating
		5139	a loop.
		5140
		5141	=head3 C<select> is buggy
		5142
		5143	All that's left is C<select>, and of course Apple found a way to fuck this
		5144	one up as well: On OS/X, C<select> actively limits the number of file
		5145	descriptors you can pass in to 1024 - your program suddenly crashes when
		5146	you use more.
		5147
		5148	There is an undocumented "workaround" for this - defining
		5149	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5150	work on OS/X.
		5151
		5152	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5153
		5154	=head3 C<errno> reentrancy
		5155
		5156	The default compile environment on Solaris is unfortunately so
		5157	thread-unsafe that you can't even use components/libraries compiled
		5158	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5159	defined by default. A valid, if stupid, implementation choice.
		5160
		5161	If you want to use libev in threaded environments you have to make sure
		5162	it's compiled with C<_REENTRANT> defined.
		5163
		5164	=head3 Event port backend
		5165
		5166	The scalable event interface for Solaris is called "event
		5167	ports". Unfortunately, this mechanism is very buggy in all major
		5168	releases. If you run into high CPU usage, your program freezes or you get
		5169	a large number of spurious wakeups, make sure you have all the relevant
		5170	and latest kernel patches applied. No, I don't know which ones, but there
		5171	are multiple ones to apply, and afterwards, event ports actually work
		5172	great.
		5173
		5174	If you can't get it to work, you can try running the program by setting
		5175	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5176	C<select> backends.
		5177
		5178	=head2 AIX POLL BUG
		5179
		5180	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5181	this by trying to avoid the poll backend altogether (i.e. it's not even
		5182	compiled in), which normally isn't a big problem as C<select> works fine
		5183	with large bitsets on AIX, and AIX is dead anyway.
		5184
3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5185	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5186
		5187	=head3 General issues
3775		5188
3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5189	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3777	requires, and its I/O model is fundamentally incompatible with the POSIX	5190	requires, and its I/O model is fundamentally incompatible with the POSIX
3778	model. Libev still offers limited functionality on this platform in	5191	model. Libev still offers limited functionality on this platform in
3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5192	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3780	descriptors. This only applies when using Win32 natively, not when using	5193	descriptors. This only applies when using Win32 natively, not when using
3781	e.g. cygwin.	5194	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5195	as every compiler comes with a slightly differently broken/incompatible
		5196	environment.
3782		5197
3783	Lifting these limitations would basically require the full	5198	Lifting these limitations would basically require the full
3784	re-implementation of the I/O system. If you are into these kinds of	5199	re-implementation of the I/O system. If you are into this kind of thing,
3785	things, then note that glib does exactly that for you in a very portable	5200	then note that glib does exactly that for you in a very portable way (note
3786	way (note also that glib is the slowest event library known to man).	5201	also that glib is the slowest event library known to man).
3787		5202
3788	There is no supported compilation method available on windows except	5203	There is no supported compilation method available on windows except
3789	embedding it into other applications.	5204	embedding it into other applications.
		5205
		5206	Sensible signal handling is officially unsupported by Microsoft - libev
		5207	tries its best, but under most conditions, signals will simply not work.
3790		5208
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	5209	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	5210	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	5211	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	5212	so make sure you only write small amounts into your sockets (less than a
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	5217	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	5218	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	5219	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	5220	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	5221	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	5222	(due to Microsoft monopoly games).
3805		5223
3806	A typical way to use libev under windows is to embed it (see the embedding	5224	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	5225	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	5226	of F<ev.h>:
3809		5227
…		…
3816	you do I<not> compile the F<ev.c> or any other embedded source files!):	5234	you do I<not> compile the F<ev.c> or any other embedded source files!):
3817		5235
3818	#include "evwrap.h"	5236	#include "evwrap.h"
3819	#include "ev.c"	5237	#include "ev.c"
3820		5238
3821	=over 4
3822
3823	=item The winsocket select function	5239	=head3 The winsocket C<select> function
3824		5240
3825	The winsocket C<select> function doesn't follow POSIX in that it	5241	The winsocket C<select> function doesn't follow POSIX in that it
3826	requires socket I<handles> and not socket I<file descriptors> (it is	5242	requires socket I<handles> and not socket I<file descriptors> (it is
3827	also extremely buggy). This makes select very inefficient, and also	5243	also extremely buggy). This makes select very inefficient, and also
3828	requires a mapping from file descriptors to socket handles (the Microsoft	5244	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5253	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3838		5254
3839	Note that winsockets handling of fd sets is O(n), so you can easily get a	5255	Note that winsockets handling of fd sets is O(n), so you can easily get a
3840	complexity in the O(n²) range when using win32.	5256	complexity in the O(n²) range when using win32.
3841		5257
3842	=item Limited number of file descriptors	5258	=head3 Limited number of file descriptors
3843		5259
3844	Windows has numerous arbitrary (and low) limits on things.	5260	Windows has numerous arbitrary (and low) limits on things.
3845		5261
3846	Early versions of winsocket's select only supported waiting for a maximum	5262	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	5263	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	5264	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	5265	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	5266	previous thread in each. Sounds great!).
3851		5267
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5268	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	5269	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	5270	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	5271	other interpreters do their own select emulation on windows).
3856		5272
3857	Another limit is the number of file descriptors in the Microsoft runtime	5273	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5274	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	5275	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5276	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	5277	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	5278	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	5279	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	5280	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	5281	the cost of calling select (O(n²)) will likely make this unworkable.
3868
3869	=back
3870		5282
3871	=head2 PORTABILITY REQUIREMENTS	5283	=head2 PORTABILITY REQUIREMENTS
3872		5284
3873	In addition to a working ISO-C implementation and of course the	5285	In addition to a working ISO-C implementation and of course the
3874	backend-specific APIs, libev relies on a few additional extensions:	5286	backend-specific APIs, libev relies on a few additional extensions:
…		…
3881	Libev assumes not only that all watcher pointers have the same internal	5293	Libev assumes not only that all watcher pointers have the same internal
3882	structure (guaranteed by POSIX but not by ISO C for example), but it also	5294	structure (guaranteed by POSIX but not by ISO C for example), but it also
3883	assumes that the same (machine) code can be used to call any watcher	5295	assumes that the same (machine) code can be used to call any watcher
3884	callback: The watcher callbacks have different type signatures, but libev	5296	callback: The watcher callbacks have different type signatures, but libev
3885	calls them using an C<ev_watcher *> internally.	5297	calls them using an C<ev_watcher *> internally.
		5298
		5299	=item pointer accesses must be thread-atomic
		5300
		5301	Accessing a pointer value must be atomic, it must both be readable and
		5302	writable in one piece - this is the case on all current architectures.
3886		5303
3887	=item C<sig_atomic_t volatile> must be thread-atomic as well	5304	=item C<sig_atomic_t volatile> must be thread-atomic as well
3888		5305
3889	The type C<sig_atomic_t volatile> (or whatever is defined as	5306	The type C<sig_atomic_t volatile> (or whatever is defined as
3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5307	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3899	thread" or will block signals process-wide, both behaviours would	5316	thread" or will block signals process-wide, both behaviours would
3900	be compatible with libev. Interaction between C<sigprocmask> and	5317	be compatible with libev. Interaction between C<sigprocmask> and
3901	C<pthread_sigmask> could complicate things, however.	5318	C<pthread_sigmask> could complicate things, however.
3902		5319
3903	The most portable way to handle signals is to block signals in all threads	5320	The most portable way to handle signals is to block signals in all threads
3904	except the initial one, and run the default loop in the initial thread as	5321	except the initial one, and run the signal handling loop in the initial
3905	well.	5322	thread as well.
3906		5323
3907	=item C<long> must be large enough for common memory allocation sizes	5324	=item C<long> must be large enough for common memory allocation sizes
3908		5325
3909	To improve portability and simplify its API, libev uses C<long> internally	5326	To improve portability and simplify its API, libev uses C<long> internally
3910	instead of C<size_t> when allocating its data structures. On non-POSIX	5327	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3913	watchers.	5330	watchers.
3914		5331
3915	=item C<double> must hold a time value in seconds with enough accuracy	5332	=item C<double> must hold a time value in seconds with enough accuracy
3916		5333
3917	The type C<double> is used to represent timestamps. It is required to	5334	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5335	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3919	enough for at least into the year 4000. This requirement is fulfilled by	5336	good enough for at least into the year 4000 with millisecond accuracy
		5337	(the design goal for libev). This requirement is overfulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	5338	implementations using IEEE 754, which is basically all existing ones.
		5339
		5340	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5341	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5342	is either obsolete or somebody patched it to use C<long double> or
		5343	something like that, just kidding).
3921		5344
3922	=back	5345	=back
3923		5346
3924	If you know of other additional requirements drop me a note.	5347	If you know of other additional requirements drop me a note.
3925		5348
…		…
3987	=item Processing ev_async_send: O(number_of_async_watchers)	5410	=item Processing ev_async_send: O(number_of_async_watchers)
3988		5411
3989	=item Processing signals: O(max_signal_number)	5412	=item Processing signals: O(max_signal_number)
3990		5413
3991	Sending involves a system call I<iff> there were no other C<ev_async_send>	5414	Sending involves a system call I<iff> there were no other C<ev_async_send>
3992	calls in the current loop iteration. Checking for async and signal events	5415	calls in the current loop iteration and the loop is currently
		5416	blocked. Checking for async and signal events involves iterating over all
3993	involves iterating over all running async watchers or all signal numbers.	5417	running async watchers or all signal numbers.
3994		5418
3995	=back	5419	=back
3996		5420
3997		5421
		5422	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5423
		5424	The major version 4 introduced some incompatible changes to the API.
		5425
		5426	At the moment, the C<ev.h> header file provides compatibility definitions
		5427	for all changes, so most programs should still compile. The compatibility
		5428	layer might be removed in later versions of libev, so better update to the
		5429	new API early than late.
		5430
		5431	=over 4
		5432
		5433	=item C<EV_COMPAT3> backwards compatibility mechanism
		5434
		5435	The backward compatibility mechanism can be controlled by
		5436	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5437	section.
		5438
		5439	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5440
		5441	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5442
		5443	ev_loop_destroy (EV_DEFAULT_UC);
		5444	ev_loop_fork (EV_DEFAULT);
		5445
		5446	=item function/symbol renames
		5447
		5448	A number of functions and symbols have been renamed:
		5449
		5450	ev_loop => ev_run
		5451	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5452	EVLOOP_ONESHOT => EVRUN_ONCE
		5453
		5454	ev_unloop => ev_break
		5455	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5456	EVUNLOOP_ONE => EVBREAK_ONE
		5457	EVUNLOOP_ALL => EVBREAK_ALL
		5458
		5459	EV_TIMEOUT => EV_TIMER
		5460
		5461	ev_loop_count => ev_iteration
		5462	ev_loop_depth => ev_depth
		5463	ev_loop_verify => ev_verify
		5464
		5465	Most functions working on C<struct ev_loop> objects don't have an
		5466	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5467	associated constants have been renamed to not collide with the C<struct
		5468	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5469	as all other watcher types. Note that C<ev_loop_fork> is still called
		5470	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5471	typedef.
		5472
		5473	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5474
		5475	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5476	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5477	and work, but the library code will of course be larger.
		5478
		5479	=back
		5480
		5481
		5482	=head1 GLOSSARY
		5483
		5484	=over 4
		5485
		5486	=item active
		5487
		5488	A watcher is active as long as it has been started and not yet stopped.
		5489	See L</WATCHER STATES> for details.
		5490
		5491	=item application
		5492
		5493	In this document, an application is whatever is using libev.
		5494
		5495	=item backend
		5496
		5497	The part of the code dealing with the operating system interfaces.
		5498
		5499	=item callback
		5500
		5501	The address of a function that is called when some event has been
		5502	detected. Callbacks are being passed the event loop, the watcher that
		5503	received the event, and the actual event bitset.
		5504
		5505	=item callback/watcher invocation
		5506
		5507	The act of calling the callback associated with a watcher.
		5508
		5509	=item event
		5510
		5511	A change of state of some external event, such as data now being available
		5512	for reading on a file descriptor, time having passed or simply not having
		5513	any other events happening anymore.
		5514
		5515	In libev, events are represented as single bits (such as C<EV_READ> or
		5516	C<EV_TIMER>).
		5517
		5518	=item event library
		5519
		5520	A software package implementing an event model and loop.
		5521
		5522	=item event loop
		5523
		5524	An entity that handles and processes external events and converts them
		5525	into callback invocations.
		5526
		5527	=item event model
		5528
		5529	The model used to describe how an event loop handles and processes
		5530	watchers and events.
		5531
		5532	=item pending
		5533
		5534	A watcher is pending as soon as the corresponding event has been
		5535	detected. See L</WATCHER STATES> for details.
		5536
		5537	=item real time
		5538
		5539	The physical time that is observed. It is apparently strictly monotonic :)
		5540
		5541	=item wall-clock time
		5542
		5543	The time and date as shown on clocks. Unlike real time, it can actually
		5544	be wrong and jump forwards and backwards, e.g. when you adjust your
		5545	clock.
		5546
		5547	=item watcher
		5548
		5549	A data structure that describes interest in certain events. Watchers need
		5550	to be started (attached to an event loop) before they can receive events.
		5551
		5552	=back
		5553
3998	=head1 AUTHOR	5554	=head1 AUTHOR
3999		5555
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5556	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5557	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4001		5558

Diff Legend

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