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		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
…		…
9	=head2 EXAMPLE PROGRAM	11	=head2 EXAMPLE PROGRAM
10		12
11	// a single header file is required	13	// a single header file is required
12	#include <ev.h>	14	#include <ev.h>
13		15
		16	#include <stdio.h> // for puts
		17
14	// every watcher type has its own typedef'd struct	18	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	19	// with the name ev_TYPE
16	ev_io stdin_watcher;	20	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	21	ev_timer timeout_watcher;
18		22
19	// all watcher callbacks have a similar signature	23	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	24	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	28	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	30	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
28		32
29	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
31	}	35	}
32		36
33	// another callback, this time for a time-out	37	// another callback, this time for a time-out
34	static void	38	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	40	{
37	puts ("timeout");	41	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
40	}	44	}
41		45
42	int	46	int
43	main (void)	47	main (void)
44	{	48	{
45	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
47		51
48	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
57		61
58	// now wait for events to arrive	62	// now wait for events to arrive
59	ev_loop (loop, 0);	63	ev_run (loop, 0);
60		64
61	// unloop was called, so exit	65	// break was called, so exit
62	return 0;	66	return 0;
63	}	67	}
64		68
65	=head1 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
66		72
67	The newest version of this document is also available as an html-formatted	73	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	74	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	75	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		76
		77	While this document tries to be as complete as possible in documenting
		78	libev, its usage and the rationale behind its design, it is not a tutorial
		79	on event-based programming, nor will it introduce event-based programming
		80	with libev.
		81
		82	Familiarity with event based programming techniques in general is assumed
		83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
		93	=head1 ABOUT LIBEV
70		94
71	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	97	these event sources and provide your program with events.
74		98
…		…
84	=head2 FEATURES	108	=head2 FEATURES
85		109
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	117	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	119	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		120	limited support for fork events (C<ev_fork>).
96		121
97	It also is quite fast (see this	122	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	123	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	124	for example).
100		125
…		…
103	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	134	this argument.
110		135
111	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
112		137
113	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
119	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	146	time differences (e.g. delays) throughout libev.
121		147
122	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
123		149
124	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	151	and internal errors (bugs).
…		…
149		175
150	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
151		177
152	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
155		182
156	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
157		184
158	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
160	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
161		194
162	=item int ev_version_major ()	195	=item int ev_version_major ()
163		196
164	=item int ev_version_minor ()	197	=item int ev_version_minor ()
165		198
…		…
176	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	211	not a problem.
179		212
180	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
182		216
183	assert (("libev version mismatch",	217	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
186		220
…		…
197	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
199		233
200	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
201		235
202	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
208		243
209	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
210		245
211	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
216		251
217	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
218		253
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		255
221	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	285	}
251		286
252	...	287	...
253	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
254		289
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		291
257	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	307	}
273		308
274	...	309	...
275	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
276		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
277	=back	325	=back
278		326
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		328
281	An event loop is described by a C<ev_loop *>. The library knows two	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	331	libev 3 had an C<ev_loop> function colliding with the struct name).
		332
		333	The library knows two types of such loops, the I<default> loop, which
		334	supports child process events, and dynamically created event loops which
		335	do not.
284		336
285	=over 4	337	=over 4
286		338
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		340
289	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
290	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
291	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
292	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".
293		351
294	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
295	function.	353	function (or via the C<EV_DEFAULT> macro).
296		354
297	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
298	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
299	as loops cannot bes hared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
300		359
301	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,
302	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
303	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
304	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
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	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.
307		384
308	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
309	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>).
310		387
311	The following flags are supported:	388	The following flags are supported:
…		…
321		398
322	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
323	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
324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
325	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
326	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
327	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).
328		407
329	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
330		409
331	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
332	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.
333	enabling this flag.
334		412
335	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,
336	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
337	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
338	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
339	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	without a system call and thus I<very> fast, but my GNU/Linux system also has
340	C<pthread_atfork> which is even faster).	418	C<pthread_atfork> which is even faster).
341		419
342	The big advantage of this flag is that you can forget about fork (and	420	The big advantage of this flag is that you can forget about fork (and
343	forget about forgetting to tell libev about forking) when you use this	421	forget about forgetting to tell libev about forking, although you still
344	flag.	422	have to ignore C<SIGPIPE>) when you use this flag.
345		423
346	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>
347	environment variable.	425	environment variable.
		426
		427	=item C<EVFLAG_NOINOTIFY>
		428
		429	When this flag is specified, then libev will not attempt to use the
		430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		431	testing, this flag can be useful to conserve inotify file descriptors, as
		432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		433
		434	=item C<EVFLAG_SIGNALFD>
		435
		436	When this flag is specified, then libev will attempt to use the
		437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		438	delivers signals synchronously, which makes it both faster and might make
		439	it possible to get the queued signal data. It can also simplify signal
		440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
		442
		443	Signalfd will not be used by default as this changes your signal mask, and
		444	there are a lot of shoddy libraries and programs (glib's threadpool for
		445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
348		461
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		463
351	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
352	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,
…		…
377	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
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	491	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		492
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		494
		495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		496	kernels).
		497
382	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
383	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
384	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
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	501	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	502
387	cases and requiring a system call per fd change, no fork support and bad	503	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	504	of the more advanced event mechanisms: mere annoyances include silently
		505	dropping file descriptors, requiring a system call per change per file
		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
		509	0.1ms) and so on. The biggest issue is fork races, however - if a program
		510	forks then I<both> parent and child process have to recreate the epoll
		511	set, which can take considerable time (one syscall per file descriptor)
		512	and is of course hard to detect.
		513
		514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		515	but of course I<doesn't>, and epoll just loves to report events for
		516	totally I<different> file descriptors (even already closed ones, so
		517	one cannot even remove them from the set) than registered in the set
		518	(especially on SMP systems). Libev tries to counter these spurious
		519	notifications by employing an additional generation counter and comparing
		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...
389		530
390	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
391	will result in some caching, there is still a system call per such incident	532	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	533	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	535	file descriptors might not work very well if you register events for both
395		536	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		537
400	Best performance from this backend is achieved by not unregistering all	538	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	539	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	540	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	541	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	542	extra overhead. A fork can both result in spurious notifications as well
		543	as in libev having to destroy and recreate the epoll object, which can
		544	take considerable time and thus should be avoided.
		545
		546	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		547	faster than epoll for maybe up to a hundred file descriptors, depending on
		548	the usage. So sad.
405		549
406	While nominally embeddable in other event loops, this feature is broken in	550	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	551	all kernel versions tested so far.
408		552
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	553	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	554	C<EVBACKEND_POLL>.
411		555
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	556	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		557
414	Kqueue deserves special mention, as at the time of this writing, it was	558	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	559	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	560	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	561	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	562	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	563	without API changes to existing programs. For this reason it's not being
		564	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		565	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		566	system like NetBSD.
420		567
421	You still can embed kqueue into a normal poll or select backend and use it	568	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	569	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	570	the target platform). See C<ev_embed> watchers for more info.
424		571
425	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
426	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
427	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
428	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
429	two event changes per incident. Support for C<fork ()> is very bad and it	576	two event changes per incident. Support for C<fork ()> is very bad (you
		577	might have to leak fd's on fork, but it's more sane than epoll) and it
430	drops fds silently in similarly hard-to-detect cases.	578	drops fds silently in similarly hard-to-detect cases.
431		579
432	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
433		581
434	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
435	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
436	almost everywhere, you should only use it when you have a lot of sockets	584	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	585	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	586	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	587	also broken on OS X)) and, did I mention it, using it only for sockets.
440		588
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	589	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	590	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	591	C<NOTE_EOF>.
444		592
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		601
454	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,
455	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)).
456		604
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	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
462	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
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	608	might perform better.
465		609
466	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	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
469	OS-specific backends.	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.
470		624
471	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
472	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
473		627
474	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
475		629
476	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
477	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
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		633
480	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).
481		643
482	=back	644	=back
483		645
484	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,
485	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
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	648	here). If none are specified, all backends in C<ev_recommended_backends
487		649	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		650
516	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.
517		652
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	654	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
521		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
522	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
523		663
524	Destroys the default loop again (frees all memory and kernel state	664	Destroys an event loop object (frees all memory and kernel state
525	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
526	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
527	responsibility to either stop all watchers cleanly yourself I<before>	667	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	670	for example).
531		671
532	Note that certain global state, such as signal state, will not be freed by	672	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	673	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
535		675
536	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
537	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.
538	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>
539	C<ev_loop_new> and C<ev_loop_destroy>).	683	and C<ev_loop_destroy>.
540		684
541	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
542		686
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	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
549	to reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
550	name, you can call it anytime, but it makes most sense after forking, in	689	the name, you can call it anytime you are allowed to start or stop
551	the child process (or both child and parent, but that again makes little	690	watchers (except inside an C<ev_prepare> callback), but it makes most
552	sense). You I<must> call it in the child before using any of the libev	691	sense after forking, in the child process. You I<must> call it (or use
553	functions, and it will only take effect at the next C<ev_loop> iteration.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		693
		694	In addition, if you want to reuse a loop (via this function of
		695	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		696
		697	Again, you I<have> to call it on I<any> loop that you want to re-use after
		698	a fork, I<even if you do not plan to use the loop in the parent>. This is
		699	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		700	during fork.
554		701
555	On the other hand, you only need to call this function in the child	702	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	703	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	704	you just fork+exec or create a new loop in the child, you don't have to
		705	call it at all (in fact, C<epoll> is so badly broken that it makes a
		706	difference, but libev will usually detect this case on its own and do a
		707	costly reset of the backend).
558		708
559	The function itself is quite fast and it's usually not a problem to call	709	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	710	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		711
		712	Example: Automate calling C<ev_loop_fork> on the default loop when
		713	using pthreads.
		714
		715	static void
		716	post_fork_child (void)
		717	{
		718	ev_loop_fork (EV_DEFAULT);
		719	}
		720
		721	...
563	pthread_atfork (0, 0, ev_default_fork);	722	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		723
572	=item int ev_is_default_loop (loop)	724	=item int ev_is_default_loop (loop)
573		725
574	Returns true when the given loop is, in fact, the default loop, and false	726	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	727	otherwise.
576		728
577	=item unsigned int ev_loop_count (loop)	729	=item unsigned int ev_iteration (loop)
578		730
579	Returns the count of loop iterations for the loop, which is identical to	731	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	732	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	733	and happily wraps around with enough iterations.
582		734
583	This value can sometimes be useful as a generation counter of sorts (it	735	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	736	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	737	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		738	prepare and check phases.
		739
		740	=item unsigned int ev_depth (loop)
		741
		742	Returns the number of times C<ev_run> was entered minus the number of
		743	times C<ev_run> was exited normally, in other words, the recursion depth.
		744
		745	Outside C<ev_run>, this number is zero. In a callback, this number is
		746	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		747	in which case it is higher.
		748
		749	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		750	throwing an exception etc.), doesn't count as "exit" - consider this
		751	as a hint to avoid such ungentleman-like behaviour unless it's really
		752	convenient, in which case it is fully supported.
586		753
587	=item unsigned int ev_backend (loop)	754	=item unsigned int ev_backend (loop)
588		755
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	756	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	757	use.
…		…
599		766
600	=item ev_now_update (loop)	767	=item ev_now_update (loop)
601		768
602	Establishes the current time by querying the kernel, updating the time	769	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	770	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	771	is usually done automatically within C<ev_run ()>.
605		772
606	This function is rarely useful, but when some event callback runs for a	773	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	774	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	775	the current time is a good idea.
609		776
610	See also "The special problem of time updates" in the C<ev_timer> section.	777	See also L</The special problem of time updates> in the C<ev_timer> section.
611		778
		779	=item ev_suspend (loop)
		780
		781	=item ev_resume (loop)
		782
		783	These two functions suspend and resume an event loop, for use when the
		784	loop is not used for a while and timeouts should not be processed.
		785
		786	A typical use case would be an interactive program such as a game: When
		787	the user presses C<^Z> to suspend the game and resumes it an hour later it
		788	would be best to handle timeouts as if no time had actually passed while
		789	the program was suspended. This can be achieved by calling C<ev_suspend>
		790	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		791	C<ev_resume> directly afterwards to resume timer processing.
		792
		793	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		794	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		795	will be rescheduled (that is, they will lose any events that would have
		796	occurred while suspended).
		797
		798	After calling C<ev_suspend> you B<must not> call I<any> function on the
		799	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		800	without a previous call to C<ev_suspend>.
		801
		802	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		803	event loop time (see C<ev_now_update>).
		804
612	=item ev_loop (loop, int flags)	805	=item bool ev_run (loop, int flags)
613		806
614	Finally, this is it, the event handler. This function usually is called	807	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	808	after you have initialised all your watchers and you want to start
616	events.	809	handling events. It will ask the operating system for any new events, call
		810	the watcher callbacks, and then repeat the whole process indefinitely: This
		811	is why event loops are called I<loops>.
617		812
618	If the flags argument is specified as C<0>, it will not return until	813	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	814	until either no event watchers are active anymore or C<ev_break> was
		815	called.
620		816
		817	The return value is false if there are no more active watchers (which
		818	usually means "all jobs done" or "deadlock"), and true in all other cases
		819	(which usually means " you should call C<ev_run> again").
		820
621	Please note that an explicit C<ev_unloop> is usually better than	821	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	822	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	823	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	824	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	825	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	826	beauty.
627		827
		828	This function is I<mostly> exception-safe - you can break out of a
		829	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		830	exception and so on. This does not decrement the C<ev_depth> value, nor
		831	will it clear any outstanding C<EVBREAK_ONE> breaks.
		832
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	833	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	834	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	835	block your process in case there are no events and will return after one
631	the loop.	836	iteration of the loop. This is sometimes useful to poll and handle new
		837	events while doing lengthy calculations, to keep the program responsive.
632		838
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	839	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	840	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	841	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	842	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	843	user-registered callback will be called), and will return after one
638	iteration of the loop.	844	iteration of the loop.
639		845
640	This is useful if you are waiting for some external event in conjunction	846	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	847	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	848	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	849	usually a better approach for this kind of thing.
644		850
645	Here are the gory details of what C<ev_loop> does:	851	Here are the gory details of what C<ev_run> does (this is for your
		852	understanding, not a guarantee that things will work exactly like this in
		853	future versions):
646		854
		855	- Increment loop depth.
		856	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	857	- Before the first iteration, call any pending watchers.
		858	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	859	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	860	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	861	- Queue and call all prepare watchers.
		862	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	863	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	864	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	865	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	866	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	867	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	868	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	869	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	870	- Sleep if the I/O and timer collect interval say so.
		871	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	872	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	873	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	874	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	875	- Queue all expired timers.
663	- Queue all expired periodics.	876	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	877	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	878	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	879	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	880	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	881	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	882	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	883	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	884	continue with step LOOP.
		885	FINISH:
		886	- Reset the ev_break status iff it was EVBREAK_ONE.
		887	- Decrement the loop depth.
		888	- Return.
672		889
673	Example: Queue some jobs and then loop until no events are outstanding	890	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	891	anymore.
675		892
676	... queue jobs here, make sure they register event watchers as long	893	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	894	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	895	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	896	... jobs done or somebody called break. yeah!
680		897
681	=item ev_unloop (loop, how)	898	=item ev_break (loop, how)
682		899
683	Can be used to make a call to C<ev_loop> return early (but only after it	900	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	901	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	902	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	903	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		904
688	This "unloop state" will be cleared when entering C<ev_loop> again.	905	This "break state" will be cleared on the next call to C<ev_run>.
689		906
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	907	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		908	which case it will have no effect.
691		909
692	=item ev_ref (loop)	910	=item ev_ref (loop)
693		911
694	=item ev_unref (loop)	912	=item ev_unref (loop)
695		913
696	Ref/unref can be used to add or remove a reference count on the event	914	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	915	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	916	count is nonzero, C<ev_run> will not return on its own.
699		917
700	If you have a watcher you never unregister that should not keep C<ev_loop>	918	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	919	unregister, but that nevertheless should not keep C<ev_run> from
		920	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	921	before stopping it.
703		922
704	As an example, libev itself uses this for its internal signal pipe: It is	923	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	924	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	925	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	926	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	927	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	928	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	929	before, respectively. Note also that libev might stop watchers itself
		930	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		931	in the callback).
711		932
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	933	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	934	running when nothing else is active.
714		935
715	ev_signal exitsig;	936	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	937	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	938	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	939	ev_unref (loop);
719		940
720	Example: For some weird reason, unregister the above signal handler again.	941	Example: For some weird reason, unregister the above signal handler again.
721		942
722	ev_ref (loop);	943	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	944	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	964	overhead for the actual polling but can deliver many events at once.
744		965
745	By setting a higher I<io collect interval> you allow libev to spend more	966	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	967	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	968	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	969	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	970	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		971	sleep time ensures that libev will not poll for I/O events more often then
		972	once per this interval, on average (as long as the host time resolution is
		973	good enough).
750		974
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	975	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	976	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	977	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	978	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		980
757	Many (busy) programs can usually benefit by setting the I/O collect	981	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	982	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	983	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	984	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	985	as this approaches the timing granularity of most systems. Note that if
		986	you do transactions with the outside world and you can't increase the
		987	parallelity, then this setting will limit your transaction rate (if you
		988	need to poll once per transaction and the I/O collect interval is 0.01,
		989	then you can't do more than 100 transactions per second).
762		990
763	Setting the I<timeout collect interval> can improve the opportunity for	991	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	992	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	993	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	994	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	995	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	996	they fire on, say, one-second boundaries only.
769		997
		998	Example: we only need 0.1s timeout granularity, and we wish not to poll
		999	more often than 100 times per second:
		1000
		1001	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1002	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1003
		1004	=item ev_invoke_pending (loop)
		1005
		1006	This call will simply invoke all pending watchers while resetting their
		1007	pending state. Normally, C<ev_run> does this automatically when required,
		1008	but when overriding the invoke callback this call comes handy. This
		1009	function can be invoked from a watcher - this can be useful for example
		1010	when you want to do some lengthy calculation and want to pass further
		1011	event handling to another thread (you still have to make sure only one
		1012	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1013
		1014	=item int ev_pending_count (loop)
		1015
		1016	Returns the number of pending watchers - zero indicates that no watchers
		1017	are pending.
		1018
		1019	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1020
		1021	This overrides the invoke pending functionality of the loop: Instead of
		1022	invoking all pending watchers when there are any, C<ev_run> will call
		1023	this callback instead. This is useful, for example, when you want to
		1024	invoke the actual watchers inside another context (another thread etc.).
		1025
		1026	If you want to reset the callback, use C<ev_invoke_pending> as new
		1027	callback.
		1028
		1029	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1030
		1031	Sometimes you want to share the same loop between multiple threads. This
		1032	can be done relatively simply by putting mutex_lock/unlock calls around
		1033	each call to a libev function.
		1034
		1035	However, C<ev_run> can run an indefinite time, so it is not feasible
		1036	to wait for it to return. One way around this is to wake up the event
		1037	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1038	I<release> and I<acquire> callbacks on the loop.
		1039
		1040	When set, then C<release> will be called just before the thread is
		1041	suspended waiting for new events, and C<acquire> is called just
		1042	afterwards.
		1043
		1044	Ideally, C<release> will just call your mutex_unlock function, and
		1045	C<acquire> will just call the mutex_lock function again.
		1046
		1047	While event loop modifications are allowed between invocations of
		1048	C<release> and C<acquire> (that's their only purpose after all), no
		1049	modifications done will affect the event loop, i.e. adding watchers will
		1050	have no effect on the set of file descriptors being watched, or the time
		1051	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1052	to take note of any changes you made.
		1053
		1054	In theory, threads executing C<ev_run> will be async-cancel safe between
		1055	invocations of C<release> and C<acquire>.
		1056
		1057	See also the locking example in the C<THREADS> section later in this
		1058	document.
		1059
		1060	=item ev_set_userdata (loop, void *data)
		1061
		1062	=item void *ev_userdata (loop)
		1063
		1064	Set and retrieve a single C<void *> associated with a loop. When
		1065	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1066	C<0>.
		1067
		1068	These two functions can be used to associate arbitrary data with a loop,
		1069	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1070	C<acquire> callbacks described above, but of course can be (ab-)used for
		1071	any other purpose as well.
		1072
770	=item ev_loop_verify (loop)	1073	=item ev_verify (loop)
771		1074
772	This function only does something when C<EV_VERIFY> support has been	1075	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1076	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1077	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	1078	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1079	error and call C<abort ()>.
777		1080
778	This can be used to catch bugs inside libev itself: under normal	1081	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1085	=back
783		1086
784		1087
785	=head1 ANATOMY OF A WATCHER	1088	=head1 ANATOMY OF A WATCHER
786		1089
		1090	In the following description, uppercase C<TYPE> in names stands for the
		1091	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1092	watchers and C<ev_io_start> for I/O watchers.
		1093
787	A watcher is a structure that you create and register to record your	1094	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1095	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1096	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1097	for that:
790		1098
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1100	{
793	ev_io_stop (w);	1101	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1102	ev_break (loop, EVBREAK_ALL);
795	}	1103	}
796		1104
797	struct ev_loop *loop = ev_default_loop (0);	1105	struct ev_loop *loop = ev_default_loop (0);
		1106
798	ev_io stdin_watcher;	1107	ev_io stdin_watcher;
		1108
799	ev_init (&stdin_watcher, my_cb);	1109	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1110	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1111	ev_io_start (loop, &stdin_watcher);
		1112
802	ev_loop (loop, 0);	1113	ev_run (loop, 0);
803		1114
804	As you can see, you are responsible for allocating the memory for your	1115	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1116	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1117	stack).
807		1118
		1119	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1120	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1121
808	Each watcher structure must be initialised by a call to C<ev_init	1122	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1123	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1124	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1125	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1126	and/or writable).
813		1127
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1128	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1129	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1130	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1131	ev_TYPE_init (watcher *, callback, ...) >>.
818		1132
819	To make the watcher actually watch out for events, you have to start it	1133	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1134	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1135	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1136	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1137
824	As long as your watcher is active (has been started but not stopped) you	1138	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1139	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1140	reinitialise it or call its C<ev_TYPE_set> macro.
827		1141
828	Each and every callback receives the event loop pointer as first, the	1142	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1143	registered watcher structure as second, and a bitset of received events as
830	third argument.	1144	third argument.
831		1145
…		…
840	=item C<EV_WRITE>	1154	=item C<EV_WRITE>
841		1155
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1156	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1157	writable.
844		1158
845	=item C<EV_TIMEOUT>	1159	=item C<EV_TIMER>
846		1160
847	The C<ev_timer> watcher has timed out.	1161	The C<ev_timer> watcher has timed out.
848		1162
849	=item C<EV_PERIODIC>	1163	=item C<EV_PERIODIC>
850		1164
…		…
868		1182
869	=item C<EV_PREPARE>	1183	=item C<EV_PREPARE>
870		1184
871	=item C<EV_CHECK>	1185	=item C<EV_CHECK>
872		1186
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1187	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
874	to gather new events, and all C<ev_check> watchers are invoked just after	1188	gather new events, and all C<ev_check> watchers are queued (not invoked)
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1189	just after C<ev_run> has gathered them, but before it queues any callbacks
		1190	for any received events. That means C<ev_prepare> watchers are the last
		1191	watchers invoked before the event loop sleeps or polls for new events, and
		1192	C<ev_check> watchers will be invoked before any other watchers of the same
		1193	or lower priority within an event loop iteration.
		1194
876	received events. Callbacks of both watcher types can start and stop as	1195	Callbacks of both watcher types can start and stop as many watchers as
877	many watchers as they want, and all of them will be taken into account	1196	they want, and all of them will be taken into account (for example, a
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1197	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
879	C<ev_loop> from blocking).	1198	blocking).
880		1199
881	=item C<EV_EMBED>	1200	=item C<EV_EMBED>
882		1201
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1202	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1203
885	=item C<EV_FORK>	1204	=item C<EV_FORK>
886		1205
887	The event loop has been resumed in the child process after fork (see	1206	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1207	C<ev_fork>).
889		1208
		1209	=item C<EV_CLEANUP>
		1210
		1211	The event loop is about to be destroyed (see C<ev_cleanup>).
		1212
890	=item C<EV_ASYNC>	1213	=item C<EV_ASYNC>
891		1214
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1215	The given async watcher has been asynchronously notified (see C<ev_async>).
		1216
		1217	=item C<EV_CUSTOM>
		1218
		1219	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1220	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1221
894	=item C<EV_ERROR>	1222	=item C<EV_ERROR>
895		1223
896	An unspecified error has occurred, the watcher has been stopped. This might	1224	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1225	happen because the watcher could not be properly started because libev
…		…
912		1240
913	=back	1241	=back
914		1242
915	=head2 GENERIC WATCHER FUNCTIONS	1243	=head2 GENERIC WATCHER FUNCTIONS
916		1244
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1245	=over 4
921		1246
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1247	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1248
924	This macro initialises the generic portion of a watcher. The contents	1249	This macro initialises the generic portion of a watcher. The contents
…		…
938		1263
939	ev_io w;	1264	ev_io w;
940	ev_init (&w, my_cb);	1265	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1266	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1267
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1268	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1269
945	This macro initialises the type-specific parts of a watcher. You need to	1270	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1271	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1272	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1273	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1286
962	Example: Initialise and set an C<ev_io> watcher in one step.	1287	Example: Initialise and set an C<ev_io> watcher in one step.
963		1288
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1289	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1290
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1291	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1292
968	Starts (activates) the given watcher. Only active watchers will receive	1293	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1294	events. If the watcher is already active nothing will happen.
970		1295
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1296	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1297	whole section.
973		1298
974	ev_io_start (EV_DEFAULT_UC, &w);	1299	ev_io_start (EV_DEFAULT_UC, &w);
975		1300
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1301	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1302
978	Stops the given watcher if active, and clears the pending status (whether	1303	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1304	the watcher was active or not).
980		1305
981	It is possible that stopped watchers are pending - for example,	1306	It is possible that stopped watchers are pending - for example,
…		…
1001		1326
1002	=item callback ev_cb (ev_TYPE *watcher)	1327	=item callback ev_cb (ev_TYPE *watcher)
1003		1328
1004	Returns the callback currently set on the watcher.	1329	Returns the callback currently set on the watcher.
1005		1330
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1331	=item ev_set_cb (ev_TYPE *watcher, callback)
1007		1332
1008	Change the callback. You can change the callback at virtually any time	1333	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1334	(modulo threads).
1010		1335
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1336	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1337
1013	=item int ev_priority (ev_TYPE *watcher)	1338	=item int ev_priority (ev_TYPE *watcher)
1014		1339
1015	Set and query the priority of the watcher. The priority is a small	1340	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1341	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1342	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1343	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1344	from being executed (except for C<ev_idle> watchers).
1020		1345
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1346	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1347	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1348
1029	You I<must not> change the priority of a watcher as long as it is active or	1349	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1350	pending.
1031		1351
		1352	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1353	fine, as long as you do not mind that the priority value you query might
		1354	or might not have been clamped to the valid range.
		1355
1032	The default priority used by watchers when no priority has been set is	1356	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1357	always C<0>, which is supposed to not be too high and not be too low :).
1034		1358
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1359	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1360	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1361
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1362	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1363
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1364	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1365	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1373	watcher isn't pending it does nothing and returns C<0>.
1051		1374
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1375	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1376	callback to be invoked, which can be accomplished with this function.
1054		1377
		1378	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1379
		1380	Feeds the given event set into the event loop, as if the specified event
		1381	had happened for the specified watcher (which must be a pointer to an
		1382	initialised but not necessarily started event watcher). Obviously you must
		1383	not free the watcher as long as it has pending events.
		1384
		1385	Stopping the watcher, letting libev invoke it, or calling
		1386	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1387	not started in the first place.
		1388
		1389	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1390	functions that do not need a watcher.
		1391
1055	=back	1392	=back
1056		1393
		1394	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1395	OWN COMPOSITE WATCHERS> idioms.
1057		1396
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1397	=head2 WATCHER STATES
1059		1398
1060	Each watcher has, by default, a member C<void *data> that you can change	1399	There are various watcher states mentioned throughout this manual -
1061	and read at any time: libev will completely ignore it. This can be used	1400	active, pending and so on. In this section these states and the rules to
1062	to associate arbitrary data with your watcher. If you need more data and	1401	transition between them will be described in more detail - and while these
1063	don't want to allocate memory and store a pointer to it in that data	1402	rules might look complicated, they usually do "the right thing".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1403
1067	struct my_io	1404	=over 4
		1405
		1406	=item initialised
		1407
		1408	Before a watcher can be registered with the event loop it has to be
		1409	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1410	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1411
		1412	In this state it is simply some block of memory that is suitable for
		1413	use in an event loop. It can be moved around, freed, reused etc. at
		1414	will - as long as you either keep the memory contents intact, or call
		1415	C<ev_TYPE_init> again.
		1416
		1417	=item started/running/active
		1418
		1419	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1420	property of the event loop, and is actively waiting for events. While in
		1421	this state it cannot be accessed (except in a few documented ways), moved,
		1422	freed or anything else - the only legal thing is to keep a pointer to it,
		1423	and call libev functions on it that are documented to work on active watchers.
		1424
		1425	=item pending
		1426
		1427	If a watcher is active and libev determines that an event it is interested
		1428	in has occurred (such as a timer expiring), it will become pending. It will
		1429	stay in this pending state until either it is stopped or its callback is
		1430	about to be invoked, so it is not normally pending inside the watcher
		1431	callback.
		1432
		1433	The watcher might or might not be active while it is pending (for example,
		1434	an expired non-repeating timer can be pending but no longer active). If it
		1435	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1436	but it is still property of the event loop at this time, so cannot be
		1437	moved, freed or reused. And if it is active the rules described in the
		1438	previous item still apply.
		1439
		1440	It is also possible to feed an event on a watcher that is not active (e.g.
		1441	via C<ev_feed_event>), in which case it becomes pending without being
		1442	active.
		1443
		1444	=item stopped
		1445
		1446	A watcher can be stopped implicitly by libev (in which case it might still
		1447	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1448	latter will clear any pending state the watcher might be in, regardless
		1449	of whether it was active or not, so stopping a watcher explicitly before
		1450	freeing it is often a good idea.
		1451
		1452	While stopped (and not pending) the watcher is essentially in the
		1453	initialised state, that is, it can be reused, moved, modified in any way
		1454	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1455	it again).
		1456
		1457	=back
		1458
		1459	=head2 WATCHER PRIORITY MODELS
		1460
		1461	Many event loops support I<watcher priorities>, which are usually small
		1462	integers that influence the ordering of event callback invocation
		1463	between watchers in some way, all else being equal.
		1464
		1465	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1466	description for the more technical details such as the actual priority
		1467	range.
		1468
		1469	There are two common ways how these these priorities are being interpreted
		1470	by event loops:
		1471
		1472	In the more common lock-out model, higher priorities "lock out" invocation
		1473	of lower priority watchers, which means as long as higher priority
		1474	watchers receive events, lower priority watchers are not being invoked.
		1475
		1476	The less common only-for-ordering model uses priorities solely to order
		1477	callback invocation within a single event loop iteration: Higher priority
		1478	watchers are invoked before lower priority ones, but they all get invoked
		1479	before polling for new events.
		1480
		1481	Libev uses the second (only-for-ordering) model for all its watchers
		1482	except for idle watchers (which use the lock-out model).
		1483
		1484	The rationale behind this is that implementing the lock-out model for
		1485	watchers is not well supported by most kernel interfaces, and most event
		1486	libraries will just poll for the same events again and again as long as
		1487	their callbacks have not been executed, which is very inefficient in the
		1488	common case of one high-priority watcher locking out a mass of lower
		1489	priority ones.
		1490
		1491	Static (ordering) priorities are most useful when you have two or more
		1492	watchers handling the same resource: a typical usage example is having an
		1493	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1494	timeouts. Under load, data might be received while the program handles
		1495	other jobs, but since timers normally get invoked first, the timeout
		1496	handler will be executed before checking for data. In that case, giving
		1497	the timer a lower priority than the I/O watcher ensures that I/O will be
		1498	handled first even under adverse conditions (which is usually, but not
		1499	always, what you want).
		1500
		1501	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1502	will only be executed when no same or higher priority watchers have
		1503	received events, they can be used to implement the "lock-out" model when
		1504	required.
		1505
		1506	For example, to emulate how many other event libraries handle priorities,
		1507	you can associate an C<ev_idle> watcher to each such watcher, and in
		1508	the normal watcher callback, you just start the idle watcher. The real
		1509	processing is done in the idle watcher callback. This causes libev to
		1510	continuously poll and process kernel event data for the watcher, but when
		1511	the lock-out case is known to be rare (which in turn is rare :), this is
		1512	workable.
		1513
		1514	Usually, however, the lock-out model implemented that way will perform
		1515	miserably under the type of load it was designed to handle. In that case,
		1516	it might be preferable to stop the real watcher before starting the
		1517	idle watcher, so the kernel will not have to process the event in case
		1518	the actual processing will be delayed for considerable time.
		1519
		1520	Here is an example of an I/O watcher that should run at a strictly lower
		1521	priority than the default, and which should only process data when no
		1522	other events are pending:
		1523
		1524	ev_idle idle; // actual processing watcher
		1525	ev_io io; // actual event watcher
		1526
		1527	static void
		1528	io_cb (EV_P_ ev_io *w, int revents)
1068	{	1529	{
1069	ev_io io;	1530	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1531	// are not yet ready to handle it.
1071	void *somedata;	1532	ev_io_stop (EV_A_ w);
1072	struct whatever *mostinteresting;	1533
		1534	// start the idle watcher to handle the actual event.
		1535	// it will not be executed as long as other watchers
		1536	// with the default priority are receiving events.
		1537	ev_idle_start (EV_A_ &idle);
1073	};	1538	}
1074		1539
1075	...	1540	static void
1076	struct my_io w;	1541	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1542	{
1084	struct my_io *w = (struct my_io *)w_;	1543	// actual processing
1085	...	1544	read (STDIN_FILENO, ...);
		1545
		1546	// have to start the I/O watcher again, as
		1547	// we have handled the event
		1548	ev_io_start (EV_P_ &io);
1086	}	1549	}
1087		1550
1088	More interesting and less C-conformant ways of casting your callback type	1551	// initialisation
1089	instead have been omitted.	1552	ev_idle_init (&idle, idle_cb);
		1553	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1554	ev_io_start (EV_DEFAULT_ &io);
1090		1555
1091	Another common scenario is to use some data structure with multiple	1556	In the "real" world, it might also be beneficial to start a timer, so that
1092	embedded watchers:	1557	low-priority connections can not be locked out forever under load. This
1093		1558	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1559	during short periods of high load, while not completely locking out less
1095	{	1560	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1561
1123		1562
1124	=head1 WATCHER TYPES	1563	=head1 WATCHER TYPES
1125		1564
1126	This section describes each watcher in detail, but will not repeat	1565	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1589	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1590	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1591	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1592	required if you know what you are doing).
1154		1593
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1594	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1595	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1596	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1597	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1598	with a relatively standard program structure. Thus it is best to always
1164	this situation even with a relatively standard program structure. Thus	1599	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1600	preferable to a program hanging until some data arrives.
1167		1601
1168	If you cannot run the fd in non-blocking mode (for example you should	1602	If you cannot run the fd in non-blocking mode (for example you should
1169	not play around with an Xlib connection), then you have to separately	1603	not play around with an Xlib connection), then you have to separately
1170	re-test whether a file descriptor is really ready with a known-to-be good	1604	re-test whether a file descriptor is really ready with a known-to-be good
1171	interface such as poll (fortunately in our Xlib example, Xlib already	1605	interface such as poll (fortunately in the case of Xlib, it already does
1172	does this on its own, so its quite safe to use). Some people additionally	1606	this on its own, so its quite safe to use). Some people additionally
1173	use C<SIGALRM> and an interval timer, just to be sure you won't block	1607	use C<SIGALRM> and an interval timer, just to be sure you won't block
1174	indefinitely.	1608	indefinitely.
1175		1609
1176	But really, best use non-blocking mode.	1610	But really, best use non-blocking mode.
1177		1611
…		…
1205		1639
1206	There is no workaround possible except not registering events	1640	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1641	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1642	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		1643
		1644	=head3 The special problem of files
		1645
		1646	Many people try to use C<select> (or libev) on file descriptors
		1647	representing files, and expect it to become ready when their program
		1648	doesn't block on disk accesses (which can take a long time on their own).
		1649
		1650	However, this cannot ever work in the "expected" way - you get a readiness
		1651	notification as soon as the kernel knows whether and how much data is
		1652	there, and in the case of open files, that's always the case, so you
		1653	always get a readiness notification instantly, and your read (or possibly
		1654	write) will still block on the disk I/O.
		1655
		1656	Another way to view it is that in the case of sockets, pipes, character
		1657	devices and so on, there is another party (the sender) that delivers data
		1658	on its own, but in the case of files, there is no such thing: the disk
		1659	will not send data on its own, simply because it doesn't know what you
		1660	wish to read - you would first have to request some data.
		1661
		1662	Since files are typically not-so-well supported by advanced notification
		1663	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1664	to files, even though you should not use it. The reason for this is
		1665	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1666	usually a tty, often a pipe, but also sometimes files or special devices
		1667	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1668	F</dev/urandom>), and even though the file might better be served with
		1669	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1670	it "just works" instead of freezing.
		1671
		1672	So avoid file descriptors pointing to files when you know it (e.g. use
		1673	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1674	when you rarely read from a file instead of from a socket, and want to
		1675	reuse the same code path.
		1676
1210	=head3 The special problem of fork	1677	=head3 The special problem of fork
1211		1678
1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1679	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1213	useless behaviour. Libev fully supports fork, but needs to be told about	1680	useless behaviour. Libev fully supports fork, but needs to be told about
1214	it in the child.	1681	it in the child if you want to continue to use it in the child.
1215		1682
1216	To support fork in your programs, you either have to call	1683	To support fork in your child processes, you have to call C<ev_loop_fork
1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1684	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1685	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1686
1221	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1222		1688
1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1689	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1224	when writing to a pipe whose other end has been closed, your program gets	1690	when writing to a pipe whose other end has been closed, your program gets
…		…
1227		1693
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1694	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1695	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1696	somewhere, as that would have given you a big clue).
1231		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1232		1736
1233	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1234		1738
1235	=over 4	1739	=over 4
1236		1740
…		…
1268	...	1772	...
1269	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1774	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1274		1778
1275		1779
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1781
1278	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1787	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1286		1790
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1793	might introduce a small delay, see "the special problem of being too
		1794	early", below). If multiple timers become ready during the same loop
		1795	iteration then the ones with earlier time-out values are invoked before
		1796	ones of the same priority with later time-out values (but this is no
		1797	longer true when a callback calls C<ev_run> recursively).
1290		1798
1291	=head3 Be smart about timeouts	1799	=head3 Be smart about timeouts
1292		1800
1293	Many real-world problems invole some kind of time-out, usually for error	1801	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1802	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1803	you want to raise some error after a while.
1296		1804
1297	Here are some ways on how to handle this problem, from simple and	1805	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1806	inefficient to smart and efficient.
1299		1807
1300	In the following examples a 60 second activity timeout is assumed - a	1808	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1809	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1810	data or other life sign was received).
1303		1811
1304	=over 4	1812	=over 4
1305		1813
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1814	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1815
1308	This is the most obvious, but not the most simple way: In the beginning,	1816	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1817	start the watcher:
1310		1818
1311	ev_timer_init (timer, callback, 60., 0.);	1819	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1820	ev_timer_start (loop, timer);
1313		1821
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1822	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1823	and start it again:
1316		1824
1317	ev_timer_stop (loop, timer);	1825	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1826	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1827	ev_timer_start (loop, timer);
1320		1828
1321	This is relatively simple to implement, but means that each time there	1829	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1830	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1831	data structure and then add it again. Libev tries to be fast, but it's
		1832	still not a constant-time operation.
1324		1833
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1834	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1835
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1836	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1837	C<ev_timer_start>.
1329		1838
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1839	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1840	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1841	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1842	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1843	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1844
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1845	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1846	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1847	member and C<ev_timer_again>.
1338		1848
1339	At start:	1849	At start:
1340		1850
1341	ev_timer_init (timer, callback, 0., 60.);	1851	ev_init (timer, callback);
		1852	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1853	ev_timer_again (loop, timer);
1343		1854
1344	Each time you receive some data:	1855	Each time there is some activity:
1345		1856
1346	ev_timer_again (loop, timer);	1857	ev_timer_again (loop, timer);
1347		1858
1348	It is even possible to change the time-out on the fly:	1859	It is even possible to change the time-out on the fly, regardless of
		1860	whether the watcher is active or not:
1349		1861
1350	timer->repeat = 30.;	1862	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1863	ev_timer_again (loop, timer);
1352		1864
1353	This is slightly more efficient then stopping/starting the timer each time	1865	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1866	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1867	remove and re-insert the timer from/into its internal data structure.
		1868
		1869	It is, however, even simpler than the "obvious" way to do it.
1356		1870
1357	=item 3. Let the timer time out, but then re-arm it as required.	1871	=item 3. Let the timer time out, but then re-arm it as required.
1358		1872
1359	This method is more tricky, but usually most efficient: Most timeouts are	1873	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1874	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1875	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1876	associated activity resets.
1363		1877
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1878	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1879	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1880	within the callback:
1367		1881
		1882	ev_tstamp timeout = 60.;
1368	ev_tstamp last_activity; // time of last activity	1883	ev_tstamp last_activity; // time of last activity
		1884	ev_timer timer;
1369		1885
1370	static void	1886	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1887	callback (EV_P_ ev_timer *w, int revents)
1372	{	1888	{
1373	ev_tstamp now = ev_now (EV_A);	1889	// calculate when the timeout would happen
1374	ev_tstamp timeout = last_activity + 60.;	1890	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1375		1891
1376	// if last_activity is older than now - timeout, we did time out	1892	// if negative, it means we the timeout already occurred
1377	if (timeout < now)	1893	if (after < 0.)
1378	{	1894	{
1379	// timeout occured, take action	1895	// timeout occurred, take action
1380	}	1896	}
1381	else	1897	else
1382	{	1898	{
1383	// callback was invoked, but there was some activity, re-arm	1899	// callback was invoked, but there was some recent
1384	// to fire in last_activity + 60.	1900	// activity. simply restart the timer to time out
1385	w->again = timeout - now;	1901	// after "after" seconds, which is the earliest time
		1902	// the timeout can occur.
		1903	ev_timer_set (w, after, 0.);
1386	ev_timer_again (EV_A_ w);	1904	ev_timer_start (EV_A_ w);
1387	}	1905	}
1388	}	1906	}
1389		1907
1390	To summarise the callback: first calculate the real time-out (defined as	1908	To summarise the callback: first calculate in how many seconds the
1391	"60 seconds after the last activity"), then check if that time has been	1909	timeout will occur (by calculating the absolute time when it would occur,
1392	reached, which means there was a real timeout. Otherwise the callback was	1910	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1911	(EV_A)> from that).
1394	fire at that future time.
1395		1912
1396	Note how C<ev_timer_again> is used, taking advantage of the	1913	If this value is negative, then we are already past the timeout, i.e. we
1397	C<ev_timer_again> optimisation when the timer is already running.	1914	timed out, and need to do whatever is needed in this case.
1398		1915
		1916	Otherwise, we now the earliest time at which the timeout would trigger,
		1917	and simply start the timer with this timeout value.
		1918
		1919	In other words, each time the callback is invoked it will check whether
		1920	the timeout occurred. If not, it will simply reschedule itself to check
		1921	again at the earliest time it could time out. Rinse. Repeat.
		1922
1399	This scheme causes more callback invocations (about one every 60 seconds),	1923	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1924	minus half the average time between activity), but virtually no calls to
		1925	libev to change the timeout.
1401		1926
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1927	To start the machinery, simply initialise the watcher and set
1403	then call the callback:	1928	C<last_activity> to the current time (meaning there was some activity just
		1929	now), then call the callback, which will "do the right thing" and start
		1930	the timer:
1404		1931
		1932	last_activity = ev_now (EV_A);
1405	ev_timer_init (timer, callback);	1933	ev_init (&timer, callback);
		1934	callback (EV_A_ &timer, 0);
		1935
		1936	When there is some activity, simply store the current time in
		1937	C<last_activity>, no libev calls at all:
		1938
		1939	if (activity detected)
1406	last_activity = ev_now (loop);	1940	last_activity = ev_now (EV_A);
1407	callback (loop, timer, EV_TIMEOUT);
1408		1941
1409	And when there is some activity, simply remember the time in	1942	When your timeout value changes, then the timeout can be changed by simply
1410	C<last_activity>:	1943	providing a new value, stopping the timer and calling the callback, which
		1944	will again do the right thing (for example, time out immediately :).
1411		1945
1412	last_actiivty = ev_now (loop);	1946	timeout = new_value;
		1947	ev_timer_stop (EV_A_ &timer);
		1948	callback (EV_A_ &timer, 0);
1413		1949
1414	This technique is slightly more complex, but in most cases where the	1950	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1951	time-out is unlikely to be triggered, much more efficient.
1416		1952
		1953	=item 4. Wee, just use a double-linked list for your timeouts.
		1954
		1955	If there is not one request, but many thousands (millions...), all
		1956	employing some kind of timeout with the same timeout value, then one can
		1957	do even better:
		1958
		1959	When starting the timeout, calculate the timeout value and put the timeout
		1960	at the I<end> of the list.
		1961
		1962	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1963	the list is expected to fire (for example, using the technique #3).
		1964
		1965	When there is some activity, remove the timer from the list, recalculate
		1966	the timeout, append it to the end of the list again, and make sure to
		1967	update the C<ev_timer> if it was taken from the beginning of the list.
		1968
		1969	This way, one can manage an unlimited number of timeouts in O(1) time for
		1970	starting, stopping and updating the timers, at the expense of a major
		1971	complication, and having to use a constant timeout. The constant timeout
		1972	ensures that the list stays sorted.
		1973
1417	=back	1974	=back
1418		1975
		1976	So which method the best?
		1977
		1978	Method #2 is a simple no-brain-required solution that is adequate in most
		1979	situations. Method #3 requires a bit more thinking, but handles many cases
		1980	better, and isn't very complicated either. In most case, choosing either
		1981	one is fine, with #3 being better in typical situations.
		1982
		1983	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1984	rather complicated, but extremely efficient, something that really pays
		1985	off after the first million or so of active timers, i.e. it's usually
		1986	overkill :)
		1987
		1988	=head3 The special problem of being too early
		1989
		1990	If you ask a timer to call your callback after three seconds, then
		1991	you expect it to be invoked after three seconds - but of course, this
		1992	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1993	guaranteed to any precision by libev - imagine somebody suspending the
		1994	process with a STOP signal for a few hours for example.
		1995
		1996	So, libev tries to invoke your callback as soon as possible I<after> the
		1997	delay has occurred, but cannot guarantee this.
		1998
		1999	A less obvious failure mode is calling your callback too early: many event
		2000	loops compare timestamps with a "elapsed delay >= requested delay", but
		2001	this can cause your callback to be invoked much earlier than you would
		2002	expect.
		2003
		2004	To see why, imagine a system with a clock that only offers full second
		2005	resolution (think windows if you can't come up with a broken enough OS
		2006	yourself). If you schedule a one-second timer at the time 500.9, then the
		2007	event loop will schedule your timeout to elapse at a system time of 500
		2008	(500.9 truncated to the resolution) + 1, or 501.
		2009
		2010	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2011	501" and invoke the callback 0.1s after it was started, even though a
		2012	one-second delay was requested - this is being "too early", despite best
		2013	intentions.
		2014
		2015	This is the reason why libev will never invoke the callback if the elapsed
		2016	delay equals the requested delay, but only when the elapsed delay is
		2017	larger than the requested delay. In the example above, libev would only invoke
		2018	the callback at system time 502, or 1.1s after the timer was started.
		2019
		2020	So, while libev cannot guarantee that your callback will be invoked
		2021	exactly when requested, it I<can> and I<does> guarantee that the requested
		2022	delay has actually elapsed, or in other words, it always errs on the "too
		2023	late" side of things.
		2024
1419	=head3 The special problem of time updates	2025	=head3 The special problem of time updates
1420		2026
1421	Establishing the current time is a costly operation (it usually takes at	2027	Establishing the current time is a costly operation (it usually takes
1422	least two system calls): EV therefore updates its idea of the current	2028	at least one system call): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	2029	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2030	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	2031	lots of events in one iteration.
1426		2032
1427	The relative timeouts are calculated relative to the C<ev_now ()>	2033	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	2034	time. This is usually the right thing as this timestamp refers to the time
1429	of the event triggering whatever timeout you are modifying/starting. If	2035	of the event triggering whatever timeout you are modifying/starting. If
1430	you suspect event processing to be delayed and you I<need> to base the	2036	you suspect event processing to be delayed and you I<need> to base the
1431	timeout on the current time, use something like this to adjust for this:	2037	timeout on the current time, use something like the following to adjust
		2038	for it:
1432		2039
1433	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2040	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1434		2041
1435	If the event loop is suspended for a long time, you can also force an	2042	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2043	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	2044	()>, although that will push the event time of all outstanding events
		2045	further into the future.
		2046
		2047	=head3 The special problem of unsynchronised clocks
		2048
		2049	Modern systems have a variety of clocks - libev itself uses the normal
		2050	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2051	jumps).
		2052
		2053	Neither of these clocks is synchronised with each other or any other clock
		2054	on the system, so C<ev_time ()> might return a considerably different time
		2055	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2056	a call to C<gettimeofday> might return a second count that is one higher
		2057	than a directly following call to C<time>.
		2058
		2059	The moral of this is to only compare libev-related timestamps with
		2060	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2061	a second or so.
		2062
		2063	One more problem arises due to this lack of synchronisation: if libev uses
		2064	the system monotonic clock and you compare timestamps from C<ev_time>
		2065	or C<ev_now> from when you started your timer and when your callback is
		2066	invoked, you will find that sometimes the callback is a bit "early".
		2067
		2068	This is because C<ev_timer>s work in real time, not wall clock time, so
		2069	libev makes sure your callback is not invoked before the delay happened,
		2070	I<measured according to the real time>, not the system clock.
		2071
		2072	If your timeouts are based on a physical timescale (e.g. "time out this
		2073	connection after 100 seconds") then this shouldn't bother you as it is
		2074	exactly the right behaviour.
		2075
		2076	If you want to compare wall clock/system timestamps to your timers, then
		2077	you need to use C<ev_periodic>s, as these are based on the wall clock
		2078	time, where your comparisons will always generate correct results.
		2079
		2080	=head3 The special problems of suspended animation
		2081
		2082	When you leave the server world it is quite customary to hit machines that
		2083	can suspend/hibernate - what happens to the clocks during such a suspend?
		2084
		2085	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2086	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2087	to run until the system is suspended, but they will not advance while the
		2088	system is suspended. That means, on resume, it will be as if the program
		2089	was frozen for a few seconds, but the suspend time will not be counted
		2090	towards C<ev_timer> when a monotonic clock source is used. The real time
		2091	clock advanced as expected, but if it is used as sole clocksource, then a
		2092	long suspend would be detected as a time jump by libev, and timers would
		2093	be adjusted accordingly.
		2094
		2095	I would not be surprised to see different behaviour in different between
		2096	operating systems, OS versions or even different hardware.
		2097
		2098	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2099	time jump in the monotonic clocks and the realtime clock. If the program
		2100	is suspended for a very long time, and monotonic clock sources are in use,
		2101	then you can expect C<ev_timer>s to expire as the full suspension time
		2102	will be counted towards the timers. When no monotonic clock source is in
		2103	use, then libev will again assume a timejump and adjust accordingly.
		2104
		2105	It might be beneficial for this latter case to call C<ev_suspend>
		2106	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2107	deterministic behaviour in this case (you can do nothing against
		2108	C<SIGSTOP>).
1438		2109
1439	=head3 Watcher-Specific Functions and Data Members	2110	=head3 Watcher-Specific Functions and Data Members
1440		2111
1441	=over 4	2112	=over 4
1442		2113
…		…
1456	keep up with the timer (because it takes longer than those 10 seconds to	2127	keep up with the timer (because it takes longer than those 10 seconds to
1457	do stuff) the timer will not fire more than once per event loop iteration.	2128	do stuff) the timer will not fire more than once per event loop iteration.
1458		2129
1459	=item ev_timer_again (loop, ev_timer *)	2130	=item ev_timer_again (loop, ev_timer *)
1460		2131
1461	This will act as if the timer timed out and restart it again if it is	2132	This will act as if the timer timed out, and restarts it again if it is
1462	repeating. The exact semantics are:	2133	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2134	timeout to the C<repeat> value and calling C<ev_timer_start>.
1463		2135
		2136	The exact semantics are as in the following rules, all of which will be
		2137	applied to the watcher:
		2138
		2139	=over 4
		2140
1464	If the timer is pending, its pending status is cleared.	2141	=item If the timer is pending, the pending status is always cleared.
1465		2142
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2143	=item If the timer is started but non-repeating, stop it (as if it timed
		2144	out, without invoking it).
1467		2145
1468	If the timer is repeating, either start it if necessary (with the	2146	=item If the timer is repeating, make the C<repeat> value the new timeout
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2147	and start the timer, if necessary.
1470		2148
		2149	=back
		2150
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2151	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1472	usage example.	2152	usage example.
		2153
		2154	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2155
		2156	Returns the remaining time until a timer fires. If the timer is active,
		2157	then this time is relative to the current event loop time, otherwise it's
		2158	the timeout value currently configured.
		2159
		2160	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2161	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2162	will return C<4>. When the timer expires and is restarted, it will return
		2163	roughly C<7> (likely slightly less as callback invocation takes some time,
		2164	too), and so on.
1473		2165
1474	=item ev_tstamp repeat [read-write]	2166	=item ev_tstamp repeat [read-write]
1475		2167
1476	The current C<repeat> value. Will be used each time the watcher times out	2168	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2169	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2195	}
1504		2196
1505	ev_timer mytimer;	2197	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2198	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2199	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2200	ev_run (loop, 0);
1509		2201
1510	// and in some piece of code that gets executed on any "activity":	2202	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2203	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2204	ev_timer_again (&mytimer);
1513		2205
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2207	=head2 C<ev_periodic> - to cron or not to cron?
1516		2208
1517	Periodic watchers are also timers of a kind, but they are very versatile	2209	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2210	(and unfortunately a bit complex).
1519		2211
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2212	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2213	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2214	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2215	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2216	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2217	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2218
		2219	You can tell a periodic watcher to trigger after some specific point
		2220	in time: for example, if you tell a periodic watcher to trigger "in 10
		2221	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2222	not a delay) and then reset your system clock to January of the previous
		2223	year, then it will take a year or more to trigger the event (unlike an
		2224	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2225	it, as it uses a relative timeout).
		2226
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2227	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2228	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2229	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2230	those cannot react to time jumps.
1532		2231
1533	As with timers, the callback is guaranteed to be invoked only when the	2232	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2233	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2234	timers become ready during the same loop iteration then the ones with
		2235	earlier time-out values are invoked before ones with later time-out values
		2236	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2237
1537	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1538		2239
1539	=over 4	2240	=over 4
1540		2241
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2242	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2243
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2244	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2245
1545	Lots of arguments, lets sort it out... There are basically three modes of	2246	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2247	operation, and we will explain them from simplest to most complex:
1547		2248
1548	=over 4	2249	=over 4
1549		2250
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2251	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2252
1552	In this configuration the watcher triggers an event after the wall clock	2253	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2254	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2255	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2256	will be stopped and invoked when the system clock reaches or surpasses
		2257	this point in time.
1556		2258
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2259	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2260
1559	In this mode the watcher will always be scheduled to time out at the next	2261	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2262	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2263	negative) and then repeat, regardless of any time jumps. The C<offset>
		2264	argument is merely an offset into the C<interval> periods.
1562		2265
1563	This can be used to create timers that do not drift with respect to the	2266	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2267	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2268	hour, on the hour (with respect to UTC):
1566		2269
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2270	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2271
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2272	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2273	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2274	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2275	by 3600.
1573		2276
1574	Another way to think about it (for the mathematically inclined) is that	2277	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2278	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2279	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2280
1578	For numerical stability it is preferable that the C<at> value is near	2281	The C<interval> I<MUST> be positive, and for numerical stability, the
1579	C<ev_now ()> (the current time), but there is no range requirement for	2282	interval value should be higher than C<1/8192> (which is around 100
1580	this value, and in fact is often specified as zero.	2283	microseconds) and C<offset> should be higher than C<0> and should have
		2284	at most a similar magnitude as the current time (say, within a factor of
		2285	ten). Typical values for offset are, in fact, C<0> or something between
		2286	C<0> and C<interval>, which is also the recommended range.
1581		2287
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2288	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2289	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2290	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2291	millisecond (if the OS supports it and the machine is fast enough).
1586		2292
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2293	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2294
1589	In this mode the values for C<interval> and C<at> are both being	2295	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2296	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2297	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2298	current time as second argument.
1593		2299
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2300	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2301	or make ANY other event loop modifications whatsoever, unless explicitly
		2302	allowed by documentation here>.
1596		2303
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2304	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2305	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2306	only event loop modification you are allowed to do).
1600		2307
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2337	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2338	program when the crontabs have changed).
1632		2339
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2340	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2341
1635	When active, returns the absolute time that the watcher is supposed to	2342	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2343	to trigger next. This is not the same as the C<offset> argument to
		2344	C<ev_periodic_set>, but indeed works even in interval and manual
		2345	rescheduling modes.
1637		2346
1638	=item ev_tstamp offset [read-write]	2347	=item ev_tstamp offset [read-write]
1639		2348
1640	When repeating, this contains the offset value, otherwise this is the	2349	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2350	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2351	although libev might modify this value for better numerical stability).
1642		2352
1643	Can be modified any time, but changes only take effect when the periodic	2353	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2354	timer fires or C<ev_periodic_again> is being called.
1645		2355
1646	=item ev_tstamp interval [read-write]	2356	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2372	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2373	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2374	potentially a lot of jitter, but good long-term stability.
1665		2375
1666	static void	2376	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2377	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2378	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2379	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2380	}
1671		2381
1672	ev_periodic hourly_tick;	2382	ev_periodic hourly_tick;
…		…
1689		2399
1690	ev_periodic hourly_tick;	2400	ev_periodic hourly_tick;
1691	ev_periodic_init (&hourly_tick, clock_cb,	2401	ev_periodic_init (&hourly_tick, clock_cb,
1692	fmod (ev_now (loop), 3600.), 3600., 0);	2402	fmod (ev_now (loop), 3600.), 3600., 0);
1693	ev_periodic_start (loop, &hourly_tick);	2403	ev_periodic_start (loop, &hourly_tick);
1694		2404
1695		2405
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2406	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2407
1698	Signal watchers will trigger an event when the process receives a specific	2408	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2409	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2410	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2411	normal event processing, like any other event.
1702		2412
1703	If you want signals asynchronously, just use C<sigaction> as you would	2413	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2414	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2415	the signal. You can even use C<ev_async> from a signal handler to
		2416	synchronously wake up an event loop.
1706		2417
1707	You can configure as many watchers as you like per signal. Only when the	2418	You can configure as many watchers as you like for the same signal, but
1708	first watcher gets started will libev actually register a signal handler	2419	only within the same loop, i.e. you can watch for C<SIGINT> in your
1709	with the kernel (thus it coexists with your own signal handlers as long as	2420	default loop and for C<SIGIO> in another loop, but you cannot watch for
1710	you don't register any with libev for the same signal). Similarly, when	2421	C<SIGINT> in both the default loop and another loop at the same time. At
1711	the last signal watcher for a signal is stopped, libev will reset the	2422	the moment, C<SIGCHLD> is permanently tied to the default loop.
1712	signal handler to SIG_DFL (regardless of what it was set to before).	2423
		2424	Only after the first watcher for a signal is started will libev actually
		2425	register something with the kernel. It thus coexists with your own signal
		2426	handlers as long as you don't register any with libev for the same signal.
1713		2427
1714	If possible and supported, libev will install its handlers with	2428	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2429	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2430	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2431	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2432	and unblock them in an C<ev_prepare> watcher.
		2433
		2434	=head3 The special problem of inheritance over fork/execve/pthread_create
		2435
		2436	Both the signal mask (C<sigprocmask>) and the signal disposition
		2437	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2438	stopping it again), that is, libev might or might not block the signal,
		2439	and might or might not set or restore the installed signal handler (but
		2440	see C<EVFLAG_NOSIGMASK>).
		2441
		2442	While this does not matter for the signal disposition (libev never
		2443	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2444	C<execve>), this matters for the signal mask: many programs do not expect
		2445	certain signals to be blocked.
		2446
		2447	This means that before calling C<exec> (from the child) you should reset
		2448	the signal mask to whatever "default" you expect (all clear is a good
		2449	choice usually).
		2450
		2451	The simplest way to ensure that the signal mask is reset in the child is
		2452	to install a fork handler with C<pthread_atfork> that resets it. That will
		2453	catch fork calls done by libraries (such as the libc) as well.
		2454
		2455	In current versions of libev, the signal will not be blocked indefinitely
		2456	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2457	the window of opportunity for problems, it will not go away, as libev
		2458	I<has> to modify the signal mask, at least temporarily.
		2459
		2460	So I can't stress this enough: I<If you do not reset your signal mask when
		2461	you expect it to be empty, you have a race condition in your code>. This
		2462	is not a libev-specific thing, this is true for most event libraries.
		2463
		2464	=head3 The special problem of threads signal handling
		2465
		2466	POSIX threads has problematic signal handling semantics, specifically,
		2467	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2468	threads in a process block signals, which is hard to achieve.
		2469
		2470	When you want to use sigwait (or mix libev signal handling with your own
		2471	for the same signals), you can tackle this problem by globally blocking
		2472	all signals before creating any threads (or creating them with a fully set
		2473	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2474	loops. Then designate one thread as "signal receiver thread" which handles
		2475	these signals. You can pass on any signals that libev might be interested
		2476	in by calling C<ev_feed_signal>.
1719		2477
1720	=head3 Watcher-Specific Functions and Data Members	2478	=head3 Watcher-Specific Functions and Data Members
1721		2479
1722	=over 4	2480	=over 4
1723		2481
…		…
1739	Example: Try to exit cleanly on SIGINT.	2497	Example: Try to exit cleanly on SIGINT.
1740		2498
1741	static void	2499	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2500	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2501	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2502	ev_break (loop, EVBREAK_ALL);
1745	}	2503	}
1746		2504
1747	ev_signal signal_watcher;	2505	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2506	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2507	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2513	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2514	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2515	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2516	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2517	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2518	but forking and registering a watcher a few event loop iterations later or
1761	not.	2519	in the next callback invocation is not.
1762		2520
1763	Only the default event loop is capable of handling signals, and therefore	2521	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2522	you can only register child watchers in the default event loop.
1765		2523
		2524	Due to some design glitches inside libev, child watchers will always be
		2525	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2526	libev)
		2527
1766	=head3 Process Interaction	2528	=head3 Process Interaction
1767		2529
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2530	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2531	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2532	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2533	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2534	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2535	children, even ones not watched.
1774		2536
1775	=head3 Overriding the Built-In Processing	2537	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2547	=head3 Stopping the Child Watcher
1786		2548
1787	Currently, the child watcher never gets stopped, even when the	2549	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2550	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2551	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2552	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2553	problem).
1791		2554
1792	=head3 Watcher-Specific Functions and Data Members	2555	=head3 Watcher-Specific Functions and Data Members
1793		2556
1794	=over 4	2557	=over 4
1795		2558
…		…
1852		2615
1853		2616
1854	=head2 C<ev_stat> - did the file attributes just change?	2617	=head2 C<ev_stat> - did the file attributes just change?
1855		2618
1856	This watches a file system path for attribute changes. That is, it calls	2619	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2620	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2621	and sees if it changed compared to the last time, invoking the callback
		2622	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2623	happen after the watcher has been started will be reported.
1859		2624
1860	The path does not need to exist: changing from "path exists" to "path does	2625	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2626	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2627	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2628	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2629	least one) and all the other fields of the stat buffer having unspecified
		2630	contents.
1865		2631
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2632	The path I<must not> end in a slash or contain special components such as
		2633	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2634	your working directory changes, then the behaviour is undefined.
1868		2635
1869	Since there is no standard kernel interface to do this, the portable	2636	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2637	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2638	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2639	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2640	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2641	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2642	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2643	currently around C<0.1>, but that's usually overkill.
1877		2644
1878	This watcher type is not meant for massive numbers of stat watchers,	2645	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2646	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2647	resource-intensive.
1881		2648
1882	At the time of this writing, the only OS-specific interface implemented	2649	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2650	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2651	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2652	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2653
1887	=head3 ABI Issues (Largefile Support)	2654	=head3 ABI Issues (Largefile Support)
1888		2655
1889	Libev by default (unless the user overrides this) uses the default	2656	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2657	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2658	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2659	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2660	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2661	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2662	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2663	most noticeably displayed with ev_stat and large file support.
1897		2664
1898	The solution for this is to lobby your distribution maker to make large	2665	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2666	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2667	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2668	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2669	default compilation environment.
1903		2670
1904	=head3 Inotify and Kqueue	2671	=head3 Inotify and Kqueue
1905		2672
1906	When C<inotify (7)> support has been compiled into libev (generally	2673	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2674	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2675	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2676	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2677
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2678	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2679	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2680	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2681	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2682	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2683	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2684	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2685	xfs are fully working) libev usually gets away without polling.
1917		2686
1918	There is no support for kqueue, as apparently it cannot be used to	2687	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2688	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2689	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2690	etc. is difficult.
1922		2691
		2692	=head3 C<stat ()> is a synchronous operation
		2693
		2694	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2695	the process. The exception are C<ev_stat> watchers - those call C<stat
		2696	()>, which is a synchronous operation.
		2697
		2698	For local paths, this usually doesn't matter: unless the system is very
		2699	busy or the intervals between stat's are large, a stat call will be fast,
		2700	as the path data is usually in memory already (except when starting the
		2701	watcher).
		2702
		2703	For networked file systems, calling C<stat ()> can block an indefinite
		2704	time due to network issues, and even under good conditions, a stat call
		2705	often takes multiple milliseconds.
		2706
		2707	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2708	paths, although this is fully supported by libev.
		2709
1923	=head3 The special problem of stat time resolution	2710	=head3 The special problem of stat time resolution
1924		2711
1925	The C<stat ()> system call only supports full-second resolution portably, and	2712	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2713	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2714	still only support whole seconds.
1928		2715
1929	That means that, if the time is the only thing that changes, you can	2716	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2717	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2718	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2719	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2071	Apart from keeping your process non-blocking (which is a useful	2858	Apart from keeping your process non-blocking (which is a useful
2072	effect on its own sometimes), idle watchers are a good place to do	2859	effect on its own sometimes), idle watchers are a good place to do
2073	"pseudo-background processing", or delay processing stuff to after the	2860	"pseudo-background processing", or delay processing stuff to after the
2074	event loop has handled all outstanding events.	2861	event loop has handled all outstanding events.
2075		2862
		2863	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2864
		2865	As long as there is at least one active idle watcher, libev will never
		2866	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2867	For this to work, the idle watcher doesn't need to be invoked at all - the
		2868	lowest priority will do.
		2869
		2870	This mode of operation can be useful together with an C<ev_check> watcher,
		2871	to do something on each event loop iteration - for example to balance load
		2872	between different connections.
		2873
		2874	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2875	example.
		2876
2076	=head3 Watcher-Specific Functions and Data Members	2877	=head3 Watcher-Specific Functions and Data Members
2077		2878
2078	=over 4	2879	=over 4
2079		2880
2080	=item ev_idle_init (ev_signal *, callback)	2881	=item ev_idle_init (ev_idle *, callback)
2081		2882
2082	Initialises and configures the idle watcher - it has no parameters of any	2883	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2884	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2885	believe me.
2085		2886
…		…
2091	callback, free it. Also, use no error checking, as usual.	2892	callback, free it. Also, use no error checking, as usual.
2092		2893
2093	static void	2894	static void
2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2895	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2095	{	2896	{
		2897	// stop the watcher
		2898	ev_idle_stop (loop, w);
		2899
		2900	// now we can free it
2096	free (w);	2901	free (w);
		2902
2097	// now do something you wanted to do when the program has	2903	// now do something you wanted to do when the program has
2098	// no longer anything immediate to do.	2904	// no longer anything immediate to do.
2099	}	2905	}
2100		2906
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2907	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2908	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2909	ev_idle_start (loop, idle_watcher);
2104		2910
2105		2911
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2912	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2913
2108	Prepare and check watchers are usually (but not always) used in pairs:	2914	Prepare and check watchers are often (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2915	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2916	afterwards.
2111		2917
2112	You I<must not> call C<ev_loop> or similar functions that enter	2918	You I<must not> call C<ev_run> (or similar functions that enter the
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2919	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2114	watchers. Other loops than the current one are fine, however. The	2920	C<ev_check> watchers. Other loops than the current one are fine,
2115	rationale behind this is that you do not need to check for recursion in	2921	however. The rationale behind this is that you do not need to check
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2922	for recursion in those watchers, i.e. the sequence will always be
2117	C<ev_check> so if you have one watcher of each kind they will always be	2923	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2118	called in pairs bracketing the blocking call.	2924	kind they will always be called in pairs bracketing the blocking call.
2119		2925
2120	Their main purpose is to integrate other event mechanisms into libev and	2926	Their main purpose is to integrate other event mechanisms into libev and
2121	their use is somewhat advanced. They could be used, for example, to track	2927	their use is somewhat advanced. They could be used, for example, to track
2122	variable changes, implement your own watchers, integrate net-snmp or a	2928	variable changes, implement your own watchers, integrate net-snmp or a
2123	coroutine library and lots more. They are also occasionally useful if	2929	coroutine library and lots more. They are also occasionally useful if
…		…
2141	with priority higher than or equal to the event loop and one coroutine	2947	with priority higher than or equal to the event loop and one coroutine
2142	of lower priority, but only once, using idle watchers to keep the event	2948	of lower priority, but only once, using idle watchers to keep the event
2143	loop from blocking if lower-priority coroutines are active, thus mapping	2949	loop from blocking if lower-priority coroutines are active, thus mapping
2144	low-priority coroutines to idle/background tasks).	2950	low-priority coroutines to idle/background tasks).
2145		2951
2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2952	When used for this purpose, it is recommended to give C<ev_check> watchers
2147	priority, to ensure that they are being run before any other watchers	2953	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2148	after the poll (this doesn't matter for C<ev_prepare> watchers).	2954	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2955	watchers).
2149		2956
2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2957	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2151	activate ("feed") events into libev. While libev fully supports this, they	2958	activate ("feed") events into libev. While libev fully supports this, they
2152	might get executed before other C<ev_check> watchers did their job. As	2959	might get executed before other C<ev_check> watchers did their job. As
2153	C<ev_check> watchers are often used to embed other (non-libev) event	2960	C<ev_check> watchers are often used to embed other (non-libev) event
2154	loops those other event loops might be in an unusable state until their	2961	loops those other event loops might be in an unusable state until their
2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2962	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2156	others).	2963	others).
		2964
		2965	=head3 Abusing an C<ev_check> watcher for its side-effect
		2966
		2967	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2968	useful because they are called once per event loop iteration. For
		2969	example, if you want to handle a large number of connections fairly, you
		2970	normally only do a bit of work for each active connection, and if there
		2971	is more work to do, you wait for the next event loop iteration, so other
		2972	connections have a chance of making progress.
		2973
		2974	Using an C<ev_check> watcher is almost enough: it will be called on the
		2975	next event loop iteration. However, that isn't as soon as possible -
		2976	without external events, your C<ev_check> watcher will not be invoked.
		2977
		2978	This is where C<ev_idle> watchers come in handy - all you need is a
		2979	single global idle watcher that is active as long as you have one active
		2980	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2981	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2982	invoked. Neither watcher alone can do that.
2157		2983
2158	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2159		2985
2160	=over 4	2986	=over 4
2161		2987
…		…
2201	struct pollfd fds [nfd];	3027	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	3028	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3029	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		3030
2205	/* the callback is illegal, but won't be called as we stop during check */	3031	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	3032	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	3033	ev_timer_start (loop, &tw);
2208		3034
2209	// create one ev_io per pollfd	3035	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	3036	for (int i = 0; i < nfd; ++i)
2211	{	3037	{
…		…
2285		3111
2286	if (timeout >= 0)	3112	if (timeout >= 0)
2287	// create/start timer	3113	// create/start timer
2288		3114
2289	// poll	3115	// poll
2290	ev_loop (EV_A_ 0);	3116	ev_run (EV_A_ 0);
2291		3117
2292	// stop timer again	3118	// stop timer again
2293	if (timeout >= 0)	3119	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	3120	ev_timer_stop (EV_A_ &to);
2295		3121
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	3150	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	3151	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	3152	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	3153	the rest in a second one, and embed the second one in the first.
2328		3154
2329	As long as the watcher is active, the callback will be invoked every time	3155	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	3156	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3157	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	3158	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	3159	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	3160	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		3161
2337	As long as the watcher is started it will automatically handle events. The	3162	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	3163	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		3164
2342	Also, there have not currently been made special provisions for forking:	3165	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3166	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	3167	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3168	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3169
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3170	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3171	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3172	portable one.
2351		3173
…		…
2366		3188
2367	=over 4	3189	=over 4
2368		3190
2369	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3191	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2370		3192
2371	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3193	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2372		3194
2373	Configures the watcher to embed the given loop, which must be	3195	Configures the watcher to embed the given loop, which must be
2374	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3196	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2375	invoked automatically, otherwise it is the responsibility of the callback	3197	invoked automatically, otherwise it is the responsibility of the callback
2376	to invoke it (it will continue to be called until the sweep has been done,	3198	to invoke it (it will continue to be called until the sweep has been done,
2377	if you do not want that, you need to temporarily stop the embed watcher).	3199	if you do not want that, you need to temporarily stop the embed watcher).
2378		3200
2379	=item ev_embed_sweep (loop, ev_embed *)	3201	=item ev_embed_sweep (loop, ev_embed *)
2380		3202
2381	Make a single, non-blocking sweep over the embedded loop. This works	3203	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3204	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3205	appropriate way for embedded loops.
2384		3206
2385	=item struct ev_loop *other [read-only]	3207	=item struct ev_loop *other [read-only]
2386		3208
2387	The embedded event loop.	3209	The embedded event loop.
…		…
2397	used).	3219	used).
2398		3220
2399	struct ev_loop *loop_hi = ev_default_init (0);	3221	struct ev_loop *loop_hi = ev_default_init (0);
2400	struct ev_loop *loop_lo = 0;	3222	struct ev_loop *loop_lo = 0;
2401	ev_embed embed;	3223	ev_embed embed;
2402		3224
2403	// see if there is a chance of getting one that works	3225	// see if there is a chance of getting one that works
2404	// (remember that a flags value of 0 means autodetection)	3226	// (remember that a flags value of 0 means autodetection)
2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3227	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3228	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2407	: 0;	3229	: 0;
…		…
2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3243	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2422		3244
2423	struct ev_loop *loop = ev_default_init (0);	3245	struct ev_loop *loop = ev_default_init (0);
2424	struct ev_loop *loop_socket = 0;	3246	struct ev_loop *loop_socket = 0;
2425	ev_embed embed;	3247	ev_embed embed;
2426		3248
2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3249	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3250	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2429	{	3251	{
2430	ev_embed_init (&embed, 0, loop_socket);	3252	ev_embed_init (&embed, 0, loop_socket);
2431	ev_embed_start (loop, &embed);	3253	ev_embed_start (loop, &embed);
…		…
2439		3261
2440	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3262	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2441		3263
2442	Fork watchers are called when a C<fork ()> was detected (usually because	3264	Fork watchers are called when a C<fork ()> was detected (usually because
2443	whoever is a good citizen cared to tell libev about it by calling	3265	whoever is a good citizen cared to tell libev about it by calling
2444	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3266	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2445	event loop blocks next and before C<ev_check> watchers are being called,	3267	and before C<ev_check> watchers are being called, and only in the child
2446	and only in the child after the fork. If whoever good citizen calling	3268	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3269	and calls it in the wrong process, the fork handlers will be invoked, too,
2448	handlers will be invoked, too, of course.	3270	of course.
		3271
		3272	=head3 The special problem of life after fork - how is it possible?
		3273
		3274	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3275	up/change the process environment, followed by a call to C<exec()>. This
		3276	sequence should be handled by libev without any problems.
		3277
		3278	This changes when the application actually wants to do event handling
		3279	in the child, or both parent in child, in effect "continuing" after the
		3280	fork.
		3281
		3282	The default mode of operation (for libev, with application help to detect
		3283	forks) is to duplicate all the state in the child, as would be expected
		3284	when I<either> the parent I<or> the child process continues.
		3285
		3286	When both processes want to continue using libev, then this is usually the
		3287	wrong result. In that case, usually one process (typically the parent) is
		3288	supposed to continue with all watchers in place as before, while the other
		3289	process typically wants to start fresh, i.e. without any active watchers.
		3290
		3291	The cleanest and most efficient way to achieve that with libev is to
		3292	simply create a new event loop, which of course will be "empty", and
		3293	use that for new watchers. This has the advantage of not touching more
		3294	memory than necessary, and thus avoiding the copy-on-write, and the
		3295	disadvantage of having to use multiple event loops (which do not support
		3296	signal watchers).
		3297
		3298	When this is not possible, or you want to use the default loop for
		3299	other reasons, then in the process that wants to start "fresh", call
		3300	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3301	Destroying the default loop will "orphan" (not stop) all registered
		3302	watchers, so you have to be careful not to execute code that modifies
		3303	those watchers. Note also that in that case, you have to re-register any
		3304	signal watchers.
2449		3305
2450	=head3 Watcher-Specific Functions and Data Members	3306	=head3 Watcher-Specific Functions and Data Members
2451		3307
2452	=over 4	3308	=over 4
2453		3309
2454	=item ev_fork_init (ev_signal *, callback)	3310	=item ev_fork_init (ev_fork *, callback)
2455		3311
2456	Initialises and configures the fork watcher - it has no parameters of any	3312	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3313	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3314	really.
2459		3315
2460	=back	3316	=back
2461		3317
2462		3318
		3319	=head2 C<ev_cleanup> - even the best things end
		3320
		3321	Cleanup watchers are called just before the event loop is being destroyed
		3322	by a call to C<ev_loop_destroy>.
		3323
		3324	While there is no guarantee that the event loop gets destroyed, cleanup
		3325	watchers provide a convenient method to install cleanup hooks for your
		3326	program, worker threads and so on - you just to make sure to destroy the
		3327	loop when you want them to be invoked.
		3328
		3329	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3330	all other watchers, they do not keep a reference to the event loop (which
		3331	makes a lot of sense if you think about it). Like all other watchers, you
		3332	can call libev functions in the callback, except C<ev_cleanup_start>.
		3333
		3334	=head3 Watcher-Specific Functions and Data Members
		3335
		3336	=over 4
		3337
		3338	=item ev_cleanup_init (ev_cleanup *, callback)
		3339
		3340	Initialises and configures the cleanup watcher - it has no parameters of
		3341	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3342	pointless, I assure you.
		3343
		3344	=back
		3345
		3346	Example: Register an atexit handler to destroy the default loop, so any
		3347	cleanup functions are called.
		3348
		3349	static void
		3350	program_exits (void)
		3351	{
		3352	ev_loop_destroy (EV_DEFAULT_UC);
		3353	}
		3354
		3355	...
		3356	atexit (program_exits);
		3357
		3358
2463	=head2 C<ev_async> - how to wake up another event loop	3359	=head2 C<ev_async> - how to wake up an event loop
2464		3360
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3361	In general, you cannot use an C<ev_loop> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3362	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3363	loops - those are of course safe to use in different threads).
2468		3364
2469	Sometimes, however, you need to wake up another event loop you do not	3365	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3366	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3367	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3368	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3369
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3370	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3371	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3372	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3373	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2479		3374	of "global async watchers" by using a watcher on an otherwise unused
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3375	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2481	just the default loop.	3376	even without knowing which loop owns the signal.
2482		3377
2483	=head3 Queueing	3378	=head3 Queueing
2484		3379
2485	C<ev_async> does not support queueing of data in any way. The reason	3380	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3381	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3382	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3383	need elaborate support such as pthreads or unportable memory access
		3384	semantics.
2489		3385
2490	That means that if you want to queue data, you have to provide your own	3386	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3387	queue. But at least I can tell you how to implement locking around your
2492	queue:	3388	queue:
2493		3389
…		…
2571	=over 4	3467	=over 4
2572		3468
2573	=item ev_async_init (ev_async *, callback)	3469	=item ev_async_init (ev_async *, callback)
2574		3470
2575	Initialises and configures the async watcher - it has no parameters of any	3471	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3472	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3473	trust me.
2578		3474
2579	=item ev_async_send (loop, ev_async *)	3475	=item ev_async_send (loop, ev_async *)
2580		3476
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3477	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3478	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3479	returns.
		3480
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3481	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3482	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2585	section below on what exactly this means).	3483	embedding section below on what exactly this means).
2586		3484
2587	This call incurs the overhead of a system call only once per loop iteration,	3485	Note that, as with other watchers in libev, multiple events might get
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3486	compressed into a single callback invocation (another way to look at
2589	calls to C<ev_async_send>.	3487	this is that C<ev_async> watchers are level-triggered: they are set on
		3488	C<ev_async_send>, reset when the event loop detects that).
		3489
		3490	This call incurs the overhead of at most one extra system call per event
		3491	loop iteration, if the event loop is blocked, and no syscall at all if
		3492	the event loop (or your program) is processing events. That means that
		3493	repeated calls are basically free (there is no need to avoid calls for
		3494	performance reasons) and that the overhead becomes smaller (typically
		3495	zero) under load.
2590		3496
2591	=item bool = ev_async_pending (ev_async *)	3497	=item bool = ev_async_pending (ev_async *)
2592		3498
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3499	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3500	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3503	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3504	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3505	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3506	quickly check whether invoking the loop might be a good idea.
2601		3507
2602	Not that this does I<not> check whether the watcher itself is pending, only	3508	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3509	only whether it has been requested to make this watcher pending: there
		3510	is a time window between the event loop checking and resetting the async
		3511	notification, and the callback being invoked.
2604		3512
2605	=back	3513	=back
2606		3514
2607		3515
2608	=head1 OTHER FUNCTIONS	3516	=head1 OTHER FUNCTIONS
…		…
2625		3533
2626	If C<timeout> is less than 0, then no timeout watcher will be	3534	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3535	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3536	repeat = 0) will be started. C<0> is a valid timeout.
2629		3537
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3538	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3539	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3540	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3541	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3542	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3543	events precedence.
2636		3544
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3545	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3546
2639	static void stdin_ready (int revents, void *arg)	3547	static void stdin_ready (int revents, void *arg)
2640	{	3548	{
2641	if (revents & EV_READ)	3549	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3550	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3551	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3552	/* doh, nothing entered */;
2645	}	3553	}
2646		3554
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3555	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3556
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3557	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3558
2657	Feed an event on the given fd, as if a file descriptor backend detected	3559	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3560	the given events.
2659		3561
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3562	=item ev_feed_signal_event (loop, int signum)
2661		3563
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3564	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3565	which is async-safe.
2664		3566
2665	=back	3567	=back
		3568
		3569
		3570	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3571
		3572	This section explains some common idioms that are not immediately
		3573	obvious. Note that examples are sprinkled over the whole manual, and this
		3574	section only contains stuff that wouldn't fit anywhere else.
		3575
		3576	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3577
		3578	Each watcher has, by default, a C<void *data> member that you can read
		3579	or modify at any time: libev will completely ignore it. This can be used
		3580	to associate arbitrary data with your watcher. If you need more data and
		3581	don't want to allocate memory separately and store a pointer to it in that
		3582	data member, you can also "subclass" the watcher type and provide your own
		3583	data:
		3584
		3585	struct my_io
		3586	{
		3587	ev_io io;
		3588	int otherfd;
		3589	void *somedata;
		3590	struct whatever *mostinteresting;
		3591	};
		3592
		3593	...
		3594	struct my_io w;
		3595	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3596
		3597	And since your callback will be called with a pointer to the watcher, you
		3598	can cast it back to your own type:
		3599
		3600	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3601	{
		3602	struct my_io *w = (struct my_io *)w_;
		3603	...
		3604	}
		3605
		3606	More interesting and less C-conformant ways of casting your callback
		3607	function type instead have been omitted.
		3608
		3609	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3610
		3611	Another common scenario is to use some data structure with multiple
		3612	embedded watchers, in effect creating your own watcher that combines
		3613	multiple libev event sources into one "super-watcher":
		3614
		3615	struct my_biggy
		3616	{
		3617	int some_data;
		3618	ev_timer t1;
		3619	ev_timer t2;
		3620	}
		3621
		3622	In this case getting the pointer to C<my_biggy> is a bit more
		3623	complicated: Either you store the address of your C<my_biggy> struct in
		3624	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3625	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3626	real programmers):
		3627
		3628	#include <stddef.h>
		3629
		3630	static void
		3631	t1_cb (EV_P_ ev_timer *w, int revents)
		3632	{
		3633	struct my_biggy big = (struct my_biggy *)
		3634	(((char *)w) - offsetof (struct my_biggy, t1));
		3635	}
		3636
		3637	static void
		3638	t2_cb (EV_P_ ev_timer *w, int revents)
		3639	{
		3640	struct my_biggy big = (struct my_biggy *)
		3641	(((char *)w) - offsetof (struct my_biggy, t2));
		3642	}
		3643
		3644	=head2 AVOIDING FINISHING BEFORE RETURNING
		3645
		3646	Often you have structures like this in event-based programs:
		3647
		3648	callback ()
		3649	{
		3650	free (request);
		3651	}
		3652
		3653	request = start_new_request (..., callback);
		3654
		3655	The intent is to start some "lengthy" operation. The C<request> could be
		3656	used to cancel the operation, or do other things with it.
		3657
		3658	It's not uncommon to have code paths in C<start_new_request> that
		3659	immediately invoke the callback, for example, to report errors. Or you add
		3660	some caching layer that finds that it can skip the lengthy aspects of the
		3661	operation and simply invoke the callback with the result.
		3662
		3663	The problem here is that this will happen I<before> C<start_new_request>
		3664	has returned, so C<request> is not set.
		3665
		3666	Even if you pass the request by some safer means to the callback, you
		3667	might want to do something to the request after starting it, such as
		3668	canceling it, which probably isn't working so well when the callback has
		3669	already been invoked.
		3670
		3671	A common way around all these issues is to make sure that
		3672	C<start_new_request> I<always> returns before the callback is invoked. If
		3673	C<start_new_request> immediately knows the result, it can artificially
		3674	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3675	example, or more sneakily, by reusing an existing (stopped) watcher and
		3676	pushing it into the pending queue:
		3677
		3678	ev_set_cb (watcher, callback);
		3679	ev_feed_event (EV_A_ watcher, 0);
		3680
		3681	This way, C<start_new_request> can safely return before the callback is
		3682	invoked, while not delaying callback invocation too much.
		3683
		3684	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3685
		3686	Often (especially in GUI toolkits) there are places where you have
		3687	I<modal> interaction, which is most easily implemented by recursively
		3688	invoking C<ev_run>.
		3689
		3690	This brings the problem of exiting - a callback might want to finish the
		3691	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3692	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3693	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3694	other combination: In these cases, a simple C<ev_break> will not work.
		3695
		3696	The solution is to maintain "break this loop" variable for each C<ev_run>
		3697	invocation, and use a loop around C<ev_run> until the condition is
		3698	triggered, using C<EVRUN_ONCE>:
		3699
		3700	// main loop
		3701	int exit_main_loop = 0;
		3702
		3703	while (!exit_main_loop)
		3704	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3705
		3706	// in a modal watcher
		3707	int exit_nested_loop = 0;
		3708
		3709	while (!exit_nested_loop)
		3710	ev_run (EV_A_ EVRUN_ONCE);
		3711
		3712	To exit from any of these loops, just set the corresponding exit variable:
		3713
		3714	// exit modal loop
		3715	exit_nested_loop = 1;
		3716
		3717	// exit main program, after modal loop is finished
		3718	exit_main_loop = 1;
		3719
		3720	// exit both
		3721	exit_main_loop = exit_nested_loop = 1;
		3722
		3723	=head2 THREAD LOCKING EXAMPLE
		3724
		3725	Here is a fictitious example of how to run an event loop in a different
		3726	thread from where callbacks are being invoked and watchers are
		3727	created/added/removed.
		3728
		3729	For a real-world example, see the C<EV::Loop::Async> perl module,
		3730	which uses exactly this technique (which is suited for many high-level
		3731	languages).
		3732
		3733	The example uses a pthread mutex to protect the loop data, a condition
		3734	variable to wait for callback invocations, an async watcher to notify the
		3735	event loop thread and an unspecified mechanism to wake up the main thread.
		3736
		3737	First, you need to associate some data with the event loop:
		3738
		3739	typedef struct {
		3740	mutex_t lock; /* global loop lock */
		3741	ev_async async_w;
		3742	thread_t tid;
		3743	cond_t invoke_cv;
		3744	} userdata;
		3745
		3746	void prepare_loop (EV_P)
		3747	{
		3748	// for simplicity, we use a static userdata struct.
		3749	static userdata u;
		3750
		3751	ev_async_init (&u->async_w, async_cb);
		3752	ev_async_start (EV_A_ &u->async_w);
		3753
		3754	pthread_mutex_init (&u->lock, 0);
		3755	pthread_cond_init (&u->invoke_cv, 0);
		3756
		3757	// now associate this with the loop
		3758	ev_set_userdata (EV_A_ u);
		3759	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3760	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3761
		3762	// then create the thread running ev_run
		3763	pthread_create (&u->tid, 0, l_run, EV_A);
		3764	}
		3765
		3766	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3767	solely to wake up the event loop so it takes notice of any new watchers
		3768	that might have been added:
		3769
		3770	static void
		3771	async_cb (EV_P_ ev_async *w, int revents)
		3772	{
		3773	// just used for the side effects
		3774	}
		3775
		3776	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3777	protecting the loop data, respectively.
		3778
		3779	static void
		3780	l_release (EV_P)
		3781	{
		3782	userdata *u = ev_userdata (EV_A);
		3783	pthread_mutex_unlock (&u->lock);
		3784	}
		3785
		3786	static void
		3787	l_acquire (EV_P)
		3788	{
		3789	userdata *u = ev_userdata (EV_A);
		3790	pthread_mutex_lock (&u->lock);
		3791	}
		3792
		3793	The event loop thread first acquires the mutex, and then jumps straight
		3794	into C<ev_run>:
		3795
		3796	void *
		3797	l_run (void *thr_arg)
		3798	{
		3799	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3800
		3801	l_acquire (EV_A);
		3802	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3803	ev_run (EV_A_ 0);
		3804	l_release (EV_A);
		3805
		3806	return 0;
		3807	}
		3808
		3809	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3810	signal the main thread via some unspecified mechanism (signals? pipe
		3811	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3812	have been called (in a while loop because a) spurious wakeups are possible
		3813	and b) skipping inter-thread-communication when there are no pending
		3814	watchers is very beneficial):
		3815
		3816	static void
		3817	l_invoke (EV_P)
		3818	{
		3819	userdata *u = ev_userdata (EV_A);
		3820
		3821	while (ev_pending_count (EV_A))
		3822	{
		3823	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3824	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3825	}
		3826	}
		3827
		3828	Now, whenever the main thread gets told to invoke pending watchers, it
		3829	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3830	thread to continue:
		3831
		3832	static void
		3833	real_invoke_pending (EV_P)
		3834	{
		3835	userdata *u = ev_userdata (EV_A);
		3836
		3837	pthread_mutex_lock (&u->lock);
		3838	ev_invoke_pending (EV_A);
		3839	pthread_cond_signal (&u->invoke_cv);
		3840	pthread_mutex_unlock (&u->lock);
		3841	}
		3842
		3843	Whenever you want to start/stop a watcher or do other modifications to an
		3844	event loop, you will now have to lock:
		3845
		3846	ev_timer timeout_watcher;
		3847	userdata *u = ev_userdata (EV_A);
		3848
		3849	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3850
		3851	pthread_mutex_lock (&u->lock);
		3852	ev_timer_start (EV_A_ &timeout_watcher);
		3853	ev_async_send (EV_A_ &u->async_w);
		3854	pthread_mutex_unlock (&u->lock);
		3855
		3856	Note that sending the C<ev_async> watcher is required because otherwise
		3857	an event loop currently blocking in the kernel will have no knowledge
		3858	about the newly added timer. By waking up the loop it will pick up any new
		3859	watchers in the next event loop iteration.
		3860
		3861	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3862
		3863	While the overhead of a callback that e.g. schedules a thread is small, it
		3864	is still an overhead. If you embed libev, and your main usage is with some
		3865	kind of threads or coroutines, you might want to customise libev so that
		3866	doesn't need callbacks anymore.
		3867
		3868	Imagine you have coroutines that you can switch to using a function
		3869	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3870	and that due to some magic, the currently active coroutine is stored in a
		3871	global called C<current_coro>. Then you can build your own "wait for libev
		3872	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3873	the differing C<;> conventions):
		3874
		3875	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3876	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3877
		3878	That means instead of having a C callback function, you store the
		3879	coroutine to switch to in each watcher, and instead of having libev call
		3880	your callback, you instead have it switch to that coroutine.
		3881
		3882	A coroutine might now wait for an event with a function called
		3883	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3884	matter when, or whether the watcher is active or not when this function is
		3885	called):
		3886
		3887	void
		3888	wait_for_event (ev_watcher *w)
		3889	{
		3890	ev_set_cb (w, current_coro);
		3891	switch_to (libev_coro);
		3892	}
		3893
		3894	That basically suspends the coroutine inside C<wait_for_event> and
		3895	continues the libev coroutine, which, when appropriate, switches back to
		3896	this or any other coroutine.
		3897
		3898	You can do similar tricks if you have, say, threads with an event queue -
		3899	instead of storing a coroutine, you store the queue object and instead of
		3900	switching to a coroutine, you push the watcher onto the queue and notify
		3901	any waiters.
		3902
		3903	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3904	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3905
		3906	// my_ev.h
		3907	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3908	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3909	#include "../libev/ev.h"
		3910
		3911	// my_ev.c
		3912	#define EV_H "my_ev.h"
		3913	#include "../libev/ev.c"
		3914
		3915	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3916	F<my_ev.c> into your project. When properly specifying include paths, you
		3917	can even use F<ev.h> as header file name directly.
2666		3918
2667		3919
2668	=head1 LIBEVENT EMULATION	3920	=head1 LIBEVENT EMULATION
2669		3921
2670	Libev offers a compatibility emulation layer for libevent. It cannot	3922	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	3923	emulate the internals of libevent, so here are some usage hints:
2672		3924
2673	=over 4	3925	=over 4
		3926
		3927	=item * Only the libevent-1.4.1-beta API is being emulated.
		3928
		3929	This was the newest libevent version available when libev was implemented,
		3930	and is still mostly unchanged in 2010.
2674		3931
2675	=item * Use it by including <event.h>, as usual.	3932	=item * Use it by including <event.h>, as usual.
2676		3933
2677	=item * The following members are fully supported: ev_base, ev_callback,	3934	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	3935	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3941	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3942	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3943	is an ev_pri field.
2687		3944
2688	=item * In libevent, the last base created gets the signals, in libev, the	3945	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3946	base that registered the signal gets the signals.
2690		3947
2691	=item * Other members are not supported.	3948	=item * Other members are not supported.
2692		3949
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3950	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3951	to use the libev header file and library.
2695		3952
2696	=back	3953	=back
2697		3954
2698	=head1 C++ SUPPORT	3955	=head1 C++ SUPPORT
		3956
		3957	=head2 C API
		3958
		3959	The normal C API should work fine when used from C++: both ev.h and the
		3960	libev sources can be compiled as C++. Therefore, code that uses the C API
		3961	will work fine.
		3962
		3963	Proper exception specifications might have to be added to callbacks passed
		3964	to libev: exceptions may be thrown only from watcher callbacks, all
		3965	other callbacks (allocator, syserr, loop acquire/release and periodic
		3966	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3967	()> specification. If you have code that needs to be compiled as both C
		3968	and C++ you can use the C<EV_THROW> macro for this:
		3969
		3970	static void
		3971	fatal_error (const char *msg) EV_THROW
		3972	{
		3973	perror (msg);
		3974	abort ();
		3975	}
		3976
		3977	...
		3978	ev_set_syserr_cb (fatal_error);
		3979
		3980	The only API functions that can currently throw exceptions are C<ev_run>,
		3981	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3982	because it runs cleanup watchers).
		3983
		3984	Throwing exceptions in watcher callbacks is only supported if libev itself
		3985	is compiled with a C++ compiler or your C and C++ environments allow
		3986	throwing exceptions through C libraries (most do).
		3987
		3988	=head2 C++ API
2699		3989
2700	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3990	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2701	you to use some convenience methods to start/stop watchers and also change	3991	you to use some convenience methods to start/stop watchers and also change
2702	the callback model to a model using method callbacks on objects.	3992	the callback model to a model using method callbacks on objects.
2703		3993
2704	To use it,	3994	To use it,
2705		3995
2706	#include <ev++.h>	3996	#include <ev++.h>
2707		3997
2708	This automatically includes F<ev.h> and puts all of its definitions (many	3998	This automatically includes F<ev.h> and puts all of its definitions (many
2709	of them macros) into the global namespace. All C++ specific things are	3999	of them macros) into the global namespace. All C++ specific things are
2710	put into the C<ev> namespace. It should support all the same embedding	4000	put into the C<ev> namespace. It should support all the same embedding
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	4003	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	4004	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	4005	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	4006	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		4007
2718	Currently, functions, and static and non-static member functions can be	4008	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	4009	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	4010	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	4011	you need support for other types of functors please contact the author
2722	it).	4012	(preferably after implementing it).
		4013
		4014	For all this to work, your C++ compiler either has to use the same calling
		4015	conventions as your C compiler (for static member functions), or you have
		4016	to embed libev and compile libev itself as C++.
2723		4017
2724	Here is a list of things available in the C<ev> namespace:	4018	Here is a list of things available in the C<ev> namespace:
2725		4019
2726	=over 4	4020	=over 4
2727		4021
…		…
2737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4031	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2738		4032
2739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4033	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2740	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4034	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2741	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4035	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2742	defines by many implementations.	4036	defined by many implementations.
2743		4037
2744	All of those classes have these methods:	4038	All of those classes have these methods:
2745		4039
2746	=over 4	4040	=over 4
2747		4041
2748	=item ev::TYPE::TYPE ()	4042	=item ev::TYPE::TYPE ()
2749		4043
2750	=item ev::TYPE::TYPE (struct ev_loop *)	4044	=item ev::TYPE::TYPE (loop)
2751		4045
2752	=item ev::TYPE::~TYPE	4046	=item ev::TYPE::~TYPE
2753		4047
2754	The constructor (optionally) takes an event loop to associate the watcher	4048	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	4049	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		4081
2788	myclass obj;	4082	myclass obj;
2789	ev::io iow;	4083	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	4084	iow.set <myclass, &myclass::io_cb> (&obj);
2791		4085
		4086	=item w->set (object *)
		4087
		4088	This is a variation of a method callback - leaving out the method to call
		4089	will default the method to C<operator ()>, which makes it possible to use
		4090	functor objects without having to manually specify the C<operator ()> all
		4091	the time. Incidentally, you can then also leave out the template argument
		4092	list.
		4093
		4094	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4095	int revents)>.
		4096
		4097	See the method-C<set> above for more details.
		4098
		4099	Example: use a functor object as callback.
		4100
		4101	struct myfunctor
		4102	{
		4103	void operator() (ev::io &w, int revents)
		4104	{
		4105	...
		4106	}
		4107	}
		4108
		4109	myfunctor f;
		4110
		4111	ev::io w;
		4112	w.set (&f);
		4113
2792	=item w->set<function> (void *data = 0)	4114	=item w->set<function> (void *data = 0)
2793		4115
2794	Also sets a callback, but uses a static method or plain function as	4116	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	4117	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	4118	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	4124	Example: Use a plain function as callback.
2803		4125
2804	static void io_cb (ev::io &w, int revents) { }	4126	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	4127	iow.set <io_cb> ();
2806		4128
2807	=item w->set (struct ev_loop *)	4129	=item w->set (loop)
2808		4130
2809	Associates a different C<struct ev_loop> with this watcher. You can only	4131	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	4132	do this when the watcher is inactive (and not pending either).
2811		4133
2812	=item w->set ([arguments])	4134	=item w->set ([arguments])
2813		4135
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4136	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4137	with the same arguments. Either this method or a suitable start method
2815	called at least once. Unlike the C counterpart, an active watcher gets	4138	must be called at least once. Unlike the C counterpart, an active watcher
2816	automatically stopped and restarted when reconfiguring it with this	4139	gets automatically stopped and restarted when reconfiguring it with this
2817	method.	4140	method.
		4141
		4142	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4143	clashing with the C<set (loop)> method.
2818		4144
2819	=item w->start ()	4145	=item w->start ()
2820		4146
2821	Starts the watcher. Note that there is no C<loop> argument, as the	4147	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	4148	constructor already stores the event loop.
2823		4149
		4150	=item w->start ([arguments])
		4151
		4152	Instead of calling C<set> and C<start> methods separately, it is often
		4153	convenient to wrap them in one call. Uses the same type of arguments as
		4154	the configure C<set> method of the watcher.
		4155
2824	=item w->stop ()	4156	=item w->stop ()
2825		4157
2826	Stops the watcher if it is active. Again, no C<loop> argument.	4158	Stops the watcher if it is active. Again, no C<loop> argument.
2827		4159
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4160	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		4172
2841	=back	4173	=back
2842		4174
2843	=back	4175	=back
2844		4176
2845	Example: Define a class with an IO and idle watcher, start one of them in	4177	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	4178	watchers in the constructor.
2847		4179
2848	class myclass	4180	class myclass
2849	{	4181	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	4182	ev::io io ; void io_cb (ev::io &w, int revents);
		4183	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		4185
2853	myclass (int fd)	4186	myclass (int fd)
2854	{	4187	{
2855	io .set <myclass, &myclass::io_cb > (this);	4188	io .set <myclass, &myclass::io_cb > (this);
		4189	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	4190	idle.set <myclass, &myclass::idle_cb> (this);
2857		4191
2858	io.start (fd, ev::READ);	4192	io.set (fd, ev::WRITE); // configure the watcher
		4193	io.start (); // start it whenever convenient
		4194
		4195	io2.start (fd, ev::READ); // set + start in one call
2859	}	4196	}
2860	};	4197	};
2861		4198
2862		4199
2863	=head1 OTHER LANGUAGE BINDINGS	4200	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	4219	L<http://software.schmorp.de/pkg/EV>.
2883		4220
2884	=item Python	4221	=item Python
2885		4222
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4223	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	4224	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		4225
2893	=item Ruby	4226	=item Ruby
2894		4227
2895	Tony Arcieri has written a ruby extension that offers access to a subset	4228	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	4229	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	4230	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	4231	L<http://rev.rubyforge.org/>.
2899		4232
		4233	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4234	makes rev work even on mingw.
		4235
		4236	=item Haskell
		4237
		4238	A haskell binding to libev is available at
		4239	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4240
2900	=item D	4241	=item D
2901		4242
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4243	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4244	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4245
		4246	=item Ocaml
		4247
		4248	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4249	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4250
		4251	=item Lua
		4252
		4253	Brian Maher has written a partial interface to libev for lua (at the
		4254	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4255	L<http://github.com/brimworks/lua-ev>.
		4256
		4257	=item Javascript
		4258
		4259	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4260
		4261	=item Others
		4262
		4263	There are others, and I stopped counting.
2904		4264
2905	=back	4265	=back
2906		4266
2907		4267
2908	=head1 MACRO MAGIC	4268	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4282	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4283	C<EV_A_> is used when other arguments are following. Example:
2924		4284
2925	ev_unref (EV_A);	4285	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4286	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4287	ev_run (EV_A_ 0);
2928		4288
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4289	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4290	which is often provided by the following macro.
2931		4291
2932	=item C<EV_P>, C<EV_P_>	4292	=item C<EV_P>, C<EV_P_>
…		…
2945	suitable for use with C<EV_A>.	4305	suitable for use with C<EV_A>.
2946		4306
2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4307	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2948		4308
2949	Similar to the other two macros, this gives you the value of the default	4309	Similar to the other two macros, this gives you the value of the default
2950	loop, if multiple loops are supported ("ev loop default").	4310	loop, if multiple loops are supported ("ev loop default"). The default loop
		4311	will be initialised if it isn't already initialised.
		4312
		4313	For non-multiplicity builds, these macros do nothing, so you always have
		4314	to initialise the loop somewhere.
2951		4315
2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4316	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2953		4317
2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4318	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2955	default loop has been initialised (C<UC> == unchecked). Their behaviour	4319	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2972	}	4336	}
2973		4337
2974	ev_check check;	4338	ev_check check;
2975	ev_check_init (&check, check_cb);	4339	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4340	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4341	ev_run (EV_DEFAULT_ 0);
2978		4342
2979	=head1 EMBEDDING	4343	=head1 EMBEDDING
2980		4344
2981	Libev can (and often is) directly embedded into host	4345	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4346	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4373
3010	#define EV_STANDALONE 1	4374	#define EV_STANDALONE 1
3011	#include "ev.h"	4375	#include "ev.h"
3012		4376
3013	Both header files and implementation files can be compiled with a C++	4377	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4378	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4379	as a bug).
3016		4380
3017	You need the following files in your source tree, or in a directory	4381	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4382	in your include path (e.g. in libev/ when using -Ilibev):
3019		4383
…		…
3062	libev.m4	4426	libev.m4
3063		4427
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4428	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4429
3066	Libev can be configured via a variety of preprocessor symbols you have to	4430	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4431	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4432	the absence of autoconf is documented for every option.
		4433
		4434	Symbols marked with "(h)" do not change the ABI, and can have different
		4435	values when compiling libev vs. including F<ev.h>, so it is permissible
		4436	to redefine them before including F<ev.h> without breaking compatibility
		4437	to a compiled library. All other symbols change the ABI, which means all
		4438	users of libev and the libev code itself must be compiled with compatible
		4439	settings.
3069		4440
3070	=over 4	4441	=over 4
3071		4442
		4443	=item EV_COMPAT3 (h)
		4444
		4445	Backwards compatibility is a major concern for libev. This is why this
		4446	release of libev comes with wrappers for the functions and symbols that
		4447	have been renamed between libev version 3 and 4.
		4448
		4449	You can disable these wrappers (to test compatibility with future
		4450	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4451	sources. This has the additional advantage that you can drop the C<struct>
		4452	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4453	typedef in that case.
		4454
		4455	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4456	and in some even more future version the compatibility code will be
		4457	removed completely.
		4458
3072	=item EV_STANDALONE	4459	=item EV_STANDALONE (h)
3073		4460
3074	Must always be C<1> if you do not use autoconf configuration, which	4461	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4462	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4463	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4464	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4465	F<event.h> that are not directly supported by the libev core alone.
3079		4466
		4467	In standalone mode, libev will still try to automatically deduce the
		4468	configuration, but has to be more conservative.
		4469
		4470	=item EV_USE_FLOOR
		4471
		4472	If defined to be C<1>, libev will use the C<floor ()> function for its
		4473	periodic reschedule calculations, otherwise libev will fall back on a
		4474	portable (slower) implementation. If you enable this, you usually have to
		4475	link against libm or something equivalent. Enabling this when the C<floor>
		4476	function is not available will fail, so the safe default is to not enable
		4477	this.
		4478
3080	=item EV_USE_MONOTONIC	4479	=item EV_USE_MONOTONIC
3081		4480
3082	If defined to be C<1>, libev will try to detect the availability of the	4481	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4482	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4483	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4484	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4485	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4486	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4487	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4488
3090	=item EV_USE_REALTIME	4489	=item EV_USE_REALTIME
3091		4490
3092	If defined to be C<1>, libev will try to detect the availability of the	4491	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4492	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4493	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4494	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4495	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4496	correctness. See the note about libraries in the description of
		4497	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4498	C<EV_USE_CLOCK_SYSCALL>.
		4499
		4500	=item EV_USE_CLOCK_SYSCALL
		4501
		4502	If defined to be C<1>, libev will try to use a direct syscall instead
		4503	of calling the system-provided C<clock_gettime> function. This option
		4504	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4505	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4506	programs needlessly. Using a direct syscall is slightly slower (in
		4507	theory), because no optimised vdso implementation can be used, but avoids
		4508	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4509	higher, as it simplifies linking (no need for C<-lrt>).
3098		4510
3099	=item EV_USE_NANOSLEEP	4511	=item EV_USE_NANOSLEEP
3100		4512
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4513	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4514	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4530
3119	=item EV_SELECT_USE_FD_SET	4531	=item EV_SELECT_USE_FD_SET
3120		4532
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4533	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4534	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4535	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4536	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4537	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4538	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4539	configures the maximum size of the C<fd_set>.
3128		4540
3129	=item EV_SELECT_IS_WINSOCKET	4541	=item EV_SELECT_IS_WINSOCKET
3130		4542
3131	When defined to C<1>, the select backend will assume that	4543	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4544	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4546	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4547	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4548	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4549	on win32. Should not be defined on non-win32 platforms.
3138		4550
3139	=item EV_FD_TO_WIN32_HANDLE	4551	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4552
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4553	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4554	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4555	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4556	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4557	in which case they can provide this function to map fds to socket handles.
		4558
		4559	=item EV_WIN32_HANDLE_TO_FD(handle)
		4560
		4561	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4562	using the standard C<_open_osfhandle> function. For programs implementing
		4563	their own fd to handle mapping, overwriting this function makes it easier
		4564	to do so. This can be done by defining this macro to an appropriate value.
		4565
		4566	=item EV_WIN32_CLOSE_FD(fd)
		4567
		4568	If programs implement their own fd to handle mapping on win32, then this
		4569	macro can be used to override the C<close> function, useful to unregister
		4570	file descriptors again. Note that the replacement function has to close
		4571	the underlying OS handle.
		4572
		4573	=item EV_USE_WSASOCKET
		4574
		4575	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4576	communication socket, which works better in some environments. Otherwise,
		4577	the normal C<socket> function will be used, which works better in other
		4578	environments.
3146		4579
3147	=item EV_USE_POLL	4580	=item EV_USE_POLL
3148		4581
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4582	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4583	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3186	If defined to be C<1>, libev will compile in support for the Linux inotify	4619	If defined to be C<1>, libev will compile in support for the Linux inotify
3187	interface to speed up C<ev_stat> watchers. Its actual availability will	4620	interface to speed up C<ev_stat> watchers. Its actual availability will
3188	be detected at runtime. If undefined, it will be enabled if the headers	4621	be detected at runtime. If undefined, it will be enabled if the headers
3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4622	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3190		4623
		4624	=item EV_NO_SMP
		4625
		4626	If defined to be C<1>, libev will assume that memory is always coherent
		4627	between threads, that is, threads can be used, but threads never run on
		4628	different cpus (or different cpu cores). This reduces dependencies
		4629	and makes libev faster.
		4630
		4631	=item EV_NO_THREADS
		4632
		4633	If defined to be C<1>, libev will assume that it will never be called from
		4634	different threads (that includes signal handlers), which is a stronger
		4635	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4636	libev faster.
		4637
3191	=item EV_ATOMIC_T	4638	=item EV_ATOMIC_T
3192		4639
3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4640	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3194	access is atomic with respect to other threads or signal contexts. No such	4641	access is atomic with respect to other threads or signal contexts. No
3195	type is easily found in the C language, so you can provide your own type	4642	such type is easily found in the C language, so you can provide your own
3196	that you know is safe for your purposes. It is used both for signal handler "locking"	4643	type that you know is safe for your purposes. It is used both for signal
3197	as well as for signal and thread safety in C<ev_async> watchers.	4644	handler "locking" as well as for signal and thread safety in C<ev_async>
		4645	watchers.
3198		4646
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4647	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4648	(from F<signal.h>), which is usually good enough on most platforms.
3201		4649
3202	=item EV_H	4650	=item EV_H (h)
3203		4651
3204	The name of the F<ev.h> header file used to include it. The default if	4652	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4653	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4654	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4655
3208	=item EV_CONFIG_H	4656	=item EV_CONFIG_H (h)
3209		4657
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4658	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4659	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4660	C<EV_H>, above.
3213		4661
3214	=item EV_EVENT_H	4662	=item EV_EVENT_H (h)
3215		4663
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4664	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4665	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4666
3219	=item EV_PROTOTYPES	4667	=item EV_PROTOTYPES (h)
3220		4668
3221	If defined to be C<0>, then F<ev.h> will not define any function	4669	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4670	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4671	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4672	around libev functions.
…		…
3229	will have the C<struct ev_loop *> as first argument, and you can create	4677	will have the C<struct ev_loop *> as first argument, and you can create
3230	additional independent event loops. Otherwise there will be no support	4678	additional independent event loops. Otherwise there will be no support
3231	for multiple event loops and there is no first event loop pointer	4679	for multiple event loops and there is no first event loop pointer
3232	argument. Instead, all functions act on the single default loop.	4680	argument. Instead, all functions act on the single default loop.
3233		4681
		4682	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4683	default loop when multiplicity is switched off - you always have to
		4684	initialise the loop manually in this case.
		4685
3234	=item EV_MINPRI	4686	=item EV_MINPRI
3235		4687
3236	=item EV_MAXPRI	4688	=item EV_MAXPRI
3237		4689
3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4690	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3246	fine.	4698	fine.
3247		4699
3248	If your embedding application does not need any priorities, defining these	4700	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4701	both to C<0> will save some memory and CPU.
3250		4702
3251	=item EV_PERIODIC_ENABLE	4703	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4704	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4705	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4706
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4707	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4708	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4709	is not. Disabling watcher types mainly saves code size.
3256		4710
3257	=item EV_IDLE_ENABLE	4711	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4712
3286	If you need to shave off some kilobytes of code at the expense of some	4713	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4714	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4715	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4716	that can be enabled on the platform.
		4717
		4718	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4719	with some broad features you want) and then selectively re-enable
		4720	additional parts you want, for example if you want everything minimal,
		4721	but multiple event loop support, async and child watchers and the poll
		4722	backend, use this:
		4723
		4724	#define EV_FEATURES 0
		4725	#define EV_MULTIPLICITY 1
		4726	#define EV_USE_POLL 1
		4727	#define EV_CHILD_ENABLE 1
		4728	#define EV_ASYNC_ENABLE 1
		4729
		4730	The actual value is a bitset, it can be a combination of the following
		4731	values (by default, all of these are enabled):
		4732
		4733	=over 4
		4734
		4735	=item C<1> - faster/larger code
		4736
		4737	Use larger code to speed up some operations.
		4738
		4739	Currently this is used to override some inlining decisions (enlarging the
		4740	code size by roughly 30% on amd64).
		4741
		4742	When optimising for size, use of compiler flags such as C<-Os> with
		4743	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4744	assertions.
		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
		4748
		4749	=item C<2> - faster/larger data structures
		4750
		4751	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4752	hash table sizes and so on. This will usually further increase code size
		4753	and can additionally have an effect on the size of data structures at
		4754	runtime.
		4755
		4756	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4757	(e.g. gcc with C<-Os>).
		4758
		4759	=item C<4> - full API configuration
		4760
		4761	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4762	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4763
		4764	=item C<8> - full API
		4765
		4766	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4767	details on which parts of the API are still available without this
		4768	feature, and do not complain if this subset changes over time.
		4769
		4770	=item C<16> - enable all optional watcher types
		4771
		4772	Enables all optional watcher types. If you want to selectively enable
		4773	only some watcher types other than I/O and timers (e.g. prepare,
		4774	embed, async, child...) you can enable them manually by defining
		4775	C<EV_watchertype_ENABLE> to C<1> instead.
		4776
		4777	=item C<32> - enable all backends
		4778
		4779	This enables all backends - without this feature, you need to enable at
		4780	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4781
		4782	=item C<64> - enable OS-specific "helper" APIs
		4783
		4784	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4785	default.
		4786
		4787	=back
		4788
		4789	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4790	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4791	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4792	watchers, timers and monotonic clock support.
		4793
		4794	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4795	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4796	your program might be left out as well - a binary starting a timer and an
		4797	I/O watcher then might come out at only 5Kb.
		4798
		4799	=item EV_API_STATIC
		4800
		4801	If this symbol is defined (by default it is not), then all identifiers
		4802	will have static linkage. This means that libev will not export any
		4803	identifiers, and you cannot link against libev anymore. This can be useful
		4804	when you embed libev, only want to use libev functions in a single file,
		4805	and do not want its identifiers to be visible.
		4806
		4807	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4808	wants to use libev.
		4809
		4810	This option only works when libev is compiled with a C compiler, as C++
		4811	doesn't support the required declaration syntax.
		4812
		4813	=item EV_AVOID_STDIO
		4814
		4815	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4816	functions (printf, scanf, perror etc.). This will increase the code size
		4817	somewhat, but if your program doesn't otherwise depend on stdio and your
		4818	libc allows it, this avoids linking in the stdio library which is quite
		4819	big.
		4820
		4821	Note that error messages might become less precise when this option is
		4822	enabled.
		4823
		4824	=item EV_NSIG
		4825
		4826	The highest supported signal number, +1 (or, the number of
		4827	signals): Normally, libev tries to deduce the maximum number of signals
		4828	automatically, but sometimes this fails, in which case it can be
		4829	specified. Also, using a lower number than detected (C<32> should be
		4830	good for about any system in existence) can save some memory, as libev
		4831	statically allocates some 12-24 bytes per signal number.
3290		4832
3291	=item EV_PID_HASHSIZE	4833	=item EV_PID_HASHSIZE
3292		4834
3293	C<ev_child> watchers use a small hash table to distribute workload by	4835	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4836	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4837	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4838	might want to increase this value (I<must> be a power of two).
3297		4839
3298	=item EV_INOTIFY_HASHSIZE	4840	=item EV_INOTIFY_HASHSIZE
3299		4841
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4842	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4843	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4844	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4845	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4846	power of two).
3305		4847
3306	=item EV_USE_4HEAP	4848	=item EV_USE_4HEAP
3307		4849
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4850	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4851	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4852	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4853	faster performance with many (thousands) of watchers.
3312		4854
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4855	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4856	will be C<0>.
3315		4857
3316	=item EV_HEAP_CACHE_AT	4858	=item EV_HEAP_CACHE_AT
3317		4859
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4860	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4861	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4862	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4863	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4864	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4865	noticeably with many (hundreds) of watchers.
3324		4866
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4867	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4868	will be C<0>.
3327		4869
3328	=item EV_VERIFY	4870	=item EV_VERIFY
3329		4871
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4872	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4873	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4874	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4875	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4876	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4877	verification code will be called very frequently, which will slow down
3336	libev considerably.	4878	libev considerably.
3337		4879
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4880	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4881	will be C<0>.
3340		4882
3341	=item EV_COMMON	4883	=item EV_COMMON
3342		4884
3343	By default, all watchers have a C<void *data> member. By redefining	4885	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4886	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4887	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4888	though, and it must be identical each time.
3347		4889
3348	For example, the perl EV module uses something like this:	4890	For example, the perl EV module uses something like this:
3349		4891
…		…
3402	file.	4944	file.
3403		4945
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4946	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4947	that everybody includes and which overrides some configure choices:
3406		4948
3407	#define EV_MINIMAL 1	4949	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4950	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4951	#define EV_PREPARE_ENABLE 1
		4952	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4953	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4954	#define EV_CHILD_ENABLE 1
		4955	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4956	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4957
3417	#include "ev++.h"	4958	#include "ev++.h"
3418		4959
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4961
3421	#include "ev_cpp.h"	4962	#include "ev_cpp.h"
3422	#include "ev.c"	4963	#include "ev.c"
3423		4964
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4965	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		4966
3426	=head2 THREADS AND COROUTINES	4967	=head2 THREADS AND COROUTINES
3427		4968
3428	=head3 THREADS	4969	=head3 THREADS
3429		4970
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	5021	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	5022	watcher callback into the event loop interested in the signal.
3482		5023
3483	=back	5024	=back
3484		5025
		5026	See also L</THREAD LOCKING EXAMPLE>.
		5027
3485	=head3 COROUTINES	5028	=head3 COROUTINES
3486		5029
3487	Libev is very accommodating to coroutines ("cooperative threads"):	5030	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	5031	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5032	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	5033	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	5034	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	5035	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		5036
3494	Care has been taken to ensure that libev does not keep local state inside	5037	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5038	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	5039	they do not call any callbacks.
3497		5040
3498	=head2 COMPILER WARNINGS	5041	=head2 COMPILER WARNINGS
3499		5042
3500	Depending on your compiler and compiler settings, you might get no or a	5043	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	5044	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	5054	maintainable.
3512		5055
3513	And of course, some compiler warnings are just plain stupid, or simply	5056	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	5057	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	5058	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	5059	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	5060	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	5061	such buggy versions.
3519		5062
3520	While libev is written to generate as few warnings as possible,	5063	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	5064	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	5078	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	5079	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	5080	==2274== still reachable: 256 bytes in 1 blocks.
3538		5081
3539	Then there is no memory leak, just as memory accounted to global variables	5082	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	5083	is not a memleak - the memory is still being referenced, and didn't leak.
3541		5084
3542	Similarly, under some circumstances, valgrind might report kernel bugs	5085	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5086	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	5087	although an acceptable workaround has been found here), or it might be
3545	confused.	5088	confused.
…		…
3557	I suggest using suppression lists.	5100	I suggest using suppression lists.
3558		5101
3559		5102
3560	=head1 PORTABILITY NOTES	5103	=head1 PORTABILITY NOTES
3561		5104
		5105	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5106
		5107	GNU/Linux is the only common platform that supports 64 bit file/large file
		5108	interfaces but I<disables> them by default.
		5109
		5110	That means that libev compiled in the default environment doesn't support
		5111	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5112
		5113	Unfortunately, many programs try to work around this GNU/Linux issue
		5114	by enabling the large file API, which makes them incompatible with the
		5115	standard libev compiled for their system.
		5116
		5117	Likewise, libev cannot enable the large file API itself as this would
		5118	suddenly make it incompatible to the default compile time environment,
		5119	i.e. all programs not using special compile switches.
		5120
		5121	=head2 OS/X AND DARWIN BUGS
		5122
		5123	The whole thing is a bug if you ask me - basically any system interface
		5124	you touch is broken, whether it is locales, poll, kqueue or even the
		5125	OpenGL drivers.
		5126
		5127	=head3 C<kqueue> is buggy
		5128
		5129	The kqueue syscall is broken in all known versions - most versions support
		5130	only sockets, many support pipes.
		5131
		5132	Libev tries to work around this by not using C<kqueue> by default on this
		5133	rotten platform, but of course you can still ask for it when creating a
		5134	loop - embedding a socket-only kqueue loop into a select-based one is
		5135	probably going to work well.
		5136
		5137	=head3 C<poll> is buggy
		5138
		5139	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5140	implementation by something calling C<kqueue> internally around the 10.5.6
		5141	release, so now C<kqueue> I<and> C<poll> are broken.
		5142
		5143	Libev tries to work around this by not using C<poll> by default on
		5144	this rotten platform, but of course you can still ask for it when creating
		5145	a loop.
		5146
		5147	=head3 C<select> is buggy
		5148
		5149	All that's left is C<select>, and of course Apple found a way to fuck this
		5150	one up as well: On OS/X, C<select> actively limits the number of file
		5151	descriptors you can pass in to 1024 - your program suddenly crashes when
		5152	you use more.
		5153
		5154	There is an undocumented "workaround" for this - defining
		5155	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5156	work on OS/X.
		5157
		5158	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5159
		5160	=head3 C<errno> reentrancy
		5161
		5162	The default compile environment on Solaris is unfortunately so
		5163	thread-unsafe that you can't even use components/libraries compiled
		5164	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5165	defined by default. A valid, if stupid, implementation choice.
		5166
		5167	If you want to use libev in threaded environments you have to make sure
		5168	it's compiled with C<_REENTRANT> defined.
		5169
		5170	=head3 Event port backend
		5171
		5172	The scalable event interface for Solaris is called "event
		5173	ports". Unfortunately, this mechanism is very buggy in all major
		5174	releases. If you run into high CPU usage, your program freezes or you get
		5175	a large number of spurious wakeups, make sure you have all the relevant
		5176	and latest kernel patches applied. No, I don't know which ones, but there
		5177	are multiple ones to apply, and afterwards, event ports actually work
		5178	great.
		5179
		5180	If you can't get it to work, you can try running the program by setting
		5181	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5182	C<select> backends.
		5183
		5184	=head2 AIX POLL BUG
		5185
		5186	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5187	this by trying to avoid the poll backend altogether (i.e. it's not even
		5188	compiled in), which normally isn't a big problem as C<select> works fine
		5189	with large bitsets on AIX, and AIX is dead anyway.
		5190
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5191	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5192
		5193	=head3 General issues
3563		5194
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5195	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	5196	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	5197	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5198	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	5199	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	5200	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5201	as every compiler comes with a slightly differently broken/incompatible
		5202	environment.
3570		5203
3571	Lifting these limitations would basically require the full	5204	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	5205	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	5206	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	5207	also that glib is the slowest event library known to man).
3575		5208
3576	There is no supported compilation method available on windows except	5209	There is no supported compilation method available on windows except
3577	embedding it into other applications.	5210	embedding it into other applications.
		5211
		5212	Sensible signal handling is officially unsupported by Microsoft - libev
		5213	tries its best, but under most conditions, signals will simply not work.
3578		5214
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	5215	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	5216	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	5217	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	5218	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	5223	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	5224	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	5225	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	5226	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	5227	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	5228	(due to Microsoft monopoly games).
3593		5229
3594	A typical way to use libev under windows is to embed it (see the embedding	5230	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	5231	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	5232	of F<ev.h>:
3597		5233
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	5240	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		5241
3606	#include "evwrap.h"	5242	#include "evwrap.h"
3607	#include "ev.c"	5243	#include "ev.c"
3608		5244
3609	=over 4
3610
3611	=item The winsocket select function	5245	=head3 The winsocket C<select> function
3612		5246
3613	The winsocket C<select> function doesn't follow POSIX in that it	5247	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	5248	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	5249	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	5250	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5259	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		5260
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	5261	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	5262	complexity in the O(n²) range when using win32.
3629		5263
3630	=item Limited number of file descriptors	5264	=head3 Limited number of file descriptors
3631		5265
3632	Windows has numerous arbitrary (and low) limits on things.	5266	Windows has numerous arbitrary (and low) limits on things.
3633		5267
3634	Early versions of winsocket's select only supported waiting for a maximum	5268	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	5269	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	5270	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	5271	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	5272	previous thread in each. Sounds great!).
3639		5273
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5274	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	5275	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	5276	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	5277	other interpreters do their own select emulation on windows).
3644		5278
3645	Another limit is the number of file descriptors in the Microsoft runtime	5279	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5280	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	5281	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5282	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	5283	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	5284	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	5285	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	5286	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	5287	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		5288
3659	=head2 PORTABILITY REQUIREMENTS	5289	=head2 PORTABILITY REQUIREMENTS
3660		5290
3661	In addition to a working ISO-C implementation and of course the	5291	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	5292	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	5299	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	5300	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	5301	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	5302	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	5303	calls them using an C<ev_watcher *> internally.
		5304
		5305	=item pointer accesses must be thread-atomic
		5306
		5307	Accessing a pointer value must be atomic, it must both be readable and
		5308	writable in one piece - this is the case on all current architectures.
3674		5309
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	5310	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		5311
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	5312	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5313	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3687	thread" or will block signals process-wide, both behaviours would	5322	thread" or will block signals process-wide, both behaviours would
3688	be compatible with libev. Interaction between C<sigprocmask> and	5323	be compatible with libev. Interaction between C<sigprocmask> and
3689	C<pthread_sigmask> could complicate things, however.	5324	C<pthread_sigmask> could complicate things, however.
3690		5325
3691	The most portable way to handle signals is to block signals in all threads	5326	The most portable way to handle signals is to block signals in all threads
3692	except the initial one, and run the default loop in the initial thread as	5327	except the initial one, and run the signal handling loop in the initial
3693	well.	5328	thread as well.
3694		5329
3695	=item C<long> must be large enough for common memory allocation sizes	5330	=item C<long> must be large enough for common memory allocation sizes
3696		5331
3697	To improve portability and simplify its API, libev uses C<long> internally	5332	To improve portability and simplify its API, libev uses C<long> internally
3698	instead of C<size_t> when allocating its data structures. On non-POSIX	5333	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3701	watchers.	5336	watchers.
3702		5337
3703	=item C<double> must hold a time value in seconds with enough accuracy	5338	=item C<double> must hold a time value in seconds with enough accuracy
3704		5339
3705	The type C<double> is used to represent timestamps. It is required to	5340	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5341	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5342	good enough for at least into the year 4000 with millisecond accuracy
		5343	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5344	implementations using IEEE 754, which is basically all existing ones.
		5345
		5346	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5347	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5348	is either obsolete or somebody patched it to use C<long double> or
		5349	something like that, just kidding).
3709		5350
3710	=back	5351	=back
3711		5352
3712	If you know of other additional requirements drop me a note.	5353	If you know of other additional requirements drop me a note.
3713		5354
…		…
3775	=item Processing ev_async_send: O(number_of_async_watchers)	5416	=item Processing ev_async_send: O(number_of_async_watchers)
3776		5417
3777	=item Processing signals: O(max_signal_number)	5418	=item Processing signals: O(max_signal_number)
3778		5419
3779	Sending involves a system call I<iff> there were no other C<ev_async_send>	5420	Sending involves a system call I<iff> there were no other C<ev_async_send>
3780	calls in the current loop iteration. Checking for async and signal events	5421	calls in the current loop iteration and the loop is currently
		5422	blocked. Checking for async and signal events involves iterating over all
3781	involves iterating over all running async watchers or all signal numbers.	5423	running async watchers or all signal numbers.
3782		5424
3783	=back	5425	=back
3784		5426
3785		5427
		5428	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5429
		5430	The major version 4 introduced some incompatible changes to the API.
		5431
		5432	At the moment, the C<ev.h> header file provides compatibility definitions
		5433	for all changes, so most programs should still compile. The compatibility
		5434	layer might be removed in later versions of libev, so better update to the
		5435	new API early than late.
		5436
		5437	=over 4
		5438
		5439	=item C<EV_COMPAT3> backwards compatibility mechanism
		5440
		5441	The backward compatibility mechanism can be controlled by
		5442	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5443	section.
		5444
		5445	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5446
		5447	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5448
		5449	ev_loop_destroy (EV_DEFAULT_UC);
		5450	ev_loop_fork (EV_DEFAULT);
		5451
		5452	=item function/symbol renames
		5453
		5454	A number of functions and symbols have been renamed:
		5455
		5456	ev_loop => ev_run
		5457	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5458	EVLOOP_ONESHOT => EVRUN_ONCE
		5459
		5460	ev_unloop => ev_break
		5461	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5462	EVUNLOOP_ONE => EVBREAK_ONE
		5463	EVUNLOOP_ALL => EVBREAK_ALL
		5464
		5465	EV_TIMEOUT => EV_TIMER
		5466
		5467	ev_loop_count => ev_iteration
		5468	ev_loop_depth => ev_depth
		5469	ev_loop_verify => ev_verify
		5470
		5471	Most functions working on C<struct ev_loop> objects don't have an
		5472	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5473	associated constants have been renamed to not collide with the C<struct
		5474	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5475	as all other watcher types. Note that C<ev_loop_fork> is still called
		5476	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5477	typedef.
		5478
		5479	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5480
		5481	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5482	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5483	and work, but the library code will of course be larger.
		5484
		5485	=back
		5486
		5487
		5488	=head1 GLOSSARY
		5489
		5490	=over 4
		5491
		5492	=item active
		5493
		5494	A watcher is active as long as it has been started and not yet stopped.
		5495	See L</WATCHER STATES> for details.
		5496
		5497	=item application
		5498
		5499	In this document, an application is whatever is using libev.
		5500
		5501	=item backend
		5502
		5503	The part of the code dealing with the operating system interfaces.
		5504
		5505	=item callback
		5506
		5507	The address of a function that is called when some event has been
		5508	detected. Callbacks are being passed the event loop, the watcher that
		5509	received the event, and the actual event bitset.
		5510
		5511	=item callback/watcher invocation
		5512
		5513	The act of calling the callback associated with a watcher.
		5514
		5515	=item event
		5516
		5517	A change of state of some external event, such as data now being available
		5518	for reading on a file descriptor, time having passed or simply not having
		5519	any other events happening anymore.
		5520
		5521	In libev, events are represented as single bits (such as C<EV_READ> or
		5522	C<EV_TIMER>).
		5523
		5524	=item event library
		5525
		5526	A software package implementing an event model and loop.
		5527
		5528	=item event loop
		5529
		5530	An entity that handles and processes external events and converts them
		5531	into callback invocations.
		5532
		5533	=item event model
		5534
		5535	The model used to describe how an event loop handles and processes
		5536	watchers and events.
		5537
		5538	=item pending
		5539
		5540	A watcher is pending as soon as the corresponding event has been
		5541	detected. See L</WATCHER STATES> for details.
		5542
		5543	=item real time
		5544
		5545	The physical time that is observed. It is apparently strictly monotonic :)
		5546
		5547	=item wall-clock time
		5548
		5549	The time and date as shown on clocks. Unlike real time, it can actually
		5550	be wrong and jump forwards and backwards, e.g. when you adjust your
		5551	clock.
		5552
		5553	=item watcher
		5554
		5555	A data structure that describes interest in certain events. Watchers need
		5556	to be started (attached to an event loop) before they can receive events.
		5557
		5558	=back
		5559
3786	=head1 AUTHOR	5560	=head1 AUTHOR
3787		5561
3788	Marc Lehmann <libev@schmorp.de>.	5562	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5563	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3789		5564

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