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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
21	static void	25	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	26	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	27	{
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_ struct 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	struct 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
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	134	this argument.
110		135
111	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
112		137
113	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
119	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	146	time differences (e.g. delays) throughout libev.
121		147
122	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
123		149
124	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	151	and internal errors (bugs).
…		…
149		175
150	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
151		177
152	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
155		182
156	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
157		184
158	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
160	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
161		194
162	=item int ev_version_major ()	195	=item int ev_version_major ()
163		196
164	=item int ev_version_minor ()	197	=item int ev_version_minor ()
165		198
…		…
176	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	211	not a problem.
179		212
180	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
182		216
183	assert (("libev version mismatch",	217	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
186		220
…		…
197	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
199		233
200	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
201		235
202	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
208		243
209	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
210		245
211	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
216		251
217	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
218		253
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		255
221	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	285	}
251		286
252	...	287	...
253	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
254		289
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		291
257	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	307	}
273		308
274	...	309	...
275	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
276		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
277	=back	325	=back
278		326
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		328
281	An event loop is described by a C<struct ev_loop *>. The 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
…		…
344	flag.	422	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.
348		426
		427	=item C<EVFLAG_NOINOTIFY>
		428
		429	When this flag is specified, then libev will not attempt to use the
		430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		431	testing, this flag can be useful to conserve inotify file descriptors, as
		432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		433
		434	=item C<EVFLAG_SIGNALFD>
		435
		436	When this flag is specified, then libev will attempt to use the
		437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		438	delivers signals synchronously, which makes it both faster and might make
		439	it possible to get the queued signal data. It can also simplify signal
		440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
		442
		443	Signalfd will not be used by default as this changes your signal mask, and
		444	there are a lot of shoddy libraries and programs (glib's threadpool for
		445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
		461
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,
353	but if that fails, expect a fairly low limit on the number of fds when	466	but if that fails, expect a fairly low limit on the number of fds when
…		…
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 to
549	to reinitialise the kernel state for backends that have one. Despite the	688	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	689	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	690	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	691	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	692
		693	Again, you I<have> to call it on I<any> loop that you want to re-use after
		694	a fork, I<even if you do not plan to use the loop in the parent>. This is
		695	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		696	during fork.
554		697
555	On the other hand, you only need to call this function in the child	698	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	699	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	700	you just fork+exec or create a new loop in the child, you don't have to
		701	call it at all (in fact, C<epoll> is so badly broken that it makes a
		702	difference, but libev will usually detect this case on its own and do a
		703	costly reset of the backend).
558		704
559	The function itself is quite fast and it's usually not a problem to call	705	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	706	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		707
		708	Example: Automate calling C<ev_loop_fork> on the default loop when
		709	using pthreads.
		710
		711	static void
		712	post_fork_child (void)
		713	{
		714	ev_loop_fork (EV_DEFAULT);
		715	}
		716
		717	...
563	pthread_atfork (0, 0, ev_default_fork);	718	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		719
572	=item int ev_is_default_loop (loop)	720	=item int ev_is_default_loop (loop)
573		721
574	Returns true when the given loop is, in fact, the default loop, and false	722	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	723	otherwise.
576		724
577	=item unsigned int ev_loop_count (loop)	725	=item unsigned int ev_iteration (loop)
578		726
579	Returns the count of loop iterations for the loop, which is identical to	727	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	728	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	729	and happily wraps around with enough iterations.
582		730
583	This value can sometimes be useful as a generation counter of sorts (it	731	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	732	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	733	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		734	prepare and check phases.
		735
		736	=item unsigned int ev_depth (loop)
		737
		738	Returns the number of times C<ev_run> was entered minus the number of
		739	times C<ev_run> was exited normally, in other words, the recursion depth.
		740
		741	Outside C<ev_run>, this number is zero. In a callback, this number is
		742	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		743	in which case it is higher.
		744
		745	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		746	throwing an exception etc.), doesn't count as "exit" - consider this
		747	as a hint to avoid such ungentleman-like behaviour unless it's really
		748	convenient, in which case it is fully supported.
586		749
587	=item unsigned int ev_backend (loop)	750	=item unsigned int ev_backend (loop)
588		751
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	752	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	753	use.
…		…
599		762
600	=item ev_now_update (loop)	763	=item ev_now_update (loop)
601		764
602	Establishes the current time by querying the kernel, updating the time	765	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	766	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	767	is usually done automatically within C<ev_run ()>.
605		768
606	This function is rarely useful, but when some event callback runs for a	769	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	770	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	771	the current time is a good idea.
609		772
610	See also "The special problem of time updates" in the C<ev_timer> section.	773	See also L</The special problem of time updates> in the C<ev_timer> section.
611		774
		775	=item ev_suspend (loop)
		776
		777	=item ev_resume (loop)
		778
		779	These two functions suspend and resume an event loop, for use when the
		780	loop is not used for a while and timeouts should not be processed.
		781
		782	A typical use case would be an interactive program such as a game: When
		783	the user presses C<^Z> to suspend the game and resumes it an hour later it
		784	would be best to handle timeouts as if no time had actually passed while
		785	the program was suspended. This can be achieved by calling C<ev_suspend>
		786	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		787	C<ev_resume> directly afterwards to resume timer processing.
		788
		789	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		790	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		791	will be rescheduled (that is, they will lose any events that would have
		792	occurred while suspended).
		793
		794	After calling C<ev_suspend> you B<must not> call I<any> function on the
		795	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		796	without a previous call to C<ev_suspend>.
		797
		798	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		799	event loop time (see C<ev_now_update>).
		800
612	=item ev_loop (loop, int flags)	801	=item bool ev_run (loop, int flags)
613		802
614	Finally, this is it, the event handler. This function usually is called	803	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	804	after you have initialised all your watchers and you want to start
616	events.	805	handling events. It will ask the operating system for any new events, call
		806	the watcher callbacks, and then repeat the whole process indefinitely: This
		807	is why event loops are called I<loops>.
617		808
618	If the flags argument is specified as C<0>, it will not return until	809	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	810	until either no event watchers are active anymore or C<ev_break> was
		811	called.
620		812
		813	The return value is false if there are no more active watchers (which
		814	usually means "all jobs done" or "deadlock"), and true in all other cases
		815	(which usually means " you should call C<ev_run> again").
		816
621	Please note that an explicit C<ev_unloop> is usually better than	817	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	818	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	819	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	820	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	821	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	822	beauty.
627		823
		824	This function is I<mostly> exception-safe - you can break out of a
		825	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		826	exception and so on. This does not decrement the C<ev_depth> value, nor
		827	will it clear any outstanding C<EVBREAK_ONE> breaks.
		828
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	829	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	830	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	831	block your process in case there are no events and will return after one
631	the loop.	832	iteration of the loop. This is sometimes useful to poll and handle new
		833	events while doing lengthy calculations, to keep the program responsive.
632		834
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	835	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	836	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	837	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	838	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	839	user-registered callback will be called), and will return after one
638	iteration of the loop.	840	iteration of the loop.
639		841
640	This is useful if you are waiting for some external event in conjunction	842	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	843	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	844	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	845	usually a better approach for this kind of thing.
644		846
645	Here are the gory details of what C<ev_loop> does:	847	Here are the gory details of what C<ev_run> does (this is for your
		848	understanding, not a guarantee that things will work exactly like this in
		849	future versions):
646		850
		851	- Increment loop depth.
		852	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	853	- Before the first iteration, call any pending watchers.
		854	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	855	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	856	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	857	- Queue and call all prepare watchers.
		858	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	859	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	860	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	861	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	862	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	863	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	864	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	865	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	866	- Sleep if the I/O and timer collect interval say so.
		867	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	868	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	869	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	870	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	871	- Queue all expired timers.
663	- Queue all expired periodics.	872	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	873	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	874	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	875	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	876	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	877	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	878	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	879	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	880	continue with step LOOP.
		881	FINISH:
		882	- Reset the ev_break status iff it was EVBREAK_ONE.
		883	- Decrement the loop depth.
		884	- Return.
672		885
673	Example: Queue some jobs and then loop until no events are outstanding	886	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	887	anymore.
675		888
676	... queue jobs here, make sure they register event watchers as long	889	... 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..)	890	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	891	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	892	... jobs done or somebody called break. yeah!
680		893
681	=item ev_unloop (loop, how)	894	=item ev_break (loop, how)
682		895
683	Can be used to make a call to C<ev_loop> return early (but only after it	896	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	897	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	898	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	899	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		900
688	This "unloop state" will be cleared when entering C<ev_loop> again.	901	This "break state" will be cleared on the next call to C<ev_run>.
689		902
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	903	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		904	which case it will have no effect.
691		905
692	=item ev_ref (loop)	906	=item ev_ref (loop)
693		907
694	=item ev_unref (loop)	908	=item ev_unref (loop)
695		909
696	Ref/unref can be used to add or remove a reference count on the event	910	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	911	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	912	count is nonzero, C<ev_run> will not return on its own.
699		913
700	If you have a watcher you never unregister that should not keep C<ev_loop>	914	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	915	unregister, but that nevertheless should not keep C<ev_run> from
		916	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	917	before stopping it.
703		918
704	As an example, libev itself uses this for its internal signal pipe: It is	919	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	920	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	921	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	922	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>	923	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,	924	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	925	before, respectively. Note also that libev might stop watchers itself
		926	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		927	in the callback).
711		928
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	929	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	930	running when nothing else is active.
714		931
715	struct ev_signal exitsig;	932	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	933	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	934	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	935	ev_unref (loop);
719		936
720	Example: For some weird reason, unregister the above signal handler again.	937	Example: For some weird reason, unregister the above signal handler again.
721		938
722	ev_ref (loop);	939	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	940	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	960	overhead for the actual polling but can deliver many events at once.
744		961
745	By setting a higher I<io collect interval> you allow libev to spend more	962	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	963	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	964	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	965	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	966	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		967	sleep time ensures that libev will not poll for I/O events more often then
		968	once per this interval, on average (as long as the host time resolution is
		969	good enough).
750		970
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	971	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	972	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	973	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	974	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		976
757	Many (busy) programs can usually benefit by setting the I/O collect	977	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	978	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	979	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>,	980	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.	981	as this approaches the timing granularity of most systems. Note that if
		982	you do transactions with the outside world and you can't increase the
		983	parallelity, then this setting will limit your transaction rate (if you
		984	need to poll once per transaction and the I/O collect interval is 0.01,
		985	then you can't do more than 100 transactions per second).
762		986
763	Setting the I<timeout collect interval> can improve the opportunity for	987	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	988	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	989	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	990	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	991	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	992	they fire on, say, one-second boundaries only.
769		993
		994	Example: we only need 0.1s timeout granularity, and we wish not to poll
		995	more often than 100 times per second:
		996
		997	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		998	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		999
		1000	=item ev_invoke_pending (loop)
		1001
		1002	This call will simply invoke all pending watchers while resetting their
		1003	pending state. Normally, C<ev_run> does this automatically when required,
		1004	but when overriding the invoke callback this call comes handy. This
		1005	function can be invoked from a watcher - this can be useful for example
		1006	when you want to do some lengthy calculation and want to pass further
		1007	event handling to another thread (you still have to make sure only one
		1008	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1009
		1010	=item int ev_pending_count (loop)
		1011
		1012	Returns the number of pending watchers - zero indicates that no watchers
		1013	are pending.
		1014
		1015	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1016
		1017	This overrides the invoke pending functionality of the loop: Instead of
		1018	invoking all pending watchers when there are any, C<ev_run> will call
		1019	this callback instead. This is useful, for example, when you want to
		1020	invoke the actual watchers inside another context (another thread etc.).
		1021
		1022	If you want to reset the callback, use C<ev_invoke_pending> as new
		1023	callback.
		1024
		1025	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1026
		1027	Sometimes you want to share the same loop between multiple threads. This
		1028	can be done relatively simply by putting mutex_lock/unlock calls around
		1029	each call to a libev function.
		1030
		1031	However, C<ev_run> can run an indefinite time, so it is not feasible
		1032	to wait for it to return. One way around this is to wake up the event
		1033	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1034	I<release> and I<acquire> callbacks on the loop.
		1035
		1036	When set, then C<release> will be called just before the thread is
		1037	suspended waiting for new events, and C<acquire> is called just
		1038	afterwards.
		1039
		1040	Ideally, C<release> will just call your mutex_unlock function, and
		1041	C<acquire> will just call the mutex_lock function again.
		1042
		1043	While event loop modifications are allowed between invocations of
		1044	C<release> and C<acquire> (that's their only purpose after all), no
		1045	modifications done will affect the event loop, i.e. adding watchers will
		1046	have no effect on the set of file descriptors being watched, or the time
		1047	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1048	to take note of any changes you made.
		1049
		1050	In theory, threads executing C<ev_run> will be async-cancel safe between
		1051	invocations of C<release> and C<acquire>.
		1052
		1053	See also the locking example in the C<THREADS> section later in this
		1054	document.
		1055
		1056	=item ev_set_userdata (loop, void *data)
		1057
		1058	=item void *ev_userdata (loop)
		1059
		1060	Set and retrieve a single C<void *> associated with a loop. When
		1061	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1062	C<0>.
		1063
		1064	These two functions can be used to associate arbitrary data with a loop,
		1065	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1066	C<acquire> callbacks described above, but of course can be (ab-)used for
		1067	any other purpose as well.
		1068
770	=item ev_loop_verify (loop)	1069	=item ev_verify (loop)
771		1070
772	This function only does something when C<EV_VERIFY> support has been	1071	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1072	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1073	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	1074	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1075	error and call C<abort ()>.
777		1076
778	This can be used to catch bugs inside libev itself: under normal	1077	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1081	=back
783		1082
784		1083
785	=head1 ANATOMY OF A WATCHER	1084	=head1 ANATOMY OF A WATCHER
786		1085
		1086	In the following description, uppercase C<TYPE> in names stands for the
		1087	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1088	watchers and C<ev_io_start> for I/O watchers.
		1089
787	A watcher is a structure that you create and register to record your	1090	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1091	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1092	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1093	for that:
790		1094
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1095	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1096	{
793	ev_io_stop (w);	1097	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1098	ev_break (loop, EVBREAK_ALL);
795	}	1099	}
796		1100
797	struct ev_loop *loop = ev_default_loop (0);	1101	struct ev_loop *loop = ev_default_loop (0);
		1102
798	struct ev_io stdin_watcher;	1103	ev_io stdin_watcher;
		1104
799	ev_init (&stdin_watcher, my_cb);	1105	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1106	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1107	ev_io_start (loop, &stdin_watcher);
		1108
802	ev_loop (loop, 0);	1109	ev_run (loop, 0);
803		1110
804	As you can see, you are responsible for allocating the memory for your	1111	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1112	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1113	stack).
807		1114
		1115	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1116	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1117
808	Each watcher structure must be initialised by a call to C<ev_init	1118	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1119	*, 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	1120	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	1121	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1122	and/or writable).
813		1123
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1124	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	1125	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	1126	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1127	ev_TYPE_init (watcher *, callback, ...) >>.
818		1128
819	To make the watcher actually watch out for events, you have to start it	1129	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	1130	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	1131	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1132	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1133
824	As long as your watcher is active (has been started but not stopped) you	1134	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	1135	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1136	reinitialise it or call its C<ev_TYPE_set> macro.
827		1137
828	Each and every callback receives the event loop pointer as first, the	1138	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	1139	registered watcher structure as second, and a bitset of received events as
830	third argument.	1140	third argument.
831		1141
…		…
840	=item C<EV_WRITE>	1150	=item C<EV_WRITE>
841		1151
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1152	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1153	writable.
844		1154
845	=item C<EV_TIMEOUT>	1155	=item C<EV_TIMER>
846		1156
847	The C<ev_timer> watcher has timed out.	1157	The C<ev_timer> watcher has timed out.
848		1158
849	=item C<EV_PERIODIC>	1159	=item C<EV_PERIODIC>
850		1160
…		…
868		1178
869	=item C<EV_PREPARE>	1179	=item C<EV_PREPARE>
870		1180
871	=item C<EV_CHECK>	1181	=item C<EV_CHECK>
872		1182
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1183	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
874	to gather new events, and all C<ev_check> watchers are invoked just after	1184	gather new events, and all C<ev_check> watchers are queued (not invoked)
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1185	just after C<ev_run> has gathered them, but before it queues any callbacks
		1186	for any received events. That means C<ev_prepare> watchers are the last
		1187	watchers invoked before the event loop sleeps or polls for new events, and
		1188	C<ev_check> watchers will be invoked before any other watchers of the same
		1189	or lower priority within an event loop iteration.
		1190
876	received events. Callbacks of both watcher types can start and stop as	1191	Callbacks of both watcher types can start and stop as many watchers as
877	many watchers as they want, and all of them will be taken into account	1192	they want, and all of them will be taken into account (for example, a
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1193	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
879	C<ev_loop> from blocking).	1194	blocking).
880		1195
881	=item C<EV_EMBED>	1196	=item C<EV_EMBED>
882		1197
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1198	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1199
885	=item C<EV_FORK>	1200	=item C<EV_FORK>
886		1201
887	The event loop has been resumed in the child process after fork (see	1202	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1203	C<ev_fork>).
889		1204
		1205	=item C<EV_CLEANUP>
		1206
		1207	The event loop is about to be destroyed (see C<ev_cleanup>).
		1208
890	=item C<EV_ASYNC>	1209	=item C<EV_ASYNC>
891		1210
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1211	The given async watcher has been asynchronously notified (see C<ev_async>).
		1212
		1213	=item C<EV_CUSTOM>
		1214
		1215	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1216	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1217
894	=item C<EV_ERROR>	1218	=item C<EV_ERROR>
895		1219
896	An unspecified error has occurred, the watcher has been stopped. This might	1220	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1221	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1222	ran out of memory, a file descriptor was found to be closed or any other
		1223	problem. Libev considers these application bugs.
		1224
899	problem. You best act on it by reporting the problem and somehow coping	1225	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1226	watcher being stopped. Note that well-written programs should not receive
		1227	an error ever, so when your watcher receives it, this usually indicates a
		1228	bug in your program.
901		1229
902	Libev will usually signal a few "dummy" events together with an error, for	1230	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1231	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1232	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1233	the error from read() or write(). This will not work in multi-threaded
…		…
908		1236
909	=back	1237	=back
910		1238
911	=head2 GENERIC WATCHER FUNCTIONS	1239	=head2 GENERIC WATCHER FUNCTIONS
912		1240
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	1241	=over 4
917		1242
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1243	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1244
920	This macro initialises the generic portion of a watcher. The contents	1245	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1250	which rolls both calls into one.
926		1251
927	You can reinitialise a watcher at any time as long as it has been stopped	1252	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1253	(or never started) and there are no pending events outstanding.
929		1254
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1255	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1256	int revents)>.
932		1257
933	Example: Initialise an C<ev_io> watcher in two steps.	1258	Example: Initialise an C<ev_io> watcher in two steps.
934		1259
935	ev_io w;	1260	ev_io w;
936	ev_init (&w, my_cb);	1261	ev_init (&w, my_cb);
937	ev_io_set (&w, STDIN_FILENO, EV_READ);	1262	ev_io_set (&w, STDIN_FILENO, EV_READ);
938		1263
939	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1264	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
940		1265
941	This macro initialises the type-specific parts of a watcher. You need to	1266	This macro initialises the type-specific parts of a watcher. You need to
942	call C<ev_init> at least once before you call this macro, but you can	1267	call C<ev_init> at least once before you call this macro, but you can
943	call C<ev_TYPE_set> any number of times. You must not, however, call this	1268	call C<ev_TYPE_set> any number of times. You must not, however, call this
944	macro on a watcher that is active (it can be pending, however, which is a	1269	macro on a watcher that is active (it can be pending, however, which is a
…		…
957		1282
958	Example: Initialise and set an C<ev_io> watcher in one step.	1283	Example: Initialise and set an C<ev_io> watcher in one step.
959		1284
960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
961		1286
962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1287	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
963		1288
964	Starts (activates) the given watcher. Only active watchers will receive	1289	Starts (activates) the given watcher. Only active watchers will receive
965	events. If the watcher is already active nothing will happen.	1290	events. If the watcher is already active nothing will happen.
966		1291
967	Example: Start the C<ev_io> watcher that is being abused as example in this	1292	Example: Start the C<ev_io> watcher that is being abused as example in this
968	whole section.	1293	whole section.
969		1294
970	ev_io_start (EV_DEFAULT_UC, &w);	1295	ev_io_start (EV_DEFAULT_UC, &w);
971		1296
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1297	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
973		1298
974	Stops the given watcher if active, and clears the pending status (whether	1299	Stops the given watcher if active, and clears the pending status (whether
975	the watcher was active or not).	1300	the watcher was active or not).
976		1301
977	It is possible that stopped watchers are pending - for example,	1302	It is possible that stopped watchers are pending - for example,
…		…
997		1322
998	=item callback ev_cb (ev_TYPE *watcher)	1323	=item callback ev_cb (ev_TYPE *watcher)
999		1324
1000	Returns the callback currently set on the watcher.	1325	Returns the callback currently set on the watcher.
1001		1326
1002	=item ev_cb_set (ev_TYPE *watcher, callback)	1327	=item ev_set_cb (ev_TYPE *watcher, callback)
1003		1328
1004	Change the callback. You can change the callback at virtually any time	1329	Change the callback. You can change the callback at virtually any time
1005	(modulo threads).	1330	(modulo threads).
1006		1331
1007	=item ev_set_priority (ev_TYPE *watcher, priority)	1332	=item ev_set_priority (ev_TYPE *watcher, int priority)
1008		1333
1009	=item int ev_priority (ev_TYPE *watcher)	1334	=item int ev_priority (ev_TYPE *watcher)
1010		1335
1011	Set and query the priority of the watcher. The priority is a small	1336	Set and query the priority of the watcher. The priority is a small
1012	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1337	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1013	(default: C<-2>). Pending watchers with higher priority will be invoked	1338	(default: C<-2>). Pending watchers with higher priority will be invoked
1014	before watchers with lower priority, but priority will not keep watchers	1339	before watchers with lower priority, but priority will not keep watchers
1015	from being executed (except for C<ev_idle> watchers).	1340	from being executed (except for C<ev_idle> watchers).
1016		1341
1017	This means that priorities are I<only> used for ordering callback
1018	invocation after new events have been received. This is useful, for
1019	example, to reduce latency after idling, or more often, to bind two
1020	watchers on the same event and make sure one is called first.
1021
1022	If you need to suppress invocation when higher priority events are pending	1342	If you need to suppress invocation when higher priority events are pending
1023	you need to look at C<ev_idle> watchers, which provide this functionality.	1343	you need to look at C<ev_idle> watchers, which provide this functionality.
1024		1344
1025	You I<must not> change the priority of a watcher as long as it is active or	1345	You I<must not> change the priority of a watcher as long as it is active or
1026	pending.	1346	pending.
1027		1347
		1348	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1349	fine, as long as you do not mind that the priority value you query might
		1350	or might not have been clamped to the valid range.
		1351
1028	The default priority used by watchers when no priority has been set is	1352	The default priority used by watchers when no priority has been set is
1029	always C<0>, which is supposed to not be too high and not be too low :).	1353	always C<0>, which is supposed to not be too high and not be too low :).
1030		1354
1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1355	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1032	fine, as long as you do not mind that the priority value you query might	1356	priorities.
1033	or might not have been adjusted to be within valid range.
1034		1357
1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1358	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1036		1359
1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1360	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1038	C<loop> nor C<revents> need to be valid as long as the watcher callback	1361	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1046	watcher isn't pending it does nothing and returns C<0>.	1369	watcher isn't pending it does nothing and returns C<0>.
1047		1370
1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1371	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1049	callback to be invoked, which can be accomplished with this function.	1372	callback to be invoked, which can be accomplished with this function.
1050		1373
		1374	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1375
		1376	Feeds the given event set into the event loop, as if the specified event
		1377	had happened for the specified watcher (which must be a pointer to an
		1378	initialised but not necessarily started event watcher). Obviously you must
		1379	not free the watcher as long as it has pending events.
		1380
		1381	Stopping the watcher, letting libev invoke it, or calling
		1382	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1383	not started in the first place.
		1384
		1385	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1386	functions that do not need a watcher.
		1387
1051	=back	1388	=back
1052		1389
		1390	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1391	OWN COMPOSITE WATCHERS> idioms.
1053		1392
1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1393	=head2 WATCHER STATES
1055		1394
1056	Each watcher has, by default, a member C<void *data> that you can change	1395	There are various watcher states mentioned throughout this manual -
1057	and read at any time: libev will completely ignore it. This can be used	1396	active, pending and so on. In this section these states and the rules to
1058	to associate arbitrary data with your watcher. If you need more data and	1397	transition between them will be described in more detail - and while these
1059	don't want to allocate memory and store a pointer to it in that data	1398	rules might look complicated, they usually do "the right thing".
1060	member, you can also "subclass" the watcher type and provide your own
1061	data:
1062		1399
1063	struct my_io	1400	=over 4
		1401
		1402	=item initialised
		1403
		1404	Before a watcher can be registered with the event loop it has to be
		1405	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1406	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1407
		1408	In this state it is simply some block of memory that is suitable for
		1409	use in an event loop. It can be moved around, freed, reused etc. at
		1410	will - as long as you either keep the memory contents intact, or call
		1411	C<ev_TYPE_init> again.
		1412
		1413	=item started/running/active
		1414
		1415	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1416	property of the event loop, and is actively waiting for events. While in
		1417	this state it cannot be accessed (except in a few documented ways), moved,
		1418	freed or anything else - the only legal thing is to keep a pointer to it,
		1419	and call libev functions on it that are documented to work on active watchers.
		1420
		1421	=item pending
		1422
		1423	If a watcher is active and libev determines that an event it is interested
		1424	in has occurred (such as a timer expiring), it will become pending. It will
		1425	stay in this pending state until either it is stopped or its callback is
		1426	about to be invoked, so it is not normally pending inside the watcher
		1427	callback.
		1428
		1429	The watcher might or might not be active while it is pending (for example,
		1430	an expired non-repeating timer can be pending but no longer active). If it
		1431	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1432	but it is still property of the event loop at this time, so cannot be
		1433	moved, freed or reused. And if it is active the rules described in the
		1434	previous item still apply.
		1435
		1436	It is also possible to feed an event on a watcher that is not active (e.g.
		1437	via C<ev_feed_event>), in which case it becomes pending without being
		1438	active.
		1439
		1440	=item stopped
		1441
		1442	A watcher can be stopped implicitly by libev (in which case it might still
		1443	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1444	latter will clear any pending state the watcher might be in, regardless
		1445	of whether it was active or not, so stopping a watcher explicitly before
		1446	freeing it is often a good idea.
		1447
		1448	While stopped (and not pending) the watcher is essentially in the
		1449	initialised state, that is, it can be reused, moved, modified in any way
		1450	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1451	it again).
		1452
		1453	=back
		1454
		1455	=head2 WATCHER PRIORITY MODELS
		1456
		1457	Many event loops support I<watcher priorities>, which are usually small
		1458	integers that influence the ordering of event callback invocation
		1459	between watchers in some way, all else being equal.
		1460
		1461	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1462	description for the more technical details such as the actual priority
		1463	range.
		1464
		1465	There are two common ways how these these priorities are being interpreted
		1466	by event loops:
		1467
		1468	In the more common lock-out model, higher priorities "lock out" invocation
		1469	of lower priority watchers, which means as long as higher priority
		1470	watchers receive events, lower priority watchers are not being invoked.
		1471
		1472	The less common only-for-ordering model uses priorities solely to order
		1473	callback invocation within a single event loop iteration: Higher priority
		1474	watchers are invoked before lower priority ones, but they all get invoked
		1475	before polling for new events.
		1476
		1477	Libev uses the second (only-for-ordering) model for all its watchers
		1478	except for idle watchers (which use the lock-out model).
		1479
		1480	The rationale behind this is that implementing the lock-out model for
		1481	watchers is not well supported by most kernel interfaces, and most event
		1482	libraries will just poll for the same events again and again as long as
		1483	their callbacks have not been executed, which is very inefficient in the
		1484	common case of one high-priority watcher locking out a mass of lower
		1485	priority ones.
		1486
		1487	Static (ordering) priorities are most useful when you have two or more
		1488	watchers handling the same resource: a typical usage example is having an
		1489	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1490	timeouts. Under load, data might be received while the program handles
		1491	other jobs, but since timers normally get invoked first, the timeout
		1492	handler will be executed before checking for data. In that case, giving
		1493	the timer a lower priority than the I/O watcher ensures that I/O will be
		1494	handled first even under adverse conditions (which is usually, but not
		1495	always, what you want).
		1496
		1497	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1498	will only be executed when no same or higher priority watchers have
		1499	received events, they can be used to implement the "lock-out" model when
		1500	required.
		1501
		1502	For example, to emulate how many other event libraries handle priorities,
		1503	you can associate an C<ev_idle> watcher to each such watcher, and in
		1504	the normal watcher callback, you just start the idle watcher. The real
		1505	processing is done in the idle watcher callback. This causes libev to
		1506	continuously poll and process kernel event data for the watcher, but when
		1507	the lock-out case is known to be rare (which in turn is rare :), this is
		1508	workable.
		1509
		1510	Usually, however, the lock-out model implemented that way will perform
		1511	miserably under the type of load it was designed to handle. In that case,
		1512	it might be preferable to stop the real watcher before starting the
		1513	idle watcher, so the kernel will not have to process the event in case
		1514	the actual processing will be delayed for considerable time.
		1515
		1516	Here is an example of an I/O watcher that should run at a strictly lower
		1517	priority than the default, and which should only process data when no
		1518	other events are pending:
		1519
		1520	ev_idle idle; // actual processing watcher
		1521	ev_io io; // actual event watcher
		1522
		1523	static void
		1524	io_cb (EV_P_ ev_io *w, int revents)
1064	{	1525	{
1065	struct ev_io io;	1526	// stop the I/O watcher, we received the event, but
1066	int otherfd;	1527	// are not yet ready to handle it.
1067	void *somedata;	1528	ev_io_stop (EV_A_ w);
1068	struct whatever *mostinteresting;	1529
		1530	// start the idle watcher to handle the actual event.
		1531	// it will not be executed as long as other watchers
		1532	// with the default priority are receiving events.
		1533	ev_idle_start (EV_A_ &idle);
1069	};	1534	}
1070		1535
1071	...	1536	static void
1072	struct my_io w;	1537	idle_cb (EV_P_ ev_idle *w, int revents)
1073	ev_io_init (&w.io, my_cb, fd, EV_READ);
1074
1075	And since your callback will be called with a pointer to the watcher, you
1076	can cast it back to your own type:
1077
1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
1079	{	1538	{
1080	struct my_io *w = (struct my_io *)w_;	1539	// actual processing
1081	...	1540	read (STDIN_FILENO, ...);
		1541
		1542	// have to start the I/O watcher again, as
		1543	// we have handled the event
		1544	ev_io_start (EV_P_ &io);
1082	}	1545	}
1083		1546
1084	More interesting and less C-conformant ways of casting your callback type	1547	// initialisation
1085	instead have been omitted.	1548	ev_idle_init (&idle, idle_cb);
		1549	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1550	ev_io_start (EV_DEFAULT_ &io);
1086		1551
1087	Another common scenario is to use some data structure with multiple	1552	In the "real" world, it might also be beneficial to start a timer, so that
1088	embedded watchers:	1553	low-priority connections can not be locked out forever under load. This
1089		1554	enables your program to keep a lower latency for important connections
1090	struct my_biggy	1555	during short periods of high load, while not completely locking out less
1091	{	1556	important ones.
1092	int some_data;
1093	ev_timer t1;
1094	ev_timer t2;
1095	}
1096
1097	In this case getting the pointer to C<my_biggy> is a bit more
1098	complicated: Either you store the address of your C<my_biggy> struct
1099	in the C<data> member of the watcher (for woozies), or you need to use
1100	some pointer arithmetic using C<offsetof> inside your watchers (for real
1101	programmers):
1102
1103	#include <stddef.h>
1104
1105	static void
1106	t1_cb (EV_P_ struct ev_timer *w, int revents)
1107	{
1108	struct my_biggy big = (struct my_biggy *
1109	(((char *)w) - offsetof (struct my_biggy, t1));
1110	}
1111
1112	static void
1113	t2_cb (EV_P_ struct ev_timer *w, int revents)
1114	{
1115	struct my_biggy big = (struct my_biggy *
1116	(((char *)w) - offsetof (struct my_biggy, t2));
1117	}
1118		1557
1119		1558
1120	=head1 WATCHER TYPES	1559	=head1 WATCHER TYPES
1121		1560
1122	This section describes each watcher in detail, but will not repeat	1561	This section describes each watcher in detail, but will not repeat
…		…
1146	In general you can register as many read and/or write event watchers per	1585	In general you can register as many read and/or write event watchers per
1147	fd as you want (as long as you don't confuse yourself). Setting all file	1586	fd as you want (as long as you don't confuse yourself). Setting all file
1148	descriptors to non-blocking mode is also usually a good idea (but not	1587	descriptors to non-blocking mode is also usually a good idea (but not
1149	required if you know what you are doing).	1588	required if you know what you are doing).
1150		1589
1151	If you cannot use non-blocking mode, then force the use of a
1152	known-to-be-good backend (at the time of this writing, this includes only
1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1154
1155	Another thing you have to watch out for is that it is quite easy to	1590	Another thing you have to watch out for is that it is quite easy to
1156	receive "spurious" readiness notifications, that is your callback might	1591	receive "spurious" readiness notifications, that is, your callback might
1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1592	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1158	because there is no data. Not only are some backends known to create a	1593	because there is no data. It is very easy to get into this situation even
1159	lot of those (for example Solaris ports), it is very easy to get into	1594	with a relatively standard program structure. Thus it is best to always
1160	this situation even with a relatively standard program structure. Thus	1595	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1161	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1162	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1596	preferable to a program hanging until some data arrives.
1163		1597
1164	If you cannot run the fd in non-blocking mode (for example you should	1598	If you cannot run the fd in non-blocking mode (for example you should
1165	not play around with an Xlib connection), then you have to separately	1599	not play around with an Xlib connection), then you have to separately
1166	re-test whether a file descriptor is really ready with a known-to-be good	1600	re-test whether a file descriptor is really ready with a known-to-be good
1167	interface such as poll (fortunately in our Xlib example, Xlib already	1601	interface such as poll (fortunately in the case of Xlib, it already does
1168	does this on its own, so its quite safe to use). Some people additionally	1602	this on its own, so its quite safe to use). Some people additionally
1169	use C<SIGALRM> and an interval timer, just to be sure you won't block	1603	use C<SIGALRM> and an interval timer, just to be sure you won't block
1170	indefinitely.	1604	indefinitely.
1171		1605
1172	But really, best use non-blocking mode.	1606	But really, best use non-blocking mode.
1173		1607
…		…
1201		1635
1202	There is no workaround possible except not registering events	1636	There is no workaround possible except not registering events
1203	for potentially C<dup ()>'ed file descriptors, or to resort to	1637	for potentially C<dup ()>'ed file descriptors, or to resort to
1204	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1638	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1205		1639
		1640	=head3 The special problem of files
		1641
		1642	Many people try to use C<select> (or libev) on file descriptors
		1643	representing files, and expect it to become ready when their program
		1644	doesn't block on disk accesses (which can take a long time on their own).
		1645
		1646	However, this cannot ever work in the "expected" way - you get a readiness
		1647	notification as soon as the kernel knows whether and how much data is
		1648	there, and in the case of open files, that's always the case, so you
		1649	always get a readiness notification instantly, and your read (or possibly
		1650	write) will still block on the disk I/O.
		1651
		1652	Another way to view it is that in the case of sockets, pipes, character
		1653	devices and so on, there is another party (the sender) that delivers data
		1654	on its own, but in the case of files, there is no such thing: the disk
		1655	will not send data on its own, simply because it doesn't know what you
		1656	wish to read - you would first have to request some data.
		1657
		1658	Since files are typically not-so-well supported by advanced notification
		1659	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1660	to files, even though you should not use it. The reason for this is
		1661	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1662	usually a tty, often a pipe, but also sometimes files or special devices
		1663	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1664	F</dev/urandom>), and even though the file might better be served with
		1665	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1666	it "just works" instead of freezing.
		1667
		1668	So avoid file descriptors pointing to files when you know it (e.g. use
		1669	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1670	when you rarely read from a file instead of from a socket, and want to
		1671	reuse the same code path.
		1672
1206	=head3 The special problem of fork	1673	=head3 The special problem of fork
1207		1674
1208	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1675	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1209	useless behaviour. Libev fully supports fork, but needs to be told about	1676	useless behaviour. Libev fully supports fork, but needs to be told about
1210	it in the child.	1677	it in the child if you want to continue to use it in the child.
1211		1678
1212	To support fork in your programs, you either have to call	1679	To support fork in your child processes, you have to call C<ev_loop_fork
1213	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1680	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1214	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1681	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1215	C<EVBACKEND_POLL>.
1216		1682
1217	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1218		1684
1219	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1220	when writing to a pipe whose other end has been closed, your program gets	1686	when writing to a pipe whose other end has been closed, your program gets
…		…
1223		1689
1224	So when you encounter spurious, unexplained daemon exits, make sure you	1690	So when you encounter spurious, unexplained daemon exits, make sure you
1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1691	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1226	somewhere, as that would have given you a big clue).	1692	somewhere, as that would have given you a big clue).
1227		1693
		1694	=head3 The special problem of accept()ing when you can't
		1695
		1696	Many implementations of the POSIX C<accept> function (for example,
		1697	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1698	connection from the pending queue in all error cases.
		1699
		1700	For example, larger servers often run out of file descriptors (because
		1701	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1702	rejecting the connection, leading to libev signalling readiness on
		1703	the next iteration again (the connection still exists after all), and
		1704	typically causing the program to loop at 100% CPU usage.
		1705
		1706	Unfortunately, the set of errors that cause this issue differs between
		1707	operating systems, there is usually little the app can do to remedy the
		1708	situation, and no known thread-safe method of removing the connection to
		1709	cope with overload is known (to me).
		1710
		1711	One of the easiest ways to handle this situation is to just ignore it
		1712	- when the program encounters an overload, it will just loop until the
		1713	situation is over. While this is a form of busy waiting, no OS offers an
		1714	event-based way to handle this situation, so it's the best one can do.
		1715
		1716	A better way to handle the situation is to log any errors other than
		1717	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1718	messages, and continue as usual, which at least gives the user an idea of
		1719	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1720	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1721	usage.
		1722
		1723	If your program is single-threaded, then you could also keep a dummy file
		1724	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1725	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1726	close that fd, and create a new dummy fd. This will gracefully refuse
		1727	clients under typical overload conditions.
		1728
		1729	The last way to handle it is to simply log the error and C<exit>, as
		1730	is often done with C<malloc> failures, but this results in an easy
		1731	opportunity for a DoS attack.
1228		1732
1229	=head3 Watcher-Specific Functions	1733	=head3 Watcher-Specific Functions
1230		1734
1231	=over 4	1735	=over 4
1232		1736
…		…
1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1757	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1254	readable, but only once. Since it is likely line-buffered, you could	1758	readable, but only once. Since it is likely line-buffered, you could
1255	attempt to read a whole line in the callback.	1759	attempt to read a whole line in the callback.
1256		1760
1257	static void	1761	static void
1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1762	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1259	{	1763	{
1260	ev_io_stop (loop, w);	1764	ev_io_stop (loop, w);
1261	.. read from stdin here (or from w->fd) and handle any I/O errors	1765	.. read from stdin here (or from w->fd) and handle any I/O errors
1262	}	1766	}
1263		1767
1264	...	1768	...
1265	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1266	struct ev_io stdin_readable;	1770	ev_io stdin_readable;
1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1268	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1269	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1270		1774
1271		1775
1272	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1273		1777
1274	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
…		…
1279	year, it will still time out after (roughly) one hour. "Roughly" because	1783	year, it will still time out after (roughly) one hour. "Roughly" because
1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1281	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1282		1786
1283	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
1284	passed, but if multiple timers become ready during the same loop iteration	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1285	then order of execution is undefined.	1789	might introduce a small delay, see "the special problem of being too
		1790	early", below). If multiple timers become ready during the same loop
		1791	iteration then the ones with earlier time-out values are invoked before
		1792	ones of the same priority with later time-out values (but this is no
		1793	longer true when a callback calls C<ev_run> recursively).
		1794
		1795	=head3 Be smart about timeouts
		1796
		1797	Many real-world problems involve some kind of timeout, usually for error
		1798	recovery. A typical example is an HTTP request - if the other side hangs,
		1799	you want to raise some error after a while.
		1800
		1801	What follows are some ways to handle this problem, from obvious and
		1802	inefficient to smart and efficient.
		1803
		1804	In the following, a 60 second activity timeout is assumed - a timeout that
		1805	gets reset to 60 seconds each time there is activity (e.g. each time some
		1806	data or other life sign was received).
		1807
		1808	=over 4
		1809
		1810	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1811
		1812	This is the most obvious, but not the most simple way: In the beginning,
		1813	start the watcher:
		1814
		1815	ev_timer_init (timer, callback, 60., 0.);
		1816	ev_timer_start (loop, timer);
		1817
		1818	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1819	and start it again:
		1820
		1821	ev_timer_stop (loop, timer);
		1822	ev_timer_set (timer, 60., 0.);
		1823	ev_timer_start (loop, timer);
		1824
		1825	This is relatively simple to implement, but means that each time there is
		1826	some activity, libev will first have to remove the timer from its internal
		1827	data structure and then add it again. Libev tries to be fast, but it's
		1828	still not a constant-time operation.
		1829
		1830	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1831
		1832	This is the easiest way, and involves using C<ev_timer_again> instead of
		1833	C<ev_timer_start>.
		1834
		1835	To implement this, configure an C<ev_timer> with a C<repeat> value
		1836	of C<60> and then call C<ev_timer_again> at start and each time you
		1837	successfully read or write some data. If you go into an idle state where
		1838	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1839	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1840
		1841	That means you can ignore both the C<ev_timer_start> function and the
		1842	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1843	member and C<ev_timer_again>.
		1844
		1845	At start:
		1846
		1847	ev_init (timer, callback);
		1848	timer->repeat = 60.;
		1849	ev_timer_again (loop, timer);
		1850
		1851	Each time there is some activity:
		1852
		1853	ev_timer_again (loop, timer);
		1854
		1855	It is even possible to change the time-out on the fly, regardless of
		1856	whether the watcher is active or not:
		1857
		1858	timer->repeat = 30.;
		1859	ev_timer_again (loop, timer);
		1860
		1861	This is slightly more efficient then stopping/starting the timer each time
		1862	you want to modify its timeout value, as libev does not have to completely
		1863	remove and re-insert the timer from/into its internal data structure.
		1864
		1865	It is, however, even simpler than the "obvious" way to do it.
		1866
		1867	=item 3. Let the timer time out, but then re-arm it as required.
		1868
		1869	This method is more tricky, but usually most efficient: Most timeouts are
		1870	relatively long compared to the intervals between other activity - in
		1871	our example, within 60 seconds, there are usually many I/O events with
		1872	associated activity resets.
		1873
		1874	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1875	but remember the time of last activity, and check for a real timeout only
		1876	within the callback:
		1877
		1878	ev_tstamp timeout = 60.;
		1879	ev_tstamp last_activity; // time of last activity
		1880	ev_timer timer;
		1881
		1882	static void
		1883	callback (EV_P_ ev_timer *w, int revents)
		1884	{
		1885	// calculate when the timeout would happen
		1886	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
		1887
		1888	// if negative, it means we the timeout already occurred
		1889	if (after < 0.)
		1890	{
		1891	// timeout occurred, take action
		1892	}
		1893	else
		1894	{
		1895	// callback was invoked, but there was some recent
		1896	// activity. simply restart the timer to time out
		1897	// after "after" seconds, which is the earliest time
		1898	// the timeout can occur.
		1899	ev_timer_set (w, after, 0.);
		1900	ev_timer_start (EV_A_ w);
		1901	}
		1902	}
		1903
		1904	To summarise the callback: first calculate in how many seconds the
		1905	timeout will occur (by calculating the absolute time when it would occur,
		1906	C<last_activity + timeout>, and subtracting the current time, C<ev_now
		1907	(EV_A)> from that).
		1908
		1909	If this value is negative, then we are already past the timeout, i.e. we
		1910	timed out, and need to do whatever is needed in this case.
		1911
		1912	Otherwise, we now the earliest time at which the timeout would trigger,
		1913	and simply start the timer with this timeout value.
		1914
		1915	In other words, each time the callback is invoked it will check whether
		1916	the timeout occurred. If not, it will simply reschedule itself to check
		1917	again at the earliest time it could time out. Rinse. Repeat.
		1918
		1919	This scheme causes more callback invocations (about one every 60 seconds
		1920	minus half the average time between activity), but virtually no calls to
		1921	libev to change the timeout.
		1922
		1923	To start the machinery, simply initialise the watcher and set
		1924	C<last_activity> to the current time (meaning there was some activity just
		1925	now), then call the callback, which will "do the right thing" and start
		1926	the timer:
		1927
		1928	last_activity = ev_now (EV_A);
		1929	ev_init (&timer, callback);
		1930	callback (EV_A_ &timer, 0);
		1931
		1932	When there is some activity, simply store the current time in
		1933	C<last_activity>, no libev calls at all:
		1934
		1935	if (activity detected)
		1936	last_activity = ev_now (EV_A);
		1937
		1938	When your timeout value changes, then the timeout can be changed by simply
		1939	providing a new value, stopping the timer and calling the callback, which
		1940	will again do the right thing (for example, time out immediately :).
		1941
		1942	timeout = new_value;
		1943	ev_timer_stop (EV_A_ &timer);
		1944	callback (EV_A_ &timer, 0);
		1945
		1946	This technique is slightly more complex, but in most cases where the
		1947	time-out is unlikely to be triggered, much more efficient.
		1948
		1949	=item 4. Wee, just use a double-linked list for your timeouts.
		1950
		1951	If there is not one request, but many thousands (millions...), all
		1952	employing some kind of timeout with the same timeout value, then one can
		1953	do even better:
		1954
		1955	When starting the timeout, calculate the timeout value and put the timeout
		1956	at the I<end> of the list.
		1957
		1958	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1959	the list is expected to fire (for example, using the technique #3).
		1960
		1961	When there is some activity, remove the timer from the list, recalculate
		1962	the timeout, append it to the end of the list again, and make sure to
		1963	update the C<ev_timer> if it was taken from the beginning of the list.
		1964
		1965	This way, one can manage an unlimited number of timeouts in O(1) time for
		1966	starting, stopping and updating the timers, at the expense of a major
		1967	complication, and having to use a constant timeout. The constant timeout
		1968	ensures that the list stays sorted.
		1969
		1970	=back
		1971
		1972	So which method the best?
		1973
		1974	Method #2 is a simple no-brain-required solution that is adequate in most
		1975	situations. Method #3 requires a bit more thinking, but handles many cases
		1976	better, and isn't very complicated either. In most case, choosing either
		1977	one is fine, with #3 being better in typical situations.
		1978
		1979	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1980	rather complicated, but extremely efficient, something that really pays
		1981	off after the first million or so of active timers, i.e. it's usually
		1982	overkill :)
		1983
		1984	=head3 The special problem of being too early
		1985
		1986	If you ask a timer to call your callback after three seconds, then
		1987	you expect it to be invoked after three seconds - but of course, this
		1988	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1989	guaranteed to any precision by libev - imagine somebody suspending the
		1990	process with a STOP signal for a few hours for example.
		1991
		1992	So, libev tries to invoke your callback as soon as possible I<after> the
		1993	delay has occurred, but cannot guarantee this.
		1994
		1995	A less obvious failure mode is calling your callback too early: many event
		1996	loops compare timestamps with a "elapsed delay >= requested delay", but
		1997	this can cause your callback to be invoked much earlier than you would
		1998	expect.
		1999
		2000	To see why, imagine a system with a clock that only offers full second
		2001	resolution (think windows if you can't come up with a broken enough OS
		2002	yourself). If you schedule a one-second timer at the time 500.9, then the
		2003	event loop will schedule your timeout to elapse at a system time of 500
		2004	(500.9 truncated to the resolution) + 1, or 501.
		2005
		2006	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2007	501" and invoke the callback 0.1s after it was started, even though a
		2008	one-second delay was requested - this is being "too early", despite best
		2009	intentions.
		2010
		2011	This is the reason why libev will never invoke the callback if the elapsed
		2012	delay equals the requested delay, but only when the elapsed delay is
		2013	larger than the requested delay. In the example above, libev would only invoke
		2014	the callback at system time 502, or 1.1s after the timer was started.
		2015
		2016	So, while libev cannot guarantee that your callback will be invoked
		2017	exactly when requested, it I<can> and I<does> guarantee that the requested
		2018	delay has actually elapsed, or in other words, it always errs on the "too
		2019	late" side of things.
1286		2020
1287	=head3 The special problem of time updates	2021	=head3 The special problem of time updates
1288		2022
1289	Establishing the current time is a costly operation (it usually takes at	2023	Establishing the current time is a costly operation (it usually takes
1290	least two system calls): EV therefore updates its idea of the current	2024	at least one system call): EV therefore updates its idea of the current
1291	time only before and after C<ev_loop> collects new events, which causes a	2025	time only before and after C<ev_run> collects new events, which causes a
1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2026	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1293	lots of events in one iteration.	2027	lots of events in one iteration.
1294		2028
1295	The relative timeouts are calculated relative to the C<ev_now ()>	2029	The relative timeouts are calculated relative to the C<ev_now ()>
1296	time. This is usually the right thing as this timestamp refers to the time	2030	time. This is usually the right thing as this timestamp refers to the time
…		…
1302		2036
1303	If the event loop is suspended for a long time, you can also force an	2037	If the event loop is suspended for a long time, you can also force an
1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2038	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1305	()>.	2039	()>.
1306		2040
		2041	=head3 The special problem of unsynchronised clocks
		2042
		2043	Modern systems have a variety of clocks - libev itself uses the normal
		2044	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2045	jumps).
		2046
		2047	Neither of these clocks is synchronised with each other or any other clock
		2048	on the system, so C<ev_time ()> might return a considerably different time
		2049	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2050	a call to C<gettimeofday> might return a second count that is one higher
		2051	than a directly following call to C<time>.
		2052
		2053	The moral of this is to only compare libev-related timestamps with
		2054	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2055	a second or so.
		2056
		2057	One more problem arises due to this lack of synchronisation: if libev uses
		2058	the system monotonic clock and you compare timestamps from C<ev_time>
		2059	or C<ev_now> from when you started your timer and when your callback is
		2060	invoked, you will find that sometimes the callback is a bit "early".
		2061
		2062	This is because C<ev_timer>s work in real time, not wall clock time, so
		2063	libev makes sure your callback is not invoked before the delay happened,
		2064	I<measured according to the real time>, not the system clock.
		2065
		2066	If your timeouts are based on a physical timescale (e.g. "time out this
		2067	connection after 100 seconds") then this shouldn't bother you as it is
		2068	exactly the right behaviour.
		2069
		2070	If you want to compare wall clock/system timestamps to your timers, then
		2071	you need to use C<ev_periodic>s, as these are based on the wall clock
		2072	time, where your comparisons will always generate correct results.
		2073
		2074	=head3 The special problems of suspended animation
		2075
		2076	When you leave the server world it is quite customary to hit machines that
		2077	can suspend/hibernate - what happens to the clocks during such a suspend?
		2078
		2079	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2080	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2081	to run until the system is suspended, but they will not advance while the
		2082	system is suspended. That means, on resume, it will be as if the program
		2083	was frozen for a few seconds, but the suspend time will not be counted
		2084	towards C<ev_timer> when a monotonic clock source is used. The real time
		2085	clock advanced as expected, but if it is used as sole clocksource, then a
		2086	long suspend would be detected as a time jump by libev, and timers would
		2087	be adjusted accordingly.
		2088
		2089	I would not be surprised to see different behaviour in different between
		2090	operating systems, OS versions or even different hardware.
		2091
		2092	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2093	time jump in the monotonic clocks and the realtime clock. If the program
		2094	is suspended for a very long time, and monotonic clock sources are in use,
		2095	then you can expect C<ev_timer>s to expire as the full suspension time
		2096	will be counted towards the timers. When no monotonic clock source is in
		2097	use, then libev will again assume a timejump and adjust accordingly.
		2098
		2099	It might be beneficial for this latter case to call C<ev_suspend>
		2100	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2101	deterministic behaviour in this case (you can do nothing against
		2102	C<SIGSTOP>).
		2103
1307	=head3 Watcher-Specific Functions and Data Members	2104	=head3 Watcher-Specific Functions and Data Members
1308		2105
1309	=over 4	2106	=over 4
1310		2107
1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2108	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1324	keep up with the timer (because it takes longer than those 10 seconds to	2121	keep up with the timer (because it takes longer than those 10 seconds to
1325	do stuff) the timer will not fire more than once per event loop iteration.	2122	do stuff) the timer will not fire more than once per event loop iteration.
1326		2123
1327	=item ev_timer_again (loop, ev_timer *)	2124	=item ev_timer_again (loop, ev_timer *)
1328		2125
1329	This will act as if the timer timed out and restart it again if it is	2126	This will act as if the timer timed out, and restarts it again if it is
1330	repeating. The exact semantics are:	2127	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2128	timeout to the C<repeat> value and calling C<ev_timer_start>.
1331		2129
		2130	The exact semantics are as in the following rules, all of which will be
		2131	applied to the watcher:
		2132
		2133	=over 4
		2134
1332	If the timer is pending, its pending status is cleared.	2135	=item If the timer is pending, the pending status is always cleared.
1333		2136
1334	If the timer is started but non-repeating, stop it (as if it timed out).	2137	=item If the timer is started but non-repeating, stop it (as if it timed
		2138	out, without invoking it).
1335		2139
1336	If the timer is repeating, either start it if necessary (with the	2140	=item If the timer is repeating, make the C<repeat> value the new timeout
1337	C<repeat> value), or reset the running timer to the C<repeat> value.	2141	and start the timer, if necessary.
1338		2142
1339	This sounds a bit complicated, but here is a useful and typical	2143	=back
1340	example: Imagine you have a TCP connection and you want a so-called idle
1341	timeout, that is, you want to be called when there have been, say, 60
1342	seconds of inactivity on the socket. The easiest way to do this is to
1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1344	C<ev_timer_again> each time you successfully read or write some data. If
1345	you go into an idle state where you do not expect data to travel on the
1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1347	automatically restart it if need be.
1348		2144
1349	That means you can ignore the C<after> value and C<ev_timer_start>	2145	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:	2146	usage example.
1351		2147
1352	ev_timer_init (timer, callback, 0., 5.);	2148	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1353	ev_timer_again (loop, timer);
1354	...
1355	timer->again = 17.;
1356	ev_timer_again (loop, timer);
1357	...
1358	timer->again = 10.;
1359	ev_timer_again (loop, timer);
1360		2149
1361	This is more slightly efficient then stopping/starting the timer each time	2150	Returns the remaining time until a timer fires. If the timer is active,
1362	you want to modify its timeout value.	2151	then this time is relative to the current event loop time, otherwise it's
		2152	the timeout value currently configured.
1363		2153
1364	Note, however, that it is often even more efficient to remember the	2154	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1365	time of the last activity and let the timer time-out naturally. In the	2155	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1366	callback, you then check whether the time-out is real, or, if there was	2156	will return C<4>. When the timer expires and is restarted, it will return
1367	some activity, you reschedule the watcher to time-out in "last_activity +	2157	roughly C<7> (likely slightly less as callback invocation takes some time,
1368	timeout - ev_now ()" seconds.	2158	too), and so on.
1369		2159
1370	=item ev_tstamp repeat [read-write]	2160	=item ev_tstamp repeat [read-write]
1371		2161
1372	The current C<repeat> value. Will be used each time the watcher times out	2162	The current C<repeat> value. Will be used each time the watcher times out
1373	or C<ev_timer_again> is called, and determines the next timeout (if any),	2163	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1378	=head3 Examples	2168	=head3 Examples
1379		2169
1380	Example: Create a timer that fires after 60 seconds.	2170	Example: Create a timer that fires after 60 seconds.
1381		2171
1382	static void	2172	static void
1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2173	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1384	{	2174	{
1385	.. one minute over, w is actually stopped right here	2175	.. one minute over, w is actually stopped right here
1386	}	2176	}
1387		2177
1388	struct ev_timer mytimer;	2178	ev_timer mytimer;
1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2179	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1390	ev_timer_start (loop, &mytimer);	2180	ev_timer_start (loop, &mytimer);
1391		2181
1392	Example: Create a timeout timer that times out after 10 seconds of	2182	Example: Create a timeout timer that times out after 10 seconds of
1393	inactivity.	2183	inactivity.
1394		2184
1395	static void	2185	static void
1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2186	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1397	{	2187	{
1398	.. ten seconds without any activity	2188	.. ten seconds without any activity
1399	}	2189	}
1400		2190
1401	struct ev_timer mytimer;	2191	ev_timer mytimer;
1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2192	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1403	ev_timer_again (&mytimer); /* start timer */	2193	ev_timer_again (&mytimer); /* start timer */
1404	ev_loop (loop, 0);	2194	ev_run (loop, 0);
1405		2195
1406	// and in some piece of code that gets executed on any "activity":	2196	// and in some piece of code that gets executed on any "activity":
1407	// reset the timeout to start ticking again at 10 seconds	2197	// reset the timeout to start ticking again at 10 seconds
1408	ev_timer_again (&mytimer);	2198	ev_timer_again (&mytimer);
1409		2199
…		…
1411	=head2 C<ev_periodic> - to cron or not to cron?	2201	=head2 C<ev_periodic> - to cron or not to cron?
1412		2202
1413	Periodic watchers are also timers of a kind, but they are very versatile	2203	Periodic watchers are also timers of a kind, but they are very versatile
1414	(and unfortunately a bit complex).	2204	(and unfortunately a bit complex).
1415		2205
1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2206	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1417	but on wall clock time (absolute time). You can tell a periodic watcher	2207	relative time, the physical time that passes) but on wall clock time
1418	to trigger after some specific point in time. For example, if you tell a	2208	(absolute time, the thing you can read on your calender or clock). The
1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2209	difference is that wall clock time can run faster or slower than real
1420	+ 10.>, that is, an absolute time not a delay) and then reset your system	2210	time, and time jumps are not uncommon (e.g. when you adjust your
1421	clock to January of the previous year, then it will take more than year	2211	wrist-watch).
1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1423	roughly 10 seconds later as it uses a relative timeout).
1424		2212
		2213	You can tell a periodic watcher to trigger after some specific point
		2214	in time: for example, if you tell a periodic watcher to trigger "in 10
		2215	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2216	not a delay) and then reset your system clock to January of the previous
		2217	year, then it will take a year or more to trigger the event (unlike an
		2218	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2219	it, as it uses a relative timeout).
		2220
1425	C<ev_periodic>s can also be used to implement vastly more complex timers,	2221	C<ev_periodic> watchers can also be used to implement vastly more complex
1426	such as triggering an event on each "midnight, local time", or other	2222	timers, such as triggering an event on each "midnight, local time", or
1427	complicated rules.	2223	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2224	those cannot react to time jumps.
1428		2225
1429	As with timers, the callback is guaranteed to be invoked only when the	2226	As with timers, the callback is guaranteed to be invoked only when the
1430	time (C<at>) has passed, but if multiple periodic timers become ready	2227	point in time where it is supposed to trigger has passed. If multiple
1431	during the same loop iteration, then order of execution is undefined.	2228	timers become ready during the same loop iteration then the ones with
		2229	earlier time-out values are invoked before ones with later time-out values
		2230	(but this is no longer true when a callback calls C<ev_run> recursively).
1432		2231
1433	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1434		2233
1435	=over 4	2234	=over 4
1436		2235
1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2236	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		2237
1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2238	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1440		2239
1441	Lots of arguments, lets sort it out... There are basically three modes of	2240	Lots of arguments, let's sort it out... There are basically three modes of
1442	operation, and we will explain them from simplest to most complex:	2241	operation, and we will explain them from simplest to most complex:
1443		2242
1444	=over 4	2243	=over 4
1445		2244
1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2245	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1447		2246
1448	In this configuration the watcher triggers an event after the wall clock	2247	In this configuration the watcher triggers an event after the wall clock
1449	time C<at> has passed. It will not repeat and will not adjust when a time	2248	time C<offset> has passed. It will not repeat and will not adjust when a
1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2249	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1451	only run when the system clock reaches or surpasses this time.	2250	will be stopped and invoked when the system clock reaches or surpasses
		2251	this point in time.
1452		2252
1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2253	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1454		2254
1455	In this mode the watcher will always be scheduled to time out at the next	2255	In this mode the watcher will always be scheduled to time out at the next
1456	C<at + N * interval> time (for some integer N, which can also be negative)	2256	C<offset + N * interval> time (for some integer N, which can also be
1457	and then repeat, regardless of any time jumps.	2257	negative) and then repeat, regardless of any time jumps. The C<offset>
		2258	argument is merely an offset into the C<interval> periods.
1458		2259
1459	This can be used to create timers that do not drift with respect to the	2260	This can be used to create timers that do not drift with respect to the
1460	system clock, for example, here is a C<ev_periodic> that triggers each	2261	system clock, for example, here is an C<ev_periodic> that triggers each
1461	hour, on the hour:	2262	hour, on the hour (with respect to UTC):
1462		2263
1463	ev_periodic_set (&periodic, 0., 3600., 0);	2264	ev_periodic_set (&periodic, 0., 3600., 0);
1464		2265
1465	This doesn't mean there will always be 3600 seconds in between triggers,	2266	This doesn't mean there will always be 3600 seconds in between triggers,
1466	but only that the callback will be called when the system time shows a	2267	but only that the callback will be called when the system time shows a
1467	full hour (UTC), or more correctly, when the system time is evenly divisible	2268	full hour (UTC), or more correctly, when the system time is evenly divisible
1468	by 3600.	2269	by 3600.
1469		2270
1470	Another way to think about it (for the mathematically inclined) is that	2271	Another way to think about it (for the mathematically inclined) is that
1471	C<ev_periodic> will try to run the callback in this mode at the next possible	2272	C<ev_periodic> will try to run the callback in this mode at the next possible
1472	time where C<time = at (mod interval)>, regardless of any time jumps.	2273	time where C<time = offset (mod interval)>, regardless of any time jumps.
1473		2274
1474	For numerical stability it is preferable that the C<at> value is near	2275	The C<interval> I<MUST> be positive, and for numerical stability, the
1475	C<ev_now ()> (the current time), but there is no range requirement for	2276	interval value should be higher than C<1/8192> (which is around 100
1476	this value, and in fact is often specified as zero.	2277	microseconds) and C<offset> should be higher than C<0> and should have
		2278	at most a similar magnitude as the current time (say, within a factor of
		2279	ten). Typical values for offset are, in fact, C<0> or something between
		2280	C<0> and C<interval>, which is also the recommended range.
1477		2281
1478	Note also that there is an upper limit to how often a timer can fire (CPU	2282	Note also that there is an upper limit to how often a timer can fire (CPU
1479	speed for example), so if C<interval> is very small then timing stability	2283	speed for example), so if C<interval> is very small then timing stability
1480	will of course deteriorate. Libev itself tries to be exact to be about one	2284	will of course deteriorate. Libev itself tries to be exact to be about one
1481	millisecond (if the OS supports it and the machine is fast enough).	2285	millisecond (if the OS supports it and the machine is fast enough).
1482		2286
1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2287	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1484		2288
1485	In this mode the values for C<interval> and C<at> are both being	2289	In this mode the values for C<interval> and C<offset> are both being
1486	ignored. Instead, each time the periodic watcher gets scheduled, the	2290	ignored. Instead, each time the periodic watcher gets scheduled, the
1487	reschedule callback will be called with the watcher as first, and the	2291	reschedule callback will be called with the watcher as first, and the
1488	current time as second argument.	2292	current time as second argument.
1489		2293
1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2294	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1491	ever, or make ANY event loop modifications whatsoever>.	2295	or make ANY other event loop modifications whatsoever, unless explicitly
		2296	allowed by documentation here>.
1492		2297
1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2298	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2299	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1495	only event loop modification you are allowed to do).	2300	only event loop modification you are allowed to do).
1496		2301
1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2302	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1498	*w, ev_tstamp now)>, e.g.:	2303	*w, ev_tstamp now)>, e.g.:
1499		2304
		2305	static ev_tstamp
1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2306	my_rescheduler (ev_periodic *w, ev_tstamp now)
1501	{	2307	{
1502	return now + 60.;	2308	return now + 60.;
1503	}	2309	}
1504		2310
1505	It must return the next time to trigger, based on the passed time value	2311	It must return the next time to trigger, based on the passed time value
…		…
1525	a different time than the last time it was called (e.g. in a crond like	2331	a different time than the last time it was called (e.g. in a crond like
1526	program when the crontabs have changed).	2332	program when the crontabs have changed).
1527		2333
1528	=item ev_tstamp ev_periodic_at (ev_periodic *)	2334	=item ev_tstamp ev_periodic_at (ev_periodic *)
1529		2335
1530	When active, returns the absolute time that the watcher is supposed to	2336	When active, returns the absolute time that the watcher is supposed
1531	trigger next.	2337	to trigger next. This is not the same as the C<offset> argument to
		2338	C<ev_periodic_set>, but indeed works even in interval and manual
		2339	rescheduling modes.
1532		2340
1533	=item ev_tstamp offset [read-write]	2341	=item ev_tstamp offset [read-write]
1534		2342
1535	When repeating, this contains the offset value, otherwise this is the	2343	When repeating, this contains the offset value, otherwise this is the
1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2344	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2345	although libev might modify this value for better numerical stability).
1537		2346
1538	Can be modified any time, but changes only take effect when the periodic	2347	Can be modified any time, but changes only take effect when the periodic
1539	timer fires or C<ev_periodic_again> is being called.	2348	timer fires or C<ev_periodic_again> is being called.
1540		2349
1541	=item ev_tstamp interval [read-write]	2350	=item ev_tstamp interval [read-write]
1542		2351
1543	The current interval value. Can be modified any time, but changes only	2352	The current interval value. Can be modified any time, but changes only
1544	take effect when the periodic timer fires or C<ev_periodic_again> is being	2353	take effect when the periodic timer fires or C<ev_periodic_again> is being
1545	called.	2354	called.
1546		2355
1547	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2356	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1548		2357
1549	The current reschedule callback, or C<0>, if this functionality is	2358	The current reschedule callback, or C<0>, if this functionality is
1550	switched off. Can be changed any time, but changes only take effect when	2359	switched off. Can be changed any time, but changes only take effect when
1551	the periodic timer fires or C<ev_periodic_again> is being called.	2360	the periodic timer fires or C<ev_periodic_again> is being called.
1552		2361
…		…
1557	Example: Call a callback every hour, or, more precisely, whenever the	2366	Example: Call a callback every hour, or, more precisely, whenever the
1558	system time is divisible by 3600. The callback invocation times have	2367	system time is divisible by 3600. The callback invocation times have
1559	potentially a lot of jitter, but good long-term stability.	2368	potentially a lot of jitter, but good long-term stability.
1560		2369
1561	static void	2370	static void
1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2371	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1563	{	2372	{
1564	... its now a full hour (UTC, or TAI or whatever your clock follows)	2373	... its now a full hour (UTC, or TAI or whatever your clock follows)
1565	}	2374	}
1566		2375
1567	struct ev_periodic hourly_tick;	2376	ev_periodic hourly_tick;
1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2377	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1569	ev_periodic_start (loop, &hourly_tick);	2378	ev_periodic_start (loop, &hourly_tick);
1570		2379
1571	Example: The same as above, but use a reschedule callback to do it:	2380	Example: The same as above, but use a reschedule callback to do it:
1572		2381
1573	#include <math.h>	2382	#include <math.h>
1574		2383
1575	static ev_tstamp	2384	static ev_tstamp
1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2385	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1577	{	2386	{
1578	return now + (3600. - fmod (now, 3600.));	2387	return now + (3600. - fmod (now, 3600.));
1579	}	2388	}
1580		2389
1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2390	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1582		2391
1583	Example: Call a callback every hour, starting now:	2392	Example: Call a callback every hour, starting now:
1584		2393
1585	struct ev_periodic hourly_tick;	2394	ev_periodic hourly_tick;
1586	ev_periodic_init (&hourly_tick, clock_cb,	2395	ev_periodic_init (&hourly_tick, clock_cb,
1587	fmod (ev_now (loop), 3600.), 3600., 0);	2396	fmod (ev_now (loop), 3600.), 3600., 0);
1588	ev_periodic_start (loop, &hourly_tick);	2397	ev_periodic_start (loop, &hourly_tick);
1589		2398
1590		2399
1591	=head2 C<ev_signal> - signal me when a signal gets signalled!	2400	=head2 C<ev_signal> - signal me when a signal gets signalled!
1592		2401
1593	Signal watchers will trigger an event when the process receives a specific	2402	Signal watchers will trigger an event when the process receives a specific
1594	signal one or more times. Even though signals are very asynchronous, libev	2403	signal one or more times. Even though signals are very asynchronous, libev
1595	will try it's best to deliver signals synchronously, i.e. as part of the	2404	will try its best to deliver signals synchronously, i.e. as part of the
1596	normal event processing, like any other event.	2405	normal event processing, like any other event.
1597		2406
1598	If you want signals asynchronously, just use C<sigaction> as you would	2407	If you want signals to be delivered truly asynchronously, just use
1599	do without libev and forget about sharing the signal. You can even use	2408	C<sigaction> as you would do without libev and forget about sharing
1600	C<ev_async> from a signal handler to synchronously wake up an event loop.	2409	the signal. You can even use C<ev_async> from a signal handler to
		2410	synchronously wake up an event loop.
1601		2411
1602	You can configure as many watchers as you like per signal. Only when the	2412	You can configure as many watchers as you like for the same signal, but
1603	first watcher gets started will libev actually register a signal handler	2413	only within the same loop, i.e. you can watch for C<SIGINT> in your
1604	with the kernel (thus it coexists with your own signal handlers as long as	2414	default loop and for C<SIGIO> in another loop, but you cannot watch for
1605	you don't register any with libev for the same signal). Similarly, when	2415	C<SIGINT> in both the default loop and another loop at the same time. At
1606	the last signal watcher for a signal is stopped, libev will reset the	2416	the moment, C<SIGCHLD> is permanently tied to the default loop.
1607	signal handler to SIG_DFL (regardless of what it was set to before).	2417
		2418	Only after the first watcher for a signal is started will libev actually
		2419	register something with the kernel. It thus coexists with your own signal
		2420	handlers as long as you don't register any with libev for the same signal.
1608		2421
1609	If possible and supported, libev will install its handlers with	2422	If possible and supported, libev will install its handlers with
1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2423	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1611	interrupted. If you have a problem with system calls getting interrupted by	2424	not be unduly interrupted. If you have a problem with system calls getting
1612	signals you can block all signals in an C<ev_check> watcher and unblock	2425	interrupted by signals you can block all signals in an C<ev_check> watcher
1613	them in an C<ev_prepare> watcher.	2426	and unblock them in an C<ev_prepare> watcher.
		2427
		2428	=head3 The special problem of inheritance over fork/execve/pthread_create
		2429
		2430	Both the signal mask (C<sigprocmask>) and the signal disposition
		2431	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2432	stopping it again), that is, libev might or might not block the signal,
		2433	and might or might not set or restore the installed signal handler (but
		2434	see C<EVFLAG_NOSIGMASK>).
		2435
		2436	While this does not matter for the signal disposition (libev never
		2437	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2438	C<execve>), this matters for the signal mask: many programs do not expect
		2439	certain signals to be blocked.
		2440
		2441	This means that before calling C<exec> (from the child) you should reset
		2442	the signal mask to whatever "default" you expect (all clear is a good
		2443	choice usually).
		2444
		2445	The simplest way to ensure that the signal mask is reset in the child is
		2446	to install a fork handler with C<pthread_atfork> that resets it. That will
		2447	catch fork calls done by libraries (such as the libc) as well.
		2448
		2449	In current versions of libev, the signal will not be blocked indefinitely
		2450	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2451	the window of opportunity for problems, it will not go away, as libev
		2452	I<has> to modify the signal mask, at least temporarily.
		2453
		2454	So I can't stress this enough: I<If you do not reset your signal mask when
		2455	you expect it to be empty, you have a race condition in your code>. This
		2456	is not a libev-specific thing, this is true for most event libraries.
		2457
		2458	=head3 The special problem of threads signal handling
		2459
		2460	POSIX threads has problematic signal handling semantics, specifically,
		2461	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2462	threads in a process block signals, which is hard to achieve.
		2463
		2464	When you want to use sigwait (or mix libev signal handling with your own
		2465	for the same signals), you can tackle this problem by globally blocking
		2466	all signals before creating any threads (or creating them with a fully set
		2467	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2468	loops. Then designate one thread as "signal receiver thread" which handles
		2469	these signals. You can pass on any signals that libev might be interested
		2470	in by calling C<ev_feed_signal>.
1614		2471
1615	=head3 Watcher-Specific Functions and Data Members	2472	=head3 Watcher-Specific Functions and Data Members
1616		2473
1617	=over 4	2474	=over 4
1618		2475
…		…
1632	=head3 Examples	2489	=head3 Examples
1633		2490
1634	Example: Try to exit cleanly on SIGINT.	2491	Example: Try to exit cleanly on SIGINT.
1635		2492
1636	static void	2493	static void
1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2494	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1638	{	2495	{
1639	ev_unloop (loop, EVUNLOOP_ALL);	2496	ev_break (loop, EVBREAK_ALL);
1640	}	2497	}
1641		2498
1642	struct ev_signal signal_watcher;	2499	ev_signal signal_watcher;
1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2500	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1644	ev_signal_start (loop, &signal_watcher);	2501	ev_signal_start (loop, &signal_watcher);
1645		2502
1646		2503
1647	=head2 C<ev_child> - watch out for process status changes	2504	=head2 C<ev_child> - watch out for process status changes
…		…
1650	some child status changes (most typically when a child of yours dies or	2507	some child status changes (most typically when a child of yours dies or
1651	exits). It is permissible to install a child watcher I<after> the child	2508	exits). It is permissible to install a child watcher I<after> the child
1652	has been forked (which implies it might have already exited), as long	2509	has been forked (which implies it might have already exited), as long
1653	as the event loop isn't entered (or is continued from a watcher), i.e.,	2510	as the event loop isn't entered (or is continued from a watcher), i.e.,
1654	forking and then immediately registering a watcher for the child is fine,	2511	forking and then immediately registering a watcher for the child is fine,
1655	but forking and registering a watcher a few event loop iterations later is	2512	but forking and registering a watcher a few event loop iterations later or
1656	not.	2513	in the next callback invocation is not.
1657		2514
1658	Only the default event loop is capable of handling signals, and therefore	2515	Only the default event loop is capable of handling signals, and therefore
1659	you can only register child watchers in the default event loop.	2516	you can only register child watchers in the default event loop.
1660		2517
		2518	Due to some design glitches inside libev, child watchers will always be
		2519	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2520	libev)
		2521
1661	=head3 Process Interaction	2522	=head3 Process Interaction
1662		2523
1663	Libev grabs C<SIGCHLD> as soon as the default event loop is	2524	Libev grabs C<SIGCHLD> as soon as the default event loop is
1664	initialised. This is necessary to guarantee proper behaviour even if	2525	initialised. This is necessary to guarantee proper behaviour even if the
1665	the first child watcher is started after the child exits. The occurrence	2526	first child watcher is started after the child exits. The occurrence
1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2527	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1667	synchronously as part of the event loop processing. Libev always reaps all	2528	synchronously as part of the event loop processing. Libev always reaps all
1668	children, even ones not watched.	2529	children, even ones not watched.
1669		2530
1670	=head3 Overriding the Built-In Processing	2531	=head3 Overriding the Built-In Processing
…		…
1680	=head3 Stopping the Child Watcher	2541	=head3 Stopping the Child Watcher
1681		2542
1682	Currently, the child watcher never gets stopped, even when the	2543	Currently, the child watcher never gets stopped, even when the
1683	child terminates, so normally one needs to stop the watcher in the	2544	child terminates, so normally one needs to stop the watcher in the
1684	callback. Future versions of libev might stop the watcher automatically	2545	callback. Future versions of libev might stop the watcher automatically
1685	when a child exit is detected.	2546	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2547	problem).
1686		2548
1687	=head3 Watcher-Specific Functions and Data Members	2549	=head3 Watcher-Specific Functions and Data Members
1688		2550
1689	=over 4	2551	=over 4
1690		2552
…		…
1722	its completion.	2584	its completion.
1723		2585
1724	ev_child cw;	2586	ev_child cw;
1725		2587
1726	static void	2588	static void
1727	child_cb (EV_P_ struct ev_child *w, int revents)	2589	child_cb (EV_P_ ev_child *w, int revents)
1728	{	2590	{
1729	ev_child_stop (EV_A_ w);	2591	ev_child_stop (EV_A_ w);
1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2592	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1731	}	2593	}
1732		2594
…		…
1747		2609
1748		2610
1749	=head2 C<ev_stat> - did the file attributes just change?	2611	=head2 C<ev_stat> - did the file attributes just change?
1750		2612
1751	This watches a file system path for attribute changes. That is, it calls	2613	This watches a file system path for attribute changes. That is, it calls
1752	C<stat> regularly (or when the OS says it changed) and sees if it changed	2614	C<stat> on that path in regular intervals (or when the OS says it changed)
1753	compared to the last time, invoking the callback if it did.	2615	and sees if it changed compared to the last time, invoking the callback
		2616	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2617	happen after the watcher has been started will be reported.
1754		2618
1755	The path does not need to exist: changing from "path exists" to "path does	2619	The path does not need to exist: changing from "path exists" to "path does
1756	not exist" is a status change like any other. The condition "path does	2620	not exist" is a status change like any other. The condition "path does not
1757	not exist" is signified by the C<st_nlink> field being zero (which is	2621	exist" (or more correctly "path cannot be stat'ed") is signified by the
1758	otherwise always forced to be at least one) and all the other fields of	2622	C<st_nlink> field being zero (which is otherwise always forced to be at
1759	the stat buffer having unspecified contents.	2623	least one) and all the other fields of the stat buffer having unspecified
		2624	contents.
1760		2625
1761	The path I<should> be absolute and I<must not> end in a slash. If it is	2626	The path I<must not> end in a slash or contain special components such as
		2627	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1762	relative and your working directory changes, the behaviour is undefined.	2628	your working directory changes, then the behaviour is undefined.
1763		2629
1764	Since there is no standard kernel interface to do this, the portable	2630	Since there is no portable change notification interface available, the
1765	implementation simply calls C<stat (2)> regularly on the path to see if	2631	portable implementation simply calls C<stat(2)> regularly on the path
1766	it changed somehow. You can specify a recommended polling interval for	2632	to see if it changed somehow. You can specify a recommended polling
1767	this case. If you specify a polling interval of C<0> (highly recommended!)	2633	interval for this case. If you specify a polling interval of C<0> (highly
1768	then a I<suitable, unspecified default> value will be used (which	2634	recommended!) then a I<suitable, unspecified default> value will be used
1769	you can expect to be around five seconds, although this might change	2635	(which you can expect to be around five seconds, although this might
1770	dynamically). Libev will also impose a minimum interval which is currently	2636	change dynamically). Libev will also impose a minimum interval which is
1771	around C<0.1>, but thats usually overkill.	2637	currently around C<0.1>, but that's usually overkill.
1772		2638
1773	This watcher type is not meant for massive numbers of stat watchers,	2639	This watcher type is not meant for massive numbers of stat watchers,
1774	as even with OS-supported change notifications, this can be	2640	as even with OS-supported change notifications, this can be
1775	resource-intensive.	2641	resource-intensive.
1776		2642
1777	At the time of this writing, the only OS-specific interface implemented	2643	At the time of this writing, the only OS-specific interface implemented
1778	is the Linux inotify interface (implementing kqueue support is left as	2644	is the Linux inotify interface (implementing kqueue support is left as an
1779	an exercise for the reader. Note, however, that the author sees no way	2645	exercise for the reader. Note, however, that the author sees no way of
1780	of implementing C<ev_stat> semantics with kqueue).	2646	implementing C<ev_stat> semantics with kqueue, except as a hint).
1781		2647
1782	=head3 ABI Issues (Largefile Support)	2648	=head3 ABI Issues (Largefile Support)
1783		2649
1784	Libev by default (unless the user overrides this) uses the default	2650	Libev by default (unless the user overrides this) uses the default
1785	compilation environment, which means that on systems with large file	2651	compilation environment, which means that on systems with large file
1786	support disabled by default, you get the 32 bit version of the stat	2652	support disabled by default, you get the 32 bit version of the stat
1787	structure. When using the library from programs that change the ABI to	2653	structure. When using the library from programs that change the ABI to
1788	use 64 bit file offsets the programs will fail. In that case you have to	2654	use 64 bit file offsets the programs will fail. In that case you have to
1789	compile libev with the same flags to get binary compatibility. This is	2655	compile libev with the same flags to get binary compatibility. This is
1790	obviously the case with any flags that change the ABI, but the problem is	2656	obviously the case with any flags that change the ABI, but the problem is
1791	most noticeably disabled with ev_stat and large file support.	2657	most noticeably displayed with ev_stat and large file support.
1792		2658
1793	The solution for this is to lobby your distribution maker to make large	2659	The solution for this is to lobby your distribution maker to make large
1794	file interfaces available by default (as e.g. FreeBSD does) and not	2660	file interfaces available by default (as e.g. FreeBSD does) and not
1795	optional. Libev cannot simply switch on large file support because it has	2661	optional. Libev cannot simply switch on large file support because it has
1796	to exchange stat structures with application programs compiled using the	2662	to exchange stat structures with application programs compiled using the
1797	default compilation environment.	2663	default compilation environment.
1798		2664
1799	=head3 Inotify and Kqueue	2665	=head3 Inotify and Kqueue
1800		2666
1801	When C<inotify (7)> support has been compiled into libev (generally	2667	When C<inotify (7)> support has been compiled into libev and present at
1802	only available with Linux 2.6.25 or above due to bugs in earlier	2668	runtime, it will be used to speed up change detection where possible. The
1803	implementations) and present at runtime, it will be used to speed up	2669	inotify descriptor will be created lazily when the first C<ev_stat>
1804	change detection where possible. The inotify descriptor will be created	2670	watcher is being started.
1805	lazily when the first C<ev_stat> watcher is being started.
1806		2671
1807	Inotify presence does not change the semantics of C<ev_stat> watchers	2672	Inotify presence does not change the semantics of C<ev_stat> watchers
1808	except that changes might be detected earlier, and in some cases, to avoid	2673	except that changes might be detected earlier, and in some cases, to avoid
1809	making regular C<stat> calls. Even in the presence of inotify support	2674	making regular C<stat> calls. Even in the presence of inotify support
1810	there are many cases where libev has to resort to regular C<stat> polling,	2675	there are many cases where libev has to resort to regular C<stat> polling,
1811	but as long as the path exists, libev usually gets away without polling.	2676	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2677	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2678	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2679	xfs are fully working) libev usually gets away without polling.
1812		2680
1813	There is no support for kqueue, as apparently it cannot be used to	2681	There is no support for kqueue, as apparently it cannot be used to
1814	implement this functionality, due to the requirement of having a file	2682	implement this functionality, due to the requirement of having a file
1815	descriptor open on the object at all times, and detecting renames, unlinks	2683	descriptor open on the object at all times, and detecting renames, unlinks
1816	etc. is difficult.	2684	etc. is difficult.
1817		2685
		2686	=head3 C<stat ()> is a synchronous operation
		2687
		2688	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2689	the process. The exception are C<ev_stat> watchers - those call C<stat
		2690	()>, which is a synchronous operation.
		2691
		2692	For local paths, this usually doesn't matter: unless the system is very
		2693	busy or the intervals between stat's are large, a stat call will be fast,
		2694	as the path data is usually in memory already (except when starting the
		2695	watcher).
		2696
		2697	For networked file systems, calling C<stat ()> can block an indefinite
		2698	time due to network issues, and even under good conditions, a stat call
		2699	often takes multiple milliseconds.
		2700
		2701	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2702	paths, although this is fully supported by libev.
		2703
1818	=head3 The special problem of stat time resolution	2704	=head3 The special problem of stat time resolution
1819		2705
1820	The C<stat ()> system call only supports full-second resolution portably, and	2706	The C<stat ()> system call only supports full-second resolution portably,
1821	even on systems where the resolution is higher, most file systems still	2707	and even on systems where the resolution is higher, most file systems
1822	only support whole seconds.	2708	still only support whole seconds.
1823		2709
1824	That means that, if the time is the only thing that changes, you can	2710	That means that, if the time is the only thing that changes, you can
1825	easily miss updates: on the first update, C<ev_stat> detects a change and	2711	easily miss updates: on the first update, C<ev_stat> detects a change and
1826	calls your callback, which does something. When there is another update	2712	calls your callback, which does something. When there is another update
1827	within the same second, C<ev_stat> will be unable to detect unless the	2713	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1966	Apart from keeping your process non-blocking (which is a useful	2852	Apart from keeping your process non-blocking (which is a useful
1967	effect on its own sometimes), idle watchers are a good place to do	2853	effect on its own sometimes), idle watchers are a good place to do
1968	"pseudo-background processing", or delay processing stuff to after the	2854	"pseudo-background processing", or delay processing stuff to after the
1969	event loop has handled all outstanding events.	2855	event loop has handled all outstanding events.
1970		2856
		2857	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2858
		2859	As long as there is at least one active idle watcher, libev will never
		2860	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2861	For this to work, the idle watcher doesn't need to be invoked at all - the
		2862	lowest priority will do.
		2863
		2864	This mode of operation can be useful together with an C<ev_check> watcher,
		2865	to do something on each event loop iteration - for example to balance load
		2866	between different connections.
		2867
		2868	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2869	example.
		2870
1971	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
1972		2872
1973	=over 4	2873	=over 4
1974		2874
1975	=item ev_idle_init (ev_signal *, callback)	2875	=item ev_idle_init (ev_idle *, callback)
1976		2876
1977	Initialises and configures the idle watcher - it has no parameters of any	2877	Initialises and configures the idle watcher - it has no parameters of any
1978	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2878	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1979	believe me.	2879	believe me.
1980		2880
…		…
1984		2884
1985	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2885	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1986	callback, free it. Also, use no error checking, as usual.	2886	callback, free it. Also, use no error checking, as usual.
1987		2887
1988	static void	2888	static void
1989	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2889	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1990	{	2890	{
		2891	// stop the watcher
		2892	ev_idle_stop (loop, w);
		2893
		2894	// now we can free it
1991	free (w);	2895	free (w);
		2896
1992	// now do something you wanted to do when the program has	2897	// now do something you wanted to do when the program has
1993	// no longer anything immediate to do.	2898	// no longer anything immediate to do.
1994	}	2899	}
1995		2900
1996	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2901	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1997	ev_idle_init (idle_watcher, idle_cb);	2902	ev_idle_init (idle_watcher, idle_cb);
1998	ev_idle_start (loop, idle_cb);	2903	ev_idle_start (loop, idle_watcher);
1999		2904
2000		2905
2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2906	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2002		2907
2003	Prepare and check watchers are usually (but not always) used in pairs:	2908	Prepare and check watchers are often (but not always) used in pairs:
2004	prepare watchers get invoked before the process blocks and check watchers	2909	prepare watchers get invoked before the process blocks and check watchers
2005	afterwards.	2910	afterwards.
2006		2911
2007	You I<must not> call C<ev_loop> or similar functions that enter	2912	You I<must not> call C<ev_run> or similar functions that enter
2008	the current event loop from either C<ev_prepare> or C<ev_check>	2913	the current event loop from either C<ev_prepare> or C<ev_check>
2009	watchers. Other loops than the current one are fine, however. The	2914	watchers. Other loops than the current one are fine, however. The
2010	rationale behind this is that you do not need to check for recursion in	2915	rationale behind this is that you do not need to check for recursion in
2011	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2916	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2012	C<ev_check> so if you have one watcher of each kind they will always be	2917	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2036	with priority higher than or equal to the event loop and one coroutine	2941	with priority higher than or equal to the event loop and one coroutine
2037	of lower priority, but only once, using idle watchers to keep the event	2942	of lower priority, but only once, using idle watchers to keep the event
2038	loop from blocking if lower-priority coroutines are active, thus mapping	2943	loop from blocking if lower-priority coroutines are active, thus mapping
2039	low-priority coroutines to idle/background tasks).	2944	low-priority coroutines to idle/background tasks).
2040		2945
2041	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2946	When used for this purpose, it is recommended to give C<ev_check> watchers
2042	priority, to ensure that they are being run before any other watchers	2947	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2043	after the poll (this doesn't matter for C<ev_prepare> watchers).	2948	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2949	watchers).
2044		2950
2045	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2951	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2046	activate ("feed") events into libev. While libev fully supports this, they	2952	activate ("feed") events into libev. While libev fully supports this, they
2047	might get executed before other C<ev_check> watchers did their job. As	2953	might get executed before other C<ev_check> watchers did their job. As
2048	C<ev_check> watchers are often used to embed other (non-libev) event	2954	C<ev_check> watchers are often used to embed other (non-libev) event
2049	loops those other event loops might be in an unusable state until their	2955	loops those other event loops might be in an unusable state until their
2050	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2956	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2051	others).	2957	others).
2052		2958
		2959	=head3 Abusing an C<ev_check> watcher for its side-effect
		2960
		2961	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2962	useful because they are called once per event loop iteration. For
		2963	example, if you want to handle a large number of connections fairly, you
		2964	normally only do a bit of work for each active connection, and if there
		2965	is more work to do, you wait for the next event loop iteration, so other
		2966	connections have a chance of making progress.
		2967
		2968	Using an C<ev_check> watcher is almost enough: it will be called on the
		2969	next event loop iteration. However, that isn't as soon as possible -
		2970	without external events, your C<ev_check> watcher will not be invoked.
		2971
		2972	This is where C<ev_idle> watchers come in handy - all you need is a
		2973	single global idle watcher that is active as long as you have one active
		2974	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2975	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2976	invoked. Neither watcher alone can do that.
		2977
2053	=head3 Watcher-Specific Functions and Data Members	2978	=head3 Watcher-Specific Functions and Data Members
2054		2979
2055	=over 4	2980	=over 4
2056		2981
2057	=item ev_prepare_init (ev_prepare *, callback)	2982	=item ev_prepare_init (ev_prepare *, callback)
…		…
2082		3007
2083	static ev_io iow [nfd];	3008	static ev_io iow [nfd];
2084	static ev_timer tw;	3009	static ev_timer tw;
2085		3010
2086	static void	3011	static void
2087	io_cb (ev_loop *loop, ev_io *w, int revents)	3012	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2088	{	3013	{
2089	}	3014	}
2090		3015
2091	// create io watchers for each fd and a timer before blocking	3016	// create io watchers for each fd and a timer before blocking
2092	static void	3017	static void
2093	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	3018	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2094	{	3019	{
2095	int timeout = 3600000;	3020	int timeout = 3600000;
2096	struct pollfd fds [nfd];	3021	struct pollfd fds [nfd];
2097	// actual code will need to loop here and realloc etc.	3022	// actual code will need to loop here and realloc etc.
2098	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3023	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2099		3024
2100	/* the callback is illegal, but won't be called as we stop during check */	3025	/* the callback is illegal, but won't be called as we stop during check */
2101	ev_timer_init (&tw, 0, timeout * 1e-3);	3026	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2102	ev_timer_start (loop, &tw);	3027	ev_timer_start (loop, &tw);
2103		3028
2104	// create one ev_io per pollfd	3029	// create one ev_io per pollfd
2105	for (int i = 0; i < nfd; ++i)	3030	for (int i = 0; i < nfd; ++i)
2106	{	3031	{
…		…
2113	}	3038	}
2114	}	3039	}
2115		3040
2116	// stop all watchers after blocking	3041	// stop all watchers after blocking
2117	static void	3042	static void
2118	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	3043	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2119	{	3044	{
2120	ev_timer_stop (loop, &tw);	3045	ev_timer_stop (loop, &tw);
2121		3046
2122	for (int i = 0; i < nfd; ++i)	3047	for (int i = 0; i < nfd; ++i)
2123	{	3048	{
…		…
2180		3105
2181	if (timeout >= 0)	3106	if (timeout >= 0)
2182	// create/start timer	3107	// create/start timer
2183		3108
2184	// poll	3109	// poll
2185	ev_loop (EV_A_ 0);	3110	ev_run (EV_A_ 0);
2186		3111
2187	// stop timer again	3112	// stop timer again
2188	if (timeout >= 0)	3113	if (timeout >= 0)
2189	ev_timer_stop (EV_A_ &to);	3114	ev_timer_stop (EV_A_ &to);
2190		3115
…		…
2219	some fds have to be watched and handled very quickly (with low latency),	3144	some fds have to be watched and handled very quickly (with low latency),
2220	and even priorities and idle watchers might have too much overhead. In	3145	and even priorities and idle watchers might have too much overhead. In
2221	this case you would put all the high priority stuff in one loop and all	3146	this case you would put all the high priority stuff in one loop and all
2222	the rest in a second one, and embed the second one in the first.	3147	the rest in a second one, and embed the second one in the first.
2223		3148
2224	As long as the watcher is active, the callback will be invoked every time	3149	As long as the watcher is active, the callback will be invoked every
2225	there might be events pending in the embedded loop. The callback must then	3150	time there might be events pending in the embedded loop. The callback
2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3151	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2227	their callbacks (you could also start an idle watcher to give the embedded	3152	sweep and invoke their callbacks (the callback doesn't need to invoke the
2228	loop strictly lower priority for example). You can also set the callback	3153	C<ev_embed_sweep> function directly, it could also start an idle watcher
2229	to C<0>, in which case the embed watcher will automatically execute the	3154	to give the embedded loop strictly lower priority for example).
2230	embedded loop sweep.
2231		3155
2232	As long as the watcher is started it will automatically handle events. The	3156	You can also set the callback to C<0>, in which case the embed watcher
2233	callback will be invoked whenever some events have been handled. You can	3157	will automatically execute the embedded loop sweep whenever necessary.
2234	set the callback to C<0> to avoid having to specify one if you are not
2235	interested in that.
2236		3158
2237	Also, there have not currently been made special provisions for forking:	3159	Fork detection will be handled transparently while the C<ev_embed> watcher
2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3160	is active, i.e., the embedded loop will automatically be forked when the
2239	but you will also have to stop and restart any C<ev_embed> watchers	3161	embedding loop forks. In other cases, the user is responsible for calling
2240	yourself - but you can use a fork watcher to handle this automatically,	3162	C<ev_loop_fork> on the embedded loop.
2241	and future versions of libev might do just that.
2242		3163
2243	Unfortunately, not all backends are embeddable: only the ones returned by	3164	Unfortunately, not all backends are embeddable: only the ones returned by
2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3165	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2245	portable one.	3166	portable one.
2246		3167
…		…
2261		3182
2262	=over 4	3183	=over 4
2263		3184
2264	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2265		3186
2266	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3187	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2267		3188
2268	Configures the watcher to embed the given loop, which must be	3189	Configures the watcher to embed the given loop, which must be
2269	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3190	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2270	invoked automatically, otherwise it is the responsibility of the callback	3191	invoked automatically, otherwise it is the responsibility of the callback
2271	to invoke it (it will continue to be called until the sweep has been done,	3192	to invoke it (it will continue to be called until the sweep has been done,
2272	if you do not want that, you need to temporarily stop the embed watcher).	3193	if you do not want that, you need to temporarily stop the embed watcher).
2273		3194
2274	=item ev_embed_sweep (loop, ev_embed *)	3195	=item ev_embed_sweep (loop, ev_embed *)
2275		3196
2276	Make a single, non-blocking sweep over the embedded loop. This works	3197	Make a single, non-blocking sweep over the embedded loop. This works
2277	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3198	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2278	appropriate way for embedded loops.	3199	appropriate way for embedded loops.
2279		3200
2280	=item struct ev_loop *other [read-only]	3201	=item struct ev_loop *other [read-only]
2281		3202
2282	The embedded event loop.	3203	The embedded event loop.
…		…
2291	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3212	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2292	used).	3213	used).
2293		3214
2294	struct ev_loop *loop_hi = ev_default_init (0);	3215	struct ev_loop *loop_hi = ev_default_init (0);
2295	struct ev_loop *loop_lo = 0;	3216	struct ev_loop *loop_lo = 0;
2296	struct ev_embed embed;	3217	ev_embed embed;
2297		3218
2298	// see if there is a chance of getting one that works	3219	// see if there is a chance of getting one that works
2299	// (remember that a flags value of 0 means autodetection)	3220	// (remember that a flags value of 0 means autodetection)
2300	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3221	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2301	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3222	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2302	: 0;	3223	: 0;
…		…
2315	kqueue implementation). Store the kqueue/socket-only event loop in	3236	kqueue implementation). Store the kqueue/socket-only event loop in
2316	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3237	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2317		3238
2318	struct ev_loop *loop = ev_default_init (0);	3239	struct ev_loop *loop = ev_default_init (0);
2319	struct ev_loop *loop_socket = 0;	3240	struct ev_loop *loop_socket = 0;
2320	struct ev_embed embed;	3241	ev_embed embed;
2321		3242
2322	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3243	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2323	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3244	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2324	{	3245	{
2325	ev_embed_init (&embed, 0, loop_socket);	3246	ev_embed_init (&embed, 0, loop_socket);
2326	ev_embed_start (loop, &embed);	3247	ev_embed_start (loop, &embed);
…		…
2334		3255
2335	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3256	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2336		3257
2337	Fork watchers are called when a C<fork ()> was detected (usually because	3258	Fork watchers are called when a C<fork ()> was detected (usually because
2338	whoever is a good citizen cared to tell libev about it by calling	3259	whoever is a good citizen cared to tell libev about it by calling
2339	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3260	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2340	event loop blocks next and before C<ev_check> watchers are being called,	3261	and before C<ev_check> watchers are being called, and only in the child
2341	and only in the child after the fork. If whoever good citizen calling	3262	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2342	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3263	and calls it in the wrong process, the fork handlers will be invoked, too,
2343	handlers will be invoked, too, of course.	3264	of course.
		3265
		3266	=head3 The special problem of life after fork - how is it possible?
		3267
		3268	Most uses of C<fork()> consist of forking, then some simple calls to set
		3269	up/change the process environment, followed by a call to C<exec()>. This
		3270	sequence should be handled by libev without any problems.
		3271
		3272	This changes when the application actually wants to do event handling
		3273	in the child, or both parent in child, in effect "continuing" after the
		3274	fork.
		3275
		3276	The default mode of operation (for libev, with application help to detect
		3277	forks) is to duplicate all the state in the child, as would be expected
		3278	when I<either> the parent I<or> the child process continues.
		3279
		3280	When both processes want to continue using libev, then this is usually the
		3281	wrong result. In that case, usually one process (typically the parent) is
		3282	supposed to continue with all watchers in place as before, while the other
		3283	process typically wants to start fresh, i.e. without any active watchers.
		3284
		3285	The cleanest and most efficient way to achieve that with libev is to
		3286	simply create a new event loop, which of course will be "empty", and
		3287	use that for new watchers. This has the advantage of not touching more
		3288	memory than necessary, and thus avoiding the copy-on-write, and the
		3289	disadvantage of having to use multiple event loops (which do not support
		3290	signal watchers).
		3291
		3292	When this is not possible, or you want to use the default loop for
		3293	other reasons, then in the process that wants to start "fresh", call
		3294	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3295	Destroying the default loop will "orphan" (not stop) all registered
		3296	watchers, so you have to be careful not to execute code that modifies
		3297	those watchers. Note also that in that case, you have to re-register any
		3298	signal watchers.
2344		3299
2345	=head3 Watcher-Specific Functions and Data Members	3300	=head3 Watcher-Specific Functions and Data Members
2346		3301
2347	=over 4	3302	=over 4
2348		3303
2349	=item ev_fork_init (ev_signal *, callback)	3304	=item ev_fork_init (ev_fork *, callback)
2350		3305
2351	Initialises and configures the fork watcher - it has no parameters of any	3306	Initialises and configures the fork watcher - it has no parameters of any
2352	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3307	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2353	believe me.	3308	really.
2354		3309
2355	=back	3310	=back
2356		3311
2357		3312
		3313	=head2 C<ev_cleanup> - even the best things end
		3314
		3315	Cleanup watchers are called just before the event loop is being destroyed
		3316	by a call to C<ev_loop_destroy>.
		3317
		3318	While there is no guarantee that the event loop gets destroyed, cleanup
		3319	watchers provide a convenient method to install cleanup hooks for your
		3320	program, worker threads and so on - you just to make sure to destroy the
		3321	loop when you want them to be invoked.
		3322
		3323	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3324	all other watchers, they do not keep a reference to the event loop (which
		3325	makes a lot of sense if you think about it). Like all other watchers, you
		3326	can call libev functions in the callback, except C<ev_cleanup_start>.
		3327
		3328	=head3 Watcher-Specific Functions and Data Members
		3329
		3330	=over 4
		3331
		3332	=item ev_cleanup_init (ev_cleanup *, callback)
		3333
		3334	Initialises and configures the cleanup watcher - it has no parameters of
		3335	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3336	pointless, I assure you.
		3337
		3338	=back
		3339
		3340	Example: Register an atexit handler to destroy the default loop, so any
		3341	cleanup functions are called.
		3342
		3343	static void
		3344	program_exits (void)
		3345	{
		3346	ev_loop_destroy (EV_DEFAULT_UC);
		3347	}
		3348
		3349	...
		3350	atexit (program_exits);
		3351
		3352
2358	=head2 C<ev_async> - how to wake up another event loop	3353	=head2 C<ev_async> - how to wake up an event loop
2359		3354
2360	In general, you cannot use an C<ev_loop> from multiple threads or other	3355	In general, you cannot use an C<ev_loop> from multiple threads or other
2361	asynchronous sources such as signal handlers (as opposed to multiple event	3356	asynchronous sources such as signal handlers (as opposed to multiple event
2362	loops - those are of course safe to use in different threads).	3357	loops - those are of course safe to use in different threads).
2363		3358
2364	Sometimes, however, you need to wake up another event loop you do not	3359	Sometimes, however, you need to wake up an event loop you do not control,
2365	control, for example because it belongs to another thread. This is what	3360	for example because it belongs to another thread. This is what C<ev_async>
2366	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3361	watchers do: as long as the C<ev_async> watcher is active, you can signal
2367	can signal it by calling C<ev_async_send>, which is thread- and signal	3362	it by calling C<ev_async_send>, which is thread- and signal safe.
2368	safe.
2369		3363
2370	This functionality is very similar to C<ev_signal> watchers, as signals,	3364	This functionality is very similar to C<ev_signal> watchers, as signals,
2371	too, are asynchronous in nature, and signals, too, will be compressed	3365	too, are asynchronous in nature, and signals, too, will be compressed
2372	(i.e. the number of callback invocations may be less than the number of	3366	(i.e. the number of callback invocations may be less than the number of
2373	C<ev_async_sent> calls).	3367	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2374		3368	of "global async watchers" by using a watcher on an otherwise unused
2375	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3369	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2376	just the default loop.	3370	even without knowing which loop owns the signal.
2377		3371
2378	=head3 Queueing	3372	=head3 Queueing
2379		3373
2380	C<ev_async> does not support queueing of data in any way. The reason	3374	C<ev_async> does not support queueing of data in any way. The reason
2381	is that the author does not know of a simple (or any) algorithm for a	3375	is that the author does not know of a simple (or any) algorithm for a
2382	multiple-writer-single-reader queue that works in all cases and doesn't	3376	multiple-writer-single-reader queue that works in all cases and doesn't
2383	need elaborate support such as pthreads.	3377	need elaborate support such as pthreads or unportable memory access
		3378	semantics.
2384		3379
2385	That means that if you want to queue data, you have to provide your own	3380	That means that if you want to queue data, you have to provide your own
2386	queue. But at least I can tell you how to implement locking around your	3381	queue. But at least I can tell you how to implement locking around your
2387	queue:	3382	queue:
2388		3383
…		…
2466	=over 4	3461	=over 4
2467		3462
2468	=item ev_async_init (ev_async *, callback)	3463	=item ev_async_init (ev_async *, callback)
2469		3464
2470	Initialises and configures the async watcher - it has no parameters of any	3465	Initialises and configures the async watcher - it has no parameters of any
2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3466	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2472	trust me.	3467	trust me.
2473		3468
2474	=item ev_async_send (loop, ev_async *)	3469	=item ev_async_send (loop, ev_async *)
2475		3470
2476	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2477	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3472	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3473	returns.
		3474
2478	C<ev_feed_event>, this call is safe to do from other threads, signal or	3475	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3476	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2480	section below on what exactly this means).	3477	embedding section below on what exactly this means).
2481		3478
2482	This call incurs the overhead of a system call only once per loop iteration,	3479	Note that, as with other watchers in libev, multiple events might get
2483	so while the overhead might be noticeable, it doesn't apply to repeated	3480	compressed into a single callback invocation (another way to look at
2484	calls to C<ev_async_send>.	3481	this is that C<ev_async> watchers are level-triggered: they are set on
		3482	C<ev_async_send>, reset when the event loop detects that).
		3483
		3484	This call incurs the overhead of at most one extra system call per event
		3485	loop iteration, if the event loop is blocked, and no syscall at all if
		3486	the event loop (or your program) is processing events. That means that
		3487	repeated calls are basically free (there is no need to avoid calls for
		3488	performance reasons) and that the overhead becomes smaller (typically
		3489	zero) under load.
2485		3490
2486	=item bool = ev_async_pending (ev_async *)	3491	=item bool = ev_async_pending (ev_async *)
2487		3492
2488	Returns a non-zero value when C<ev_async_send> has been called on the	3493	Returns a non-zero value when C<ev_async_send> has been called on the
2489	watcher but the event has not yet been processed (or even noted) by the	3494	watcher but the event has not yet been processed (or even noted) by the
…		…
2492	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3497	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2493	the loop iterates next and checks for the watcher to have become active,	3498	the loop iterates next and checks for the watcher to have become active,
2494	it will reset the flag again. C<ev_async_pending> can be used to very	3499	it will reset the flag again. C<ev_async_pending> can be used to very
2495	quickly check whether invoking the loop might be a good idea.	3500	quickly check whether invoking the loop might be a good idea.
2496		3501
2497	Not that this does I<not> check whether the watcher itself is pending, only	3502	Not that this does I<not> check whether the watcher itself is pending,
2498	whether it has been requested to make this watcher pending.	3503	only whether it has been requested to make this watcher pending: there
		3504	is a time window between the event loop checking and resetting the async
		3505	notification, and the callback being invoked.
2499		3506
2500	=back	3507	=back
2501		3508
2502		3509
2503	=head1 OTHER FUNCTIONS	3510	=head1 OTHER FUNCTIONS
…		…
2520		3527
2521	If C<timeout> is less than 0, then no timeout watcher will be	3528	If C<timeout> is less than 0, then no timeout watcher will be
2522	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3529	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2523	repeat = 0) will be started. C<0> is a valid timeout.	3530	repeat = 0) will be started. C<0> is a valid timeout.
2524		3531
2525	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3532	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2526	passed an C<revents> set like normal event callbacks (a combination of	3533	passed an C<revents> set like normal event callbacks (a combination of
2527	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3534	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2528	value passed to C<ev_once>. Note that it is possible to receive I<both>	3535	value passed to C<ev_once>. Note that it is possible to receive I<both>
2529	a timeout and an io event at the same time - you probably should give io	3536	a timeout and an io event at the same time - you probably should give io
2530	events precedence.	3537	events precedence.
2531		3538
2532	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3539	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2533		3540
2534	static void stdin_ready (int revents, void *arg)	3541	static void stdin_ready (int revents, void *arg)
2535	{	3542	{
2536	if (revents & EV_READ)	3543	if (revents & EV_READ)
2537	/* stdin might have data for us, joy! */;	3544	/* stdin might have data for us, joy! */;
2538	else if (revents & EV_TIMEOUT)	3545	else if (revents & EV_TIMER)
2539	/* doh, nothing entered */;	3546	/* doh, nothing entered */;
2540	}	3547	}
2541		3548
2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3549	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2543		3550
2544	=item ev_feed_event (ev_loop *, watcher *, int revents)
2545
2546	Feeds the given event set into the event loop, as if the specified event
2547	had happened for the specified watcher (which must be a pointer to an
2548	initialised but not necessarily started event watcher).
2549
2550	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3551	=item ev_feed_fd_event (loop, int fd, int revents)
2551		3552
2552	Feed an event on the given fd, as if a file descriptor backend detected	3553	Feed an event on the given fd, as if a file descriptor backend detected
2553	the given events it.	3554	the given events.
2554		3555
2555	=item ev_feed_signal_event (ev_loop *loop, int signum)	3556	=item ev_feed_signal_event (loop, int signum)
2556		3557
2557	Feed an event as if the given signal occurred (C<loop> must be the default	3558	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2558	loop!).	3559	which is async-safe.
2559		3560
2560	=back	3561	=back
		3562
		3563
		3564	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3565
		3566	This section explains some common idioms that are not immediately
		3567	obvious. Note that examples are sprinkled over the whole manual, and this
		3568	section only contains stuff that wouldn't fit anywhere else.
		3569
		3570	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3571
		3572	Each watcher has, by default, a C<void *data> member that you can read
		3573	or modify at any time: libev will completely ignore it. This can be used
		3574	to associate arbitrary data with your watcher. If you need more data and
		3575	don't want to allocate memory separately and store a pointer to it in that
		3576	data member, you can also "subclass" the watcher type and provide your own
		3577	data:
		3578
		3579	struct my_io
		3580	{
		3581	ev_io io;
		3582	int otherfd;
		3583	void *somedata;
		3584	struct whatever *mostinteresting;
		3585	};
		3586
		3587	...
		3588	struct my_io w;
		3589	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3590
		3591	And since your callback will be called with a pointer to the watcher, you
		3592	can cast it back to your own type:
		3593
		3594	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3595	{
		3596	struct my_io *w = (struct my_io *)w_;
		3597	...
		3598	}
		3599
		3600	More interesting and less C-conformant ways of casting your callback
		3601	function type instead have been omitted.
		3602
		3603	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3604
		3605	Another common scenario is to use some data structure with multiple
		3606	embedded watchers, in effect creating your own watcher that combines
		3607	multiple libev event sources into one "super-watcher":
		3608
		3609	struct my_biggy
		3610	{
		3611	int some_data;
		3612	ev_timer t1;
		3613	ev_timer t2;
		3614	}
		3615
		3616	In this case getting the pointer to C<my_biggy> is a bit more
		3617	complicated: Either you store the address of your C<my_biggy> struct in
		3618	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3619	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3620	real programmers):
		3621
		3622	#include <stddef.h>
		3623
		3624	static void
		3625	t1_cb (EV_P_ ev_timer *w, int revents)
		3626	{
		3627	struct my_biggy big = (struct my_biggy *)
		3628	(((char *)w) - offsetof (struct my_biggy, t1));
		3629	}
		3630
		3631	static void
		3632	t2_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t2));
		3636	}
		3637
		3638	=head2 AVOIDING FINISHING BEFORE RETURNING
		3639
		3640	Often you have structures like this in event-based programs:
		3641
		3642	callback ()
		3643	{
		3644	free (request);
		3645	}
		3646
		3647	request = start_new_request (..., callback);
		3648
		3649	The intent is to start some "lengthy" operation. The C<request> could be
		3650	used to cancel the operation, or do other things with it.
		3651
		3652	It's not uncommon to have code paths in C<start_new_request> that
		3653	immediately invoke the callback, for example, to report errors. Or you add
		3654	some caching layer that finds that it can skip the lengthy aspects of the
		3655	operation and simply invoke the callback with the result.
		3656
		3657	The problem here is that this will happen I<before> C<start_new_request>
		3658	has returned, so C<request> is not set.
		3659
		3660	Even if you pass the request by some safer means to the callback, you
		3661	might want to do something to the request after starting it, such as
		3662	canceling it, which probably isn't working so well when the callback has
		3663	already been invoked.
		3664
		3665	A common way around all these issues is to make sure that
		3666	C<start_new_request> I<always> returns before the callback is invoked. If
		3667	C<start_new_request> immediately knows the result, it can artificially
		3668	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3669	example, or more sneakily, by reusing an existing (stopped) watcher and
		3670	pushing it into the pending queue:
		3671
		3672	ev_set_cb (watcher, callback);
		3673	ev_feed_event (EV_A_ watcher, 0);
		3674
		3675	This way, C<start_new_request> can safely return before the callback is
		3676	invoked, while not delaying callback invocation too much.
		3677
		3678	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3679
		3680	Often (especially in GUI toolkits) there are places where you have
		3681	I<modal> interaction, which is most easily implemented by recursively
		3682	invoking C<ev_run>.
		3683
		3684	This brings the problem of exiting - a callback might want to finish the
		3685	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3686	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3687	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3688	other combination: In these cases, a simple C<ev_break> will not work.
		3689
		3690	The solution is to maintain "break this loop" variable for each C<ev_run>
		3691	invocation, and use a loop around C<ev_run> until the condition is
		3692	triggered, using C<EVRUN_ONCE>:
		3693
		3694	// main loop
		3695	int exit_main_loop = 0;
		3696
		3697	while (!exit_main_loop)
		3698	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3699
		3700	// in a modal watcher
		3701	int exit_nested_loop = 0;
		3702
		3703	while (!exit_nested_loop)
		3704	ev_run (EV_A_ EVRUN_ONCE);
		3705
		3706	To exit from any of these loops, just set the corresponding exit variable:
		3707
		3708	// exit modal loop
		3709	exit_nested_loop = 1;
		3710
		3711	// exit main program, after modal loop is finished
		3712	exit_main_loop = 1;
		3713
		3714	// exit both
		3715	exit_main_loop = exit_nested_loop = 1;
		3716
		3717	=head2 THREAD LOCKING EXAMPLE
		3718
		3719	Here is a fictitious example of how to run an event loop in a different
		3720	thread from where callbacks are being invoked and watchers are
		3721	created/added/removed.
		3722
		3723	For a real-world example, see the C<EV::Loop::Async> perl module,
		3724	which uses exactly this technique (which is suited for many high-level
		3725	languages).
		3726
		3727	The example uses a pthread mutex to protect the loop data, a condition
		3728	variable to wait for callback invocations, an async watcher to notify the
		3729	event loop thread and an unspecified mechanism to wake up the main thread.
		3730
		3731	First, you need to associate some data with the event loop:
		3732
		3733	typedef struct {
		3734	mutex_t lock; /* global loop lock */
		3735	ev_async async_w;
		3736	thread_t tid;
		3737	cond_t invoke_cv;
		3738	} userdata;
		3739
		3740	void prepare_loop (EV_P)
		3741	{
		3742	// for simplicity, we use a static userdata struct.
		3743	static userdata u;
		3744
		3745	ev_async_init (&u->async_w, async_cb);
		3746	ev_async_start (EV_A_ &u->async_w);
		3747
		3748	pthread_mutex_init (&u->lock, 0);
		3749	pthread_cond_init (&u->invoke_cv, 0);
		3750
		3751	// now associate this with the loop
		3752	ev_set_userdata (EV_A_ u);
		3753	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3754	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3755
		3756	// then create the thread running ev_run
		3757	pthread_create (&u->tid, 0, l_run, EV_A);
		3758	}
		3759
		3760	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3761	solely to wake up the event loop so it takes notice of any new watchers
		3762	that might have been added:
		3763
		3764	static void
		3765	async_cb (EV_P_ ev_async *w, int revents)
		3766	{
		3767	// just used for the side effects
		3768	}
		3769
		3770	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3771	protecting the loop data, respectively.
		3772
		3773	static void
		3774	l_release (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777	pthread_mutex_unlock (&u->lock);
		3778	}
		3779
		3780	static void
		3781	l_acquire (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_lock (&u->lock);
		3785	}
		3786
		3787	The event loop thread first acquires the mutex, and then jumps straight
		3788	into C<ev_run>:
		3789
		3790	void *
		3791	l_run (void *thr_arg)
		3792	{
		3793	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3794
		3795	l_acquire (EV_A);
		3796	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3797	ev_run (EV_A_ 0);
		3798	l_release (EV_A);
		3799
		3800	return 0;
		3801	}
		3802
		3803	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3804	signal the main thread via some unspecified mechanism (signals? pipe
		3805	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3806	have been called (in a while loop because a) spurious wakeups are possible
		3807	and b) skipping inter-thread-communication when there are no pending
		3808	watchers is very beneficial):
		3809
		3810	static void
		3811	l_invoke (EV_P)
		3812	{
		3813	userdata *u = ev_userdata (EV_A);
		3814
		3815	while (ev_pending_count (EV_A))
		3816	{
		3817	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3818	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3819	}
		3820	}
		3821
		3822	Now, whenever the main thread gets told to invoke pending watchers, it
		3823	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3824	thread to continue:
		3825
		3826	static void
		3827	real_invoke_pending (EV_P)
		3828	{
		3829	userdata *u = ev_userdata (EV_A);
		3830
		3831	pthread_mutex_lock (&u->lock);
		3832	ev_invoke_pending (EV_A);
		3833	pthread_cond_signal (&u->invoke_cv);
		3834	pthread_mutex_unlock (&u->lock);
		3835	}
		3836
		3837	Whenever you want to start/stop a watcher or do other modifications to an
		3838	event loop, you will now have to lock:
		3839
		3840	ev_timer timeout_watcher;
		3841	userdata *u = ev_userdata (EV_A);
		3842
		3843	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3844
		3845	pthread_mutex_lock (&u->lock);
		3846	ev_timer_start (EV_A_ &timeout_watcher);
		3847	ev_async_send (EV_A_ &u->async_w);
		3848	pthread_mutex_unlock (&u->lock);
		3849
		3850	Note that sending the C<ev_async> watcher is required because otherwise
		3851	an event loop currently blocking in the kernel will have no knowledge
		3852	about the newly added timer. By waking up the loop it will pick up any new
		3853	watchers in the next event loop iteration.
		3854
		3855	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3856
		3857	While the overhead of a callback that e.g. schedules a thread is small, it
		3858	is still an overhead. If you embed libev, and your main usage is with some
		3859	kind of threads or coroutines, you might want to customise libev so that
		3860	doesn't need callbacks anymore.
		3861
		3862	Imagine you have coroutines that you can switch to using a function
		3863	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3864	and that due to some magic, the currently active coroutine is stored in a
		3865	global called C<current_coro>. Then you can build your own "wait for libev
		3866	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3867	the differing C<;> conventions):
		3868
		3869	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3870	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3871
		3872	That means instead of having a C callback function, you store the
		3873	coroutine to switch to in each watcher, and instead of having libev call
		3874	your callback, you instead have it switch to that coroutine.
		3875
		3876	A coroutine might now wait for an event with a function called
		3877	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3878	matter when, or whether the watcher is active or not when this function is
		3879	called):
		3880
		3881	void
		3882	wait_for_event (ev_watcher *w)
		3883	{
		3884	ev_set_cb (w, current_coro);
		3885	switch_to (libev_coro);
		3886	}
		3887
		3888	That basically suspends the coroutine inside C<wait_for_event> and
		3889	continues the libev coroutine, which, when appropriate, switches back to
		3890	this or any other coroutine.
		3891
		3892	You can do similar tricks if you have, say, threads with an event queue -
		3893	instead of storing a coroutine, you store the queue object and instead of
		3894	switching to a coroutine, you push the watcher onto the queue and notify
		3895	any waiters.
		3896
		3897	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3898	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3899
		3900	// my_ev.h
		3901	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3902	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3903	#include "../libev/ev.h"
		3904
		3905	// my_ev.c
		3906	#define EV_H "my_ev.h"
		3907	#include "../libev/ev.c"
		3908
		3909	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3910	F<my_ev.c> into your project. When properly specifying include paths, you
		3911	can even use F<ev.h> as header file name directly.
2561		3912
2562		3913
2563	=head1 LIBEVENT EMULATION	3914	=head1 LIBEVENT EMULATION
2564		3915
2565	Libev offers a compatibility emulation layer for libevent. It cannot	3916	Libev offers a compatibility emulation layer for libevent. It cannot
2566	emulate the internals of libevent, so here are some usage hints:	3917	emulate the internals of libevent, so here are some usage hints:
2567		3918
2568	=over 4	3919	=over 4
		3920
		3921	=item * Only the libevent-1.4.1-beta API is being emulated.
		3922
		3923	This was the newest libevent version available when libev was implemented,
		3924	and is still mostly unchanged in 2010.
2569		3925
2570	=item * Use it by including <event.h>, as usual.	3926	=item * Use it by including <event.h>, as usual.
2571		3927
2572	=item * The following members are fully supported: ev_base, ev_callback,	3928	=item * The following members are fully supported: ev_base, ev_callback,
2573	ev_arg, ev_fd, ev_res, ev_events.	3929	ev_arg, ev_fd, ev_res, ev_events.
…		…
2579	=item * Priorities are not currently supported. Initialising priorities	3935	=item * Priorities are not currently supported. Initialising priorities
2580	will fail and all watchers will have the same priority, even though there	3936	will fail and all watchers will have the same priority, even though there
2581	is an ev_pri field.	3937	is an ev_pri field.
2582		3938
2583	=item * In libevent, the last base created gets the signals, in libev, the	3939	=item * In libevent, the last base created gets the signals, in libev, the
2584	first base created (== the default loop) gets the signals.	3940	base that registered the signal gets the signals.
2585		3941
2586	=item * Other members are not supported.	3942	=item * Other members are not supported.
2587		3943
2588	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3944	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2589	to use the libev header file and library.	3945	to use the libev header file and library.
2590		3946
2591	=back	3947	=back
2592		3948
2593	=head1 C++ SUPPORT	3949	=head1 C++ SUPPORT
		3950
		3951	=head2 C API
		3952
		3953	The normal C API should work fine when used from C++: both ev.h and the
		3954	libev sources can be compiled as C++. Therefore, code that uses the C API
		3955	will work fine.
		3956
		3957	Proper exception specifications might have to be added to callbacks passed
		3958	to libev: exceptions may be thrown only from watcher callbacks, all
		3959	other callbacks (allocator, syserr, loop acquire/release and periodic
		3960	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3961	()> specification. If you have code that needs to be compiled as both C
		3962	and C++ you can use the C<EV_THROW> macro for this:
		3963
		3964	static void
		3965	fatal_error (const char *msg) EV_THROW
		3966	{
		3967	perror (msg);
		3968	abort ();
		3969	}
		3970
		3971	...
		3972	ev_set_syserr_cb (fatal_error);
		3973
		3974	The only API functions that can currently throw exceptions are C<ev_run>,
		3975	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3976	because it runs cleanup watchers).
		3977
		3978	Throwing exceptions in watcher callbacks is only supported if libev itself
		3979	is compiled with a C++ compiler or your C and C++ environments allow
		3980	throwing exceptions through C libraries (most do).
		3981
		3982	=head2 C++ API
2594		3983
2595	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3984	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2596	you to use some convenience methods to start/stop watchers and also change	3985	you to use some convenience methods to start/stop watchers and also change
2597	the callback model to a model using method callbacks on objects.	3986	the callback model to a model using method callbacks on objects.
2598		3987
2599	To use it,	3988	To use it,
2600		3989
2601	#include <ev++.h>	3990	#include <ev++.h>
2602		3991
2603	This automatically includes F<ev.h> and puts all of its definitions (many	3992	This automatically includes F<ev.h> and puts all of its definitions (many
2604	of them macros) into the global namespace. All C++ specific things are	3993	of them macros) into the global namespace. All C++ specific things are
2605	put into the C<ev> namespace. It should support all the same embedding	3994	put into the C<ev> namespace. It should support all the same embedding
…		…
2608	Care has been taken to keep the overhead low. The only data member the C++	3997	Care has been taken to keep the overhead low. The only data member the C++
2609	classes add (compared to plain C-style watchers) is the event loop pointer	3998	classes add (compared to plain C-style watchers) is the event loop pointer
2610	that the watcher is associated with (or no additional members at all if	3999	that the watcher is associated with (or no additional members at all if
2611	you disable C<EV_MULTIPLICITY> when embedding libev).	4000	you disable C<EV_MULTIPLICITY> when embedding libev).
2612		4001
2613	Currently, functions, and static and non-static member functions can be	4002	Currently, functions, static and non-static member functions and classes
2614	used as callbacks. Other types should be easy to add as long as they only	4003	with C<operator ()> can be used as callbacks. Other types should be easy
2615	need one additional pointer for context. If you need support for other	4004	to add as long as they only need one additional pointer for context. If
2616	types of functors please contact the author (preferably after implementing	4005	you need support for other types of functors please contact the author
2617	it).	4006	(preferably after implementing it).
		4007
		4008	For all this to work, your C++ compiler either has to use the same calling
		4009	conventions as your C compiler (for static member functions), or you have
		4010	to embed libev and compile libev itself as C++.
2618		4011
2619	Here is a list of things available in the C<ev> namespace:	4012	Here is a list of things available in the C<ev> namespace:
2620		4013
2621	=over 4	4014	=over 4
2622		4015
…		…
2632	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4025	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2633		4026
2634	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4027	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2635	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4028	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2636	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4029	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2637	defines by many implementations.	4030	defined by many implementations.
2638		4031
2639	All of those classes have these methods:	4032	All of those classes have these methods:
2640		4033
2641	=over 4	4034	=over 4
2642		4035
2643	=item ev::TYPE::TYPE ()	4036	=item ev::TYPE::TYPE ()
2644		4037
2645	=item ev::TYPE::TYPE (struct ev_loop *)	4038	=item ev::TYPE::TYPE (loop)
2646		4039
2647	=item ev::TYPE::~TYPE	4040	=item ev::TYPE::~TYPE
2648		4041
2649	The constructor (optionally) takes an event loop to associate the watcher	4042	The constructor (optionally) takes an event loop to associate the watcher
2650	with. If it is omitted, it will use C<EV_DEFAULT>.	4043	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2682		4075
2683	myclass obj;	4076	myclass obj;
2684	ev::io iow;	4077	ev::io iow;
2685	iow.set <myclass, &myclass::io_cb> (&obj);	4078	iow.set <myclass, &myclass::io_cb> (&obj);
2686		4079
		4080	=item w->set (object *)
		4081
		4082	This is a variation of a method callback - leaving out the method to call
		4083	will default the method to C<operator ()>, which makes it possible to use
		4084	functor objects without having to manually specify the C<operator ()> all
		4085	the time. Incidentally, you can then also leave out the template argument
		4086	list.
		4087
		4088	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4089	int revents)>.
		4090
		4091	See the method-C<set> above for more details.
		4092
		4093	Example: use a functor object as callback.
		4094
		4095	struct myfunctor
		4096	{
		4097	void operator() (ev::io &w, int revents)
		4098	{
		4099	...
		4100	}
		4101	}
		4102
		4103	myfunctor f;
		4104
		4105	ev::io w;
		4106	w.set (&f);
		4107
2687	=item w->set<function> (void *data = 0)	4108	=item w->set<function> (void *data = 0)
2688		4109
2689	Also sets a callback, but uses a static method or plain function as	4110	Also sets a callback, but uses a static method or plain function as
2690	callback. The optional C<data> argument will be stored in the watcher's	4111	callback. The optional C<data> argument will be stored in the watcher's
2691	C<data> member and is free for you to use.	4112	C<data> member and is free for you to use.
…		…
2697	Example: Use a plain function as callback.	4118	Example: Use a plain function as callback.
2698		4119
2699	static void io_cb (ev::io &w, int revents) { }	4120	static void io_cb (ev::io &w, int revents) { }
2700	iow.set <io_cb> ();	4121	iow.set <io_cb> ();
2701		4122
2702	=item w->set (struct ev_loop *)	4123	=item w->set (loop)
2703		4124
2704	Associates a different C<struct ev_loop> with this watcher. You can only	4125	Associates a different C<struct ev_loop> with this watcher. You can only
2705	do this when the watcher is inactive (and not pending either).	4126	do this when the watcher is inactive (and not pending either).
2706		4127
2707	=item w->set ([arguments])	4128	=item w->set ([arguments])
2708		4129
2709	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4130	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4131	with the same arguments. Either this method or a suitable start method
2710	called at least once. Unlike the C counterpart, an active watcher gets	4132	must be called at least once. Unlike the C counterpart, an active watcher
2711	automatically stopped and restarted when reconfiguring it with this	4133	gets automatically stopped and restarted when reconfiguring it with this
2712	method.	4134	method.
		4135
		4136	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4137	clashing with the C<set (loop)> method.
2713		4138
2714	=item w->start ()	4139	=item w->start ()
2715		4140
2716	Starts the watcher. Note that there is no C<loop> argument, as the	4141	Starts the watcher. Note that there is no C<loop> argument, as the
2717	constructor already stores the event loop.	4142	constructor already stores the event loop.
2718		4143
		4144	=item w->start ([arguments])
		4145
		4146	Instead of calling C<set> and C<start> methods separately, it is often
		4147	convenient to wrap them in one call. Uses the same type of arguments as
		4148	the configure C<set> method of the watcher.
		4149
2719	=item w->stop ()	4150	=item w->stop ()
2720		4151
2721	Stops the watcher if it is active. Again, no C<loop> argument.	4152	Stops the watcher if it is active. Again, no C<loop> argument.
2722		4153
2723	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4154	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2735		4166
2736	=back	4167	=back
2737		4168
2738	=back	4169	=back
2739		4170
2740	Example: Define a class with an IO and idle watcher, start one of them in	4171	Example: Define a class with two I/O and idle watchers, start the I/O
2741	the constructor.	4172	watchers in the constructor.
2742		4173
2743	class myclass	4174	class myclass
2744	{	4175	{
2745	ev::io io ; void io_cb (ev::io &w, int revents);	4176	ev::io io ; void io_cb (ev::io &w, int revents);
		4177	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2746	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4178	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2747		4179
2748	myclass (int fd)	4180	myclass (int fd)
2749	{	4181	{
2750	io .set <myclass, &myclass::io_cb > (this);	4182	io .set <myclass, &myclass::io_cb > (this);
		4183	io2 .set <myclass, &myclass::io2_cb > (this);
2751	idle.set <myclass, &myclass::idle_cb> (this);	4184	idle.set <myclass, &myclass::idle_cb> (this);
2752		4185
2753	io.start (fd, ev::READ);	4186	io.set (fd, ev::WRITE); // configure the watcher
		4187	io.start (); // start it whenever convenient
		4188
		4189	io2.start (fd, ev::READ); // set + start in one call
2754	}	4190	}
2755	};	4191	};
2756		4192
2757		4193
2758	=head1 OTHER LANGUAGE BINDINGS	4194	=head1 OTHER LANGUAGE BINDINGS
…		…
2777	L<http://software.schmorp.de/pkg/EV>.	4213	L<http://software.schmorp.de/pkg/EV>.
2778		4214
2779	=item Python	4215	=item Python
2780		4216
2781	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4217	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2782	seems to be quite complete and well-documented. Note, however, that the	4218	seems to be quite complete and well-documented.
2783	patch they require for libev is outright dangerous as it breaks the ABI
2784	for everybody else, and therefore, should never be applied in an installed
2785	libev (if python requires an incompatible ABI then it needs to embed
2786	libev).
2787		4219
2788	=item Ruby	4220	=item Ruby
2789		4221
2790	Tony Arcieri has written a ruby extension that offers access to a subset	4222	Tony Arcieri has written a ruby extension that offers access to a subset
2791	of the libev API and adds file handle abstractions, asynchronous DNS and	4223	of the libev API and adds file handle abstractions, asynchronous DNS and
2792	more on top of it. It can be found via gem servers. Its homepage is at	4224	more on top of it. It can be found via gem servers. Its homepage is at
2793	L<http://rev.rubyforge.org/>.	4225	L<http://rev.rubyforge.org/>.
2794		4226
		4227	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4228	makes rev work even on mingw.
		4229
		4230	=item Haskell
		4231
		4232	A haskell binding to libev is available at
		4233	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4234
2795	=item D	4235	=item D
2796		4236
2797	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4237	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4238	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4239
		4240	=item Ocaml
		4241
		4242	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4243	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4244
		4245	=item Lua
		4246
		4247	Brian Maher has written a partial interface to libev for lua (at the
		4248	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4249	L<http://github.com/brimworks/lua-ev>.
		4250
		4251	=item Javascript
		4252
		4253	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4254
		4255	=item Others
		4256
		4257	There are others, and I stopped counting.
2799		4258
2800	=back	4259	=back
2801		4260
2802		4261
2803	=head1 MACRO MAGIC	4262	=head1 MACRO MAGIC
…		…
2817	loop argument"). The C<EV_A> form is used when this is the sole argument,	4276	loop argument"). The C<EV_A> form is used when this is the sole argument,
2818	C<EV_A_> is used when other arguments are following. Example:	4277	C<EV_A_> is used when other arguments are following. Example:
2819		4278
2820	ev_unref (EV_A);	4279	ev_unref (EV_A);
2821	ev_timer_add (EV_A_ watcher);	4280	ev_timer_add (EV_A_ watcher);
2822	ev_loop (EV_A_ 0);	4281	ev_run (EV_A_ 0);
2823		4282
2824	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4283	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2825	which is often provided by the following macro.	4284	which is often provided by the following macro.
2826		4285
2827	=item C<EV_P>, C<EV_P_>	4286	=item C<EV_P>, C<EV_P_>
…		…
2840	suitable for use with C<EV_A>.	4299	suitable for use with C<EV_A>.
2841		4300
2842	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4301	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2843		4302
2844	Similar to the other two macros, this gives you the value of the default	4303	Similar to the other two macros, this gives you the value of the default
2845	loop, if multiple loops are supported ("ev loop default").	4304	loop, if multiple loops are supported ("ev loop default"). The default loop
		4305	will be initialised if it isn't already initialised.
		4306
		4307	For non-multiplicity builds, these macros do nothing, so you always have
		4308	to initialise the loop somewhere.
2846		4309
2847	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4310	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2848		4311
2849	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4312	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2850	default loop has been initialised (C<UC> == unchecked). Their behaviour	4313	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2867	}	4330	}
2868		4331
2869	ev_check check;	4332	ev_check check;
2870	ev_check_init (&check, check_cb);	4333	ev_check_init (&check, check_cb);
2871	ev_check_start (EV_DEFAULT_ &check);	4334	ev_check_start (EV_DEFAULT_ &check);
2872	ev_loop (EV_DEFAULT_ 0);	4335	ev_run (EV_DEFAULT_ 0);
2873		4336
2874	=head1 EMBEDDING	4337	=head1 EMBEDDING
2875		4338
2876	Libev can (and often is) directly embedded into host	4339	Libev can (and often is) directly embedded into host
2877	applications. Examples of applications that embed it include the Deliantra	4340	applications. Examples of applications that embed it include the Deliantra
…		…
2904		4367
2905	#define EV_STANDALONE 1	4368	#define EV_STANDALONE 1
2906	#include "ev.h"	4369	#include "ev.h"
2907		4370
2908	Both header files and implementation files can be compiled with a C++	4371	Both header files and implementation files can be compiled with a C++
2909	compiler (at least, thats a stated goal, and breakage will be treated	4372	compiler (at least, that's a stated goal, and breakage will be treated
2910	as a bug).	4373	as a bug).
2911		4374
2912	You need the following files in your source tree, or in a directory	4375	You need the following files in your source tree, or in a directory
2913	in your include path (e.g. in libev/ when using -Ilibev):	4376	in your include path (e.g. in libev/ when using -Ilibev):
2914		4377
…		…
2957	libev.m4	4420	libev.m4
2958		4421
2959	=head2 PREPROCESSOR SYMBOLS/MACROS	4422	=head2 PREPROCESSOR SYMBOLS/MACROS
2960		4423
2961	Libev can be configured via a variety of preprocessor symbols you have to	4424	Libev can be configured via a variety of preprocessor symbols you have to
2962	define before including any of its files. The default in the absence of	4425	define before including (or compiling) any of its files. The default in
2963	autoconf is documented for every option.	4426	the absence of autoconf is documented for every option.
		4427
		4428	Symbols marked with "(h)" do not change the ABI, and can have different
		4429	values when compiling libev vs. including F<ev.h>, so it is permissible
		4430	to redefine them before including F<ev.h> without breaking compatibility
		4431	to a compiled library. All other symbols change the ABI, which means all
		4432	users of libev and the libev code itself must be compiled with compatible
		4433	settings.
2964		4434
2965	=over 4	4435	=over 4
2966		4436
		4437	=item EV_COMPAT3 (h)
		4438
		4439	Backwards compatibility is a major concern for libev. This is why this
		4440	release of libev comes with wrappers for the functions and symbols that
		4441	have been renamed between libev version 3 and 4.
		4442
		4443	You can disable these wrappers (to test compatibility with future
		4444	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4445	sources. This has the additional advantage that you can drop the C<struct>
		4446	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4447	typedef in that case.
		4448
		4449	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4450	and in some even more future version the compatibility code will be
		4451	removed completely.
		4452
2967	=item EV_STANDALONE	4453	=item EV_STANDALONE (h)
2968		4454
2969	Must always be C<1> if you do not use autoconf configuration, which	4455	Must always be C<1> if you do not use autoconf configuration, which
2970	keeps libev from including F<config.h>, and it also defines dummy	4456	keeps libev from including F<config.h>, and it also defines dummy
2971	implementations for some libevent functions (such as logging, which is not	4457	implementations for some libevent functions (such as logging, which is not
2972	supported). It will also not define any of the structs usually found in	4458	supported). It will also not define any of the structs usually found in
2973	F<event.h> that are not directly supported by the libev core alone.	4459	F<event.h> that are not directly supported by the libev core alone.
2974		4460
		4461	In standalone mode, libev will still try to automatically deduce the
		4462	configuration, but has to be more conservative.
		4463
		4464	=item EV_USE_FLOOR
		4465
		4466	If defined to be C<1>, libev will use the C<floor ()> function for its
		4467	periodic reschedule calculations, otherwise libev will fall back on a
		4468	portable (slower) implementation. If you enable this, you usually have to
		4469	link against libm or something equivalent. Enabling this when the C<floor>
		4470	function is not available will fail, so the safe default is to not enable
		4471	this.
		4472
2975	=item EV_USE_MONOTONIC	4473	=item EV_USE_MONOTONIC
2976		4474
2977	If defined to be C<1>, libev will try to detect the availability of the	4475	If defined to be C<1>, libev will try to detect the availability of the
2978	monotonic clock option at both compile time and runtime. Otherwise no use	4476	monotonic clock option at both compile time and runtime. Otherwise no
2979	of the monotonic clock option will be attempted. If you enable this, you	4477	use of the monotonic clock option will be attempted. If you enable this,
2980	usually have to link against librt or something similar. Enabling it when	4478	you usually have to link against librt or something similar. Enabling it
2981	the functionality isn't available is safe, though, although you have	4479	when the functionality isn't available is safe, though, although you have
2982	to make sure you link against any libraries where the C<clock_gettime>	4480	to make sure you link against any libraries where the C<clock_gettime>
2983	function is hiding in (often F<-lrt>).	4481	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2984		4482
2985	=item EV_USE_REALTIME	4483	=item EV_USE_REALTIME
2986		4484
2987	If defined to be C<1>, libev will try to detect the availability of the	4485	If defined to be C<1>, libev will try to detect the availability of the
2988	real-time clock option at compile time (and assume its availability at	4486	real-time clock option at compile time (and assume its availability
2989	runtime if successful). Otherwise no use of the real-time clock option will	4487	at runtime if successful). Otherwise no use of the real-time clock
2990	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4488	option will be attempted. This effectively replaces C<gettimeofday>
2991	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4489	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2992	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4490	correctness. See the note about libraries in the description of
		4491	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4492	C<EV_USE_CLOCK_SYSCALL>.
		4493
		4494	=item EV_USE_CLOCK_SYSCALL
		4495
		4496	If defined to be C<1>, libev will try to use a direct syscall instead
		4497	of calling the system-provided C<clock_gettime> function. This option
		4498	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4499	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4500	programs needlessly. Using a direct syscall is slightly slower (in
		4501	theory), because no optimised vdso implementation can be used, but avoids
		4502	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4503	higher, as it simplifies linking (no need for C<-lrt>).
2993		4504
2994	=item EV_USE_NANOSLEEP	4505	=item EV_USE_NANOSLEEP
2995		4506
2996	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4507	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2997	and will use it for delays. Otherwise it will use C<select ()>.	4508	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3013		4524
3014	=item EV_SELECT_USE_FD_SET	4525	=item EV_SELECT_USE_FD_SET
3015		4526
3016	If defined to C<1>, then the select backend will use the system C<fd_set>	4527	If defined to C<1>, then the select backend will use the system C<fd_set>
3017	structure. This is useful if libev doesn't compile due to a missing	4528	structure. This is useful if libev doesn't compile due to a missing
3018	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4529	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3019	exotic systems. This usually limits the range of file descriptors to some	4530	on exotic systems. This usually limits the range of file descriptors to
3020	low limit such as 1024 or might have other limitations (winsocket only	4531	some low limit such as 1024 or might have other limitations (winsocket
3021	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4532	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3022	influence the size of the C<fd_set> used.	4533	configures the maximum size of the C<fd_set>.
3023		4534
3024	=item EV_SELECT_IS_WINSOCKET	4535	=item EV_SELECT_IS_WINSOCKET
3025		4536
3026	When defined to C<1>, the select backend will assume that	4537	When defined to C<1>, the select backend will assume that
3027	select/socket/connect etc. don't understand file descriptors but	4538	select/socket/connect etc. don't understand file descriptors but
…		…
3029	be used is the winsock select). This means that it will call	4540	be used is the winsock select). This means that it will call
3030	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4541	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3031	it is assumed that all these functions actually work on fds, even	4542	it is assumed that all these functions actually work on fds, even
3032	on win32. Should not be defined on non-win32 platforms.	4543	on win32. Should not be defined on non-win32 platforms.
3033		4544
3034	=item EV_FD_TO_WIN32_HANDLE	4545	=item EV_FD_TO_WIN32_HANDLE(fd)
3035		4546
3036	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4547	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3037	file descriptors to socket handles. When not defining this symbol (the	4548	file descriptors to socket handles. When not defining this symbol (the
3038	default), then libev will call C<_get_osfhandle>, which is usually	4549	default), then libev will call C<_get_osfhandle>, which is usually
3039	correct. In some cases, programs use their own file descriptor management,	4550	correct. In some cases, programs use their own file descriptor management,
3040	in which case they can provide this function to map fds to socket handles.	4551	in which case they can provide this function to map fds to socket handles.
		4552
		4553	=item EV_WIN32_HANDLE_TO_FD(handle)
		4554
		4555	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4556	using the standard C<_open_osfhandle> function. For programs implementing
		4557	their own fd to handle mapping, overwriting this function makes it easier
		4558	to do so. This can be done by defining this macro to an appropriate value.
		4559
		4560	=item EV_WIN32_CLOSE_FD(fd)
		4561
		4562	If programs implement their own fd to handle mapping on win32, then this
		4563	macro can be used to override the C<close> function, useful to unregister
		4564	file descriptors again. Note that the replacement function has to close
		4565	the underlying OS handle.
		4566
		4567	=item EV_USE_WSASOCKET
		4568
		4569	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4570	communication socket, which works better in some environments. Otherwise,
		4571	the normal C<socket> function will be used, which works better in other
		4572	environments.
3041		4573
3042	=item EV_USE_POLL	4574	=item EV_USE_POLL
3043		4575
3044	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4576	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3045	backend. Otherwise it will be enabled on non-win32 platforms. It	4577	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3081	If defined to be C<1>, libev will compile in support for the Linux inotify	4613	If defined to be C<1>, libev will compile in support for the Linux inotify
3082	interface to speed up C<ev_stat> watchers. Its actual availability will	4614	interface to speed up C<ev_stat> watchers. Its actual availability will
3083	be detected at runtime. If undefined, it will be enabled if the headers	4615	be detected at runtime. If undefined, it will be enabled if the headers
3084	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4616	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3085		4617
		4618	=item EV_NO_SMP
		4619
		4620	If defined to be C<1>, libev will assume that memory is always coherent
		4621	between threads, that is, threads can be used, but threads never run on
		4622	different cpus (or different cpu cores). This reduces dependencies
		4623	and makes libev faster.
		4624
		4625	=item EV_NO_THREADS
		4626
		4627	If defined to be C<1>, libev will assume that it will never be called from
		4628	different threads (that includes signal handlers), which is a stronger
		4629	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4630	libev faster.
		4631
3086	=item EV_ATOMIC_T	4632	=item EV_ATOMIC_T
3087		4633
3088	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4634	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3089	access is atomic with respect to other threads or signal contexts. No such	4635	access is atomic with respect to other threads or signal contexts. No
3090	type is easily found in the C language, so you can provide your own type	4636	such type is easily found in the C language, so you can provide your own
3091	that you know is safe for your purposes. It is used both for signal handler "locking"	4637	type that you know is safe for your purposes. It is used both for signal
3092	as well as for signal and thread safety in C<ev_async> watchers.	4638	handler "locking" as well as for signal and thread safety in C<ev_async>
		4639	watchers.
3093		4640
3094	In the absence of this define, libev will use C<sig_atomic_t volatile>	4641	In the absence of this define, libev will use C<sig_atomic_t volatile>
3095	(from F<signal.h>), which is usually good enough on most platforms.	4642	(from F<signal.h>), which is usually good enough on most platforms.
3096		4643
3097	=item EV_H	4644	=item EV_H (h)
3098		4645
3099	The name of the F<ev.h> header file used to include it. The default if	4646	The name of the F<ev.h> header file used to include it. The default if
3100	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4647	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3101	used to virtually rename the F<ev.h> header file in case of conflicts.	4648	used to virtually rename the F<ev.h> header file in case of conflicts.
3102		4649
3103	=item EV_CONFIG_H	4650	=item EV_CONFIG_H (h)
3104		4651
3105	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4652	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3106	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4653	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3107	C<EV_H>, above.	4654	C<EV_H>, above.
3108		4655
3109	=item EV_EVENT_H	4656	=item EV_EVENT_H (h)
3110		4657
3111	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4658	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3112	of how the F<event.h> header can be found, the default is C<"event.h">.	4659	of how the F<event.h> header can be found, the default is C<"event.h">.
3113		4660
3114	=item EV_PROTOTYPES	4661	=item EV_PROTOTYPES (h)
3115		4662
3116	If defined to be C<0>, then F<ev.h> will not define any function	4663	If defined to be C<0>, then F<ev.h> will not define any function
3117	prototypes, but still define all the structs and other symbols. This is	4664	prototypes, but still define all the structs and other symbols. This is
3118	occasionally useful if you want to provide your own wrapper functions	4665	occasionally useful if you want to provide your own wrapper functions
3119	around libev functions.	4666	around libev functions.
…		…
3124	will have the C<struct ev_loop *> as first argument, and you can create	4671	will have the C<struct ev_loop *> as first argument, and you can create
3125	additional independent event loops. Otherwise there will be no support	4672	additional independent event loops. Otherwise there will be no support
3126	for multiple event loops and there is no first event loop pointer	4673	for multiple event loops and there is no first event loop pointer
3127	argument. Instead, all functions act on the single default loop.	4674	argument. Instead, all functions act on the single default loop.
3128		4675
		4676	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4677	default loop when multiplicity is switched off - you always have to
		4678	initialise the loop manually in this case.
		4679
3129	=item EV_MINPRI	4680	=item EV_MINPRI
3130		4681
3131	=item EV_MAXPRI	4682	=item EV_MAXPRI
3132		4683
3133	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4684	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3141	fine.	4692	fine.
3142		4693
3143	If your embedding application does not need any priorities, defining these	4694	If your embedding application does not need any priorities, defining these
3144	both to C<0> will save some memory and CPU.	4695	both to C<0> will save some memory and CPU.
3145		4696
3146	=item EV_PERIODIC_ENABLE	4697	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4698	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4699	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3147		4700
3148	If undefined or defined to be C<1>, then periodic timers are supported. If	4701	If undefined or defined to be C<1> (and the platform supports it), then
3149	defined to be C<0>, then they are not. Disabling them saves a few kB of	4702	the respective watcher type is supported. If defined to be C<0>, then it
3150	code.	4703	is not. Disabling watcher types mainly saves code size.
3151		4704
3152	=item EV_IDLE_ENABLE	4705	=item EV_FEATURES
3153
3154	If undefined or defined to be C<1>, then idle watchers are supported. If
3155	defined to be C<0>, then they are not. Disabling them saves a few kB of
3156	code.
3157
3158	=item EV_EMBED_ENABLE
3159
3160	If undefined or defined to be C<1>, then embed watchers are supported. If
3161	defined to be C<0>, then they are not. Embed watchers rely on most other
3162	watcher types, which therefore must not be disabled.
3163
3164	=item EV_STAT_ENABLE
3165
3166	If undefined or defined to be C<1>, then stat watchers are supported. If
3167	defined to be C<0>, then they are not.
3168
3169	=item EV_FORK_ENABLE
3170
3171	If undefined or defined to be C<1>, then fork watchers are supported. If
3172	defined to be C<0>, then they are not.
3173
3174	=item EV_ASYNC_ENABLE
3175
3176	If undefined or defined to be C<1>, then async watchers are supported. If
3177	defined to be C<0>, then they are not.
3178
3179	=item EV_MINIMAL
3180		4706
3181	If you need to shave off some kilobytes of code at the expense of some	4707	If you need to shave off some kilobytes of code at the expense of some
3182	speed, define this symbol to C<1>. Currently this is used to override some	4708	speed (but with the full API), you can define this symbol to request
3183	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4709	certain subsets of functionality. The default is to enable all features
3184	much smaller 2-heap for timer management over the default 4-heap.	4710	that can be enabled on the platform.
		4711
		4712	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4713	with some broad features you want) and then selectively re-enable
		4714	additional parts you want, for example if you want everything minimal,
		4715	but multiple event loop support, async and child watchers and the poll
		4716	backend, use this:
		4717
		4718	#define EV_FEATURES 0
		4719	#define EV_MULTIPLICITY 1
		4720	#define EV_USE_POLL 1
		4721	#define EV_CHILD_ENABLE 1
		4722	#define EV_ASYNC_ENABLE 1
		4723
		4724	The actual value is a bitset, it can be a combination of the following
		4725	values (by default, all of these are enabled):
		4726
		4727	=over 4
		4728
		4729	=item C<1> - faster/larger code
		4730
		4731	Use larger code to speed up some operations.
		4732
		4733	Currently this is used to override some inlining decisions (enlarging the
		4734	code size by roughly 30% on amd64).
		4735
		4736	When optimising for size, use of compiler flags such as C<-Os> with
		4737	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4738	assertions.
		4739
		4740	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4741	(e.g. gcc with C<-Os>).
		4742
		4743	=item C<2> - faster/larger data structures
		4744
		4745	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4746	hash table sizes and so on. This will usually further increase code size
		4747	and can additionally have an effect on the size of data structures at
		4748	runtime.
		4749
		4750	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4751	(e.g. gcc with C<-Os>).
		4752
		4753	=item C<4> - full API configuration
		4754
		4755	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4756	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4757
		4758	=item C<8> - full API
		4759
		4760	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4761	details on which parts of the API are still available without this
		4762	feature, and do not complain if this subset changes over time.
		4763
		4764	=item C<16> - enable all optional watcher types
		4765
		4766	Enables all optional watcher types. If you want to selectively enable
		4767	only some watcher types other than I/O and timers (e.g. prepare,
		4768	embed, async, child...) you can enable them manually by defining
		4769	C<EV_watchertype_ENABLE> to C<1> instead.
		4770
		4771	=item C<32> - enable all backends
		4772
		4773	This enables all backends - without this feature, you need to enable at
		4774	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4775
		4776	=item C<64> - enable OS-specific "helper" APIs
		4777
		4778	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4779	default.
		4780
		4781	=back
		4782
		4783	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4784	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4785	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4786	watchers, timers and monotonic clock support.
		4787
		4788	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4789	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4790	your program might be left out as well - a binary starting a timer and an
		4791	I/O watcher then might come out at only 5Kb.
		4792
		4793	=item EV_API_STATIC
		4794
		4795	If this symbol is defined (by default it is not), then all identifiers
		4796	will have static linkage. This means that libev will not export any
		4797	identifiers, and you cannot link against libev anymore. This can be useful
		4798	when you embed libev, only want to use libev functions in a single file,
		4799	and do not want its identifiers to be visible.
		4800
		4801	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4802	wants to use libev.
		4803
		4804	This option only works when libev is compiled with a C compiler, as C++
		4805	doesn't support the required declaration syntax.
		4806
		4807	=item EV_AVOID_STDIO
		4808
		4809	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4810	functions (printf, scanf, perror etc.). This will increase the code size
		4811	somewhat, but if your program doesn't otherwise depend on stdio and your
		4812	libc allows it, this avoids linking in the stdio library which is quite
		4813	big.
		4814
		4815	Note that error messages might become less precise when this option is
		4816	enabled.
		4817
		4818	=item EV_NSIG
		4819
		4820	The highest supported signal number, +1 (or, the number of
		4821	signals): Normally, libev tries to deduce the maximum number of signals
		4822	automatically, but sometimes this fails, in which case it can be
		4823	specified. Also, using a lower number than detected (C<32> should be
		4824	good for about any system in existence) can save some memory, as libev
		4825	statically allocates some 12-24 bytes per signal number.
3185		4826
3186	=item EV_PID_HASHSIZE	4827	=item EV_PID_HASHSIZE
3187		4828
3188	C<ev_child> watchers use a small hash table to distribute workload by	4829	C<ev_child> watchers use a small hash table to distribute workload by
3189	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4830	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3190	than enough. If you need to manage thousands of children you might want to	4831	usually more than enough. If you need to manage thousands of children you
3191	increase this value (I<must> be a power of two).	4832	might want to increase this value (I<must> be a power of two).
3192		4833
3193	=item EV_INOTIFY_HASHSIZE	4834	=item EV_INOTIFY_HASHSIZE
3194		4835
3195	C<ev_stat> watchers use a small hash table to distribute workload by	4836	C<ev_stat> watchers use a small hash table to distribute workload by
3196	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4837	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3197	usually more than enough. If you need to manage thousands of C<ev_stat>	4838	disabled), usually more than enough. If you need to manage thousands of
3198	watchers you might want to increase this value (I<must> be a power of	4839	C<ev_stat> watchers you might want to increase this value (I<must> be a
3199	two).	4840	power of two).
3200		4841
3201	=item EV_USE_4HEAP	4842	=item EV_USE_4HEAP
3202		4843
3203	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4844	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3204	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4845	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3205	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4846	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3206	faster performance with many (thousands) of watchers.	4847	faster performance with many (thousands) of watchers.
3207		4848
3208	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4849	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3209	(disabled).	4850	will be C<0>.
3210		4851
3211	=item EV_HEAP_CACHE_AT	4852	=item EV_HEAP_CACHE_AT
3212		4853
3213	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4854	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3214	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4855	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3215	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4856	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3216	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4857	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3217	but avoids random read accesses on heap changes. This improves performance	4858	but avoids random read accesses on heap changes. This improves performance
3218	noticeably with many (hundreds) of watchers.	4859	noticeably with many (hundreds) of watchers.
3219		4860
3220	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4861	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3221	(disabled).	4862	will be C<0>.
3222		4863
3223	=item EV_VERIFY	4864	=item EV_VERIFY
3224		4865
3225	Controls how much internal verification (see C<ev_loop_verify ()>) will	4866	Controls how much internal verification (see C<ev_verify ()>) will
3226	be done: If set to C<0>, no internal verification code will be compiled	4867	be done: If set to C<0>, no internal verification code will be compiled
3227	in. If set to C<1>, then verification code will be compiled in, but not	4868	in. If set to C<1>, then verification code will be compiled in, but not
3228	called. If set to C<2>, then the internal verification code will be	4869	called. If set to C<2>, then the internal verification code will be
3229	called once per loop, which can slow down libev. If set to C<3>, then the	4870	called once per loop, which can slow down libev. If set to C<3>, then the
3230	verification code will be called very frequently, which will slow down	4871	verification code will be called very frequently, which will slow down
3231	libev considerably.	4872	libev considerably.
3232		4873
3233	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4874	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3234	C<0>.	4875	will be C<0>.
3235		4876
3236	=item EV_COMMON	4877	=item EV_COMMON
3237		4878
3238	By default, all watchers have a C<void *data> member. By redefining	4879	By default, all watchers have a C<void *data> member. By redefining
3239	this macro to a something else you can include more and other types of	4880	this macro to something else you can include more and other types of
3240	members. You have to define it each time you include one of the files,	4881	members. You have to define it each time you include one of the files,
3241	though, and it must be identical each time.	4882	though, and it must be identical each time.
3242		4883
3243	For example, the perl EV module uses something like this:	4884	For example, the perl EV module uses something like this:
3244		4885
…		…
3297	file.	4938	file.
3298		4939
3299	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4940	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3300	that everybody includes and which overrides some configure choices:	4941	that everybody includes and which overrides some configure choices:
3301		4942
3302	#define EV_MINIMAL 1	4943	#define EV_FEATURES 8
3303	#define EV_USE_POLL 0	4944	#define EV_USE_SELECT 1
3304	#define EV_MULTIPLICITY 0
3305	#define EV_PERIODIC_ENABLE 0	4945	#define EV_PREPARE_ENABLE 1
		4946	#define EV_IDLE_ENABLE 1
3306	#define EV_STAT_ENABLE 0	4947	#define EV_SIGNAL_ENABLE 1
3307	#define EV_FORK_ENABLE 0	4948	#define EV_CHILD_ENABLE 1
		4949	#define EV_USE_STDEXCEPT 0
3308	#define EV_CONFIG_H <config.h>	4950	#define EV_CONFIG_H <config.h>
3309	#define EV_MINPRI 0
3310	#define EV_MAXPRI 0
3311		4951
3312	#include "ev++.h"	4952	#include "ev++.h"
3313		4953
3314	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4954	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3315		4955
3316	#include "ev_cpp.h"	4956	#include "ev_cpp.h"
3317	#include "ev.c"	4957	#include "ev.c"
3318		4958
3319	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4959	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3320		4960
3321	=head2 THREADS AND COROUTINES	4961	=head2 THREADS AND COROUTINES
3322		4962
3323	=head3 THREADS	4963	=head3 THREADS
3324		4964
…		…
3375	default loop and triggering an C<ev_async> watcher from the default loop	5015	default loop and triggering an C<ev_async> watcher from the default loop
3376	watcher callback into the event loop interested in the signal.	5016	watcher callback into the event loop interested in the signal.
3377		5017
3378	=back	5018	=back
3379		5019
		5020	See also L</THREAD LOCKING EXAMPLE>.
		5021
3380	=head3 COROUTINES	5022	=head3 COROUTINES
3381		5023
3382	Libev is very accommodating to coroutines ("cooperative threads"):	5024	Libev is very accommodating to coroutines ("cooperative threads"):
3383	libev fully supports nesting calls to its functions from different	5025	libev fully supports nesting calls to its functions from different
3384	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5026	coroutines (e.g. you can call C<ev_run> on the same loop from two
3385	different coroutines, and switch freely between both coroutines running the	5027	different coroutines, and switch freely between both coroutines running
3386	loop, as long as you don't confuse yourself). The only exception is that	5028	the loop, as long as you don't confuse yourself). The only exception is
3387	you must not do this from C<ev_periodic> reschedule callbacks.	5029	that you must not do this from C<ev_periodic> reschedule callbacks.
3388		5030
3389	Care has been taken to ensure that libev does not keep local state inside	5031	Care has been taken to ensure that libev does not keep local state inside
3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5032	C<ev_run>, and other calls do not usually allow for coroutine switches as
3391	they do not clal any callbacks.	5033	they do not call any callbacks.
3392		5034
3393	=head2 COMPILER WARNINGS	5035	=head2 COMPILER WARNINGS
3394		5036
3395	Depending on your compiler and compiler settings, you might get no or a	5037	Depending on your compiler and compiler settings, you might get no or a
3396	lot of warnings when compiling libev code. Some people are apparently	5038	lot of warnings when compiling libev code. Some people are apparently
…		…
3406	maintainable.	5048	maintainable.
3407		5049
3408	And of course, some compiler warnings are just plain stupid, or simply	5050	And of course, some compiler warnings are just plain stupid, or simply
3409	wrong (because they don't actually warn about the condition their message	5051	wrong (because they don't actually warn about the condition their message
3410	seems to warn about). For example, certain older gcc versions had some	5052	seems to warn about). For example, certain older gcc versions had some
3411	warnings that resulted an extreme number of false positives. These have	5053	warnings that resulted in an extreme number of false positives. These have
3412	been fixed, but some people still insist on making code warn-free with	5054	been fixed, but some people still insist on making code warn-free with
3413	such buggy versions.	5055	such buggy versions.
3414		5056
3415	While libev is written to generate as few warnings as possible,	5057	While libev is written to generate as few warnings as possible,
3416	"warn-free" code is not a goal, and it is recommended not to build libev	5058	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3430	==2274== definitely lost: 0 bytes in 0 blocks.	5072	==2274== definitely lost: 0 bytes in 0 blocks.
3431	==2274== possibly lost: 0 bytes in 0 blocks.	5073	==2274== possibly lost: 0 bytes in 0 blocks.
3432	==2274== still reachable: 256 bytes in 1 blocks.	5074	==2274== still reachable: 256 bytes in 1 blocks.
3433		5075
3434	Then there is no memory leak, just as memory accounted to global variables	5076	Then there is no memory leak, just as memory accounted to global variables
3435	is not a memleak - the memory is still being refernced, and didn't leak.	5077	is not a memleak - the memory is still being referenced, and didn't leak.
3436		5078
3437	Similarly, under some circumstances, valgrind might report kernel bugs	5079	Similarly, under some circumstances, valgrind might report kernel bugs
3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5080	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3439	although an acceptable workaround has been found here), or it might be	5081	although an acceptable workaround has been found here), or it might be
3440	confused.	5082	confused.
…		…
3452	I suggest using suppression lists.	5094	I suggest using suppression lists.
3453		5095
3454		5096
3455	=head1 PORTABILITY NOTES	5097	=head1 PORTABILITY NOTES
3456		5098
		5099	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5100
		5101	GNU/Linux is the only common platform that supports 64 bit file/large file
		5102	interfaces but I<disables> them by default.
		5103
		5104	That means that libev compiled in the default environment doesn't support
		5105	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5106
		5107	Unfortunately, many programs try to work around this GNU/Linux issue
		5108	by enabling the large file API, which makes them incompatible with the
		5109	standard libev compiled for their system.
		5110
		5111	Likewise, libev cannot enable the large file API itself as this would
		5112	suddenly make it incompatible to the default compile time environment,
		5113	i.e. all programs not using special compile switches.
		5114
		5115	=head2 OS/X AND DARWIN BUGS
		5116
		5117	The whole thing is a bug if you ask me - basically any system interface
		5118	you touch is broken, whether it is locales, poll, kqueue or even the
		5119	OpenGL drivers.
		5120
		5121	=head3 C<kqueue> is buggy
		5122
		5123	The kqueue syscall is broken in all known versions - most versions support
		5124	only sockets, many support pipes.
		5125
		5126	Libev tries to work around this by not using C<kqueue> by default on this
		5127	rotten platform, but of course you can still ask for it when creating a
		5128	loop - embedding a socket-only kqueue loop into a select-based one is
		5129	probably going to work well.
		5130
		5131	=head3 C<poll> is buggy
		5132
		5133	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5134	implementation by something calling C<kqueue> internally around the 10.5.6
		5135	release, so now C<kqueue> I<and> C<poll> are broken.
		5136
		5137	Libev tries to work around this by not using C<poll> by default on
		5138	this rotten platform, but of course you can still ask for it when creating
		5139	a loop.
		5140
		5141	=head3 C<select> is buggy
		5142
		5143	All that's left is C<select>, and of course Apple found a way to fuck this
		5144	one up as well: On OS/X, C<select> actively limits the number of file
		5145	descriptors you can pass in to 1024 - your program suddenly crashes when
		5146	you use more.
		5147
		5148	There is an undocumented "workaround" for this - defining
		5149	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5150	work on OS/X.
		5151
		5152	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5153
		5154	=head3 C<errno> reentrancy
		5155
		5156	The default compile environment on Solaris is unfortunately so
		5157	thread-unsafe that you can't even use components/libraries compiled
		5158	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5159	defined by default. A valid, if stupid, implementation choice.
		5160
		5161	If you want to use libev in threaded environments you have to make sure
		5162	it's compiled with C<_REENTRANT> defined.
		5163
		5164	=head3 Event port backend
		5165
		5166	The scalable event interface for Solaris is called "event
		5167	ports". Unfortunately, this mechanism is very buggy in all major
		5168	releases. If you run into high CPU usage, your program freezes or you get
		5169	a large number of spurious wakeups, make sure you have all the relevant
		5170	and latest kernel patches applied. No, I don't know which ones, but there
		5171	are multiple ones to apply, and afterwards, event ports actually work
		5172	great.
		5173
		5174	If you can't get it to work, you can try running the program by setting
		5175	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5176	C<select> backends.
		5177
		5178	=head2 AIX POLL BUG
		5179
		5180	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5181	this by trying to avoid the poll backend altogether (i.e. it's not even
		5182	compiled in), which normally isn't a big problem as C<select> works fine
		5183	with large bitsets on AIX, and AIX is dead anyway.
		5184
3457	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5185	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5186
		5187	=head3 General issues
3458		5188
3459	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5189	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3460	requires, and its I/O model is fundamentally incompatible with the POSIX	5190	requires, and its I/O model is fundamentally incompatible with the POSIX
3461	model. Libev still offers limited functionality on this platform in	5191	model. Libev still offers limited functionality on this platform in
3462	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5192	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3463	descriptors. This only applies when using Win32 natively, not when using	5193	descriptors. This only applies when using Win32 natively, not when using
3464	e.g. cygwin.	5194	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5195	as every compiler comes with a slightly differently broken/incompatible
		5196	environment.
3465		5197
3466	Lifting these limitations would basically require the full	5198	Lifting these limitations would basically require the full
3467	re-implementation of the I/O system. If you are into these kinds of	5199	re-implementation of the I/O system. If you are into this kind of thing,
3468	things, then note that glib does exactly that for you in a very portable	5200	then note that glib does exactly that for you in a very portable way (note
3469	way (note also that glib is the slowest event library known to man).	5201	also that glib is the slowest event library known to man).
3470		5202
3471	There is no supported compilation method available on windows except	5203	There is no supported compilation method available on windows except
3472	embedding it into other applications.	5204	embedding it into other applications.
		5205
		5206	Sensible signal handling is officially unsupported by Microsoft - libev
		5207	tries its best, but under most conditions, signals will simply not work.
3473		5208
3474	Not a libev limitation but worth mentioning: windows apparently doesn't	5209	Not a libev limitation but worth mentioning: windows apparently doesn't
3475	accept large writes: instead of resulting in a partial write, windows will	5210	accept large writes: instead of resulting in a partial write, windows will
3476	either accept everything or return C<ENOBUFS> if the buffer is too large,	5211	either accept everything or return C<ENOBUFS> if the buffer is too large,
3477	so make sure you only write small amounts into your sockets (less than a	5212	so make sure you only write small amounts into your sockets (less than a
…		…
3482	the abysmal performance of winsockets, using a large number of sockets	5217	the abysmal performance of winsockets, using a large number of sockets
3483	is not recommended (and not reasonable). If your program needs to use	5218	is not recommended (and not reasonable). If your program needs to use
3484	more than a hundred or so sockets, then likely it needs to use a totally	5219	more than a hundred or so sockets, then likely it needs to use a totally
3485	different implementation for windows, as libev offers the POSIX readiness	5220	different implementation for windows, as libev offers the POSIX readiness
3486	notification model, which cannot be implemented efficiently on windows	5221	notification model, which cannot be implemented efficiently on windows
3487	(Microsoft monopoly games).	5222	(due to Microsoft monopoly games).
3488		5223
3489	A typical way to use libev under windows is to embed it (see the embedding	5224	A typical way to use libev under windows is to embed it (see the embedding
3490	section for details) and use the following F<evwrap.h> header file instead	5225	section for details) and use the following F<evwrap.h> header file instead
3491	of F<ev.h>:	5226	of F<ev.h>:
3492		5227
…		…
3499	you do I<not> compile the F<ev.c> or any other embedded source files!):	5234	you do I<not> compile the F<ev.c> or any other embedded source files!):
3500		5235
3501	#include "evwrap.h"	5236	#include "evwrap.h"
3502	#include "ev.c"	5237	#include "ev.c"
3503		5238
3504	=over 4
3505
3506	=item The winsocket select function	5239	=head3 The winsocket C<select> function
3507		5240
3508	The winsocket C<select> function doesn't follow POSIX in that it	5241	The winsocket C<select> function doesn't follow POSIX in that it
3509	requires socket I<handles> and not socket I<file descriptors> (it is	5242	requires socket I<handles> and not socket I<file descriptors> (it is
3510	also extremely buggy). This makes select very inefficient, and also	5243	also extremely buggy). This makes select very inefficient, and also
3511	requires a mapping from file descriptors to socket handles (the Microsoft	5244	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3520	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5253	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3521		5254
3522	Note that winsockets handling of fd sets is O(n), so you can easily get a	5255	Note that winsockets handling of fd sets is O(n), so you can easily get a
3523	complexity in the O(n²) range when using win32.	5256	complexity in the O(n²) range when using win32.
3524		5257
3525	=item Limited number of file descriptors	5258	=head3 Limited number of file descriptors
3526		5259
3527	Windows has numerous arbitrary (and low) limits on things.	5260	Windows has numerous arbitrary (and low) limits on things.
3528		5261
3529	Early versions of winsocket's select only supported waiting for a maximum	5262	Early versions of winsocket's select only supported waiting for a maximum
3530	of C<64> handles (probably owning to the fact that all windows kernels	5263	of C<64> handles (probably owning to the fact that all windows kernels
3531	can only wait for C<64> things at the same time internally; Microsoft	5264	can only wait for C<64> things at the same time internally; Microsoft
3532	recommends spawning a chain of threads and wait for 63 handles and the	5265	recommends spawning a chain of threads and wait for 63 handles and the
3533	previous thread in each. Great).	5266	previous thread in each. Sounds great!).
3534		5267
3535	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5268	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3536	to some high number (e.g. C<2048>) before compiling the winsocket select	5269	to some high number (e.g. C<2048>) before compiling the winsocket select
3537	call (which might be in libev or elsewhere, for example, perl does its own	5270	call (which might be in libev or elsewhere, for example, perl and many
3538	select emulation on windows).	5271	other interpreters do their own select emulation on windows).
3539		5272
3540	Another limit is the number of file descriptors in the Microsoft runtime	5273	Another limit is the number of file descriptors in the Microsoft runtime
3541	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5274	libraries, which by default is C<64> (there must be a hidden I<64>
3542	or something like this inside Microsoft). You can increase this by calling	5275	fetish or something like this inside Microsoft). You can increase this
3543	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5276	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3544	arbitrary limit), but is broken in many versions of the Microsoft runtime	5277	(another arbitrary limit), but is broken in many versions of the Microsoft
3545	libraries.
3546
3547	This might get you to about C<512> or C<2048> sockets (depending on	5278	runtime libraries. This might get you to about C<512> or C<2048> sockets
3548	windows version and/or the phase of the moon). To get more, you need to	5279	(depending on windows version and/or the phase of the moon). To get more,
3549	wrap all I/O functions and provide your own fd management, but the cost of	5280	you need to wrap all I/O functions and provide your own fd management, but
3550	calling select (O(n²)) will likely make this unworkable.	5281	the cost of calling select (O(n²)) will likely make this unworkable.
3551
3552	=back
3553		5282
3554	=head2 PORTABILITY REQUIREMENTS	5283	=head2 PORTABILITY REQUIREMENTS
3555		5284
3556	In addition to a working ISO-C implementation and of course the	5285	In addition to a working ISO-C implementation and of course the
3557	backend-specific APIs, libev relies on a few additional extensions:	5286	backend-specific APIs, libev relies on a few additional extensions:
…		…
3564	Libev assumes not only that all watcher pointers have the same internal	5293	Libev assumes not only that all watcher pointers have the same internal
3565	structure (guaranteed by POSIX but not by ISO C for example), but it also	5294	structure (guaranteed by POSIX but not by ISO C for example), but it also
3566	assumes that the same (machine) code can be used to call any watcher	5295	assumes that the same (machine) code can be used to call any watcher
3567	callback: The watcher callbacks have different type signatures, but libev	5296	callback: The watcher callbacks have different type signatures, but libev
3568	calls them using an C<ev_watcher *> internally.	5297	calls them using an C<ev_watcher *> internally.
		5298
		5299	=item pointer accesses must be thread-atomic
		5300
		5301	Accessing a pointer value must be atomic, it must both be readable and
		5302	writable in one piece - this is the case on all current architectures.
3569		5303
3570	=item C<sig_atomic_t volatile> must be thread-atomic as well	5304	=item C<sig_atomic_t volatile> must be thread-atomic as well
3571		5305
3572	The type C<sig_atomic_t volatile> (or whatever is defined as	5306	The type C<sig_atomic_t volatile> (or whatever is defined as
3573	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5307	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3582	thread" or will block signals process-wide, both behaviours would	5316	thread" or will block signals process-wide, both behaviours would
3583	be compatible with libev. Interaction between C<sigprocmask> and	5317	be compatible with libev. Interaction between C<sigprocmask> and
3584	C<pthread_sigmask> could complicate things, however.	5318	C<pthread_sigmask> could complicate things, however.
3585		5319
3586	The most portable way to handle signals is to block signals in all threads	5320	The most portable way to handle signals is to block signals in all threads
3587	except the initial one, and run the default loop in the initial thread as	5321	except the initial one, and run the signal handling loop in the initial
3588	well.	5322	thread as well.
3589		5323
3590	=item C<long> must be large enough for common memory allocation sizes	5324	=item C<long> must be large enough for common memory allocation sizes
3591		5325
3592	To improve portability and simplify its API, libev uses C<long> internally	5326	To improve portability and simplify its API, libev uses C<long> internally
3593	instead of C<size_t> when allocating its data structures. On non-POSIX	5327	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3596	watchers.	5330	watchers.
3597		5331
3598	=item C<double> must hold a time value in seconds with enough accuracy	5332	=item C<double> must hold a time value in seconds with enough accuracy
3599		5333
3600	The type C<double> is used to represent timestamps. It is required to	5334	The type C<double> is used to represent timestamps. It is required to
3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5335	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3602	enough for at least into the year 4000. This requirement is fulfilled by	5336	good enough for at least into the year 4000 with millisecond accuracy
		5337	(the design goal for libev). This requirement is overfulfilled by
3603	implementations implementing IEEE 754 (basically all existing ones).	5338	implementations using IEEE 754, which is basically all existing ones.
		5339
		5340	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5341	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5342	is either obsolete or somebody patched it to use C<long double> or
		5343	something like that, just kidding).
3604		5344
3605	=back	5345	=back
3606		5346
3607	If you know of other additional requirements drop me a note.	5347	If you know of other additional requirements drop me a note.
3608		5348
…		…
3670	=item Processing ev_async_send: O(number_of_async_watchers)	5410	=item Processing ev_async_send: O(number_of_async_watchers)
3671		5411
3672	=item Processing signals: O(max_signal_number)	5412	=item Processing signals: O(max_signal_number)
3673		5413
3674	Sending involves a system call I<iff> there were no other C<ev_async_send>	5414	Sending involves a system call I<iff> there were no other C<ev_async_send>
3675	calls in the current loop iteration. Checking for async and signal events	5415	calls in the current loop iteration and the loop is currently
		5416	blocked. Checking for async and signal events involves iterating over all
3676	involves iterating over all running async watchers or all signal numbers.	5417	running async watchers or all signal numbers.
3677		5418
3678	=back	5419	=back
3679		5420
3680		5421
		5422	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5423
		5424	The major version 4 introduced some incompatible changes to the API.
		5425
		5426	At the moment, the C<ev.h> header file provides compatibility definitions
		5427	for all changes, so most programs should still compile. The compatibility
		5428	layer might be removed in later versions of libev, so better update to the
		5429	new API early than late.
		5430
		5431	=over 4
		5432
		5433	=item C<EV_COMPAT3> backwards compatibility mechanism
		5434
		5435	The backward compatibility mechanism can be controlled by
		5436	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5437	section.
		5438
		5439	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5440
		5441	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5442
		5443	ev_loop_destroy (EV_DEFAULT_UC);
		5444	ev_loop_fork (EV_DEFAULT);
		5445
		5446	=item function/symbol renames
		5447
		5448	A number of functions and symbols have been renamed:
		5449
		5450	ev_loop => ev_run
		5451	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5452	EVLOOP_ONESHOT => EVRUN_ONCE
		5453
		5454	ev_unloop => ev_break
		5455	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5456	EVUNLOOP_ONE => EVBREAK_ONE
		5457	EVUNLOOP_ALL => EVBREAK_ALL
		5458
		5459	EV_TIMEOUT => EV_TIMER
		5460
		5461	ev_loop_count => ev_iteration
		5462	ev_loop_depth => ev_depth
		5463	ev_loop_verify => ev_verify
		5464
		5465	Most functions working on C<struct ev_loop> objects don't have an
		5466	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5467	associated constants have been renamed to not collide with the C<struct
		5468	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5469	as all other watcher types. Note that C<ev_loop_fork> is still called
		5470	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5471	typedef.
		5472
		5473	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5474
		5475	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5476	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5477	and work, but the library code will of course be larger.
		5478
		5479	=back
		5480
		5481
		5482	=head1 GLOSSARY
		5483
		5484	=over 4
		5485
		5486	=item active
		5487
		5488	A watcher is active as long as it has been started and not yet stopped.
		5489	See L</WATCHER STATES> for details.
		5490
		5491	=item application
		5492
		5493	In this document, an application is whatever is using libev.
		5494
		5495	=item backend
		5496
		5497	The part of the code dealing with the operating system interfaces.
		5498
		5499	=item callback
		5500
		5501	The address of a function that is called when some event has been
		5502	detected. Callbacks are being passed the event loop, the watcher that
		5503	received the event, and the actual event bitset.
		5504
		5505	=item callback/watcher invocation
		5506
		5507	The act of calling the callback associated with a watcher.
		5508
		5509	=item event
		5510
		5511	A change of state of some external event, such as data now being available
		5512	for reading on a file descriptor, time having passed or simply not having
		5513	any other events happening anymore.
		5514
		5515	In libev, events are represented as single bits (such as C<EV_READ> or
		5516	C<EV_TIMER>).
		5517
		5518	=item event library
		5519
		5520	A software package implementing an event model and loop.
		5521
		5522	=item event loop
		5523
		5524	An entity that handles and processes external events and converts them
		5525	into callback invocations.
		5526
		5527	=item event model
		5528
		5529	The model used to describe how an event loop handles and processes
		5530	watchers and events.
		5531
		5532	=item pending
		5533
		5534	A watcher is pending as soon as the corresponding event has been
		5535	detected. See L</WATCHER STATES> for details.
		5536
		5537	=item real time
		5538
		5539	The physical time that is observed. It is apparently strictly monotonic :)
		5540
		5541	=item wall-clock time
		5542
		5543	The time and date as shown on clocks. Unlike real time, it can actually
		5544	be wrong and jump forwards and backwards, e.g. when you adjust your
		5545	clock.
		5546
		5547	=item watcher
		5548
		5549	A data structure that describes interest in certain events. Watchers need
		5550	to be started (attached to an event loop) before they can receive events.
		5551
		5552	=back
		5553
3681	=head1 AUTHOR	5554	=head1 AUTHOR
3682		5555
3683	Marc Lehmann <libev@schmorp.de>.	5556	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5557	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3684		5558

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