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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
72		92
73	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
74	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	122	for example).
102		123
…		…
105	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
121	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
155	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
161	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
162	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
163		192
164	=item int ev_version_major ()	193	=item int ev_version_major ()
165		194
166	=item int ev_version_minor ()	195	=item int ev_version_minor ()
167		196
…		…
178	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	209	not a problem.
181		210
182	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
184		214
185	assert (("libev version mismatch",	215	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
188		218
…		…
199	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
201		231
202	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
203		233
204	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
210		241
211	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
212		243
213	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
218		249
219	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
220		251
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
222		253
223	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
252	}	283	}
253		284
254	...	285	...
255	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
256		287
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
258		289
259	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
260	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	305	}
275		306
276	...	307	...
277	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
278		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
279	=back	323	=back
280		324
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		326
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
286		330
287	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
289	not.	333	do not.
290		334
291	=over 4	335	=over 4
292		336
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		338
295	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
299		349
300	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
301	function.	351	function (or via the C<EV_DEFAULT> macro).
302		352
303	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
306		357
307	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
313		382
314	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		385
317	The following flags are supported:	386	The following flags are supported:
…		…
332	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
333	around bugs.	402	around bugs.
334		403
335	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
336		405
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		408
341	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	418	flag.
351		419
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	421	environment variable.
354		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		459
357	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		488
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
388	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
389	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
390	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
391	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
392		498
393	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	508	and is of course hard to detect.
401		509
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
403	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
404	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
405	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
406	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
409		526
410	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		597
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
483		600
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	604	might perform better.
492		605
493	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
497		620
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
500		623
501	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
502		625
503	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		629
507	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		639
509	=back	640	=back
510		641
511	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
514		645	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		646
543	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
544		648
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	650	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
548		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
549	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
550		659
551	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		667
559	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
562		671
563	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
567		680
568	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
569		682
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
581		693
582	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
585		700
586	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
590	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		715
599	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
600		717
601	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	719	otherwise.
603		720
604	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
605		722
606	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
609		726
610	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
613		745
614	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
615		747
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	749	use.
…		…
626		758
627	=item ev_now_update (loop)	759	=item ev_now_update (loop)
628		760
629	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
632		764
633	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	767	the current time is a good idea.
636		768
637	See also "The special problem of time updates" in the C<ev_timer> section.	769	See also L<The special problem of time updates> in the C<ev_timer> section.
638		770
639	=item ev_suspend (loop)	771	=item ev_suspend (loop)
640		772
641	=item ev_resume (loop)	773	=item ev_resume (loop)
642		774
643	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
644	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
645		777
646	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
647	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
648	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
649	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
651	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
652		784
653	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
655	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
656	occured while suspended).	788	occurred while suspended).
657		789
658	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
660	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
661		793
662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
663	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
664		796
665	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
666		798
667	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
669	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
670		804
671	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
672	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
673		808
674	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
675	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
676	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
677	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
678	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
679	beauty.	814	beauty.
680		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
682	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
683	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
684	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
685		826
686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
687	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
688	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
689	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
690	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
691	iteration of the loop.	832	iteration of the loop.
692		833
693	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
694	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
696	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
697		838
698	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
699		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
700	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
701	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
702	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
703	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
704	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
705	as to not disturb the other process.	852	as to not disturb the other process.
706	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
707	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
708	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
709	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
710	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
711	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
712	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
713	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
715	- Queue all expired timers.	863	- Queue all expired timers.
716	- Queue all expired periodics.	864	- Queue all expired periodics.
717	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
718	- Queue all check watchers.	866	- Queue all check watchers.
719	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
720	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
721	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
723	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
724	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
725		877
726	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
727	anymore.	879	anymore.
728		880
729	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
730	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
731	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
732	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
733		885
734	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
735		887
736	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
737	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
740		892
741	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
742		894
743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
744		897
745	=item ev_ref (loop)	898	=item ev_ref (loop)
746		899
747	=item ev_unref (loop)	900	=item ev_unref (loop)
748		901
749	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
752		905
753	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	909	before stopping it.
756		910
757	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
759	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
761	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
762	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
763	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
764	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
765	in the callback).	919	in the callback).
766		920
767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
768	running when nothing else is active.	922	running when nothing else is active.
769		923
770	ev_signal exitsig;	924	ev_signal exitsig;
771	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
772	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
773	evf_unref (loop);	927	ev_unref (loop);
774		928
775	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
776		930
777	ev_ref (loop);	931	ev_ref (loop);
778	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
798	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
799		953
800	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		959	sleep time ensures that libev will not poll for I/O events more often then
		960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
805		962
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		968
812	Many (busy) programs can usually benefit by setting the I/O collect	969	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	970	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	971	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	973	as this approaches the timing granularity of most systems. Note that if
		974	you do transactions with the outside world and you can't increase the
		975	parallelity, then this setting will limit your transaction rate (if you
		976	need to poll once per transaction and the I/O collect interval is 0.01,
		977	then you can't do more than 100 transactions per second).
817		978
818	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
820	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
821	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	983	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	984	they fire on, say, one-second boundaries only.
824		985
		986	Example: we only need 0.1s timeout granularity, and we wish not to poll
		987	more often than 100 times per second:
		988
		989	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		991
		992	=item ev_invoke_pending (loop)
		993
		994	This call will simply invoke all pending watchers while resetting their
		995	pending state. Normally, C<ev_run> does this automatically when required,
		996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1001
		1002	=item int ev_pending_count (loop)
		1003
		1004	Returns the number of pending watchers - zero indicates that no watchers
		1005	are pending.
		1006
		1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1008
		1009	This overrides the invoke pending functionality of the loop: Instead of
		1010	invoking all pending watchers when there are any, C<ev_run> will call
		1011	this callback instead. This is useful, for example, when you want to
		1012	invoke the actual watchers inside another context (another thread etc.).
		1013
		1014	If you want to reset the callback, use C<ev_invoke_pending> as new
		1015	callback.
		1016
		1017	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1018
		1019	Sometimes you want to share the same loop between multiple threads. This
		1020	can be done relatively simply by putting mutex_lock/unlock calls around
		1021	each call to a libev function.
		1022
		1023	However, C<ev_run> can run an indefinite time, so it is not feasible
		1024	to wait for it to return. One way around this is to wake up the event
		1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1026	I<release> and I<acquire> callbacks on the loop.
		1027
		1028	When set, then C<release> will be called just before the thread is
		1029	suspended waiting for new events, and C<acquire> is called just
		1030	afterwards.
		1031
		1032	Ideally, C<release> will just call your mutex_unlock function, and
		1033	C<acquire> will just call the mutex_lock function again.
		1034
		1035	While event loop modifications are allowed between invocations of
		1036	C<release> and C<acquire> (that's their only purpose after all), no
		1037	modifications done will affect the event loop, i.e. adding watchers will
		1038	have no effect on the set of file descriptors being watched, or the time
		1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1040	to take note of any changes you made.
		1041
		1042	In theory, threads executing C<ev_run> will be async-cancel safe between
		1043	invocations of C<release> and C<acquire>.
		1044
		1045	See also the locking example in the C<THREADS> section later in this
		1046	document.
		1047
		1048	=item ev_set_userdata (loop, void *data)
		1049
		1050	=item void *ev_userdata (loop)
		1051
		1052	Set and retrieve a single C<void *> associated with a loop. When
		1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1054	C<0>.
		1055
		1056	These two functions can be used to associate arbitrary data with a loop,
		1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1058	C<acquire> callbacks described above, but of course can be (ab-)used for
		1059	any other purpose as well.
		1060
825	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
826		1062
827	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
828	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
829	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
830	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
841		1077
842	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
844	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
845		1081
846	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
847	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
848	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
849		1086
850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
851	{	1088	{
852	ev_io_stop (w);	1089	ev_io_stop (w);
853	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
854	}	1091	}
855		1092
856	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
857		1094
858	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
859		1096
860	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
862	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
863		1100
864	ev_loop (loop, 0);	1101	ev_run (loop, 0);
865		1102
866	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
867	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
868	stack).	1105	stack).
869		1106
870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
872		1109
873	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
874	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
875	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
876	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
877	is readable and/or writable).	1114	and/or writable).
878		1115
879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
880	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
881	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
882	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
905	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
906		1143
907	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
908	writable.	1145	writable.
909		1146
910	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
911		1148
912	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
913		1150
914	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
915		1152
…		…
933		1170
934	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
935		1172
936	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
937		1174
938	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
939	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
940	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
941	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
942	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
943	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
944	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
945		1182
946	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
947		1184
948	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
949		1186
950	=item C<EV_FORK>	1187	=item C<EV_FORK>
951		1188
952	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
953	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
954		1195
955	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
956		1197
957	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
958		1199
…		…
1005		1246
1006	ev_io w;	1247	ev_io w;
1007	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1250
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1252
1012	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1269
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1271
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1273
1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1275
1035	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1037		1278
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1280	whole section.
1040		1281
1041	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1042		1283
1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1285
1045	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1287	the watcher was active or not).
1047		1288
1048	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1074		1315
1075	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1317	(modulo threads).
1077		1318
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1320
1080	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1081		1322
1082	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1325	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1326	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1327	from being executed (except for C<ev_idle> watchers).
1087		1328
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1329	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1330	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1331
1096	You I<must not> change the priority of a watcher as long as it is active or	1332	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1333	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1334
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1335	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1336	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1337	or might not have been clamped to the valid range.
		1338
		1339	The default priority used by watchers when no priority has been set is
		1340	always C<0>, which is supposed to not be too high and not be too low :).
		1341
		1342	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1343	priorities.
1105		1344
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1345	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1346
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1347	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1348	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1117	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1118		1357
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1121		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
1122	=back	1375	=back
1123		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1124		1379
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1126		1381
1127	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1128	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1129	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1130	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1131	member, you can also "subclass" the watcher type and provide your own
1132	data:
1133		1386
1134	struct my_io	1387	=over 4
		1388
		1389	=item initialiased
		1390
		1391	Before a watcher can be registered with the event loop it has to be
		1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1394
		1395	In this state it is simply some block of memory that is suitable for
		1396	use in an event loop. It can be moved around, freed, reused etc. at
		1397	will - as long as you either keep the memory contents intact, or call
		1398	C<ev_TYPE_init> again.
		1399
		1400	=item started/running/active
		1401
		1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
		1407
		1408	=item pending
		1409
		1410	If a watcher is active and libev determines that an event it is interested
		1411	in has occurred (such as a timer expiring), it will become pending. It will
		1412	stay in this pending state until either it is stopped or its callback is
		1413	about to be invoked, so it is not normally pending inside the watcher
		1414	callback.
		1415
		1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
		1422
		1423	It is also possible to feed an event on a watcher that is not active (e.g.
		1424	via C<ev_feed_event>), in which case it becomes pending without being
		1425	active.
		1426
		1427	=item stopped
		1428
		1429	A watcher can be stopped implicitly by libev (in which case it might still
		1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1431	latter will clear any pending state the watcher might be in, regardless
		1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
		1441
		1442	=head2 WATCHER PRIORITY MODELS
		1443
		1444	Many event loops support I<watcher priorities>, which are usually small
		1445	integers that influence the ordering of event callback invocation
		1446	between watchers in some way, all else being equal.
		1447
		1448	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1449	description for the more technical details such as the actual priority
		1450	range.
		1451
		1452	There are two common ways how these these priorities are being interpreted
		1453	by event loops:
		1454
		1455	In the more common lock-out model, higher priorities "lock out" invocation
		1456	of lower priority watchers, which means as long as higher priority
		1457	watchers receive events, lower priority watchers are not being invoked.
		1458
		1459	The less common only-for-ordering model uses priorities solely to order
		1460	callback invocation within a single event loop iteration: Higher priority
		1461	watchers are invoked before lower priority ones, but they all get invoked
		1462	before polling for new events.
		1463
		1464	Libev uses the second (only-for-ordering) model for all its watchers
		1465	except for idle watchers (which use the lock-out model).
		1466
		1467	The rationale behind this is that implementing the lock-out model for
		1468	watchers is not well supported by most kernel interfaces, and most event
		1469	libraries will just poll for the same events again and again as long as
		1470	their callbacks have not been executed, which is very inefficient in the
		1471	common case of one high-priority watcher locking out a mass of lower
		1472	priority ones.
		1473
		1474	Static (ordering) priorities are most useful when you have two or more
		1475	watchers handling the same resource: a typical usage example is having an
		1476	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1477	timeouts. Under load, data might be received while the program handles
		1478	other jobs, but since timers normally get invoked first, the timeout
		1479	handler will be executed before checking for data. In that case, giving
		1480	the timer a lower priority than the I/O watcher ensures that I/O will be
		1481	handled first even under adverse conditions (which is usually, but not
		1482	always, what you want).
		1483
		1484	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1485	will only be executed when no same or higher priority watchers have
		1486	received events, they can be used to implement the "lock-out" model when
		1487	required.
		1488
		1489	For example, to emulate how many other event libraries handle priorities,
		1490	you can associate an C<ev_idle> watcher to each such watcher, and in
		1491	the normal watcher callback, you just start the idle watcher. The real
		1492	processing is done in the idle watcher callback. This causes libev to
		1493	continuously poll and process kernel event data for the watcher, but when
		1494	the lock-out case is known to be rare (which in turn is rare :), this is
		1495	workable.
		1496
		1497	Usually, however, the lock-out model implemented that way will perform
		1498	miserably under the type of load it was designed to handle. In that case,
		1499	it might be preferable to stop the real watcher before starting the
		1500	idle watcher, so the kernel will not have to process the event in case
		1501	the actual processing will be delayed for considerable time.
		1502
		1503	Here is an example of an I/O watcher that should run at a strictly lower
		1504	priority than the default, and which should only process data when no
		1505	other events are pending:
		1506
		1507	ev_idle idle; // actual processing watcher
		1508	ev_io io; // actual event watcher
		1509
		1510	static void
		1511	io_cb (EV_P_ ev_io *w, int revents)
1135	{	1512	{
1136	ev_io io;	1513	// stop the I/O watcher, we received the event, but
1137	int otherfd;	1514	// are not yet ready to handle it.
1138	void *somedata;	1515	ev_io_stop (EV_A_ w);
1139	struct whatever *mostinteresting;	1516
		1517	// start the idle watcher to handle the actual event.
		1518	// it will not be executed as long as other watchers
		1519	// with the default priority are receiving events.
		1520	ev_idle_start (EV_A_ &idle);
1140	};	1521	}
1141		1522
1142	...	1523	static void
1143	struct my_io w;	1524	idle_cb (EV_P_ ev_idle *w, int revents)
1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1145
1146	And since your callback will be called with a pointer to the watcher, you
1147	can cast it back to your own type:
1148
1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1150	{	1525	{
1151	struct my_io *w = (struct my_io *)w_;	1526	// actual processing
1152	...	1527	read (STDIN_FILENO, ...);
		1528
		1529	// have to start the I/O watcher again, as
		1530	// we have handled the event
		1531	ev_io_start (EV_P_ &io);
1153	}	1532	}
1154		1533
1155	More interesting and less C-conformant ways of casting your callback type	1534	// initialisation
1156	instead have been omitted.	1535	ev_idle_init (&idle, idle_cb);
		1536	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1537	ev_io_start (EV_DEFAULT_ &io);
1157		1538
1158	Another common scenario is to use some data structure with multiple	1539	In the "real" world, it might also be beneficial to start a timer, so that
1159	embedded watchers:	1540	low-priority connections can not be locked out forever under load. This
1160		1541	enables your program to keep a lower latency for important connections
1161	struct my_biggy	1542	during short periods of high load, while not completely locking out less
1162	{	1543	important ones.
1163	int some_data;
1164	ev_timer t1;
1165	ev_timer t2;
1166	}
1167
1168	In this case getting the pointer to C<my_biggy> is a bit more
1169	complicated: Either you store the address of your C<my_biggy> struct
1170	in the C<data> member of the watcher (for woozies), or you need to use
1171	some pointer arithmetic using C<offsetof> inside your watchers (for real
1172	programmers):
1173
1174	#include <stddef.h>
1175
1176	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{
1179	struct my_biggy big = (struct my_biggy *
1180	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}
1182
1183	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{
1186	struct my_biggy big = (struct my_biggy *
1187	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}
1189		1544
1190		1545
1191	=head1 WATCHER TYPES	1546	=head1 WATCHER TYPES
1192		1547
1193	This section describes each watcher in detail, but will not repeat	1548	This section describes each watcher in detail, but will not repeat
…		…
1217	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1218	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1219	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1575	required if you know what you are doing).
1221		1576
1222	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1225
1226	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1230	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1231	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1232	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1233	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1234		1584
1235	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1236	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1237	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1238	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1239	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1240	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1241	indefinitely.	1591	indefinitely.
1242		1592
1243	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1244		1594
…		…
1272		1622
1273	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1274	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1275	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1276		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1277	=head3 The special problem of fork	1660	=head3 The special problem of fork
1278		1661
1279	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1280	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1281	it in the child.	1664	it in the child if you want to continue to use it in the child.
1282		1665
1283	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1284	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1286	C<EVBACKEND_POLL>.
1287		1669
1288	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1289		1671
1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1291	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1294		1676
1295	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1297	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1298		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1299		1719
1300	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1301		1721
1302	=over 4	1722	=over 4
1303		1723
…		…
1335	...	1755	...
1336	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1337	ev_io stdin_readable;	1757	ev_io stdin_readable;
1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1339	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1340	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1341		1761
1342		1762
1343	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1344		1764
1345	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1770	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1353		1773
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
		1775	passed (not I<at>, so on systems with very low-resolution clocks this
		1776	might introduce a small delay, see "the special problem of being too
1355	passed. If multiple timers become ready during the same loop iteration	1777	early", below). If multiple timers become ready during the same loop
1356	then the ones with earlier time-out values are invoked before ones with	1778	iteration then the ones with earlier time-out values are invoked before
1357	later time-out values (but this is no longer true when a callback calls	1779	ones of the same priority with later time-out values (but this is no
1358	C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1359		1781
1360	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1361		1783
1362	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1829	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1830	member and C<ev_timer_again>.
1409		1831
1410	At start:	1832	At start:
1411		1833
1412	ev_timer_init (timer, callback);	1834	ev_init (timer, callback);
1413	timer->repeat = 60.;	1835	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1836	ev_timer_again (loop, timer);
1415		1837
1416	Each time there is some activity:	1838	Each time there is some activity:
1417		1839
…		…
1438		1860
1439	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1440	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1441	within the callback:	1863	within the callback:
1442		1864
		1865	ev_tstamp timeout = 60.;
1443	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1444		1868
1445	static void	1869	static void
1446	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1447	{	1871	{
1448	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1449	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1450		1874
1451	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1452	if (timeout < now)	1876	if (after < 0.)
1453	{	1877	{
1454	// timeout occured, take action	1878	// timeout occurred, take action
1455	}	1879	}
1456	else	1880	else
1457	{	1881	{
1458	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1459	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1460	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1461	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1462	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1463	}	1888	}
1464	}	1889	}
1465		1890
1466	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1467	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1468	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1469	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1470	re-schedule the timer to fire at that future time, to see if maybe we have
1471	a timeout then.
1472		1895
1473	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1474	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1475		1905
1476	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1477	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1478	libev to change the timeout.	1908	libev to change the timeout.
1479		1909
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1481	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1482	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1483		1914
		1915	last_activity = ev_now (EV_A);
1484	ev_timer_init (timer, callback);	1916	ev_init (&timer, callback);
1485	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1486	callback (loop, timer, EV_TIMEOUT);
1487		1918
1488	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1490		1921
		1922	if (activity detected)
1491	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1492		1932
1493	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1494	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1495
1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
1497	callback :) - just change the timeout and invoke the callback, which will
1498	fix things for you.
1499		1935
1500	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1501		1937
1502	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1503	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1531	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1532	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1533	overkill :)	1969	overkill :)
1534		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1535	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1536		2009
1537	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1538	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1539	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1541	lots of events in one iteration.	2014	lots of events in one iteration.
1542		2015
1543	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1544	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1550		2023
1551	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	2026	()>.
1554		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
		2060
		2061	=head3 The special problems of suspended animation
		2062
		2063	When you leave the server world it is quite customary to hit machines that
		2064	can suspend/hibernate - what happens to the clocks during such a suspend?
		2065
		2066	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2067	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2068	to run until the system is suspended, but they will not advance while the
		2069	system is suspended. That means, on resume, it will be as if the program
		2070	was frozen for a few seconds, but the suspend time will not be counted
		2071	towards C<ev_timer> when a monotonic clock source is used. The real time
		2072	clock advanced as expected, but if it is used as sole clocksource, then a
		2073	long suspend would be detected as a time jump by libev, and timers would
		2074	be adjusted accordingly.
		2075
		2076	I would not be surprised to see different behaviour in different between
		2077	operating systems, OS versions or even different hardware.
		2078
		2079	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2080	time jump in the monotonic clocks and the realtime clock. If the program
		2081	is suspended for a very long time, and monotonic clock sources are in use,
		2082	then you can expect C<ev_timer>s to expire as the full suspension time
		2083	will be counted towards the timers. When no monotonic clock source is in
		2084	use, then libev will again assume a timejump and adjust accordingly.
		2085
		2086	It might be beneficial for this latter case to call C<ev_suspend>
		2087	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2088	deterministic behaviour in this case (you can do nothing against
		2089	C<SIGSTOP>).
		2090
1555	=head3 Watcher-Specific Functions and Data Members	2091	=head3 Watcher-Specific Functions and Data Members
1556		2092
1557	=over 4	2093	=over 4
1558		2094
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2095	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1572	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1573	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1574		2110
1575	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1576		2112
1577	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out, and restarts it again if it is
1578	repeating. The exact semantics are:	2114	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2115	timeout to the C<repeat> value and calling C<ev_timer_start>.
1579		2116
		2117	The exact semantics are as in the following rules, all of which will be
		2118	applied to the watcher:
		2119
		2120	=over 4
		2121
1580	If the timer is pending, its pending status is cleared.	2122	=item If the timer is pending, the pending status is always cleared.
1581		2123
1582	If the timer is started but non-repeating, stop it (as if it timed out).	2124	=item If the timer is started but non-repeating, stop it (as if it timed
		2125	out, without invoking it).
1583		2126
1584	If the timer is repeating, either start it if necessary (with the	2127	=item If the timer is repeating, make the C<repeat> value the new timeout
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	2128	and start the timer, if necessary.
1586		2129
		2130	=back
		2131
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2132	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1588	usage example.	2133	usage example.
		2134
		2135	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2136
		2137	Returns the remaining time until a timer fires. If the timer is active,
		2138	then this time is relative to the current event loop time, otherwise it's
		2139	the timeout value currently configured.
		2140
		2141	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2142	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2143	will return C<4>. When the timer expires and is restarted, it will return
		2144	roughly C<7> (likely slightly less as callback invocation takes some time,
		2145	too), and so on.
1589		2146
1590	=item ev_tstamp repeat [read-write]	2147	=item ev_tstamp repeat [read-write]
1591		2148
1592	The current C<repeat> value. Will be used each time the watcher times out	2149	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	2150	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1619	}	2176	}
1620		2177
1621	ev_timer mytimer;	2178	ev_timer mytimer;
1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2179	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1623	ev_timer_again (&mytimer); /* start timer */	2180	ev_timer_again (&mytimer); /* start timer */
1624	ev_loop (loop, 0);	2181	ev_run (loop, 0);
1625		2182
1626	// and in some piece of code that gets executed on any "activity":	2183	// and in some piece of code that gets executed on any "activity":
1627	// reset the timeout to start ticking again at 10 seconds	2184	// reset the timeout to start ticking again at 10 seconds
1628	ev_timer_again (&mytimer);	2185	ev_timer_again (&mytimer);
1629		2186
…		…
1655		2212
1656	As with timers, the callback is guaranteed to be invoked only when the	2213	As with timers, the callback is guaranteed to be invoked only when the
1657	point in time where it is supposed to trigger has passed. If multiple	2214	point in time where it is supposed to trigger has passed. If multiple
1658	timers become ready during the same loop iteration then the ones with	2215	timers become ready during the same loop iteration then the ones with
1659	earlier time-out values are invoked before ones with later time-out values	2216	earlier time-out values are invoked before ones with later time-out values
1660	(but this is no longer true when a callback calls C<ev_loop> recursively).	2217	(but this is no longer true when a callback calls C<ev_run> recursively).
1661		2218
1662	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1663		2220
1664	=over 4	2221	=over 4
1665		2222
…		…
1700		2257
1701	Another way to think about it (for the mathematically inclined) is that	2258	Another way to think about it (for the mathematically inclined) is that
1702	C<ev_periodic> will try to run the callback in this mode at the next possible	2259	C<ev_periodic> will try to run the callback in this mode at the next possible
1703	time where C<time = offset (mod interval)>, regardless of any time jumps.	2260	time where C<time = offset (mod interval)>, regardless of any time jumps.
1704		2261
1705	For numerical stability it is preferable that the C<offset> value is near	2262	The C<interval> I<MUST> be positive, and for numerical stability, the
1706	C<ev_now ()> (the current time), but there is no range requirement for	2263	interval value should be higher than C<1/8192> (which is around 100
1707	this value, and in fact is often specified as zero.	2264	microseconds) and C<offset> should be higher than C<0> and should have
		2265	at most a similar magnitude as the current time (say, within a factor of
		2266	ten). Typical values for offset are, in fact, C<0> or something between
		2267	C<0> and C<interval>, which is also the recommended range.
1708		2268
1709	Note also that there is an upper limit to how often a timer can fire (CPU	2269	Note also that there is an upper limit to how often a timer can fire (CPU
1710	speed for example), so if C<interval> is very small then timing stability	2270	speed for example), so if C<interval> is very small then timing stability
1711	will of course deteriorate. Libev itself tries to be exact to be about one	2271	will of course deteriorate. Libev itself tries to be exact to be about one
1712	millisecond (if the OS supports it and the machine is fast enough).	2272	millisecond (if the OS supports it and the machine is fast enough).
…		…
1793	Example: Call a callback every hour, or, more precisely, whenever the	2353	Example: Call a callback every hour, or, more precisely, whenever the
1794	system time is divisible by 3600. The callback invocation times have	2354	system time is divisible by 3600. The callback invocation times have
1795	potentially a lot of jitter, but good long-term stability.	2355	potentially a lot of jitter, but good long-term stability.
1796		2356
1797	static void	2357	static void
1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2358	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1799	{	2359	{
1800	... its now a full hour (UTC, or TAI or whatever your clock follows)	2360	... its now a full hour (UTC, or TAI or whatever your clock follows)
1801	}	2361	}
1802		2362
1803	ev_periodic hourly_tick;	2363	ev_periodic hourly_tick;
…		…
1826		2386
1827	=head2 C<ev_signal> - signal me when a signal gets signalled!	2387	=head2 C<ev_signal> - signal me when a signal gets signalled!
1828		2388
1829	Signal watchers will trigger an event when the process receives a specific	2389	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2390	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2391	will try its best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2392	normal event processing, like any other event.
1833		2393
1834	If you want signals asynchronously, just use C<sigaction> as you would	2394	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2395	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2396	the signal. You can even use C<ev_async> from a signal handler to
		2397	synchronously wake up an event loop.
1837		2398
1838	You can configure as many watchers as you like per signal. Only when the	2399	You can configure as many watchers as you like for the same signal, but
		2400	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2401	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2402	C<SIGINT> in both the default loop and another loop at the same time. At
		2403	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2404
1839	first watcher gets started will libev actually register a signal handler	2405	When the first watcher gets started will libev actually register something
1840	with the kernel (thus it coexists with your own signal handlers as long as	2406	with the kernel (thus it coexists with your own signal handlers as long as
1841	you don't register any with libev for the same signal). Similarly, when	2407	you don't register any with libev for the same signal).
1842	the last signal watcher for a signal is stopped, libev will reset the
1843	signal handler to SIG_DFL (regardless of what it was set to before).
1844		2408
1845	If possible and supported, libev will install its handlers with	2409	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2410	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2411	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2412	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2413	and unblock them in an C<ev_prepare> watcher.
		2414
		2415	=head3 The special problem of inheritance over fork/execve/pthread_create
		2416
		2417	Both the signal mask (C<sigprocmask>) and the signal disposition
		2418	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2419	stopping it again), that is, libev might or might not block the signal,
		2420	and might or might not set or restore the installed signal handler (but
		2421	see C<EVFLAG_NOSIGMASK>).
		2422
		2423	While this does not matter for the signal disposition (libev never
		2424	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2425	C<execve>), this matters for the signal mask: many programs do not expect
		2426	certain signals to be blocked.
		2427
		2428	This means that before calling C<exec> (from the child) you should reset
		2429	the signal mask to whatever "default" you expect (all clear is a good
		2430	choice usually).
		2431
		2432	The simplest way to ensure that the signal mask is reset in the child is
		2433	to install a fork handler with C<pthread_atfork> that resets it. That will
		2434	catch fork calls done by libraries (such as the libc) as well.
		2435
		2436	In current versions of libev, the signal will not be blocked indefinitely
		2437	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2438	the window of opportunity for problems, it will not go away, as libev
		2439	I<has> to modify the signal mask, at least temporarily.
		2440
		2441	So I can't stress this enough: I<If you do not reset your signal mask when
		2442	you expect it to be empty, you have a race condition in your code>. This
		2443	is not a libev-specific thing, this is true for most event libraries.
		2444
		2445	=head3 The special problem of threads signal handling
		2446
		2447	POSIX threads has problematic signal handling semantics, specifically,
		2448	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2449	threads in a process block signals, which is hard to achieve.
		2450
		2451	When you want to use sigwait (or mix libev signal handling with your own
		2452	for the same signals), you can tackle this problem by globally blocking
		2453	all signals before creating any threads (or creating them with a fully set
		2454	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2455	loops. Then designate one thread as "signal receiver thread" which handles
		2456	these signals. You can pass on any signals that libev might be interested
		2457	in by calling C<ev_feed_signal>.
1850		2458
1851	=head3 Watcher-Specific Functions and Data Members	2459	=head3 Watcher-Specific Functions and Data Members
1852		2460
1853	=over 4	2461	=over 4
1854		2462
…		…
1870	Example: Try to exit cleanly on SIGINT.	2478	Example: Try to exit cleanly on SIGINT.
1871		2479
1872	static void	2480	static void
1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2481	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1874	{	2482	{
1875	ev_unloop (loop, EVUNLOOP_ALL);	2483	ev_break (loop, EVBREAK_ALL);
1876	}	2484	}
1877		2485
1878	ev_signal signal_watcher;	2486	ev_signal signal_watcher;
1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2487	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1880	ev_signal_start (loop, &signal_watcher);	2488	ev_signal_start (loop, &signal_watcher);
…		…
1886	some child status changes (most typically when a child of yours dies or	2494	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2495	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2496	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2497	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2498	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2499	but forking and registering a watcher a few event loop iterations later or
1892	not.	2500	in the next callback invocation is not.
1893		2501
1894	Only the default event loop is capable of handling signals, and therefore	2502	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2503	you can only register child watchers in the default event loop.
1896		2504
		2505	Due to some design glitches inside libev, child watchers will always be
		2506	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2507	libev)
		2508
1897	=head3 Process Interaction	2509	=head3 Process Interaction
1898		2510
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2511	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2512	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2513	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2515	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2516	children, even ones not watched.
1905		2517
1906	=head3 Overriding the Built-In Processing	2518	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2528	=head3 Stopping the Child Watcher
1917		2529
1918	Currently, the child watcher never gets stopped, even when the	2530	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2531	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2532	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2533	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2534	problem).
1922		2535
1923	=head3 Watcher-Specific Functions and Data Members	2536	=head3 Watcher-Specific Functions and Data Members
1924		2537
1925	=over 4	2538	=over 4
1926		2539
…		…
2252	// no longer anything immediate to do.	2865	// no longer anything immediate to do.
2253	}	2866	}
2254		2867
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2868	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2869	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2870	ev_idle_start (loop, idle_watcher);
2258		2871
2259		2872
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2873	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2874
2262	Prepare and check watchers are usually (but not always) used in pairs:	2875	Prepare and check watchers are usually (but not always) used in pairs:
2263	prepare watchers get invoked before the process blocks and check watchers	2876	prepare watchers get invoked before the process blocks and check watchers
2264	afterwards.	2877	afterwards.
2265		2878
2266	You I<must not> call C<ev_loop> or similar functions that enter	2879	You I<must not> call C<ev_run> or similar functions that enter
2267	the current event loop from either C<ev_prepare> or C<ev_check>	2880	the current event loop from either C<ev_prepare> or C<ev_check>
2268	watchers. Other loops than the current one are fine, however. The	2881	watchers. Other loops than the current one are fine, however. The
2269	rationale behind this is that you do not need to check for recursion in	2882	rationale behind this is that you do not need to check for recursion in
2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2883	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2271	C<ev_check> so if you have one watcher of each kind they will always be	2884	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2355	struct pollfd fds [nfd];	2968	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	2969	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2970	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		2971
2359	/* the callback is illegal, but won't be called as we stop during check */	2972	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	2973	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	2974	ev_timer_start (loop, &tw);
2362		2975
2363	// create one ev_io per pollfd	2976	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	2977	for (int i = 0; i < nfd; ++i)
2365	{	2978	{
…		…
2439		3052
2440	if (timeout >= 0)	3053	if (timeout >= 0)
2441	// create/start timer	3054	// create/start timer
2442		3055
2443	// poll	3056	// poll
2444	ev_loop (EV_A_ 0);	3057	ev_run (EV_A_ 0);
2445		3058
2446	// stop timer again	3059	// stop timer again
2447	if (timeout >= 0)	3060	if (timeout >= 0)
2448	ev_timer_stop (EV_A_ &to);	3061	ev_timer_stop (EV_A_ &to);
2449		3062
…		…
2527	if you do not want that, you need to temporarily stop the embed watcher).	3140	if you do not want that, you need to temporarily stop the embed watcher).
2528		3141
2529	=item ev_embed_sweep (loop, ev_embed *)	3142	=item ev_embed_sweep (loop, ev_embed *)
2530		3143
2531	Make a single, non-blocking sweep over the embedded loop. This works	3144	Make a single, non-blocking sweep over the embedded loop. This works
2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3145	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2533	appropriate way for embedded loops.	3146	appropriate way for embedded loops.
2534		3147
2535	=item struct ev_loop *other [read-only]	3148	=item struct ev_loop *other [read-only]
2536		3149
2537	The embedded event loop.	3150	The embedded event loop.
…		…
2595	event loop blocks next and before C<ev_check> watchers are being called,	3208	event loop blocks next and before C<ev_check> watchers are being called,
2596	and only in the child after the fork. If whoever good citizen calling	3209	and only in the child after the fork. If whoever good citizen calling
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3210	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2598	handlers will be invoked, too, of course.	3211	handlers will be invoked, too, of course.
2599		3212
		3213	=head3 The special problem of life after fork - how is it possible?
		3214
		3215	Most uses of C<fork()> consist of forking, then some simple calls to set
		3216	up/change the process environment, followed by a call to C<exec()>. This
		3217	sequence should be handled by libev without any problems.
		3218
		3219	This changes when the application actually wants to do event handling
		3220	in the child, or both parent in child, in effect "continuing" after the
		3221	fork.
		3222
		3223	The default mode of operation (for libev, with application help to detect
		3224	forks) is to duplicate all the state in the child, as would be expected
		3225	when I<either> the parent I<or> the child process continues.
		3226
		3227	When both processes want to continue using libev, then this is usually the
		3228	wrong result. In that case, usually one process (typically the parent) is
		3229	supposed to continue with all watchers in place as before, while the other
		3230	process typically wants to start fresh, i.e. without any active watchers.
		3231
		3232	The cleanest and most efficient way to achieve that with libev is to
		3233	simply create a new event loop, which of course will be "empty", and
		3234	use that for new watchers. This has the advantage of not touching more
		3235	memory than necessary, and thus avoiding the copy-on-write, and the
		3236	disadvantage of having to use multiple event loops (which do not support
		3237	signal watchers).
		3238
		3239	When this is not possible, or you want to use the default loop for
		3240	other reasons, then in the process that wants to start "fresh", call
		3241	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3242	Destroying the default loop will "orphan" (not stop) all registered
		3243	watchers, so you have to be careful not to execute code that modifies
		3244	those watchers. Note also that in that case, you have to re-register any
		3245	signal watchers.
		3246
2600	=head3 Watcher-Specific Functions and Data Members	3247	=head3 Watcher-Specific Functions and Data Members
2601		3248
2602	=over 4	3249	=over 4
2603		3250
2604	=item ev_fork_init (ev_signal *, callback)	3251	=item ev_fork_init (ev_fork *, callback)
2605		3252
2606	Initialises and configures the fork watcher - it has no parameters of any	3253	Initialises and configures the fork watcher - it has no parameters of any
2607	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3254	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2608	believe me.	3255	really.
2609		3256
2610	=back	3257	=back
2611		3258
2612		3259
		3260	=head2 C<ev_cleanup> - even the best things end
		3261
		3262	Cleanup watchers are called just before the event loop is being destroyed
		3263	by a call to C<ev_loop_destroy>.
		3264
		3265	While there is no guarantee that the event loop gets destroyed, cleanup
		3266	watchers provide a convenient method to install cleanup hooks for your
		3267	program, worker threads and so on - you just to make sure to destroy the
		3268	loop when you want them to be invoked.
		3269
		3270	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3271	all other watchers, they do not keep a reference to the event loop (which
		3272	makes a lot of sense if you think about it). Like all other watchers, you
		3273	can call libev functions in the callback, except C<ev_cleanup_start>.
		3274
		3275	=head3 Watcher-Specific Functions and Data Members
		3276
		3277	=over 4
		3278
		3279	=item ev_cleanup_init (ev_cleanup *, callback)
		3280
		3281	Initialises and configures the cleanup watcher - it has no parameters of
		3282	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3283	pointless, I assure you.
		3284
		3285	=back
		3286
		3287	Example: Register an atexit handler to destroy the default loop, so any
		3288	cleanup functions are called.
		3289
		3290	static void
		3291	program_exits (void)
		3292	{
		3293	ev_loop_destroy (EV_DEFAULT_UC);
		3294	}
		3295
		3296	...
		3297	atexit (program_exits);
		3298
		3299
2613	=head2 C<ev_async> - how to wake up another event loop	3300	=head2 C<ev_async> - how to wake up an event loop
2614		3301
2615	In general, you cannot use an C<ev_loop> from multiple threads or other	3302	In general, you cannot use an C<ev_loop> from multiple threads or other
2616	asynchronous sources such as signal handlers (as opposed to multiple event	3303	asynchronous sources such as signal handlers (as opposed to multiple event
2617	loops - those are of course safe to use in different threads).	3304	loops - those are of course safe to use in different threads).
2618		3305
2619	Sometimes, however, you need to wake up another event loop you do not	3306	Sometimes, however, you need to wake up an event loop you do not control,
2620	control, for example because it belongs to another thread. This is what	3307	for example because it belongs to another thread. This is what C<ev_async>
2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3308	watchers do: as long as the C<ev_async> watcher is active, you can signal
2622	can signal it by calling C<ev_async_send>, which is thread- and signal	3309	it by calling C<ev_async_send>, which is thread- and signal safe.
2623	safe.
2624		3310
2625	This functionality is very similar to C<ev_signal> watchers, as signals,	3311	This functionality is very similar to C<ev_signal> watchers, as signals,
2626	too, are asynchronous in nature, and signals, too, will be compressed	3312	too, are asynchronous in nature, and signals, too, will be compressed
2627	(i.e. the number of callback invocations may be less than the number of	3313	(i.e. the number of callback invocations may be less than the number of
2628	C<ev_async_sent> calls).	3314	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2629		3315	of "global async watchers" by using a watcher on an otherwise unused
2630	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3316	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2631	just the default loop.	3317	even without knowing which loop owns the signal.
2632		3318
2633	=head3 Queueing	3319	=head3 Queueing
2634		3320
2635	C<ev_async> does not support queueing of data in any way. The reason	3321	C<ev_async> does not support queueing of data in any way. The reason
2636	is that the author does not know of a simple (or any) algorithm for a	3322	is that the author does not know of a simple (or any) algorithm for a
2637	multiple-writer-single-reader queue that works in all cases and doesn't	3323	multiple-writer-single-reader queue that works in all cases and doesn't
2638	need elaborate support such as pthreads.	3324	need elaborate support such as pthreads or unportable memory access
		3325	semantics.
2639		3326
2640	That means that if you want to queue data, you have to provide your own	3327	That means that if you want to queue data, you have to provide your own
2641	queue. But at least I can tell you how to implement locking around your	3328	queue. But at least I can tell you how to implement locking around your
2642	queue:	3329	queue:
2643		3330
…		…
2727	trust me.	3414	trust me.
2728		3415
2729	=item ev_async_send (loop, ev_async *)	3416	=item ev_async_send (loop, ev_async *)
2730		3417
2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3418	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3419	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3420	returns.
		3421
2733	C<ev_feed_event>, this call is safe to do from other threads, signal or	3422	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3423	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2735	section below on what exactly this means).	3424	embedding section below on what exactly this means).
2736		3425
2737	Note that, as with other watchers in libev, multiple events might get	3426	Note that, as with other watchers in libev, multiple events might get
2738	compressed into a single callback invocation (another way to look at this	3427	compressed into a single callback invocation (another way to look at
2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3428	this is that C<ev_async> watchers are level-triggered: they are set on
2740	reset when the event loop detects that).	3429	C<ev_async_send>, reset when the event loop detects that).
2741		3430
2742	This call incurs the overhead of a system call only once per event loop	3431	This call incurs the overhead of at most one extra system call per event
2743	iteration, so while the overhead might be noticeable, it doesn't apply to	3432	loop iteration, if the event loop is blocked, and no syscall at all if
2744	repeated calls to C<ev_async_send> for the same event loop.	3433	the event loop (or your program) is processing events. That means that
		3434	repeated calls are basically free (there is no need to avoid calls for
		3435	performance reasons) and that the overhead becomes smaller (typically
		3436	zero) under load.
2745		3437
2746	=item bool = ev_async_pending (ev_async *)	3438	=item bool = ev_async_pending (ev_async *)
2747		3439
2748	Returns a non-zero value when C<ev_async_send> has been called on the	3440	Returns a non-zero value when C<ev_async_send> has been called on the
2749	watcher but the event has not yet been processed (or even noted) by the	3441	watcher but the event has not yet been processed (or even noted) by the
…		…
2782		3474
2783	If C<timeout> is less than 0, then no timeout watcher will be	3475	If C<timeout> is less than 0, then no timeout watcher will be
2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3476	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2785	repeat = 0) will be started. C<0> is a valid timeout.	3477	repeat = 0) will be started. C<0> is a valid timeout.
2786		3478
2787	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3479	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2788	passed an C<revents> set like normal event callbacks (a combination of	3480	passed an C<revents> set like normal event callbacks (a combination of
2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3481	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2790	value passed to C<ev_once>. Note that it is possible to receive I<both>	3482	value passed to C<ev_once>. Note that it is possible to receive I<both>
2791	a timeout and an io event at the same time - you probably should give io	3483	a timeout and an io event at the same time - you probably should give io
2792	events precedence.	3484	events precedence.
2793		3485
2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3486	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2795		3487
2796	static void stdin_ready (int revents, void *arg)	3488	static void stdin_ready (int revents, void *arg)
2797	{	3489	{
2798	if (revents & EV_READ)	3490	if (revents & EV_READ)
2799	/* stdin might have data for us, joy! */;	3491	/* stdin might have data for us, joy! */;
2800	else if (revents & EV_TIMEOUT)	3492	else if (revents & EV_TIMER)
2801	/* doh, nothing entered */;	3493	/* doh, nothing entered */;
2802	}	3494	}
2803		3495
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3496	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805		3497
2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3498	=item ev_feed_fd_event (loop, int fd, int revents)
2813		3499
2814	Feed an event on the given fd, as if a file descriptor backend detected	3500	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3501	the given events.
2816		3502
2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3503	=item ev_feed_signal_event (loop, int signum)
2818		3504
2819	Feed an event as if the given signal occurred (C<loop> must be the default	3505	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2820	loop!).	3506	which is async-safe.
2821		3507
2822	=back	3508	=back
		3509
		3510
		3511	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3512
		3513	This section explains some common idioms that are not immediately
		3514	obvious. Note that examples are sprinkled over the whole manual, and this
		3515	section only contains stuff that wouldn't fit anywhere else.
		3516
		3517	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3518
		3519	Each watcher has, by default, a C<void *data> member that you can read
		3520	or modify at any time: libev will completely ignore it. This can be used
		3521	to associate arbitrary data with your watcher. If you need more data and
		3522	don't want to allocate memory separately and store a pointer to it in that
		3523	data member, you can also "subclass" the watcher type and provide your own
		3524	data:
		3525
		3526	struct my_io
		3527	{
		3528	ev_io io;
		3529	int otherfd;
		3530	void *somedata;
		3531	struct whatever *mostinteresting;
		3532	};
		3533
		3534	...
		3535	struct my_io w;
		3536	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3537
		3538	And since your callback will be called with a pointer to the watcher, you
		3539	can cast it back to your own type:
		3540
		3541	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3542	{
		3543	struct my_io *w = (struct my_io *)w_;
		3544	...
		3545	}
		3546
		3547	More interesting and less C-conformant ways of casting your callback
		3548	function type instead have been omitted.
		3549
		3550	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3551
		3552	Another common scenario is to use some data structure with multiple
		3553	embedded watchers, in effect creating your own watcher that combines
		3554	multiple libev event sources into one "super-watcher":
		3555
		3556	struct my_biggy
		3557	{
		3558	int some_data;
		3559	ev_timer t1;
		3560	ev_timer t2;
		3561	}
		3562
		3563	In this case getting the pointer to C<my_biggy> is a bit more
		3564	complicated: Either you store the address of your C<my_biggy> struct in
		3565	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3566	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3567	real programmers):
		3568
		3569	#include <stddef.h>
		3570
		3571	static void
		3572	t1_cb (EV_P_ ev_timer *w, int revents)
		3573	{
		3574	struct my_biggy big = (struct my_biggy *)
		3575	(((char *)w) - offsetof (struct my_biggy, t1));
		3576	}
		3577
		3578	static void
		3579	t2_cb (EV_P_ ev_timer *w, int revents)
		3580	{
		3581	struct my_biggy big = (struct my_biggy *)
		3582	(((char *)w) - offsetof (struct my_biggy, t2));
		3583	}
		3584
		3585	=head2 AVOIDING FINISHING BEFORE RETURNING
		3586
		3587	Often you have structures like this in event-based programs:
		3588
		3589	callback ()
		3590	{
		3591	free (request);
		3592	}
		3593
		3594	request = start_new_request (..., callback);
		3595
		3596	The intent is to start some "lengthy" operation. The C<request> could be
		3597	used to cancel the operation, or do other things with it.
		3598
		3599	It's not uncommon to have code paths in C<start_new_request> that
		3600	immediately invoke the callback, for example, to report errors. Or you add
		3601	some caching layer that finds that it can skip the lengthy aspects of the
		3602	operation and simply invoke the callback with the result.
		3603
		3604	The problem here is that this will happen I<before> C<start_new_request>
		3605	has returned, so C<request> is not set.
		3606
		3607	Even if you pass the request by some safer means to the callback, you
		3608	might want to do something to the request after starting it, such as
		3609	canceling it, which probably isn't working so well when the callback has
		3610	already been invoked.
		3611
		3612	A common way around all these issues is to make sure that
		3613	C<start_new_request> I<always> returns before the callback is invoked. If
		3614	C<start_new_request> immediately knows the result, it can artificially
		3615	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3616	for example, or more sneakily, by reusing an existing (stopped) watcher
		3617	and pushing it into the pending queue:
		3618
		3619	ev_set_cb (watcher, callback);
		3620	ev_feed_event (EV_A_ watcher, 0);
		3621
		3622	This way, C<start_new_request> can safely return before the callback is
		3623	invoked, while not delaying callback invocation too much.
		3624
		3625	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3626
		3627	Often (especially in GUI toolkits) there are places where you have
		3628	I<modal> interaction, which is most easily implemented by recursively
		3629	invoking C<ev_run>.
		3630
		3631	This brings the problem of exiting - a callback might want to finish the
		3632	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3633	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3634	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3635	other combination: In these cases, C<ev_break> will not work alone.
		3636
		3637	The solution is to maintain "break this loop" variable for each C<ev_run>
		3638	invocation, and use a loop around C<ev_run> until the condition is
		3639	triggered, using C<EVRUN_ONCE>:
		3640
		3641	// main loop
		3642	int exit_main_loop = 0;
		3643
		3644	while (!exit_main_loop)
		3645	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3646
		3647	// in a modal watcher
		3648	int exit_nested_loop = 0;
		3649
		3650	while (!exit_nested_loop)
		3651	ev_run (EV_A_ EVRUN_ONCE);
		3652
		3653	To exit from any of these loops, just set the corresponding exit variable:
		3654
		3655	// exit modal loop
		3656	exit_nested_loop = 1;
		3657
		3658	// exit main program, after modal loop is finished
		3659	exit_main_loop = 1;
		3660
		3661	// exit both
		3662	exit_main_loop = exit_nested_loop = 1;
		3663
		3664	=head2 THREAD LOCKING EXAMPLE
		3665
		3666	Here is a fictitious example of how to run an event loop in a different
		3667	thread from where callbacks are being invoked and watchers are
		3668	created/added/removed.
		3669
		3670	For a real-world example, see the C<EV::Loop::Async> perl module,
		3671	which uses exactly this technique (which is suited for many high-level
		3672	languages).
		3673
		3674	The example uses a pthread mutex to protect the loop data, a condition
		3675	variable to wait for callback invocations, an async watcher to notify the
		3676	event loop thread and an unspecified mechanism to wake up the main thread.
		3677
		3678	First, you need to associate some data with the event loop:
		3679
		3680	typedef struct {
		3681	mutex_t lock; /* global loop lock */
		3682	ev_async async_w;
		3683	thread_t tid;
		3684	cond_t invoke_cv;
		3685	} userdata;
		3686
		3687	void prepare_loop (EV_P)
		3688	{
		3689	// for simplicity, we use a static userdata struct.
		3690	static userdata u;
		3691
		3692	ev_async_init (&u->async_w, async_cb);
		3693	ev_async_start (EV_A_ &u->async_w);
		3694
		3695	pthread_mutex_init (&u->lock, 0);
		3696	pthread_cond_init (&u->invoke_cv, 0);
		3697
		3698	// now associate this with the loop
		3699	ev_set_userdata (EV_A_ u);
		3700	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3701	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3702
		3703	// then create the thread running ev_run
		3704	pthread_create (&u->tid, 0, l_run, EV_A);
		3705	}
		3706
		3707	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3708	solely to wake up the event loop so it takes notice of any new watchers
		3709	that might have been added:
		3710
		3711	static void
		3712	async_cb (EV_P_ ev_async *w, int revents)
		3713	{
		3714	// just used for the side effects
		3715	}
		3716
		3717	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3718	protecting the loop data, respectively.
		3719
		3720	static void
		3721	l_release (EV_P)
		3722	{
		3723	userdata *u = ev_userdata (EV_A);
		3724	pthread_mutex_unlock (&u->lock);
		3725	}
		3726
		3727	static void
		3728	l_acquire (EV_P)
		3729	{
		3730	userdata *u = ev_userdata (EV_A);
		3731	pthread_mutex_lock (&u->lock);
		3732	}
		3733
		3734	The event loop thread first acquires the mutex, and then jumps straight
		3735	into C<ev_run>:
		3736
		3737	void *
		3738	l_run (void *thr_arg)
		3739	{
		3740	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3741
		3742	l_acquire (EV_A);
		3743	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3744	ev_run (EV_A_ 0);
		3745	l_release (EV_A);
		3746
		3747	return 0;
		3748	}
		3749
		3750	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3751	signal the main thread via some unspecified mechanism (signals? pipe
		3752	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3753	have been called (in a while loop because a) spurious wakeups are possible
		3754	and b) skipping inter-thread-communication when there are no pending
		3755	watchers is very beneficial):
		3756
		3757	static void
		3758	l_invoke (EV_P)
		3759	{
		3760	userdata *u = ev_userdata (EV_A);
		3761
		3762	while (ev_pending_count (EV_A))
		3763	{
		3764	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3765	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3766	}
		3767	}
		3768
		3769	Now, whenever the main thread gets told to invoke pending watchers, it
		3770	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3771	thread to continue:
		3772
		3773	static void
		3774	real_invoke_pending (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777
		3778	pthread_mutex_lock (&u->lock);
		3779	ev_invoke_pending (EV_A);
		3780	pthread_cond_signal (&u->invoke_cv);
		3781	pthread_mutex_unlock (&u->lock);
		3782	}
		3783
		3784	Whenever you want to start/stop a watcher or do other modifications to an
		3785	event loop, you will now have to lock:
		3786
		3787	ev_timer timeout_watcher;
		3788	userdata *u = ev_userdata (EV_A);
		3789
		3790	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3791
		3792	pthread_mutex_lock (&u->lock);
		3793	ev_timer_start (EV_A_ &timeout_watcher);
		3794	ev_async_send (EV_A_ &u->async_w);
		3795	pthread_mutex_unlock (&u->lock);
		3796
		3797	Note that sending the C<ev_async> watcher is required because otherwise
		3798	an event loop currently blocking in the kernel will have no knowledge
		3799	about the newly added timer. By waking up the loop it will pick up any new
		3800	watchers in the next event loop iteration.
		3801
		3802	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3803
		3804	While the overhead of a callback that e.g. schedules a thread is small, it
		3805	is still an overhead. If you embed libev, and your main usage is with some
		3806	kind of threads or coroutines, you might want to customise libev so that
		3807	doesn't need callbacks anymore.
		3808
		3809	Imagine you have coroutines that you can switch to using a function
		3810	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3811	and that due to some magic, the currently active coroutine is stored in a
		3812	global called C<current_coro>. Then you can build your own "wait for libev
		3813	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3814	the differing C<;> conventions):
		3815
		3816	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3817	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3818
		3819	That means instead of having a C callback function, you store the
		3820	coroutine to switch to in each watcher, and instead of having libev call
		3821	your callback, you instead have it switch to that coroutine.
		3822
		3823	A coroutine might now wait for an event with a function called
		3824	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3825	matter when, or whether the watcher is active or not when this function is
		3826	called):
		3827
		3828	void
		3829	wait_for_event (ev_watcher *w)
		3830	{
		3831	ev_cb_set (w) = current_coro;
		3832	switch_to (libev_coro);
		3833	}
		3834
		3835	That basically suspends the coroutine inside C<wait_for_event> and
		3836	continues the libev coroutine, which, when appropriate, switches back to
		3837	this or any other coroutine.
		3838
		3839	You can do similar tricks if you have, say, threads with an event queue -
		3840	instead of storing a coroutine, you store the queue object and instead of
		3841	switching to a coroutine, you push the watcher onto the queue and notify
		3842	any waiters.
		3843
		3844	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3845	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3846
		3847	// my_ev.h
		3848	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3849	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3850	#include "../libev/ev.h"
		3851
		3852	// my_ev.c
		3853	#define EV_H "my_ev.h"
		3854	#include "../libev/ev.c"
		3855
		3856	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3857	F<my_ev.c> into your project. When properly specifying include paths, you
		3858	can even use F<ev.h> as header file name directly.
2823		3859
2824		3860
2825	=head1 LIBEVENT EMULATION	3861	=head1 LIBEVENT EMULATION
2826		3862
2827	Libev offers a compatibility emulation layer for libevent. It cannot	3863	Libev offers a compatibility emulation layer for libevent. It cannot
2828	emulate the internals of libevent, so here are some usage hints:	3864	emulate the internals of libevent, so here are some usage hints:
2829		3865
2830	=over 4	3866	=over 4
		3867
		3868	=item * Only the libevent-1.4.1-beta API is being emulated.
		3869
		3870	This was the newest libevent version available when libev was implemented,
		3871	and is still mostly unchanged in 2010.
2831		3872
2832	=item * Use it by including <event.h>, as usual.	3873	=item * Use it by including <event.h>, as usual.
2833		3874
2834	=item * The following members are fully supported: ev_base, ev_callback,	3875	=item * The following members are fully supported: ev_base, ev_callback,
2835	ev_arg, ev_fd, ev_res, ev_events.	3876	ev_arg, ev_fd, ev_res, ev_events.
…		…
2841	=item * Priorities are not currently supported. Initialising priorities	3882	=item * Priorities are not currently supported. Initialising priorities
2842	will fail and all watchers will have the same priority, even though there	3883	will fail and all watchers will have the same priority, even though there
2843	is an ev_pri field.	3884	is an ev_pri field.
2844		3885
2845	=item * In libevent, the last base created gets the signals, in libev, the	3886	=item * In libevent, the last base created gets the signals, in libev, the
2846	first base created (== the default loop) gets the signals.	3887	base that registered the signal gets the signals.
2847		3888
2848	=item * Other members are not supported.	3889	=item * Other members are not supported.
2849		3890
2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3891	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2851	to use the libev header file and library.	3892	to use the libev header file and library.
…		…
2870	Care has been taken to keep the overhead low. The only data member the C++	3911	Care has been taken to keep the overhead low. The only data member the C++
2871	classes add (compared to plain C-style watchers) is the event loop pointer	3912	classes add (compared to plain C-style watchers) is the event loop pointer
2872	that the watcher is associated with (or no additional members at all if	3913	that the watcher is associated with (or no additional members at all if
2873	you disable C<EV_MULTIPLICITY> when embedding libev).	3914	you disable C<EV_MULTIPLICITY> when embedding libev).
2874		3915
2875	Currently, functions, and static and non-static member functions can be	3916	Currently, functions, static and non-static member functions and classes
2876	used as callbacks. Other types should be easy to add as long as they only	3917	with C<operator ()> can be used as callbacks. Other types should be easy
2877	need one additional pointer for context. If you need support for other	3918	to add as long as they only need one additional pointer for context. If
2878	types of functors please contact the author (preferably after implementing	3919	you need support for other types of functors please contact the author
2879	it).	3920	(preferably after implementing it).
		3921
		3922	For all this to work, your C++ compiler either has to use the same calling
		3923	conventions as your C compiler (for static member functions), or you have
		3924	to embed libev and compile libev itself as C++.
2880		3925
2881	Here is a list of things available in the C<ev> namespace:	3926	Here is a list of things available in the C<ev> namespace:
2882		3927
2883	=over 4	3928	=over 4
2884		3929
…		…
2894	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3939	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2895		3940
2896	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3941	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2897	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3942	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2898	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3943	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2899	defines by many implementations.	3944	defined by many implementations.
2900		3945
2901	All of those classes have these methods:	3946	All of those classes have these methods:
2902		3947
2903	=over 4	3948	=over 4
2904		3949
2905	=item ev::TYPE::TYPE ()	3950	=item ev::TYPE::TYPE ()
2906		3951
2907	=item ev::TYPE::TYPE (struct ev_loop *)	3952	=item ev::TYPE::TYPE (loop)
2908		3953
2909	=item ev::TYPE::~TYPE	3954	=item ev::TYPE::~TYPE
2910		3955
2911	The constructor (optionally) takes an event loop to associate the watcher	3956	The constructor (optionally) takes an event loop to associate the watcher
2912	with. If it is omitted, it will use C<EV_DEFAULT>.	3957	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2945	myclass obj;	3990	myclass obj;
2946	ev::io iow;	3991	ev::io iow;
2947	iow.set <myclass, &myclass::io_cb> (&obj);	3992	iow.set <myclass, &myclass::io_cb> (&obj);
2948		3993
2949	=item w->set (object *)	3994	=item w->set (object *)
2950
2951	This is an B<experimental> feature that might go away in a future version.
2952		3995
2953	This is a variation of a method callback - leaving out the method to call	3996	This is a variation of a method callback - leaving out the method to call
2954	will default the method to C<operator ()>, which makes it possible to use	3997	will default the method to C<operator ()>, which makes it possible to use
2955	functor objects without having to manually specify the C<operator ()> all	3998	functor objects without having to manually specify the C<operator ()> all
2956	the time. Incidentally, you can then also leave out the template argument	3999	the time. Incidentally, you can then also leave out the template argument
…		…
2989	Example: Use a plain function as callback.	4032	Example: Use a plain function as callback.
2990		4033
2991	static void io_cb (ev::io &w, int revents) { }	4034	static void io_cb (ev::io &w, int revents) { }
2992	iow.set <io_cb> ();	4035	iow.set <io_cb> ();
2993		4036
2994	=item w->set (struct ev_loop *)	4037	=item w->set (loop)
2995		4038
2996	Associates a different C<struct ev_loop> with this watcher. You can only	4039	Associates a different C<struct ev_loop> with this watcher. You can only
2997	do this when the watcher is inactive (and not pending either).	4040	do this when the watcher is inactive (and not pending either).
2998		4041
2999	=item w->set ([arguments])	4042	=item w->set ([arguments])
3000		4043
3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4044	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3002	called at least once. Unlike the C counterpart, an active watcher gets	4045	method or a suitable start method must be called at least once. Unlike the
3003	automatically stopped and restarted when reconfiguring it with this	4046	C counterpart, an active watcher gets automatically stopped and restarted
3004	method.	4047	when reconfiguring it with this method.
3005		4048
3006	=item w->start ()	4049	=item w->start ()
3007		4050
3008	Starts the watcher. Note that there is no C<loop> argument, as the	4051	Starts the watcher. Note that there is no C<loop> argument, as the
3009	constructor already stores the event loop.	4052	constructor already stores the event loop.
3010		4053
		4054	=item w->start ([arguments])
		4055
		4056	Instead of calling C<set> and C<start> methods separately, it is often
		4057	convenient to wrap them in one call. Uses the same type of arguments as
		4058	the configure C<set> method of the watcher.
		4059
3011	=item w->stop ()	4060	=item w->stop ()
3012		4061
3013	Stops the watcher if it is active. Again, no C<loop> argument.	4062	Stops the watcher if it is active. Again, no C<loop> argument.
3014		4063
3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4064	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3027		4076
3028	=back	4077	=back
3029		4078
3030	=back	4079	=back
3031		4080
3032	Example: Define a class with an IO and idle watcher, start one of them in	4081	Example: Define a class with two I/O and idle watchers, start the I/O
3033	the constructor.	4082	watchers in the constructor.
3034		4083
3035	class myclass	4084	class myclass
3036	{	4085	{
3037	ev::io io ; void io_cb (ev::io &w, int revents);	4086	ev::io io ; void io_cb (ev::io &w, int revents);
		4087	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4088	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3039		4089
3040	myclass (int fd)	4090	myclass (int fd)
3041	{	4091	{
3042	io .set <myclass, &myclass::io_cb > (this);	4092	io .set <myclass, &myclass::io_cb > (this);
		4093	io2 .set <myclass, &myclass::io2_cb > (this);
3043	idle.set <myclass, &myclass::idle_cb> (this);	4094	idle.set <myclass, &myclass::idle_cb> (this);
3044		4095
3045	io.start (fd, ev::READ);	4096	io.set (fd, ev::WRITE); // configure the watcher
		4097	io.start (); // start it whenever convenient
		4098
		4099	io2.start (fd, ev::READ); // set + start in one call
3046	}	4100	}
3047	};	4101	};
3048		4102
3049		4103
3050	=head1 OTHER LANGUAGE BINDINGS	4104	=head1 OTHER LANGUAGE BINDINGS
…		…
3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4143	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3090		4144
3091	=item D	4145	=item D
3092		4146
3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4147	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4148	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3095		4149
3096	=item Ocaml	4150	=item Ocaml
3097		4151
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	4152	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4153	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4154
		4155	=item Lua
		4156
		4157	Brian Maher has written a partial interface to libev for lua (at the
		4158	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4159	L<http://github.com/brimworks/lua-ev>.
3100		4160
3101	=back	4161	=back
3102		4162
3103		4163
3104	=head1 MACRO MAGIC	4164	=head1 MACRO MAGIC
…		…
3118	loop argument"). The C<EV_A> form is used when this is the sole argument,	4178	loop argument"). The C<EV_A> form is used when this is the sole argument,
3119	C<EV_A_> is used when other arguments are following. Example:	4179	C<EV_A_> is used when other arguments are following. Example:
3120		4180
3121	ev_unref (EV_A);	4181	ev_unref (EV_A);
3122	ev_timer_add (EV_A_ watcher);	4182	ev_timer_add (EV_A_ watcher);
3123	ev_loop (EV_A_ 0);	4183	ev_run (EV_A_ 0);
3124		4184
3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4185	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3126	which is often provided by the following macro.	4186	which is often provided by the following macro.
3127		4187
3128	=item C<EV_P>, C<EV_P_>	4188	=item C<EV_P>, C<EV_P_>
…		…
3141	suitable for use with C<EV_A>.	4201	suitable for use with C<EV_A>.
3142		4202
3143	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4203	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3144		4204
3145	Similar to the other two macros, this gives you the value of the default	4205	Similar to the other two macros, this gives you the value of the default
3146	loop, if multiple loops are supported ("ev loop default").	4206	loop, if multiple loops are supported ("ev loop default"). The default loop
		4207	will be initialised if it isn't already initialised.
		4208
		4209	For non-multiplicity builds, these macros do nothing, so you always have
		4210	to initialise the loop somewhere.
3147		4211
3148	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4212	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3149		4213
3150	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4214	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3151	default loop has been initialised (C<UC> == unchecked). Their behaviour	4215	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3168	}	4232	}
3169		4233
3170	ev_check check;	4234	ev_check check;
3171	ev_check_init (&check, check_cb);	4235	ev_check_init (&check, check_cb);
3172	ev_check_start (EV_DEFAULT_ &check);	4236	ev_check_start (EV_DEFAULT_ &check);
3173	ev_loop (EV_DEFAULT_ 0);	4237	ev_run (EV_DEFAULT_ 0);
3174		4238
3175	=head1 EMBEDDING	4239	=head1 EMBEDDING
3176		4240
3177	Libev can (and often is) directly embedded into host	4241	Libev can (and often is) directly embedded into host
3178	applications. Examples of applications that embed it include the Deliantra	4242	applications. Examples of applications that embed it include the Deliantra
…		…
3258	libev.m4	4322	libev.m4
3259		4323
3260	=head2 PREPROCESSOR SYMBOLS/MACROS	4324	=head2 PREPROCESSOR SYMBOLS/MACROS
3261		4325
3262	Libev can be configured via a variety of preprocessor symbols you have to	4326	Libev can be configured via a variety of preprocessor symbols you have to
3263	define before including any of its files. The default in the absence of	4327	define before including (or compiling) any of its files. The default in
3264	autoconf is documented for every option.	4328	the absence of autoconf is documented for every option.
		4329
		4330	Symbols marked with "(h)" do not change the ABI, and can have different
		4331	values when compiling libev vs. including F<ev.h>, so it is permissible
		4332	to redefine them before including F<ev.h> without breaking compatibility
		4333	to a compiled library. All other symbols change the ABI, which means all
		4334	users of libev and the libev code itself must be compiled with compatible
		4335	settings.
3265		4336
3266	=over 4	4337	=over 4
3267		4338
		4339	=item EV_COMPAT3 (h)
		4340
		4341	Backwards compatibility is a major concern for libev. This is why this
		4342	release of libev comes with wrappers for the functions and symbols that
		4343	have been renamed between libev version 3 and 4.
		4344
		4345	You can disable these wrappers (to test compatibility with future
		4346	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4347	sources. This has the additional advantage that you can drop the C<struct>
		4348	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4349	typedef in that case.
		4350
		4351	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4352	and in some even more future version the compatibility code will be
		4353	removed completely.
		4354
3268	=item EV_STANDALONE	4355	=item EV_STANDALONE (h)
3269		4356
3270	Must always be C<1> if you do not use autoconf configuration, which	4357	Must always be C<1> if you do not use autoconf configuration, which
3271	keeps libev from including F<config.h>, and it also defines dummy	4358	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	4359	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	4360	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	4361	F<event.h> that are not directly supported by the libev core alone.
3275		4362
3276	In stanbdalone mode, libev will still try to automatically deduce the	4363	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	4364	configuration, but has to be more conservative.
		4365
		4366	=item EV_USE_FLOOR
		4367
		4368	If defined to be C<1>, libev will use the C<floor ()> function for its
		4369	periodic reschedule calculations, otherwise libev will fall back on a
		4370	portable (slower) implementation. If you enable this, you usually have to
		4371	link against libm or something equivalent. Enabling this when the C<floor>
		4372	function is not available will fail, so the safe default is to not enable
		4373	this.
3278		4374
3279	=item EV_USE_MONOTONIC	4375	=item EV_USE_MONOTONIC
3280		4376
3281	If defined to be C<1>, libev will try to detect the availability of the	4377	If defined to be C<1>, libev will try to detect the availability of the
3282	monotonic clock option at both compile time and runtime. Otherwise no	4378	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3346	be used is the winsock select). This means that it will call	4442	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4443	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	4444	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	4445	on win32. Should not be defined on non-win32 platforms.
3350		4446
3351	=item EV_FD_TO_WIN32_HANDLE	4447	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		4448
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4449	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	4450	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	4451	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	4452	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	4453	in which case they can provide this function to map fds to socket handles.
		4454
		4455	=item EV_WIN32_HANDLE_TO_FD(handle)
		4456
		4457	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4458	using the standard C<_open_osfhandle> function. For programs implementing
		4459	their own fd to handle mapping, overwriting this function makes it easier
		4460	to do so. This can be done by defining this macro to an appropriate value.
		4461
		4462	=item EV_WIN32_CLOSE_FD(fd)
		4463
		4464	If programs implement their own fd to handle mapping on win32, then this
		4465	macro can be used to override the C<close> function, useful to unregister
		4466	file descriptors again. Note that the replacement function has to close
		4467	the underlying OS handle.
3358		4468
3359	=item EV_USE_POLL	4469	=item EV_USE_POLL
3360		4470
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4471	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	4472	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3398	If defined to be C<1>, libev will compile in support for the Linux inotify	4508	If defined to be C<1>, libev will compile in support for the Linux inotify
3399	interface to speed up C<ev_stat> watchers. Its actual availability will	4509	interface to speed up C<ev_stat> watchers. Its actual availability will
3400	be detected at runtime. If undefined, it will be enabled if the headers	4510	be detected at runtime. If undefined, it will be enabled if the headers
3401	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4511	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3402		4512
		4513	=item EV_NO_SMP
		4514
		4515	If defined to be C<1>, libev will assume that memory is always coherent
		4516	between threads, that is, threads can be used, but threads never run on
		4517	different cpus (or different cpu cores). This reduces dependencies
		4518	and makes libev faster.
		4519
		4520	=item EV_NO_THREADS
		4521
		4522	If defined to be C<1>, libev will assume that it will never be called
		4523	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4524	above. This reduces dependencies and makes libev faster.
		4525
3403	=item EV_ATOMIC_T	4526	=item EV_ATOMIC_T
3404		4527
3405	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4528	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3406	access is atomic with respect to other threads or signal contexts. No such	4529	access is atomic and serialised with respect to other threads or signal
3407	type is easily found in the C language, so you can provide your own type	4530	contexts. No such type is easily found in the C language, so you can
3408	that you know is safe for your purposes. It is used both for signal handler "locking"	4531	provide your own type that you know is safe for your purposes. It is used
3409	as well as for signal and thread safety in C<ev_async> watchers.	4532	both for signal handler "locking" as well as for signal and thread safety
		4533	in C<ev_async> watchers.
3410		4534
3411	In the absence of this define, libev will use C<sig_atomic_t volatile>	4535	In the absence of this define, libev will use C<sig_atomic_t volatile>
3412	(from F<signal.h>), which is usually good enough on most platforms.	4536	(from F<signal.h>), which is usually good enough on most platforms,
		4537	although strictly speaking using a type that also implies a memory fence
		4538	is required.
3413		4539
3414	=item EV_H	4540	=item EV_H (h)
3415		4541
3416	The name of the F<ev.h> header file used to include it. The default if	4542	The name of the F<ev.h> header file used to include it. The default if
3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4543	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3418	used to virtually rename the F<ev.h> header file in case of conflicts.	4544	used to virtually rename the F<ev.h> header file in case of conflicts.
3419		4545
3420	=item EV_CONFIG_H	4546	=item EV_CONFIG_H (h)
3421		4547
3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4548	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4549	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3424	C<EV_H>, above.	4550	C<EV_H>, above.
3425		4551
3426	=item EV_EVENT_H	4552	=item EV_EVENT_H (h)
3427		4553
3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4554	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3429	of how the F<event.h> header can be found, the default is C<"event.h">.	4555	of how the F<event.h> header can be found, the default is C<"event.h">.
3430		4556
3431	=item EV_PROTOTYPES	4557	=item EV_PROTOTYPES (h)
3432		4558
3433	If defined to be C<0>, then F<ev.h> will not define any function	4559	If defined to be C<0>, then F<ev.h> will not define any function
3434	prototypes, but still define all the structs and other symbols. This is	4560	prototypes, but still define all the structs and other symbols. This is
3435	occasionally useful if you want to provide your own wrapper functions	4561	occasionally useful if you want to provide your own wrapper functions
3436	around libev functions.	4562	around libev functions.
…		…
3441	will have the C<struct ev_loop *> as first argument, and you can create	4567	will have the C<struct ev_loop *> as first argument, and you can create
3442	additional independent event loops. Otherwise there will be no support	4568	additional independent event loops. Otherwise there will be no support
3443	for multiple event loops and there is no first event loop pointer	4569	for multiple event loops and there is no first event loop pointer
3444	argument. Instead, all functions act on the single default loop.	4570	argument. Instead, all functions act on the single default loop.
3445		4571
		4572	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4573	default loop when multiplicity is switched off - you always have to
		4574	initialise the loop manually in this case.
		4575
3446	=item EV_MINPRI	4576	=item EV_MINPRI
3447		4577
3448	=item EV_MAXPRI	4578	=item EV_MAXPRI
3449		4579
3450	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4580	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3458	fine.	4588	fine.
3459		4589
3460	If your embedding application does not need any priorities, defining these	4590	If your embedding application does not need any priorities, defining these
3461	both to C<0> will save some memory and CPU.	4591	both to C<0> will save some memory and CPU.
3462		4592
3463	=item EV_PERIODIC_ENABLE	4593	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4594	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4595	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3464		4596
3465	If undefined or defined to be C<1>, then periodic timers are supported. If	4597	If undefined or defined to be C<1> (and the platform supports it), then
3466	defined to be C<0>, then they are not. Disabling them saves a few kB of	4598	the respective watcher type is supported. If defined to be C<0>, then it
3467	code.	4599	is not. Disabling watcher types mainly saves code size.
3468		4600
3469	=item EV_IDLE_ENABLE	4601	=item EV_FEATURES
3470
3471	If undefined or defined to be C<1>, then idle watchers are supported. If
3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
3473	code.
3474
3475	=item EV_EMBED_ENABLE
3476
3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3478	defined to be C<0>, then they are not. Embed watchers rely on most other
3479	watcher types, which therefore must not be disabled.
3480
3481	=item EV_STAT_ENABLE
3482
3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3484	defined to be C<0>, then they are not.
3485
3486	=item EV_FORK_ENABLE
3487
3488	If undefined or defined to be C<1>, then fork watchers are supported. If
3489	defined to be C<0>, then they are not.
3490
3491	=item EV_ASYNC_ENABLE
3492
3493	If undefined or defined to be C<1>, then async watchers are supported. If
3494	defined to be C<0>, then they are not.
3495
3496	=item EV_MINIMAL
3497		4602
3498	If you need to shave off some kilobytes of code at the expense of some	4603	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	4604	speed (but with the full API), you can define this symbol to request
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4605	certain subsets of functionality. The default is to enable all features
3501	much smaller 2-heap for timer management over the default 4-heap.	4606	that can be enabled on the platform.
		4607
		4608	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4609	with some broad features you want) and then selectively re-enable
		4610	additional parts you want, for example if you want everything minimal,
		4611	but multiple event loop support, async and child watchers and the poll
		4612	backend, use this:
		4613
		4614	#define EV_FEATURES 0
		4615	#define EV_MULTIPLICITY 1
		4616	#define EV_USE_POLL 1
		4617	#define EV_CHILD_ENABLE 1
		4618	#define EV_ASYNC_ENABLE 1
		4619
		4620	The actual value is a bitset, it can be a combination of the following
		4621	values:
		4622
		4623	=over 4
		4624
		4625	=item C<1> - faster/larger code
		4626
		4627	Use larger code to speed up some operations.
		4628
		4629	Currently this is used to override some inlining decisions (enlarging the
		4630	code size by roughly 30% on amd64).
		4631
		4632	When optimising for size, use of compiler flags such as C<-Os> with
		4633	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4634	assertions.
		4635
		4636	=item C<2> - faster/larger data structures
		4637
		4638	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4639	hash table sizes and so on. This will usually further increase code size
		4640	and can additionally have an effect on the size of data structures at
		4641	runtime.
		4642
		4643	=item C<4> - full API configuration
		4644
		4645	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4646	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4647
		4648	=item C<8> - full API
		4649
		4650	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4651	details on which parts of the API are still available without this
		4652	feature, and do not complain if this subset changes over time.
		4653
		4654	=item C<16> - enable all optional watcher types
		4655
		4656	Enables all optional watcher types. If you want to selectively enable
		4657	only some watcher types other than I/O and timers (e.g. prepare,
		4658	embed, async, child...) you can enable them manually by defining
		4659	C<EV_watchertype_ENABLE> to C<1> instead.
		4660
		4661	=item C<32> - enable all backends
		4662
		4663	This enables all backends - without this feature, you need to enable at
		4664	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4665
		4666	=item C<64> - enable OS-specific "helper" APIs
		4667
		4668	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4669	default.
		4670
		4671	=back
		4672
		4673	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4674	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4675	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4676	watchers, timers and monotonic clock support.
		4677
		4678	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4679	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4680	your program might be left out as well - a binary starting a timer and an
		4681	I/O watcher then might come out at only 5Kb.
		4682
		4683	=item EV_API_STATIC
		4684
		4685	If this symbol is defined (by default it is not), then all identifiers
		4686	will have static linkage. This means that libev will not export any
		4687	identifiers, and you cannot link against libev anymore. This can be useful
		4688	when you embed libev, only want to use libev functions in a single file,
		4689	and do not want its identifiers to be visible.
		4690
		4691	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4692	wants to use libev.
		4693
		4694	This option only works when libev is compiled with a C compiler, as C++
		4695	doesn't support the required declaration syntax.
		4696
		4697	=item EV_AVOID_STDIO
		4698
		4699	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4700	functions (printf, scanf, perror etc.). This will increase the code size
		4701	somewhat, but if your program doesn't otherwise depend on stdio and your
		4702	libc allows it, this avoids linking in the stdio library which is quite
		4703	big.
		4704
		4705	Note that error messages might become less precise when this option is
		4706	enabled.
		4707
		4708	=item EV_NSIG
		4709
		4710	The highest supported signal number, +1 (or, the number of
		4711	signals): Normally, libev tries to deduce the maximum number of signals
		4712	automatically, but sometimes this fails, in which case it can be
		4713	specified. Also, using a lower number than detected (C<32> should be
		4714	good for about any system in existence) can save some memory, as libev
		4715	statically allocates some 12-24 bytes per signal number.
3502		4716
3503	=item EV_PID_HASHSIZE	4717	=item EV_PID_HASHSIZE
3504		4718
3505	C<ev_child> watchers use a small hash table to distribute workload by	4719	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4720	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3507	than enough. If you need to manage thousands of children you might want to	4721	usually more than enough. If you need to manage thousands of children you
3508	increase this value (I<must> be a power of two).	4722	might want to increase this value (I<must> be a power of two).
3509		4723
3510	=item EV_INOTIFY_HASHSIZE	4724	=item EV_INOTIFY_HASHSIZE
3511		4725
3512	C<ev_stat> watchers use a small hash table to distribute workload by	4726	C<ev_stat> watchers use a small hash table to distribute workload by
3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4727	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3514	usually more than enough. If you need to manage thousands of C<ev_stat>	4728	disabled), usually more than enough. If you need to manage thousands of
3515	watchers you might want to increase this value (I<must> be a power of	4729	C<ev_stat> watchers you might want to increase this value (I<must> be a
3516	two).	4730	power of two).
3517		4731
3518	=item EV_USE_4HEAP	4732	=item EV_USE_4HEAP
3519		4733
3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4734	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4735	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4736	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3523	faster performance with many (thousands) of watchers.	4737	faster performance with many (thousands) of watchers.
3524		4738
3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4739	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3526	(disabled).	4740	will be C<0>.
3527		4741
3528	=item EV_HEAP_CACHE_AT	4742	=item EV_HEAP_CACHE_AT
3529		4743
3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4744	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4745	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4746	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4747	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3534	but avoids random read accesses on heap changes. This improves performance	4748	but avoids random read accesses on heap changes. This improves performance
3535	noticeably with many (hundreds) of watchers.	4749	noticeably with many (hundreds) of watchers.
3536		4750
3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4751	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3538	(disabled).	4752	will be C<0>.
3539		4753
3540	=item EV_VERIFY	4754	=item EV_VERIFY
3541		4755
3542	Controls how much internal verification (see C<ev_loop_verify ()>) will	4756	Controls how much internal verification (see C<ev_verify ()>) will
3543	be done: If set to C<0>, no internal verification code will be compiled	4757	be done: If set to C<0>, no internal verification code will be compiled
3544	in. If set to C<1>, then verification code will be compiled in, but not	4758	in. If set to C<1>, then verification code will be compiled in, but not
3545	called. If set to C<2>, then the internal verification code will be	4759	called. If set to C<2>, then the internal verification code will be
3546	called once per loop, which can slow down libev. If set to C<3>, then the	4760	called once per loop, which can slow down libev. If set to C<3>, then the
3547	verification code will be called very frequently, which will slow down	4761	verification code will be called very frequently, which will slow down
3548	libev considerably.	4762	libev considerably.
3549		4763
3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4764	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3551	C<0>.	4765	will be C<0>.
3552		4766
3553	=item EV_COMMON	4767	=item EV_COMMON
3554		4768
3555	By default, all watchers have a C<void *data> member. By redefining	4769	By default, all watchers have a C<void *data> member. By redefining
3556	this macro to a something else you can include more and other types of	4770	this macro to something else you can include more and other types of
3557	members. You have to define it each time you include one of the files,	4771	members. You have to define it each time you include one of the files,
3558	though, and it must be identical each time.	4772	though, and it must be identical each time.
3559		4773
3560	For example, the perl EV module uses something like this:	4774	For example, the perl EV module uses something like this:
3561		4775
…		…
3614	file.	4828	file.
3615		4829
3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4830	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3617	that everybody includes and which overrides some configure choices:	4831	that everybody includes and which overrides some configure choices:
3618		4832
3619	#define EV_MINIMAL 1	4833	#define EV_FEATURES 8
3620	#define EV_USE_POLL 0	4834	#define EV_USE_SELECT 1
3621	#define EV_MULTIPLICITY 0
3622	#define EV_PERIODIC_ENABLE 0	4835	#define EV_PREPARE_ENABLE 1
		4836	#define EV_IDLE_ENABLE 1
3623	#define EV_STAT_ENABLE 0	4837	#define EV_SIGNAL_ENABLE 1
3624	#define EV_FORK_ENABLE 0	4838	#define EV_CHILD_ENABLE 1
		4839	#define EV_USE_STDEXCEPT 0
3625	#define EV_CONFIG_H <config.h>	4840	#define EV_CONFIG_H <config.h>
3626	#define EV_MINPRI 0
3627	#define EV_MAXPRI 0
3628		4841
3629	#include "ev++.h"	4842	#include "ev++.h"
3630		4843
3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4844	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3632		4845
3633	#include "ev_cpp.h"	4846	#include "ev_cpp.h"
3634	#include "ev.c"	4847	#include "ev.c"
3635		4848
3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4849	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3637		4850
3638	=head2 THREADS AND COROUTINES	4851	=head2 THREADS AND COROUTINES
3639		4852
3640	=head3 THREADS	4853	=head3 THREADS
3641		4854
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	4905	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	4906	watcher callback into the event loop interested in the signal.
3694		4907
3695	=back	4908	=back
3696		4909
		4910	See also L<THREAD LOCKING EXAMPLE>.
		4911
3697	=head3 COROUTINES	4912	=head3 COROUTINES
3698		4913
3699	Libev is very accommodating to coroutines ("cooperative threads"):	4914	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	4915	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4916	coroutines (e.g. you can call C<ev_run> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	4917	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	4918	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	4919	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		4920
3706	Care has been taken to ensure that libev does not keep local state inside	4921	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4922	C<ev_run>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	4923	they do not call any callbacks.
3709		4924
3710	=head2 COMPILER WARNINGS	4925	=head2 COMPILER WARNINGS
3711		4926
3712	Depending on your compiler and compiler settings, you might get no or a	4927	Depending on your compiler and compiler settings, you might get no or a
…		…
3723	maintainable.	4938	maintainable.
3724		4939
3725	And of course, some compiler warnings are just plain stupid, or simply	4940	And of course, some compiler warnings are just plain stupid, or simply
3726	wrong (because they don't actually warn about the condition their message	4941	wrong (because they don't actually warn about the condition their message
3727	seems to warn about). For example, certain older gcc versions had some	4942	seems to warn about). For example, certain older gcc versions had some
3728	warnings that resulted an extreme number of false positives. These have	4943	warnings that resulted in an extreme number of false positives. These have
3729	been fixed, but some people still insist on making code warn-free with	4944	been fixed, but some people still insist on making code warn-free with
3730	such buggy versions.	4945	such buggy versions.
3731		4946
3732	While libev is written to generate as few warnings as possible,	4947	While libev is written to generate as few warnings as possible,
3733	"warn-free" code is not a goal, and it is recommended not to build libev	4948	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3769	I suggest using suppression lists.	4984	I suggest using suppression lists.
3770		4985
3771		4986
3772	=head1 PORTABILITY NOTES	4987	=head1 PORTABILITY NOTES
3773		4988
		4989	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4990
		4991	GNU/Linux is the only common platform that supports 64 bit file/large file
		4992	interfaces but I<disables> them by default.
		4993
		4994	That means that libev compiled in the default environment doesn't support
		4995	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4996
		4997	Unfortunately, many programs try to work around this GNU/Linux issue
		4998	by enabling the large file API, which makes them incompatible with the
		4999	standard libev compiled for their system.
		5000
		5001	Likewise, libev cannot enable the large file API itself as this would
		5002	suddenly make it incompatible to the default compile time environment,
		5003	i.e. all programs not using special compile switches.
		5004
		5005	=head2 OS/X AND DARWIN BUGS
		5006
		5007	The whole thing is a bug if you ask me - basically any system interface
		5008	you touch is broken, whether it is locales, poll, kqueue or even the
		5009	OpenGL drivers.
		5010
		5011	=head3 C<kqueue> is buggy
		5012
		5013	The kqueue syscall is broken in all known versions - most versions support
		5014	only sockets, many support pipes.
		5015
		5016	Libev tries to work around this by not using C<kqueue> by default on this
		5017	rotten platform, but of course you can still ask for it when creating a
		5018	loop - embedding a socket-only kqueue loop into a select-based one is
		5019	probably going to work well.
		5020
		5021	=head3 C<poll> is buggy
		5022
		5023	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5024	implementation by something calling C<kqueue> internally around the 10.5.6
		5025	release, so now C<kqueue> I<and> C<poll> are broken.
		5026
		5027	Libev tries to work around this by not using C<poll> by default on
		5028	this rotten platform, but of course you can still ask for it when creating
		5029	a loop.
		5030
		5031	=head3 C<select> is buggy
		5032
		5033	All that's left is C<select>, and of course Apple found a way to fuck this
		5034	one up as well: On OS/X, C<select> actively limits the number of file
		5035	descriptors you can pass in to 1024 - your program suddenly crashes when
		5036	you use more.
		5037
		5038	There is an undocumented "workaround" for this - defining
		5039	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5040	work on OS/X.
		5041
		5042	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5043
		5044	=head3 C<errno> reentrancy
		5045
		5046	The default compile environment on Solaris is unfortunately so
		5047	thread-unsafe that you can't even use components/libraries compiled
		5048	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5049	defined by default. A valid, if stupid, implementation choice.
		5050
		5051	If you want to use libev in threaded environments you have to make sure
		5052	it's compiled with C<_REENTRANT> defined.
		5053
		5054	=head3 Event port backend
		5055
		5056	The scalable event interface for Solaris is called "event
		5057	ports". Unfortunately, this mechanism is very buggy in all major
		5058	releases. If you run into high CPU usage, your program freezes or you get
		5059	a large number of spurious wakeups, make sure you have all the relevant
		5060	and latest kernel patches applied. No, I don't know which ones, but there
		5061	are multiple ones to apply, and afterwards, event ports actually work
		5062	great.
		5063
		5064	If you can't get it to work, you can try running the program by setting
		5065	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5066	C<select> backends.
		5067
		5068	=head2 AIX POLL BUG
		5069
		5070	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5071	this by trying to avoid the poll backend altogether (i.e. it's not even
		5072	compiled in), which normally isn't a big problem as C<select> works fine
		5073	with large bitsets on AIX, and AIX is dead anyway.
		5074
3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5075	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5076
		5077	=head3 General issues
3775		5078
3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3777	requires, and its I/O model is fundamentally incompatible with the POSIX	5080	requires, and its I/O model is fundamentally incompatible with the POSIX
3778	model. Libev still offers limited functionality on this platform in	5081	model. Libev still offers limited functionality on this platform in
3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3780	descriptors. This only applies when using Win32 natively, not when using	5083	descriptors. This only applies when using Win32 natively, not when using
3781	e.g. cygwin.	5084	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5085	as every compiler comes with a slightly differently broken/incompatible
		5086	environment.
3782		5087
3783	Lifting these limitations would basically require the full	5088	Lifting these limitations would basically require the full
3784	re-implementation of the I/O system. If you are into these kinds of	5089	re-implementation of the I/O system. If you are into this kind of thing,
3785	things, then note that glib does exactly that for you in a very portable	5090	then note that glib does exactly that for you in a very portable way (note
3786	way (note also that glib is the slowest event library known to man).	5091	also that glib is the slowest event library known to man).
3787		5092
3788	There is no supported compilation method available on windows except	5093	There is no supported compilation method available on windows except
3789	embedding it into other applications.	5094	embedding it into other applications.
		5095
		5096	Sensible signal handling is officially unsupported by Microsoft - libev
		5097	tries its best, but under most conditions, signals will simply not work.
3790		5098
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	5099	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	5100	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	5101	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	5102	so make sure you only write small amounts into your sockets (less than a
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	5107	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	5108	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	5109	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	5110	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	5111	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	5112	(due to Microsoft monopoly games).
3805		5113
3806	A typical way to use libev under windows is to embed it (see the embedding	5114	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	5115	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	5116	of F<ev.h>:
3809		5117
…		…
3816	you do I<not> compile the F<ev.c> or any other embedded source files!):	5124	you do I<not> compile the F<ev.c> or any other embedded source files!):
3817		5125
3818	#include "evwrap.h"	5126	#include "evwrap.h"
3819	#include "ev.c"	5127	#include "ev.c"
3820		5128
3821	=over 4
3822
3823	=item The winsocket select function	5129	=head3 The winsocket C<select> function
3824		5130
3825	The winsocket C<select> function doesn't follow POSIX in that it	5131	The winsocket C<select> function doesn't follow POSIX in that it
3826	requires socket I<handles> and not socket I<file descriptors> (it is	5132	requires socket I<handles> and not socket I<file descriptors> (it is
3827	also extremely buggy). This makes select very inefficient, and also	5133	also extremely buggy). This makes select very inefficient, and also
3828	requires a mapping from file descriptors to socket handles (the Microsoft	5134	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5143	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3838		5144
3839	Note that winsockets handling of fd sets is O(n), so you can easily get a	5145	Note that winsockets handling of fd sets is O(n), so you can easily get a
3840	complexity in the O(n²) range when using win32.	5146	complexity in the O(n²) range when using win32.
3841		5147
3842	=item Limited number of file descriptors	5148	=head3 Limited number of file descriptors
3843		5149
3844	Windows has numerous arbitrary (and low) limits on things.	5150	Windows has numerous arbitrary (and low) limits on things.
3845		5151
3846	Early versions of winsocket's select only supported waiting for a maximum	5152	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	5153	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	5154	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	5155	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	5156	previous thread in each. Sounds great!).
3851		5157
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5158	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	5159	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	5160	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	5161	other interpreters do their own select emulation on windows).
3856		5162
3857	Another limit is the number of file descriptors in the Microsoft runtime	5163	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5164	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	5165	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5166	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	5167	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	5168	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	5169	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	5170	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	5171	the cost of calling select (O(n²)) will likely make this unworkable.
3868
3869	=back
3870		5172
3871	=head2 PORTABILITY REQUIREMENTS	5173	=head2 PORTABILITY REQUIREMENTS
3872		5174
3873	In addition to a working ISO-C implementation and of course the	5175	In addition to a working ISO-C implementation and of course the
3874	backend-specific APIs, libev relies on a few additional extensions:	5176	backend-specific APIs, libev relies on a few additional extensions:
…		…
3881	Libev assumes not only that all watcher pointers have the same internal	5183	Libev assumes not only that all watcher pointers have the same internal
3882	structure (guaranteed by POSIX but not by ISO C for example), but it also	5184	structure (guaranteed by POSIX but not by ISO C for example), but it also
3883	assumes that the same (machine) code can be used to call any watcher	5185	assumes that the same (machine) code can be used to call any watcher
3884	callback: The watcher callbacks have different type signatures, but libev	5186	callback: The watcher callbacks have different type signatures, but libev
3885	calls them using an C<ev_watcher *> internally.	5187	calls them using an C<ev_watcher *> internally.
		5188
		5189	=item pointer accesses must be thread-atomic
		5190
		5191	Accessing a pointer value must be atomic, it must both be readable and
		5192	writable in one piece - this is the case on all current architectures.
3886		5193
3887	=item C<sig_atomic_t volatile> must be thread-atomic as well	5194	=item C<sig_atomic_t volatile> must be thread-atomic as well
3888		5195
3889	The type C<sig_atomic_t volatile> (or whatever is defined as	5196	The type C<sig_atomic_t volatile> (or whatever is defined as
3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5197	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3913	watchers.	5220	watchers.
3914		5221
3915	=item C<double> must hold a time value in seconds with enough accuracy	5222	=item C<double> must hold a time value in seconds with enough accuracy
3916		5223
3917	The type C<double> is used to represent timestamps. It is required to	5224	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5225	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3919	enough for at least into the year 4000. This requirement is fulfilled by	5226	good enough for at least into the year 4000 with millisecond accuracy
		5227	(the design goal for libev). This requirement is overfulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	5228	implementations using IEEE 754, which is basically all existing ones.
		5229
		5230	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5231	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5232	is either obsolete or somebody patched it to use C<long double> or
		5233	something like that, just kidding).
3921		5234
3922	=back	5235	=back
3923		5236
3924	If you know of other additional requirements drop me a note.	5237	If you know of other additional requirements drop me a note.
3925		5238
…		…
3987	=item Processing ev_async_send: O(number_of_async_watchers)	5300	=item Processing ev_async_send: O(number_of_async_watchers)
3988		5301
3989	=item Processing signals: O(max_signal_number)	5302	=item Processing signals: O(max_signal_number)
3990		5303
3991	Sending involves a system call I<iff> there were no other C<ev_async_send>	5304	Sending involves a system call I<iff> there were no other C<ev_async_send>
3992	calls in the current loop iteration. Checking for async and signal events	5305	calls in the current loop iteration and the loop is currently
		5306	blocked. Checking for async and signal events involves iterating over all
3993	involves iterating over all running async watchers or all signal numbers.	5307	running async watchers or all signal numbers.
3994		5308
3995	=back	5309	=back
3996		5310
3997		5311
		5312	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5313
		5314	The major version 4 introduced some incompatible changes to the API.
		5315
		5316	At the moment, the C<ev.h> header file provides compatibility definitions
		5317	for all changes, so most programs should still compile. The compatibility
		5318	layer might be removed in later versions of libev, so better update to the
		5319	new API early than late.
		5320
		5321	=over 4
		5322
		5323	=item C<EV_COMPAT3> backwards compatibility mechanism
		5324
		5325	The backward compatibility mechanism can be controlled by
		5326	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5327	section.
		5328
		5329	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5330
		5331	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5332
		5333	ev_loop_destroy (EV_DEFAULT_UC);
		5334	ev_loop_fork (EV_DEFAULT);
		5335
		5336	=item function/symbol renames
		5337
		5338	A number of functions and symbols have been renamed:
		5339
		5340	ev_loop => ev_run
		5341	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5342	EVLOOP_ONESHOT => EVRUN_ONCE
		5343
		5344	ev_unloop => ev_break
		5345	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5346	EVUNLOOP_ONE => EVBREAK_ONE
		5347	EVUNLOOP_ALL => EVBREAK_ALL
		5348
		5349	EV_TIMEOUT => EV_TIMER
		5350
		5351	ev_loop_count => ev_iteration
		5352	ev_loop_depth => ev_depth
		5353	ev_loop_verify => ev_verify
		5354
		5355	Most functions working on C<struct ev_loop> objects don't have an
		5356	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5357	associated constants have been renamed to not collide with the C<struct
		5358	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5359	as all other watcher types. Note that C<ev_loop_fork> is still called
		5360	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5361	typedef.
		5362
		5363	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5364
		5365	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5366	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5367	and work, but the library code will of course be larger.
		5368
		5369	=back
		5370
		5371
		5372	=head1 GLOSSARY
		5373
		5374	=over 4
		5375
		5376	=item active
		5377
		5378	A watcher is active as long as it has been started and not yet stopped.
		5379	See L<WATCHER STATES> for details.
		5380
		5381	=item application
		5382
		5383	In this document, an application is whatever is using libev.
		5384
		5385	=item backend
		5386
		5387	The part of the code dealing with the operating system interfaces.
		5388
		5389	=item callback
		5390
		5391	The address of a function that is called when some event has been
		5392	detected. Callbacks are being passed the event loop, the watcher that
		5393	received the event, and the actual event bitset.
		5394
		5395	=item callback/watcher invocation
		5396
		5397	The act of calling the callback associated with a watcher.
		5398
		5399	=item event
		5400
		5401	A change of state of some external event, such as data now being available
		5402	for reading on a file descriptor, time having passed or simply not having
		5403	any other events happening anymore.
		5404
		5405	In libev, events are represented as single bits (such as C<EV_READ> or
		5406	C<EV_TIMER>).
		5407
		5408	=item event library
		5409
		5410	A software package implementing an event model and loop.
		5411
		5412	=item event loop
		5413
		5414	An entity that handles and processes external events and converts them
		5415	into callback invocations.
		5416
		5417	=item event model
		5418
		5419	The model used to describe how an event loop handles and processes
		5420	watchers and events.
		5421
		5422	=item pending
		5423
		5424	A watcher is pending as soon as the corresponding event has been
		5425	detected. See L<WATCHER STATES> for details.
		5426
		5427	=item real time
		5428
		5429	The physical time that is observed. It is apparently strictly monotonic :)
		5430
		5431	=item wall-clock time
		5432
		5433	The time and date as shown on clocks. Unlike real time, it can actually
		5434	be wrong and jump forwards and backwards, e.g. when you adjust your
		5435	clock.
		5436
		5437	=item watcher
		5438
		5439	A data structure that describes interest in certain events. Watchers need
		5440	to be started (attached to an event loop) before they can receive events.
		5441
		5442	=back
		5443
3998	=head1 AUTHOR	5444	=head1 AUTHOR
3999		5445
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5446	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5447	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4001		5448

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