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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
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
639	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
640		798
641	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
642	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
643	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>.
644		804
645	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
646	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.
647		808
648	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
649	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
650	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
651	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
652	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
653	beauty.	814	beauty.
654		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
655	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
656	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
657	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
658	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.
659		826
660	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
661	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
662	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
663	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
664	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
665	iteration of the loop.	832	iteration of the loop.
666		833
667	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
668	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
669	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
670	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
671		838
672	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):
673		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- 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.
677	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	852	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
685	- 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.
686	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
688	- 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.
689	- Queue all expired timers.	863	- Queue all expired timers.
690	- Queue all expired periodics.	864	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	866	- Queue all check watchers.
693	- 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).
694	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
695	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
696	- 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
697	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
698	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.
699		877
700	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
701	anymore.	879	anymore.
702		880
703	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
704	... 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..)
705	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
707		885
708	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
709		887
710	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
711	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
712	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
713	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.
714		892
715	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>.
716		894
717	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.
718		897
719	=item ev_ref (loop)	898	=item ev_ref (loop)
720		899
721	=item ev_unref (loop)	900	=item ev_unref (loop)
722		901
723	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
724	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
725	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.
726		905
727	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
728	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>
729	stopping it.	909	before stopping it.
730		910
731	As an example, libev itself uses this for its internal signal pipe: It is	911	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	912	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	913	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	914	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	915	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	916	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	917	before, respectively. Note also that libev might stop watchers itself
		918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		919	in the callback).
738		920
739	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>
740	running when nothing else is active.	922	running when nothing else is active.
741		923
742	ev_signal exitsig;	924	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	927	ev_unref (loop);
746		928
747	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
748		930
749	ev_ref (loop);	931	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
770	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.
771		953
772	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
773	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,
774	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
775	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
776	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).
777		962
778	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
779	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
781	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
…		…
783		968
784	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
785	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
786	interactive servers (of course not for games), likewise for timeouts. It	971	interactive servers (of course not for games), likewise for timeouts. It
787	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>,
788	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).
789		978
790	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
792	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
793	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
794	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
795	they fire on, say, one-second boundaries only.	984	they fire on, say, one-second boundaries only.
796		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
797	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
798		1062
799	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
800	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
801	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
802	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
…		…
813		1077
814	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
815	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
816	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
817		1081
818	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
819	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
820	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:
821		1086
822	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)
823	{	1088	{
824	ev_io_stop (w);	1089	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
826	}	1091	}
827		1092
828	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
829		1094
830	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
831		1096
832	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
835		1100
836	ev_loop (loop, 0);	1101	ev_run (loop, 0);
837		1102
838	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
839	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
840	stack).	1105	stack).
841		1106
842	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>
843	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).
844		1109
845	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
846	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
847	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
848	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
849	is readable and/or writable).	1114	and/or writable).
850		1115
851	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 *, ...) >>
852	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
853	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<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
878		1143
879	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
880	writable.	1145	writable.
881		1146
882	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
883		1148
884	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
885		1150
886	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
887		1152
…		…
905		1170
906	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
907		1172
908	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
909		1174
910	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
911	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
912	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
913	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
914	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
915	(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
916	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
917		1182
918	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
919		1184
920	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.
921		1186
922	=item C<EV_FORK>	1187	=item C<EV_FORK>
923		1188
924	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
925	C<ev_fork>).	1190	C<ev_fork>).
926		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
		1195
927	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
928		1197
929	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>).
		1199
		1200	=item C<EV_CUSTOM>
		1201
		1202	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1203	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1204
931	=item C<EV_ERROR>	1205	=item C<EV_ERROR>
932		1206
933	An unspecified error has occurred, the watcher has been stopped. This might	1207	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1208	happen because the watcher could not be properly started because libev
…		…
972		1246
973	ev_io w;	1247	ev_io w;
974	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1250
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1252
979	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
980	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
981	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
982	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
…		…
995		1269
996	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.
997		1271
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1273
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1275
1002	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1004		1278
1005	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
1006	whole section.	1280	whole section.
1007		1281
1008	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1009		1283
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1285
1012	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
1013	the watcher was active or not).	1287	the watcher was active or not).
1014		1288
1015	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1041		1315
1042	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
1043	(modulo threads).	1317	(modulo threads).
1044		1318
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1320
1047	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1048		1322
1049	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
1050	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>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1325	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1326	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1327	from being executed (except for C<ev_idle> watchers).
1054		1328
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	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
1061	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.
1062		1331
1063	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
1064	pending.	1333	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1334
1069	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
1070	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
1071	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.
1072		1344
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1345	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1346
1075	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
1076	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
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1085		1357
1086	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
1087	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1088		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
1089	=back	1375	=back
1090		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1091		1379
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1093		1381
1094	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1095	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
1096	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
1097	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".
1098	member, you can also "subclass" the watcher type and provide your own
1099	data:
1100		1386
1101	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)
1102	{	1512	{
1103	ev_io io;	1513	// stop the I/O watcher, we received the event, but
1104	int otherfd;	1514	// are not yet ready to handle it.
1105	void *somedata;	1515	ev_io_stop (EV_A_ w);
1106	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);
1107	};	1521	}
1108		1522
1109	...	1523	static void
1110	struct my_io w;	1524	idle_cb (EV_P_ ev_idle *w, int revents)
1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1112
1113	And since your callback will be called with a pointer to the watcher, you
1114	can cast it back to your own type:
1115
1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1117	{	1525	{
1118	struct my_io *w = (struct my_io *)w_;	1526	// actual processing
1119	...	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);
1120	}	1532	}
1121		1533
1122	More interesting and less C-conformant ways of casting your callback type	1534	// initialisation
1123	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);
1124		1538
1125	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
1126	embedded watchers:	1540	low-priority connections can not be locked out forever under load. This
1127		1541	enables your program to keep a lower latency for important connections
1128	struct my_biggy	1542	during short periods of high load, while not completely locking out less
1129	{	1543	important ones.
1130	int some_data;
1131	ev_timer t1;
1132	ev_timer t2;
1133	}
1134
1135	In this case getting the pointer to C<my_biggy> is a bit more
1136	complicated: Either you store the address of your C<my_biggy> struct
1137	in the C<data> member of the watcher (for woozies), or you need to use
1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
1139	programmers):
1140
1141	#include <stddef.h>
1142
1143	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{
1146	struct my_biggy big = (struct my_biggy *
1147	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}
1149
1150	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{
1153	struct my_biggy big = (struct my_biggy *
1154	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}
1156		1544
1157		1545
1158	=head1 WATCHER TYPES	1546	=head1 WATCHER TYPES
1159		1547
1160	This section describes each watcher in detail, but will not repeat	1548	This section describes each watcher in detail, but will not repeat
…		…
1184	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
1185	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
1186	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
1187	required if you know what you are doing).	1575	required if you know what you are doing).
1188		1576
1189	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1192
1193	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
1194	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1195	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
1196	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
1197	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
1198	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
1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1201		1584
1202	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
1203	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
1204	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
1205	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
1206	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
1207	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
1208	indefinitely.	1591	indefinitely.
1209		1592
1210	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1211		1594
…		…
1239		1622
1240	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		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
1244	=head3 The special problem of fork	1660	=head3 The special problem of fork
1245		1661
1246	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
1247	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
1248	it in the child.	1664	it in the child if you want to continue to use it in the child.
1249		1665
1250	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
1251	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
1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1669
1255	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1256		1671
1257	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>:
1258	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
…		…
1261		1676
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1263	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
1264	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1265		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.
1266		1719
1267	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1268		1721
1269	=over 4	1722	=over 4
1270		1723
…		…
1302	...	1755	...
1303	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1757	ev_io stdin_readable;
1305	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);
1306	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1308		1761
1309		1762
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1764
1312	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
…		…
1317	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
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1320		1773
1321	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
1322	passed, but if multiple timers become ready during the same loop iteration	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
		1778	iteration then the ones with earlier time-out values are invoked before
		1779	ones of the same priority with later time-out values (but this is no
		1780	longer true when a callback calls C<ev_run> recursively).
1324		1781
1325	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1326		1783
1327	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
1328	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,
…		…
1372	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>
1373	member and C<ev_timer_again>.	1830	member and C<ev_timer_again>.
1374		1831
1375	At start:	1832	At start:
1376		1833
1377	ev_timer_init (timer, callback);	1834	ev_init (timer, callback);
1378	timer->repeat = 60.;	1835	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1836	ev_timer_again (loop, timer);
1380		1837
1381	Each time there is some activity:	1838	Each time there is some activity:
1382		1839
…		…
1414	ev_tstamp timeout = last_activity + 60.;	1871	ev_tstamp timeout = last_activity + 60.;
1415		1872
1416	// if last_activity + 60. is older than now, we did time out	1873	// if last_activity + 60. is older than now, we did time out
1417	if (timeout < now)	1874	if (timeout < now)
1418	{	1875	{
1419	// timeout occured, take action	1876	// timeout occurred, take action
1420	}	1877	}
1421	else	1878	else
1422	{	1879	{
1423	// callback was invoked, but there was some activity, re-arm	1880	// callback was invoked, but there was some activity, re-arm
1424	// the watcher to fire in last_activity + 60, which is	1881	// the watcher to fire in last_activity + 60, which is
…		…
1444		1901
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1902	To start the timer, simply initialise the watcher and set C<last_activity>
1446	to the current time (meaning we just have some activity :), then call the	1903	to the current time (meaning we just have some activity :), then call the
1447	callback, which will "do the right thing" and start the timer:	1904	callback, which will "do the right thing" and start the timer:
1448		1905
1449	ev_timer_init (timer, callback);	1906	ev_init (timer, callback);
1450	last_activity = ev_now (loop);	1907	last_activity = ev_now (loop);
1451	callback (loop, timer, EV_TIMEOUT);	1908	callback (loop, timer, EV_TIMER);
1452		1909
1453	And when there is some activity, simply store the current time in	1910	And when there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1911	C<last_activity>, no libev calls at all:
1455		1912
1456	last_actiivty = ev_now (loop);	1913	last_activity = ev_now (loop);
1457		1914
1458	This technique is slightly more complex, but in most cases where the	1915	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1916	time-out is unlikely to be triggered, much more efficient.
1460		1917
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the	1918	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1952	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1496	rather complicated, but extremely efficient, something that really pays	1953	rather complicated, but extremely efficient, something that really pays
1497	off after the first million or so of active timers, i.e. it's usually	1954	off after the first million or so of active timers, i.e. it's usually
1498	overkill :)	1955	overkill :)
1499		1956
		1957	=head3 The special problem of being too early
		1958
		1959	If you ask a timer to call your callback after three seconds, then
		1960	you expect it to be invoked after three seconds - but of course, this
		1961	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1962	guaranteed to any precision by libev - imagine somebody suspending the
		1963	process a STOP signal for a few hours for example.
		1964
		1965	So, libev tries to invoke your callback as soon as possible I<after> the
		1966	delay has occurred, but cannot guarantee this.
		1967
		1968	A less obvious failure mode is calling your callback too early: many event
		1969	loops compare timestamps with a "elapsed delay >= requested delay", but
		1970	this can cause your callback to be invoked much earlier than you would
		1971	expect.
		1972
		1973	To see why, imagine a system with a clock that only offers full second
		1974	resolution (think windows if you can't come up with a broken enough OS
		1975	yourself). If you schedule a one-second timer at the time 500.9, then the
		1976	event loop will schedule your timeout to elapse at a system time of 500
		1977	(500.9 truncated to the resolution) + 1, or 501.
		1978
		1979	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1980	501" and invoke the callback 0.1s after it was started, even though a
		1981	one-second delay was requested - this is being "too early", despite best
		1982	intentions.
		1983
		1984	This is the reason why libev will never invoke the callback if the elapsed
		1985	delay equals the requested delay, but only when the elapsed delay is
		1986	larger than the requested delay. In the example above, libev would only invoke
		1987	the callback at system time 502, or 1.1s after the timer was started.
		1988
		1989	So, while libev cannot guarantee that your callback will be invoked
		1990	exactly when requested, it I<can> and I<does> guarantee that the requested
		1991	delay has actually elapsed, or in other words, it always errs on the "too
		1992	late" side of things.
		1993
1500	=head3 The special problem of time updates	1994	=head3 The special problem of time updates
1501		1995
1502	Establishing the current time is a costly operation (it usually takes at	1996	Establishing the current time is a costly operation (it usually takes
1503	least two system calls): EV therefore updates its idea of the current	1997	at least one system call): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	1998	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1999	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2000	lots of events in one iteration.
1507		2001
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2002	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	2003	time. This is usually the right thing as this timestamp refers to the time
…		…
1515		2009
1516	If the event loop is suspended for a long time, you can also force an	2010	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2011	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2012	()>.
1519		2013
		2014	=head3 The special problem of unsynchronised clocks
		2015
		2016	Modern systems have a variety of clocks - libev itself uses the normal
		2017	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2018	jumps).
		2019
		2020	Neither of these clocks is synchronised with each other or any other clock
		2021	on the system, so C<ev_time ()> might return a considerably different time
		2022	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2023	a call to C<gettimeofday> might return a second count that is one higher
		2024	than a directly following call to C<time>.
		2025
		2026	The moral of this is to only compare libev-related timestamps with
		2027	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2028	a second or so.
		2029
		2030	One more problem arises due to this lack of synchronisation: if libev uses
		2031	the system monotonic clock and you compare timestamps from C<ev_time>
		2032	or C<ev_now> from when you started your timer and when your callback is
		2033	invoked, you will find that sometimes the callback is a bit "early".
		2034
		2035	This is because C<ev_timer>s work in real time, not wall clock time, so
		2036	libev makes sure your callback is not invoked before the delay happened,
		2037	I<measured according to the real time>, not the system clock.
		2038
		2039	If your timeouts are based on a physical timescale (e.g. "time out this
		2040	connection after 100 seconds") then this shouldn't bother you as it is
		2041	exactly the right behaviour.
		2042
		2043	If you want to compare wall clock/system timestamps to your timers, then
		2044	you need to use C<ev_periodic>s, as these are based on the wall clock
		2045	time, where your comparisons will always generate correct results.
		2046
		2047	=head3 The special problems of suspended animation
		2048
		2049	When you leave the server world it is quite customary to hit machines that
		2050	can suspend/hibernate - what happens to the clocks during such a suspend?
		2051
		2052	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2053	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2054	to run until the system is suspended, but they will not advance while the
		2055	system is suspended. That means, on resume, it will be as if the program
		2056	was frozen for a few seconds, but the suspend time will not be counted
		2057	towards C<ev_timer> when a monotonic clock source is used. The real time
		2058	clock advanced as expected, but if it is used as sole clocksource, then a
		2059	long suspend would be detected as a time jump by libev, and timers would
		2060	be adjusted accordingly.
		2061
		2062	I would not be surprised to see different behaviour in different between
		2063	operating systems, OS versions or even different hardware.
		2064
		2065	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2066	time jump in the monotonic clocks and the realtime clock. If the program
		2067	is suspended for a very long time, and monotonic clock sources are in use,
		2068	then you can expect C<ev_timer>s to expire as the full suspension time
		2069	will be counted towards the timers. When no monotonic clock source is in
		2070	use, then libev will again assume a timejump and adjust accordingly.
		2071
		2072	It might be beneficial for this latter case to call C<ev_suspend>
		2073	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2074	deterministic behaviour in this case (you can do nothing against
		2075	C<SIGSTOP>).
		2076
1520	=head3 Watcher-Specific Functions and Data Members	2077	=head3 Watcher-Specific Functions and Data Members
1521		2078
1522	=over 4	2079	=over 4
1523		2080
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2081	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1537	keep up with the timer (because it takes longer than those 10 seconds to	2094	keep up with the timer (because it takes longer than those 10 seconds to
1538	do stuff) the timer will not fire more than once per event loop iteration.	2095	do stuff) the timer will not fire more than once per event loop iteration.
1539		2096
1540	=item ev_timer_again (loop, ev_timer *)	2097	=item ev_timer_again (loop, ev_timer *)
1541		2098
1542	This will act as if the timer timed out and restart it again if it is	2099	This will act as if the timer timed out and restarts it again if it is
1543	repeating. The exact semantics are:	2100	repeating. The exact semantics are:
1544		2101
1545	If the timer is pending, its pending status is cleared.	2102	If the timer is pending, its pending status is cleared.
1546		2103
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2104	If the timer is started but non-repeating, stop it (as if it timed out).
1548		2105
1549	If the timer is repeating, either start it if necessary (with the	2106	If the timer is repeating, either start it if necessary (with the
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2107	C<repeat> value), or reset the running timer to the C<repeat> value.
1551		2108
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2109	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1553	usage example.	2110	usage example.
		2111
		2112	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2113
		2114	Returns the remaining time until a timer fires. If the timer is active,
		2115	then this time is relative to the current event loop time, otherwise it's
		2116	the timeout value currently configured.
		2117
		2118	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2119	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2120	will return C<4>. When the timer expires and is restarted, it will return
		2121	roughly C<7> (likely slightly less as callback invocation takes some time,
		2122	too), and so on.
1554		2123
1555	=item ev_tstamp repeat [read-write]	2124	=item ev_tstamp repeat [read-write]
1556		2125
1557	The current C<repeat> value. Will be used each time the watcher times out	2126	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2127	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2153	}
1585		2154
1586	ev_timer mytimer;	2155	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2156	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2157	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2158	ev_run (loop, 0);
1590		2159
1591	// and in some piece of code that gets executed on any "activity":	2160	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2161	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2162	ev_timer_again (&mytimer);
1594		2163
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2165	=head2 C<ev_periodic> - to cron or not to cron?
1597		2166
1598	Periodic watchers are also timers of a kind, but they are very versatile	2167	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2168	(and unfortunately a bit complex).
1600		2169
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2170	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2171	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2172	(absolute time, the thing you can read on your calender or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2173	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2174	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2175	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2176
		2177	You can tell a periodic watcher to trigger after some specific point
		2178	in time: for example, if you tell a periodic watcher to trigger "in 10
		2179	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2180	not a delay) and then reset your system clock to January of the previous
		2181	year, then it will take a year or more to trigger the event (unlike an
		2182	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2183	it, as it uses a relative timeout).
		2184
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2185	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2186	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2187	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2188	those cannot react to time jumps.
1613		2189
1614	As with timers, the callback is guaranteed to be invoked only when the	2190	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2191	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2192	timers become ready during the same loop iteration then the ones with
		2193	earlier time-out values are invoked before ones with later time-out values
		2194	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2195
1618	=head3 Watcher-Specific Functions and Data Members	2196	=head3 Watcher-Specific Functions and Data Members
1619		2197
1620	=over 4	2198	=over 4
1621		2199
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2200	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2201
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2202	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2203
1626	Lots of arguments, lets sort it out... There are basically three modes of	2204	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2205	operation, and we will explain them from simplest to most complex:
1628		2206
1629	=over 4	2207	=over 4
1630		2208
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2209	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2210
1633	In this configuration the watcher triggers an event after the wall clock	2211	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2212	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2213	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2214	will be stopped and invoked when the system clock reaches or surpasses
		2215	this point in time.
1637		2216
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2217	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2218
1640	In this mode the watcher will always be scheduled to time out at the next	2219	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2220	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2221	negative) and then repeat, regardless of any time jumps. The C<offset>
		2222	argument is merely an offset into the C<interval> periods.
1643		2223
1644	This can be used to create timers that do not drift with respect to the	2224	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2225	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2226	hour, on the hour (with respect to UTC):
1647		2227
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2228	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2229
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2230	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2231	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2232	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2233	by 3600.
1654		2234
1655	Another way to think about it (for the mathematically inclined) is that	2235	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2236	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2237	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2238
1659	For numerical stability it is preferable that the C<at> value is near	2239	The C<interval> I<MUST> be positive, and for numerical stability, the
1660	C<ev_now ()> (the current time), but there is no range requirement for	2240	interval value should be higher than C<1/8192> (which is around 100
1661	this value, and in fact is often specified as zero.	2241	microseconds) and C<offset> should be higher than C<0> and should have
		2242	at most a similar magnitude as the current time (say, within a factor of
		2243	ten). Typical values for offset are, in fact, C<0> or something between
		2244	C<0> and C<interval>, which is also the recommended range.
1662		2245
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2246	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2247	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2248	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2249	millisecond (if the OS supports it and the machine is fast enough).
1667		2250
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2251	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2252
1670	In this mode the values for C<interval> and C<at> are both being	2253	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2254	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2255	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2256	current time as second argument.
1674		2257
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2258	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY other event loop modifications whatsoever>.	2259	or make ANY other event loop modifications whatsoever, unless explicitly
		2260	allowed by documentation here>.
1677		2261
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2262	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2263	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2264	only event loop modification you are allowed to do).
1681		2265
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2295	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2296	program when the crontabs have changed).
1713		2297
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2298	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2299
1716	When active, returns the absolute time that the watcher is supposed to	2300	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2301	to trigger next. This is not the same as the C<offset> argument to
		2302	C<ev_periodic_set>, but indeed works even in interval and manual
		2303	rescheduling modes.
1718		2304
1719	=item ev_tstamp offset [read-write]	2305	=item ev_tstamp offset [read-write]
1720		2306
1721	When repeating, this contains the offset value, otherwise this is the	2307	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2308	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2309	although libev might modify this value for better numerical stability).
1723		2310
1724	Can be modified any time, but changes only take effect when the periodic	2311	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2312	timer fires or C<ev_periodic_again> is being called.
1726		2313
1727	=item ev_tstamp interval [read-write]	2314	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2330	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2331	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2332	potentially a lot of jitter, but good long-term stability.
1746		2333
1747	static void	2334	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2335	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2336	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2337	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2338	}
1752		2339
1753	ev_periodic hourly_tick;	2340	ev_periodic hourly_tick;
…		…
1776		2363
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2364	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2365
1779	Signal watchers will trigger an event when the process receives a specific	2366	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2367	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2368	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2369	normal event processing, like any other event.
1783		2370
1784	If you want signals asynchronously, just use C<sigaction> as you would	2371	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2372	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2373	the signal. You can even use C<ev_async> from a signal handler to
		2374	synchronously wake up an event loop.
1787		2375
1788	You can configure as many watchers as you like per signal. Only when the	2376	You can configure as many watchers as you like for the same signal, but
		2377	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2378	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2379	C<SIGINT> in both the default loop and another loop at the same time. At
		2380	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2381
1789	first watcher gets started will libev actually register a signal handler	2382	When the first watcher gets started will libev actually register something
1790	with the kernel (thus it coexists with your own signal handlers as long as	2383	with the kernel (thus it coexists with your own signal handlers as long as
1791	you don't register any with libev for the same signal). Similarly, when	2384	you don't register any with libev for the same signal).
1792	the last signal watcher for a signal is stopped, libev will reset the
1793	signal handler to SIG_DFL (regardless of what it was set to before).
1794		2385
1795	If possible and supported, libev will install its handlers with	2386	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2387	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2388	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2389	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2390	and unblock them in an C<ev_prepare> watcher.
		2391
		2392	=head3 The special problem of inheritance over fork/execve/pthread_create
		2393
		2394	Both the signal mask (C<sigprocmask>) and the signal disposition
		2395	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2396	stopping it again), that is, libev might or might not block the signal,
		2397	and might or might not set or restore the installed signal handler (but
		2398	see C<EVFLAG_NOSIGMASK>).
		2399
		2400	While this does not matter for the signal disposition (libev never
		2401	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2402	C<execve>), this matters for the signal mask: many programs do not expect
		2403	certain signals to be blocked.
		2404
		2405	This means that before calling C<exec> (from the child) you should reset
		2406	the signal mask to whatever "default" you expect (all clear is a good
		2407	choice usually).
		2408
		2409	The simplest way to ensure that the signal mask is reset in the child is
		2410	to install a fork handler with C<pthread_atfork> that resets it. That will
		2411	catch fork calls done by libraries (such as the libc) as well.
		2412
		2413	In current versions of libev, the signal will not be blocked indefinitely
		2414	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2415	the window of opportunity for problems, it will not go away, as libev
		2416	I<has> to modify the signal mask, at least temporarily.
		2417
		2418	So I can't stress this enough: I<If you do not reset your signal mask when
		2419	you expect it to be empty, you have a race condition in your code>. This
		2420	is not a libev-specific thing, this is true for most event libraries.
		2421
		2422	=head3 The special problem of threads signal handling
		2423
		2424	POSIX threads has problematic signal handling semantics, specifically,
		2425	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2426	threads in a process block signals, which is hard to achieve.
		2427
		2428	When you want to use sigwait (or mix libev signal handling with your own
		2429	for the same signals), you can tackle this problem by globally blocking
		2430	all signals before creating any threads (or creating them with a fully set
		2431	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2432	loops. Then designate one thread as "signal receiver thread" which handles
		2433	these signals. You can pass on any signals that libev might be interested
		2434	in by calling C<ev_feed_signal>.
1800		2435
1801	=head3 Watcher-Specific Functions and Data Members	2436	=head3 Watcher-Specific Functions and Data Members
1802		2437
1803	=over 4	2438	=over 4
1804		2439
…		…
1820	Example: Try to exit cleanly on SIGINT.	2455	Example: Try to exit cleanly on SIGINT.
1821		2456
1822	static void	2457	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2458	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2459	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2460	ev_break (loop, EVBREAK_ALL);
1826	}	2461	}
1827		2462
1828	ev_signal signal_watcher;	2463	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2464	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2465	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2471	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2472	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2473	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2474	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2475	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2476	but forking and registering a watcher a few event loop iterations later or
1842	not.	2477	in the next callback invocation is not.
1843		2478
1844	Only the default event loop is capable of handling signals, and therefore	2479	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2480	you can only register child watchers in the default event loop.
1846		2481
		2482	Due to some design glitches inside libev, child watchers will always be
		2483	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2484	libev)
		2485
1847	=head3 Process Interaction	2486	=head3 Process Interaction
1848		2487
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2488	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2489	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2490	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2491	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2492	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2493	children, even ones not watched.
1855		2494
1856	=head3 Overriding the Built-In Processing	2495	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2505	=head3 Stopping the Child Watcher
1867		2506
1868	Currently, the child watcher never gets stopped, even when the	2507	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2508	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2509	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2510	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2511	problem).
1872		2512
1873	=head3 Watcher-Specific Functions and Data Members	2513	=head3 Watcher-Specific Functions and Data Members
1874		2514
1875	=over 4	2515	=over 4
1876		2516
…		…
2202	// no longer anything immediate to do.	2842	// no longer anything immediate to do.
2203	}	2843	}
2204		2844
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2845	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2846	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2847	ev_idle_start (loop, idle_watcher);
2208		2848
2209		2849
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2850	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2851
2212	Prepare and check watchers are usually (but not always) used in pairs:	2852	Prepare and check watchers are usually (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2853	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2854	afterwards.
2215		2855
2216	You I<must not> call C<ev_loop> or similar functions that enter	2856	You I<must not> call C<ev_run> or similar functions that enter
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2857	the current event loop from either C<ev_prepare> or C<ev_check>
2218	watchers. Other loops than the current one are fine, however. The	2858	watchers. Other loops than the current one are fine, however. The
2219	rationale behind this is that you do not need to check for recursion in	2859	rationale behind this is that you do not need to check for recursion in
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2860	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2221	C<ev_check> so if you have one watcher of each kind they will always be	2861	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2305	struct pollfd fds [nfd];	2945	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	2946	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		2948
2309	/* the callback is illegal, but won't be called as we stop during check */	2949	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	2950	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	2951	ev_timer_start (loop, &tw);
2312		2952
2313	// create one ev_io per pollfd	2953	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	2954	for (int i = 0; i < nfd; ++i)
2315	{	2955	{
…		…
2389		3029
2390	if (timeout >= 0)	3030	if (timeout >= 0)
2391	// create/start timer	3031	// create/start timer
2392		3032
2393	// poll	3033	// poll
2394	ev_loop (EV_A_ 0);	3034	ev_run (EV_A_ 0);
2395		3035
2396	// stop timer again	3036	// stop timer again
2397	if (timeout >= 0)	3037	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3038	ev_timer_stop (EV_A_ &to);
2399		3039
…		…
2477	if you do not want that, you need to temporarily stop the embed watcher).	3117	if you do not want that, you need to temporarily stop the embed watcher).
2478		3118
2479	=item ev_embed_sweep (loop, ev_embed *)	3119	=item ev_embed_sweep (loop, ev_embed *)
2480		3120
2481	Make a single, non-blocking sweep over the embedded loop. This works	3121	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3122	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3123	appropriate way for embedded loops.
2484		3124
2485	=item struct ev_loop *other [read-only]	3125	=item struct ev_loop *other [read-only]
2486		3126
2487	The embedded event loop.	3127	The embedded event loop.
…		…
2545	event loop blocks next and before C<ev_check> watchers are being called,	3185	event loop blocks next and before C<ev_check> watchers are being called,
2546	and only in the child after the fork. If whoever good citizen calling	3186	and only in the child after the fork. If whoever good citizen calling
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3187	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2548	handlers will be invoked, too, of course.	3188	handlers will be invoked, too, of course.
2549		3189
		3190	=head3 The special problem of life after fork - how is it possible?
		3191
		3192	Most uses of C<fork()> consist of forking, then some simple calls to set
		3193	up/change the process environment, followed by a call to C<exec()>. This
		3194	sequence should be handled by libev without any problems.
		3195
		3196	This changes when the application actually wants to do event handling
		3197	in the child, or both parent in child, in effect "continuing" after the
		3198	fork.
		3199
		3200	The default mode of operation (for libev, with application help to detect
		3201	forks) is to duplicate all the state in the child, as would be expected
		3202	when I<either> the parent I<or> the child process continues.
		3203
		3204	When both processes want to continue using libev, then this is usually the
		3205	wrong result. In that case, usually one process (typically the parent) is
		3206	supposed to continue with all watchers in place as before, while the other
		3207	process typically wants to start fresh, i.e. without any active watchers.
		3208
		3209	The cleanest and most efficient way to achieve that with libev is to
		3210	simply create a new event loop, which of course will be "empty", and
		3211	use that for new watchers. This has the advantage of not touching more
		3212	memory than necessary, and thus avoiding the copy-on-write, and the
		3213	disadvantage of having to use multiple event loops (which do not support
		3214	signal watchers).
		3215
		3216	When this is not possible, or you want to use the default loop for
		3217	other reasons, then in the process that wants to start "fresh", call
		3218	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3219	Destroying the default loop will "orphan" (not stop) all registered
		3220	watchers, so you have to be careful not to execute code that modifies
		3221	those watchers. Note also that in that case, you have to re-register any
		3222	signal watchers.
		3223
2550	=head3 Watcher-Specific Functions and Data Members	3224	=head3 Watcher-Specific Functions and Data Members
2551		3225
2552	=over 4	3226	=over 4
2553		3227
2554	=item ev_fork_init (ev_signal *, callback)	3228	=item ev_fork_init (ev_fork *, callback)
2555		3229
2556	Initialises and configures the fork watcher - it has no parameters of any	3230	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3231	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3232	really.
2559		3233
2560	=back	3234	=back
2561		3235
2562		3236
		3237	=head2 C<ev_cleanup> - even the best things end
		3238
		3239	Cleanup watchers are called just before the event loop is being destroyed
		3240	by a call to C<ev_loop_destroy>.
		3241
		3242	While there is no guarantee that the event loop gets destroyed, cleanup
		3243	watchers provide a convenient method to install cleanup hooks for your
		3244	program, worker threads and so on - you just to make sure to destroy the
		3245	loop when you want them to be invoked.
		3246
		3247	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3248	all other watchers, they do not keep a reference to the event loop (which
		3249	makes a lot of sense if you think about it). Like all other watchers, you
		3250	can call libev functions in the callback, except C<ev_cleanup_start>.
		3251
		3252	=head3 Watcher-Specific Functions and Data Members
		3253
		3254	=over 4
		3255
		3256	=item ev_cleanup_init (ev_cleanup *, callback)
		3257
		3258	Initialises and configures the cleanup watcher - it has no parameters of
		3259	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3260	pointless, I assure you.
		3261
		3262	=back
		3263
		3264	Example: Register an atexit handler to destroy the default loop, so any
		3265	cleanup functions are called.
		3266
		3267	static void
		3268	program_exits (void)
		3269	{
		3270	ev_loop_destroy (EV_DEFAULT_UC);
		3271	}
		3272
		3273	...
		3274	atexit (program_exits);
		3275
		3276
2563	=head2 C<ev_async> - how to wake up another event loop	3277	=head2 C<ev_async> - how to wake up an event loop
2564		3278
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3279	In general, you cannot use an C<ev_loop> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3280	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3281	loops - those are of course safe to use in different threads).
2568		3282
2569	Sometimes, however, you need to wake up another event loop you do not	3283	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3284	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3285	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3286	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3287
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3288	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3289	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3290	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3291	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2579		3292	of "global async watchers" by using a watcher on an otherwise unused
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3293	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2581	just the default loop.	3294	even without knowing which loop owns the signal.
2582		3295
2583	=head3 Queueing	3296	=head3 Queueing
2584		3297
2585	C<ev_async> does not support queueing of data in any way. The reason	3298	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3299	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3300	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3301	need elaborate support such as pthreads or unportable memory access
		3302	semantics.
2589		3303
2590	That means that if you want to queue data, you have to provide your own	3304	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3305	queue. But at least I can tell you how to implement locking around your
2592	queue:	3306	queue:
2593		3307
…		…
2677	trust me.	3391	trust me.
2678		3392
2679	=item ev_async_send (loop, ev_async *)	3393	=item ev_async_send (loop, ev_async *)
2680		3394
2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3395	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3396	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3397	returns.
		3398
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3399	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3400	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2685	section below on what exactly this means).	3401	embedding section below on what exactly this means).
2686		3402
2687	This call incurs the overhead of a system call only once per loop iteration,	3403	Note that, as with other watchers in libev, multiple events might get
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3404	compressed into a single callback invocation (another way to look at
2689	calls to C<ev_async_send>.	3405	this is that C<ev_async> watchers are level-triggered: they are set on
		3406	C<ev_async_send>, reset when the event loop detects that).
		3407
		3408	This call incurs the overhead of at most one extra system call per event
		3409	loop iteration, if the event loop is blocked, and no syscall at all if
		3410	the event loop (or your program) is processing events. That means that
		3411	repeated calls are basically free (there is no need to avoid calls for
		3412	performance reasons) and that the overhead becomes smaller (typically
		3413	zero) under load.
2690		3414
2691	=item bool = ev_async_pending (ev_async *)	3415	=item bool = ev_async_pending (ev_async *)
2692		3416
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3417	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3418	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3421	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3422	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3423	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3424	quickly check whether invoking the loop might be a good idea.
2701		3425
2702	Not that this does I<not> check whether the watcher itself is pending, only	3426	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3427	only whether it has been requested to make this watcher pending: there
		3428	is a time window between the event loop checking and resetting the async
		3429	notification, and the callback being invoked.
2704		3430
2705	=back	3431	=back
2706		3432
2707		3433
2708	=head1 OTHER FUNCTIONS	3434	=head1 OTHER FUNCTIONS
…		…
2725		3451
2726	If C<timeout> is less than 0, then no timeout watcher will be	3452	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3453	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3454	repeat = 0) will be started. C<0> is a valid timeout.
2729		3455
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3456	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3457	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3458	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3459	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3460	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3461	events precedence.
2736		3462
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3463	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3464
2739	static void stdin_ready (int revents, void *arg)	3465	static void stdin_ready (int revents, void *arg)
2740	{	3466	{
2741	if (revents & EV_READ)	3467	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3468	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3469	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3470	/* doh, nothing entered */;
2745	}	3471	}
2746		3472
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3473	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3474
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3475	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3476
2757	Feed an event on the given fd, as if a file descriptor backend detected	3477	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3478	the given events it.
2759		3479
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3480	=item ev_feed_signal_event (loop, int signum)
2761		3481
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3482	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3483	which is async-safe.
2764		3484
2765	=back	3485	=back
		3486
		3487
		3488	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3489
		3490	This section explains some common idioms that are not immediately
		3491	obvious. Note that examples are sprinkled over the whole manual, and this
		3492	section only contains stuff that wouldn't fit anywhere else.
		3493
		3494	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3495
		3496	Each watcher has, by default, a C<void *data> member that you can read
		3497	or modify at any time: libev will completely ignore it. This can be used
		3498	to associate arbitrary data with your watcher. If you need more data and
		3499	don't want to allocate memory separately and store a pointer to it in that
		3500	data member, you can also "subclass" the watcher type and provide your own
		3501	data:
		3502
		3503	struct my_io
		3504	{
		3505	ev_io io;
		3506	int otherfd;
		3507	void *somedata;
		3508	struct whatever *mostinteresting;
		3509	};
		3510
		3511	...
		3512	struct my_io w;
		3513	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3514
		3515	And since your callback will be called with a pointer to the watcher, you
		3516	can cast it back to your own type:
		3517
		3518	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3519	{
		3520	struct my_io *w = (struct my_io *)w_;
		3521	...
		3522	}
		3523
		3524	More interesting and less C-conformant ways of casting your callback
		3525	function type instead have been omitted.
		3526
		3527	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3528
		3529	Another common scenario is to use some data structure with multiple
		3530	embedded watchers, in effect creating your own watcher that combines
		3531	multiple libev event sources into one "super-watcher":
		3532
		3533	struct my_biggy
		3534	{
		3535	int some_data;
		3536	ev_timer t1;
		3537	ev_timer t2;
		3538	}
		3539
		3540	In this case getting the pointer to C<my_biggy> is a bit more
		3541	complicated: Either you store the address of your C<my_biggy> struct in
		3542	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3543	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3544	real programmers):
		3545
		3546	#include <stddef.h>
		3547
		3548	static void
		3549	t1_cb (EV_P_ ev_timer *w, int revents)
		3550	{
		3551	struct my_biggy big = (struct my_biggy *)
		3552	(((char *)w) - offsetof (struct my_biggy, t1));
		3553	}
		3554
		3555	static void
		3556	t2_cb (EV_P_ ev_timer *w, int revents)
		3557	{
		3558	struct my_biggy big = (struct my_biggy *)
		3559	(((char *)w) - offsetof (struct my_biggy, t2));
		3560	}
		3561
		3562	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3563
		3564	Often (especially in GUI toolkits) there are places where you have
		3565	I<modal> interaction, which is most easily implemented by recursively
		3566	invoking C<ev_run>.
		3567
		3568	This brings the problem of exiting - a callback might want to finish the
		3569	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3570	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3571	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3572	other combination: In these cases, C<ev_break> will not work alone.
		3573
		3574	The solution is to maintain "break this loop" variable for each C<ev_run>
		3575	invocation, and use a loop around C<ev_run> until the condition is
		3576	triggered, using C<EVRUN_ONCE>:
		3577
		3578	// main loop
		3579	int exit_main_loop = 0;
		3580
		3581	while (!exit_main_loop)
		3582	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3583
		3584	// in a model watcher
		3585	int exit_nested_loop = 0;
		3586
		3587	while (!exit_nested_loop)
		3588	ev_run (EV_A_ EVRUN_ONCE);
		3589
		3590	To exit from any of these loops, just set the corresponding exit variable:
		3591
		3592	// exit modal loop
		3593	exit_nested_loop = 1;
		3594
		3595	// exit main program, after modal loop is finished
		3596	exit_main_loop = 1;
		3597
		3598	// exit both
		3599	exit_main_loop = exit_nested_loop = 1;
		3600
		3601	=head2 THREAD LOCKING EXAMPLE
		3602
		3603	Here is a fictitious example of how to run an event loop in a different
		3604	thread from where callbacks are being invoked and watchers are
		3605	created/added/removed.
		3606
		3607	For a real-world example, see the C<EV::Loop::Async> perl module,
		3608	which uses exactly this technique (which is suited for many high-level
		3609	languages).
		3610
		3611	The example uses a pthread mutex to protect the loop data, a condition
		3612	variable to wait for callback invocations, an async watcher to notify the
		3613	event loop thread and an unspecified mechanism to wake up the main thread.
		3614
		3615	First, you need to associate some data with the event loop:
		3616
		3617	typedef struct {
		3618	mutex_t lock; /* global loop lock */
		3619	ev_async async_w;
		3620	thread_t tid;
		3621	cond_t invoke_cv;
		3622	} userdata;
		3623
		3624	void prepare_loop (EV_P)
		3625	{
		3626	// for simplicity, we use a static userdata struct.
		3627	static userdata u;
		3628
		3629	ev_async_init (&u->async_w, async_cb);
		3630	ev_async_start (EV_A_ &u->async_w);
		3631
		3632	pthread_mutex_init (&u->lock, 0);
		3633	pthread_cond_init (&u->invoke_cv, 0);
		3634
		3635	// now associate this with the loop
		3636	ev_set_userdata (EV_A_ u);
		3637	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3638	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3639
		3640	// then create the thread running ev_run
		3641	pthread_create (&u->tid, 0, l_run, EV_A);
		3642	}
		3643
		3644	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3645	solely to wake up the event loop so it takes notice of any new watchers
		3646	that might have been added:
		3647
		3648	static void
		3649	async_cb (EV_P_ ev_async *w, int revents)
		3650	{
		3651	// just used for the side effects
		3652	}
		3653
		3654	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3655	protecting the loop data, respectively.
		3656
		3657	static void
		3658	l_release (EV_P)
		3659	{
		3660	userdata *u = ev_userdata (EV_A);
		3661	pthread_mutex_unlock (&u->lock);
		3662	}
		3663
		3664	static void
		3665	l_acquire (EV_P)
		3666	{
		3667	userdata *u = ev_userdata (EV_A);
		3668	pthread_mutex_lock (&u->lock);
		3669	}
		3670
		3671	The event loop thread first acquires the mutex, and then jumps straight
		3672	into C<ev_run>:
		3673
		3674	void *
		3675	l_run (void *thr_arg)
		3676	{
		3677	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3678
		3679	l_acquire (EV_A);
		3680	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3681	ev_run (EV_A_ 0);
		3682	l_release (EV_A);
		3683
		3684	return 0;
		3685	}
		3686
		3687	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3688	signal the main thread via some unspecified mechanism (signals? pipe
		3689	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3690	have been called (in a while loop because a) spurious wakeups are possible
		3691	and b) skipping inter-thread-communication when there are no pending
		3692	watchers is very beneficial):
		3693
		3694	static void
		3695	l_invoke (EV_P)
		3696	{
		3697	userdata *u = ev_userdata (EV_A);
		3698
		3699	while (ev_pending_count (EV_A))
		3700	{
		3701	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3702	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3703	}
		3704	}
		3705
		3706	Now, whenever the main thread gets told to invoke pending watchers, it
		3707	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3708	thread to continue:
		3709
		3710	static void
		3711	real_invoke_pending (EV_P)
		3712	{
		3713	userdata *u = ev_userdata (EV_A);
		3714
		3715	pthread_mutex_lock (&u->lock);
		3716	ev_invoke_pending (EV_A);
		3717	pthread_cond_signal (&u->invoke_cv);
		3718	pthread_mutex_unlock (&u->lock);
		3719	}
		3720
		3721	Whenever you want to start/stop a watcher or do other modifications to an
		3722	event loop, you will now have to lock:
		3723
		3724	ev_timer timeout_watcher;
		3725	userdata *u = ev_userdata (EV_A);
		3726
		3727	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3728
		3729	pthread_mutex_lock (&u->lock);
		3730	ev_timer_start (EV_A_ &timeout_watcher);
		3731	ev_async_send (EV_A_ &u->async_w);
		3732	pthread_mutex_unlock (&u->lock);
		3733
		3734	Note that sending the C<ev_async> watcher is required because otherwise
		3735	an event loop currently blocking in the kernel will have no knowledge
		3736	about the newly added timer. By waking up the loop it will pick up any new
		3737	watchers in the next event loop iteration.
		3738
		3739	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3740
		3741	While the overhead of a callback that e.g. schedules a thread is small, it
		3742	is still an overhead. If you embed libev, and your main usage is with some
		3743	kind of threads or coroutines, you might want to customise libev so that
		3744	doesn't need callbacks anymore.
		3745
		3746	Imagine you have coroutines that you can switch to using a function
		3747	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3748	and that due to some magic, the currently active coroutine is stored in a
		3749	global called C<current_coro>. Then you can build your own "wait for libev
		3750	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3751	the differing C<;> conventions):
		3752
		3753	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3754	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3755
		3756	That means instead of having a C callback function, you store the
		3757	coroutine to switch to in each watcher, and instead of having libev call
		3758	your callback, you instead have it switch to that coroutine.
		3759
		3760	A coroutine might now wait for an event with a function called
		3761	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3762	matter when, or whether the watcher is active or not when this function is
		3763	called):
		3764
		3765	void
		3766	wait_for_event (ev_watcher *w)
		3767	{
		3768	ev_cb_set (w) = current_coro;
		3769	switch_to (libev_coro);
		3770	}
		3771
		3772	That basically suspends the coroutine inside C<wait_for_event> and
		3773	continues the libev coroutine, which, when appropriate, switches back to
		3774	this or any other coroutine. I am sure if you sue this your own :)
		3775
		3776	You can do similar tricks if you have, say, threads with an event queue -
		3777	instead of storing a coroutine, you store the queue object and instead of
		3778	switching to a coroutine, you push the watcher onto the queue and notify
		3779	any waiters.
		3780
		3781	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3782	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3783
		3784	// my_ev.h
		3785	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3786	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3787	#include "../libev/ev.h"
		3788
		3789	// my_ev.c
		3790	#define EV_H "my_ev.h"
		3791	#include "../libev/ev.c"
		3792
		3793	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3794	F<my_ev.c> into your project. When properly specifying include paths, you
		3795	can even use F<ev.h> as header file name directly.
2766		3796
2767		3797
2768	=head1 LIBEVENT EMULATION	3798	=head1 LIBEVENT EMULATION
2769		3799
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3800	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3801	emulate the internals of libevent, so here are some usage hints:
2772		3802
2773	=over 4	3803	=over 4
		3804
		3805	=item * Only the libevent-1.4.1-beta API is being emulated.
		3806
		3807	This was the newest libevent version available when libev was implemented,
		3808	and is still mostly unchanged in 2010.
2774		3809
2775	=item * Use it by including <event.h>, as usual.	3810	=item * Use it by including <event.h>, as usual.
2776		3811
2777	=item * The following members are fully supported: ev_base, ev_callback,	3812	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3813	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3819	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3820	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3821	is an ev_pri field.
2787		3822
2788	=item * In libevent, the last base created gets the signals, in libev, the	3823	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3824	base that registered the signal gets the signals.
2790		3825
2791	=item * Other members are not supported.	3826	=item * Other members are not supported.
2792		3827
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3828	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3829	to use the libev header file and library.
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	3848	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	3849	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	3850	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	3851	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		3852
2818	Currently, functions, and static and non-static member functions can be	3853	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	3854	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	3855	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	3856	you need support for other types of functors please contact the author
2822	it).	3857	(preferably after implementing it).
2823		3858
2824	Here is a list of things available in the C<ev> namespace:	3859	Here is a list of things available in the C<ev> namespace:
2825		3860
2826	=over 4	3861	=over 4
2827		3862
…		…
2845		3880
2846	=over 4	3881	=over 4
2847		3882
2848	=item ev::TYPE::TYPE ()	3883	=item ev::TYPE::TYPE ()
2849		3884
2850	=item ev::TYPE::TYPE (struct ev_loop *)	3885	=item ev::TYPE::TYPE (loop)
2851		3886
2852	=item ev::TYPE::~TYPE	3887	=item ev::TYPE::~TYPE
2853		3888
2854	The constructor (optionally) takes an event loop to associate the watcher	3889	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	3890	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	3923	myclass obj;
2889	ev::io iow;	3924	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	3925	iow.set <myclass, &myclass::io_cb> (&obj);
2891		3926
2892	=item w->set (object *)	3927	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		3928
2896	This is a variation of a method callback - leaving out the method to call	3929	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	3930	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	3931	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	3932	the time. Incidentally, you can then also leave out the template argument
…		…
2932	Example: Use a plain function as callback.	3965	Example: Use a plain function as callback.
2933		3966
2934	static void io_cb (ev::io &w, int revents) { }	3967	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	3968	iow.set <io_cb> ();
2936		3969
2937	=item w->set (struct ev_loop *)	3970	=item w->set (loop)
2938		3971
2939	Associates a different C<struct ev_loop> with this watcher. You can only	3972	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	3973	do this when the watcher is inactive (and not pending either).
2941		3974
2942	=item w->set ([arguments])	3975	=item w->set ([arguments])
2943		3976
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3977	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2945	called at least once. Unlike the C counterpart, an active watcher gets	3978	method or a suitable start method must be called at least once. Unlike the
2946	automatically stopped and restarted when reconfiguring it with this	3979	C counterpart, an active watcher gets automatically stopped and restarted
2947	method.	3980	when reconfiguring it with this method.
2948		3981
2949	=item w->start ()	3982	=item w->start ()
2950		3983
2951	Starts the watcher. Note that there is no C<loop> argument, as the	3984	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	3985	constructor already stores the event loop.
2953		3986
		3987	=item w->start ([arguments])
		3988
		3989	Instead of calling C<set> and C<start> methods separately, it is often
		3990	convenient to wrap them in one call. Uses the same type of arguments as
		3991	the configure C<set> method of the watcher.
		3992
2954	=item w->stop ()	3993	=item w->stop ()
2955		3994
2956	Stops the watcher if it is active. Again, no C<loop> argument.	3995	Stops the watcher if it is active. Again, no C<loop> argument.
2957		3996
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3997	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		4009
2971	=back	4010	=back
2972		4011
2973	=back	4012	=back
2974		4013
2975	Example: Define a class with an IO and idle watcher, start one of them in	4014	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	4015	watchers in the constructor.
2977		4016
2978	class myclass	4017	class myclass
2979	{	4018	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	4019	ev::io io ; void io_cb (ev::io &w, int revents);
		4020	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4021	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		4022
2983	myclass (int fd)	4023	myclass (int fd)
2984	{	4024	{
2985	io .set <myclass, &myclass::io_cb > (this);	4025	io .set <myclass, &myclass::io_cb > (this);
		4026	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	4027	idle.set <myclass, &myclass::idle_cb> (this);
2987		4028
2988	io.start (fd, ev::READ);	4029	io.set (fd, ev::WRITE); // configure the watcher
		4030	io.start (); // start it whenever convenient
		4031
		4032	io2.start (fd, ev::READ); // set + start in one call
2989	}	4033	}
2990	};	4034	};
2991		4035
2992		4036
2993	=head1 OTHER LANGUAGE BINDINGS	4037	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	4056	L<http://software.schmorp.de/pkg/EV>.
3013		4057
3014	=item Python	4058	=item Python
3015		4059
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4060	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	4061	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		4062
3023	=item Ruby	4063	=item Ruby
3024		4064
3025	Tony Arcieri has written a ruby extension that offers access to a subset	4065	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	4066	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	4068	L<http://rev.rubyforge.org/>.
3029		4069
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	4070	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	4071	makes rev work even on mingw.
3032		4072
		4073	=item Haskell
		4074
		4075	A haskell binding to libev is available at
		4076	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4077
3033	=item D	4078	=item D
3034		4079
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4080	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4081	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3037		4082
3038	=item Ocaml	4083	=item Ocaml
3039		4084
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	4085	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4086	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4087
		4088	=item Lua
		4089
		4090	Brian Maher has written a partial interface to libev for lua (at the
		4091	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4092	L<http://github.com/brimworks/lua-ev>.
3042		4093
3043	=back	4094	=back
3044		4095
3045		4096
3046	=head1 MACRO MAGIC	4097	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	4111	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	4112	C<EV_A_> is used when other arguments are following. Example:
3062		4113
3063	ev_unref (EV_A);	4114	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	4115	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	4116	ev_run (EV_A_ 0);
3066		4117
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4118	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	4119	which is often provided by the following macro.
3069		4120
3070	=item C<EV_P>, C<EV_P_>	4121	=item C<EV_P>, C<EV_P_>
…		…
3083	suitable for use with C<EV_A>.	4134	suitable for use with C<EV_A>.
3084		4135
3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4136	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3086		4137
3087	Similar to the other two macros, this gives you the value of the default	4138	Similar to the other two macros, this gives you the value of the default
3088	loop, if multiple loops are supported ("ev loop default").	4139	loop, if multiple loops are supported ("ev loop default"). The default loop
		4140	will be initialised if it isn't already initialised.
		4141
		4142	For non-multiplicity builds, these macros do nothing, so you always have
		4143	to initialise the loop somewhere.
3089		4144
3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4145	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3091		4146
3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4147	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3093	default loop has been initialised (C<UC> == unchecked). Their behaviour	4148	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3110	}	4165	}
3111		4166
3112	ev_check check;	4167	ev_check check;
3113	ev_check_init (&check, check_cb);	4168	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4169	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4170	ev_run (EV_DEFAULT_ 0);
3116		4171
3117	=head1 EMBEDDING	4172	=head1 EMBEDDING
3118		4173
3119	Libev can (and often is) directly embedded into host	4174	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4175	applications. Examples of applications that embed it include the Deliantra
…		…
3200	libev.m4	4255	libev.m4
3201		4256
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4257	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4258
3204	Libev can be configured via a variety of preprocessor symbols you have to	4259	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	4260	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4261	the absence of autoconf is documented for every option.
		4262
		4263	Symbols marked with "(h)" do not change the ABI, and can have different
		4264	values when compiling libev vs. including F<ev.h>, so it is permissible
		4265	to redefine them before including F<ev.h> without breaking compatibility
		4266	to a compiled library. All other symbols change the ABI, which means all
		4267	users of libev and the libev code itself must be compiled with compatible
		4268	settings.
3207		4269
3208	=over 4	4270	=over 4
3209		4271
		4272	=item EV_COMPAT3 (h)
		4273
		4274	Backwards compatibility is a major concern for libev. This is why this
		4275	release of libev comes with wrappers for the functions and symbols that
		4276	have been renamed between libev version 3 and 4.
		4277
		4278	You can disable these wrappers (to test compatibility with future
		4279	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4280	sources. This has the additional advantage that you can drop the C<struct>
		4281	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4282	typedef in that case.
		4283
		4284	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4285	and in some even more future version the compatibility code will be
		4286	removed completely.
		4287
3210	=item EV_STANDALONE	4288	=item EV_STANDALONE (h)
3211		4289
3212	Must always be C<1> if you do not use autoconf configuration, which	4290	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	4291	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4292	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	4293	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	4294	F<event.h> that are not directly supported by the libev core alone.
3217		4295
3218	In stanbdalone mode, libev will still try to automatically deduce the	4296	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4297	configuration, but has to be more conservative.
		4298
		4299	=item EV_USE_FLOOR
		4300
		4301	If defined to be C<1>, libev will use the C<floor ()> function for its
		4302	periodic reschedule calculations, otherwise libev will fall back on a
		4303	portable (slower) implementation. If you enable this, you usually have to
		4304	link against libm or something equivalent. Enabling this when the C<floor>
		4305	function is not available will fail, so the safe default is to not enable
		4306	this.
3220		4307
3221	=item EV_USE_MONOTONIC	4308	=item EV_USE_MONOTONIC
3222		4309
3223	If defined to be C<1>, libev will try to detect the availability of the	4310	If defined to be C<1>, libev will try to detect the availability of the
3224	monotonic clock option at both compile time and runtime. Otherwise no	4311	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3288	be used is the winsock select). This means that it will call	4375	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4376	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4377	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4378	on win32. Should not be defined on non-win32 platforms.
3292		4379
3293	=item EV_FD_TO_WIN32_HANDLE	4380	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4381
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4382	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4383	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4384	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4385	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4386	in which case they can provide this function to map fds to socket handles.
		4387
		4388	=item EV_WIN32_HANDLE_TO_FD(handle)
		4389
		4390	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4391	using the standard C<_open_osfhandle> function. For programs implementing
		4392	their own fd to handle mapping, overwriting this function makes it easier
		4393	to do so. This can be done by defining this macro to an appropriate value.
		4394
		4395	=item EV_WIN32_CLOSE_FD(fd)
		4396
		4397	If programs implement their own fd to handle mapping on win32, then this
		4398	macro can be used to override the C<close> function, useful to unregister
		4399	file descriptors again. Note that the replacement function has to close
		4400	the underlying OS handle.
3300		4401
3301	=item EV_USE_POLL	4402	=item EV_USE_POLL
3302		4403
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4404	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4405	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3343	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4444	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3344		4445
3345	=item EV_ATOMIC_T	4446	=item EV_ATOMIC_T
3346		4447
3347	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4448	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3348	access is atomic with respect to other threads or signal contexts. No such	4449	access is atomic and serialised with respect to other threads or signal
3349	type is easily found in the C language, so you can provide your own type	4450	contexts. No such type is easily found in the C language, so you can
3350	that you know is safe for your purposes. It is used both for signal handler "locking"	4451	provide your own type that you know is safe for your purposes. It is used
3351	as well as for signal and thread safety in C<ev_async> watchers.	4452	both for signal handler "locking" as well as for signal and thread safety
		4453	in C<ev_async> watchers.
3352		4454
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4455	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4456	(from F<signal.h>), which is usually good enough on most platforms,
		4457	although strictly speaking using a type that also implies a memory fence
		4458	is required.
3355		4459
3356	=item EV_H	4460	=item EV_H (h)
3357		4461
3358	The name of the F<ev.h> header file used to include it. The default if	4462	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4463	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4464	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4465
3362	=item EV_CONFIG_H	4466	=item EV_CONFIG_H (h)
3363		4467
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4468	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4469	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4470	C<EV_H>, above.
3367		4471
3368	=item EV_EVENT_H	4472	=item EV_EVENT_H (h)
3369		4473
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4474	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4475	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4476
3373	=item EV_PROTOTYPES	4477	=item EV_PROTOTYPES (h)
3374		4478
3375	If defined to be C<0>, then F<ev.h> will not define any function	4479	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4480	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4481	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4482	around libev functions.
…		…
3383	will have the C<struct ev_loop *> as first argument, and you can create	4487	will have the C<struct ev_loop *> as first argument, and you can create
3384	additional independent event loops. Otherwise there will be no support	4488	additional independent event loops. Otherwise there will be no support
3385	for multiple event loops and there is no first event loop pointer	4489	for multiple event loops and there is no first event loop pointer
3386	argument. Instead, all functions act on the single default loop.	4490	argument. Instead, all functions act on the single default loop.
3387		4491
		4492	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4493	default loop when multiplicity is switched off - you always have to
		4494	initialise the loop manually in this case.
		4495
3388	=item EV_MINPRI	4496	=item EV_MINPRI
3389		4497
3390	=item EV_MAXPRI	4498	=item EV_MAXPRI
3391		4499
3392	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4500	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3400	fine.	4508	fine.
3401		4509
3402	If your embedding application does not need any priorities, defining these	4510	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4511	both to C<0> will save some memory and CPU.
3404		4512
3405	=item EV_PERIODIC_ENABLE	4513	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4514	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4515	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4516
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4517	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4518	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4519	is not. Disabling watcher types mainly saves code size.
3410		4520
3411	=item EV_IDLE_ENABLE	4521	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4522
3440	If you need to shave off some kilobytes of code at the expense of some	4523	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4524	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4525	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4526	that can be enabled on the platform.
		4527
		4528	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4529	with some broad features you want) and then selectively re-enable
		4530	additional parts you want, for example if you want everything minimal,
		4531	but multiple event loop support, async and child watchers and the poll
		4532	backend, use this:
		4533
		4534	#define EV_FEATURES 0
		4535	#define EV_MULTIPLICITY 1
		4536	#define EV_USE_POLL 1
		4537	#define EV_CHILD_ENABLE 1
		4538	#define EV_ASYNC_ENABLE 1
		4539
		4540	The actual value is a bitset, it can be a combination of the following
		4541	values:
		4542
		4543	=over 4
		4544
		4545	=item C<1> - faster/larger code
		4546
		4547	Use larger code to speed up some operations.
		4548
		4549	Currently this is used to override some inlining decisions (enlarging the
		4550	code size by roughly 30% on amd64).
		4551
		4552	When optimising for size, use of compiler flags such as C<-Os> with
		4553	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4554	assertions.
		4555
		4556	=item C<2> - faster/larger data structures
		4557
		4558	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4559	hash table sizes and so on. This will usually further increase code size
		4560	and can additionally have an effect on the size of data structures at
		4561	runtime.
		4562
		4563	=item C<4> - full API configuration
		4564
		4565	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4566	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4567
		4568	=item C<8> - full API
		4569
		4570	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4571	details on which parts of the API are still available without this
		4572	feature, and do not complain if this subset changes over time.
		4573
		4574	=item C<16> - enable all optional watcher types
		4575
		4576	Enables all optional watcher types. If you want to selectively enable
		4577	only some watcher types other than I/O and timers (e.g. prepare,
		4578	embed, async, child...) you can enable them manually by defining
		4579	C<EV_watchertype_ENABLE> to C<1> instead.
		4580
		4581	=item C<32> - enable all backends
		4582
		4583	This enables all backends - without this feature, you need to enable at
		4584	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4585
		4586	=item C<64> - enable OS-specific "helper" APIs
		4587
		4588	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4589	default.
		4590
		4591	=back
		4592
		4593	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4594	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4595	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4596	watchers, timers and monotonic clock support.
		4597
		4598	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4599	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4600	your program might be left out as well - a binary starting a timer and an
		4601	I/O watcher then might come out at only 5Kb.
		4602
		4603	=item EV_AVOID_STDIO
		4604
		4605	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4606	functions (printf, scanf, perror etc.). This will increase the code size
		4607	somewhat, but if your program doesn't otherwise depend on stdio and your
		4608	libc allows it, this avoids linking in the stdio library which is quite
		4609	big.
		4610
		4611	Note that error messages might become less precise when this option is
		4612	enabled.
		4613
		4614	=item EV_NSIG
		4615
		4616	The highest supported signal number, +1 (or, the number of
		4617	signals): Normally, libev tries to deduce the maximum number of signals
		4618	automatically, but sometimes this fails, in which case it can be
		4619	specified. Also, using a lower number than detected (C<32> should be
		4620	good for about any system in existence) can save some memory, as libev
		4621	statically allocates some 12-24 bytes per signal number.
3444		4622
3445	=item EV_PID_HASHSIZE	4623	=item EV_PID_HASHSIZE
3446		4624
3447	C<ev_child> watchers use a small hash table to distribute workload by	4625	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4626	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4627	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4628	might want to increase this value (I<must> be a power of two).
3451		4629
3452	=item EV_INOTIFY_HASHSIZE	4630	=item EV_INOTIFY_HASHSIZE
3453		4631
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4632	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4633	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4634	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4635	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4636	power of two).
3459		4637
3460	=item EV_USE_4HEAP	4638	=item EV_USE_4HEAP
3461		4639
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4640	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4641	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4642	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4643	faster performance with many (thousands) of watchers.
3466		4644
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4645	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4646	will be C<0>.
3469		4647
3470	=item EV_HEAP_CACHE_AT	4648	=item EV_HEAP_CACHE_AT
3471		4649
3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4650	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4651	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4652	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4653	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4654	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4655	noticeably with many (hundreds) of watchers.
3478		4656
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4657	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4658	will be C<0>.
3481		4659
3482	=item EV_VERIFY	4660	=item EV_VERIFY
3483		4661
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4662	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4663	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4664	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4665	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4666	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4667	verification code will be called very frequently, which will slow down
3490	libev considerably.	4668	libev considerably.
3491		4669
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4670	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4671	will be C<0>.
3494		4672
3495	=item EV_COMMON	4673	=item EV_COMMON
3496		4674
3497	By default, all watchers have a C<void *data> member. By redefining	4675	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4676	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4677	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4678	though, and it must be identical each time.
3501		4679
3502	For example, the perl EV module uses something like this:	4680	For example, the perl EV module uses something like this:
3503		4681
…		…
3556	file.	4734	file.
3557		4735
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4736	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	4737	that everybody includes and which overrides some configure choices:
3560		4738
3561	#define EV_MINIMAL 1	4739	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	4740	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	4741	#define EV_PREPARE_ENABLE 1
		4742	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	4743	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	4744	#define EV_CHILD_ENABLE 1
		4745	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	4746	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		4747
3571	#include "ev++.h"	4748	#include "ev++.h"
3572		4749
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4750	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		4751
3575	#include "ev_cpp.h"	4752	#include "ev_cpp.h"
3576	#include "ev.c"	4753	#include "ev.c"
3577		4754
3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4755	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3579		4756
3580	=head2 THREADS AND COROUTINES	4757	=head2 THREADS AND COROUTINES
3581		4758
3582	=head3 THREADS	4759	=head3 THREADS
3583		4760
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	4811	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	4812	watcher callback into the event loop interested in the signal.
3636		4813
3637	=back	4814	=back
3638		4815
		4816	See also L<THREAD LOCKING EXAMPLE>.
		4817
3639	=head3 COROUTINES	4818	=head3 COROUTINES
3640		4819
3641	Libev is very accommodating to coroutines ("cooperative threads"):	4820	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	4821	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4822	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	4823	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	4824	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	4825	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		4826
3648	Care has been taken to ensure that libev does not keep local state inside	4827	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4828	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	4829	they do not call any callbacks.
3651		4830
3652	=head2 COMPILER WARNINGS	4831	=head2 COMPILER WARNINGS
3653		4832
3654	Depending on your compiler and compiler settings, you might get no or a	4833	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	4844	maintainable.
3666		4845
3667	And of course, some compiler warnings are just plain stupid, or simply	4846	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	4847	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	4848	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	4849	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	4850	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	4851	such buggy versions.
3673		4852
3674	While libev is written to generate as few warnings as possible,	4853	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	4854	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	4890	I suggest using suppression lists.
3712		4891
3713		4892
3714	=head1 PORTABILITY NOTES	4893	=head1 PORTABILITY NOTES
3715		4894
		4895	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4896
		4897	GNU/Linux is the only common platform that supports 64 bit file/large file
		4898	interfaces but I<disables> them by default.
		4899
		4900	That means that libev compiled in the default environment doesn't support
		4901	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4902
		4903	Unfortunately, many programs try to work around this GNU/Linux issue
		4904	by enabling the large file API, which makes them incompatible with the
		4905	standard libev compiled for their system.
		4906
		4907	Likewise, libev cannot enable the large file API itself as this would
		4908	suddenly make it incompatible to the default compile time environment,
		4909	i.e. all programs not using special compile switches.
		4910
		4911	=head2 OS/X AND DARWIN BUGS
		4912
		4913	The whole thing is a bug if you ask me - basically any system interface
		4914	you touch is broken, whether it is locales, poll, kqueue or even the
		4915	OpenGL drivers.
		4916
		4917	=head3 C<kqueue> is buggy
		4918
		4919	The kqueue syscall is broken in all known versions - most versions support
		4920	only sockets, many support pipes.
		4921
		4922	Libev tries to work around this by not using C<kqueue> by default on this
		4923	rotten platform, but of course you can still ask for it when creating a
		4924	loop - embedding a socket-only kqueue loop into a select-based one is
		4925	probably going to work well.
		4926
		4927	=head3 C<poll> is buggy
		4928
		4929	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4930	implementation by something calling C<kqueue> internally around the 10.5.6
		4931	release, so now C<kqueue> I<and> C<poll> are broken.
		4932
		4933	Libev tries to work around this by not using C<poll> by default on
		4934	this rotten platform, but of course you can still ask for it when creating
		4935	a loop.
		4936
		4937	=head3 C<select> is buggy
		4938
		4939	All that's left is C<select>, and of course Apple found a way to fuck this
		4940	one up as well: On OS/X, C<select> actively limits the number of file
		4941	descriptors you can pass in to 1024 - your program suddenly crashes when
		4942	you use more.
		4943
		4944	There is an undocumented "workaround" for this - defining
		4945	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4946	work on OS/X.
		4947
		4948	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4949
		4950	=head3 C<errno> reentrancy
		4951
		4952	The default compile environment on Solaris is unfortunately so
		4953	thread-unsafe that you can't even use components/libraries compiled
		4954	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4955	defined by default. A valid, if stupid, implementation choice.
		4956
		4957	If you want to use libev in threaded environments you have to make sure
		4958	it's compiled with C<_REENTRANT> defined.
		4959
		4960	=head3 Event port backend
		4961
		4962	The scalable event interface for Solaris is called "event
		4963	ports". Unfortunately, this mechanism is very buggy in all major
		4964	releases. If you run into high CPU usage, your program freezes or you get
		4965	a large number of spurious wakeups, make sure you have all the relevant
		4966	and latest kernel patches applied. No, I don't know which ones, but there
		4967	are multiple ones to apply, and afterwards, event ports actually work
		4968	great.
		4969
		4970	If you can't get it to work, you can try running the program by setting
		4971	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4972	C<select> backends.
		4973
		4974	=head2 AIX POLL BUG
		4975
		4976	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4977	this by trying to avoid the poll backend altogether (i.e. it's not even
		4978	compiled in), which normally isn't a big problem as C<select> works fine
		4979	with large bitsets on AIX, and AIX is dead anyway.
		4980
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4981	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4982
		4983	=head3 General issues
3717		4984
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4985	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	4986	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	4987	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4988	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	4989	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	4990	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4991	as every compiler comes with a slightly differently broken/incompatible
		4992	environment.
3724		4993
3725	Lifting these limitations would basically require the full	4994	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	4995	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	4996	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	4997	also that glib is the slowest event library known to man).
3729		4998
3730	There is no supported compilation method available on windows except	4999	There is no supported compilation method available on windows except
3731	embedding it into other applications.	5000	embedding it into other applications.
		5001
		5002	Sensible signal handling is officially unsupported by Microsoft - libev
		5003	tries its best, but under most conditions, signals will simply not work.
3732		5004
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	5005	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	5006	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	5007	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	5008	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	5013	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	5014	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	5015	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	5016	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	5017	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	5018	(due to Microsoft monopoly games).
3747		5019
3748	A typical way to use libev under windows is to embed it (see the embedding	5020	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	5021	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	5022	of F<ev.h>:
3751		5023
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	5030	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		5031
3760	#include "evwrap.h"	5032	#include "evwrap.h"
3761	#include "ev.c"	5033	#include "ev.c"
3762		5034
3763	=over 4
3764
3765	=item The winsocket select function	5035	=head3 The winsocket C<select> function
3766		5036
3767	The winsocket C<select> function doesn't follow POSIX in that it	5037	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	5038	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	5039	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	5040	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5049	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		5050
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	5051	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	5052	complexity in the O(n²) range when using win32.
3783		5053
3784	=item Limited number of file descriptors	5054	=head3 Limited number of file descriptors
3785		5055
3786	Windows has numerous arbitrary (and low) limits on things.	5056	Windows has numerous arbitrary (and low) limits on things.
3787		5057
3788	Early versions of winsocket's select only supported waiting for a maximum	5058	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	5059	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	5060	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	5061	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	5062	previous thread in each. Sounds great!).
3793		5063
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5064	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	5065	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	5066	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	5067	other interpreters do their own select emulation on windows).
3798		5068
3799	Another limit is the number of file descriptors in the Microsoft runtime	5069	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5070	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	5071	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5072	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	5073	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	5074	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	5075	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	5076	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	5077	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		5078
3813	=head2 PORTABILITY REQUIREMENTS	5079	=head2 PORTABILITY REQUIREMENTS
3814		5080
3815	In addition to a working ISO-C implementation and of course the	5081	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	5082	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	5089	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	5090	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	5091	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	5092	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	5093	calls them using an C<ev_watcher *> internally.
		5094
		5095	=item pointer accesses must be thread-atomic
		5096
		5097	Accessing a pointer value must be atomic, it must both be readable and
		5098	writable in one piece - this is the case on all current architectures.
3828		5099
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	5100	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		5101
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	5102	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5103	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3855	watchers.	5126	watchers.
3856		5127
3857	=item C<double> must hold a time value in seconds with enough accuracy	5128	=item C<double> must hold a time value in seconds with enough accuracy
3858		5129
3859	The type C<double> is used to represent timestamps. It is required to	5130	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5131	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	5132	good enough for at least into the year 4000 with millisecond accuracy
		5133	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	5134	implementations using IEEE 754, which is basically all existing ones.
		5135
		5136	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5137	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5138	is either obsolete or somebody patched it to use C<long double> or
		5139	something like that, just kidding).
3863		5140
3864	=back	5141	=back
3865		5142
3866	If you know of other additional requirements drop me a note.	5143	If you know of other additional requirements drop me a note.
3867		5144
…		…
3929	=item Processing ev_async_send: O(number_of_async_watchers)	5206	=item Processing ev_async_send: O(number_of_async_watchers)
3930		5207
3931	=item Processing signals: O(max_signal_number)	5208	=item Processing signals: O(max_signal_number)
3932		5209
3933	Sending involves a system call I<iff> there were no other C<ev_async_send>	5210	Sending involves a system call I<iff> there were no other C<ev_async_send>
3934	calls in the current loop iteration. Checking for async and signal events	5211	calls in the current loop iteration and the loop is currently
		5212	blocked. Checking for async and signal events involves iterating over all
3935	involves iterating over all running async watchers or all signal numbers.	5213	running async watchers or all signal numbers.
3936		5214
3937	=back	5215	=back
3938		5216
3939		5217
		5218	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5219
		5220	The major version 4 introduced some incompatible changes to the API.
		5221
		5222	At the moment, the C<ev.h> header file provides compatibility definitions
		5223	for all changes, so most programs should still compile. The compatibility
		5224	layer might be removed in later versions of libev, so better update to the
		5225	new API early than late.
		5226
		5227	=over 4
		5228
		5229	=item C<EV_COMPAT3> backwards compatibility mechanism
		5230
		5231	The backward compatibility mechanism can be controlled by
		5232	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5233	section.
		5234
		5235	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5236
		5237	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5238
		5239	ev_loop_destroy (EV_DEFAULT_UC);
		5240	ev_loop_fork (EV_DEFAULT);
		5241
		5242	=item function/symbol renames
		5243
		5244	A number of functions and symbols have been renamed:
		5245
		5246	ev_loop => ev_run
		5247	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5248	EVLOOP_ONESHOT => EVRUN_ONCE
		5249
		5250	ev_unloop => ev_break
		5251	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5252	EVUNLOOP_ONE => EVBREAK_ONE
		5253	EVUNLOOP_ALL => EVBREAK_ALL
		5254
		5255	EV_TIMEOUT => EV_TIMER
		5256
		5257	ev_loop_count => ev_iteration
		5258	ev_loop_depth => ev_depth
		5259	ev_loop_verify => ev_verify
		5260
		5261	Most functions working on C<struct ev_loop> objects don't have an
		5262	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5263	associated constants have been renamed to not collide with the C<struct
		5264	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5265	as all other watcher types. Note that C<ev_loop_fork> is still called
		5266	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5267	typedef.
		5268
		5269	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5270
		5271	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5272	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5273	and work, but the library code will of course be larger.
		5274
		5275	=back
		5276
		5277
		5278	=head1 GLOSSARY
		5279
		5280	=over 4
		5281
		5282	=item active
		5283
		5284	A watcher is active as long as it has been started and not yet stopped.
		5285	See L<WATCHER STATES> for details.
		5286
		5287	=item application
		5288
		5289	In this document, an application is whatever is using libev.
		5290
		5291	=item backend
		5292
		5293	The part of the code dealing with the operating system interfaces.
		5294
		5295	=item callback
		5296
		5297	The address of a function that is called when some event has been
		5298	detected. Callbacks are being passed the event loop, the watcher that
		5299	received the event, and the actual event bitset.
		5300
		5301	=item callback/watcher invocation
		5302
		5303	The act of calling the callback associated with a watcher.
		5304
		5305	=item event
		5306
		5307	A change of state of some external event, such as data now being available
		5308	for reading on a file descriptor, time having passed or simply not having
		5309	any other events happening anymore.
		5310
		5311	In libev, events are represented as single bits (such as C<EV_READ> or
		5312	C<EV_TIMER>).
		5313
		5314	=item event library
		5315
		5316	A software package implementing an event model and loop.
		5317
		5318	=item event loop
		5319
		5320	An entity that handles and processes external events and converts them
		5321	into callback invocations.
		5322
		5323	=item event model
		5324
		5325	The model used to describe how an event loop handles and processes
		5326	watchers and events.
		5327
		5328	=item pending
		5329
		5330	A watcher is pending as soon as the corresponding event has been
		5331	detected. See L<WATCHER STATES> for details.
		5332
		5333	=item real time
		5334
		5335	The physical time that is observed. It is apparently strictly monotonic :)
		5336
		5337	=item wall-clock time
		5338
		5339	The time and date as shown on clocks. Unlike real time, it can actually
		5340	be wrong and jump forwards and backwards, e.g. when you adjust your
		5341	clock.
		5342
		5343	=item watcher
		5344
		5345	A data structure that describes interest in certain events. Watchers need
		5346	to be started (attached to an event loop) before they can receive events.
		5347
		5348	=back
		5349
3940	=head1 AUTHOR	5350	=head1 AUTHOR
3941		5351
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5352	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5353	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3943		5354

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