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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// break was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	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
68	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
69	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
70		92
71	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
72	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
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	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
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	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
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(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>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	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
99	for example).	122	for example).
100		123
…		…
103	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)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	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
107	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
108	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
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	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
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	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
153	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
154	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>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
159	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
160	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 >>).
161		192
162	=item int ev_version_major ()	193	=item int ev_version_major ()
163		194
164	=item int ev_version_minor ()	195	=item int ev_version_minor ()
165		196
…		…
176	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
177	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
178	not a problem.	209	not a problem.
179		210
180	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
181	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
182		214
183	assert (("libev version mismatch",	215	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
186		218
…		…
197	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
199		231
200	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
201		233
202	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
203	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
204	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
205	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
206	(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
207	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
208		241
209	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
210		243
211	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
212	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
216		249
217	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
218		251
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		253
221	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	283	}
251		284
252	...	285	...
253	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
254		287
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		289
257	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
258	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
259	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	305	}
273		306
274	...	307	...
275	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
276		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
277	=back	323	=back
278		324
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		326
281	An event loop is described by a C<ev_loop *>. The library knows two	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	329	libev 3 had an C<ev_loop> function colliding with the struct name).
		330
		331	The library knows two types of such loops, the I<default> loop, which
		332	supports child process events, and dynamically created event loops which
		333	do not.
284		334
285	=over 4	335	=over 4
286		336
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		338
289	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
290	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
291	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
292	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".
293		349
294	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
295	function.	351	function (or via the C<EV_DEFAULT> macro).
296		352
297	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
298	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
299	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
300		357
301	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,
302	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
303	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
304	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
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	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.
307		382
308	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
309	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>).
310		385
311	The following flags are supported:	386	The following flags are supported:
…		…
326	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
327	around bugs.	402	around bugs.
328		403
329	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
330		405
331	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
332	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.
333	enabling this flag.
334		408
335	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,
336	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
337	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
338	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
…		…
344	flag.	418	flag.
345		419
346	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>
347	environment variable.	421	environment variable.
348		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
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		459
351	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
352	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,
353	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
…		…
377	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
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		488
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
382	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
383	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
384	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	497	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	498
387	cases and requiring a system call per fd change, no fork support and bad	499	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	500	of the more advanced event mechanisms: mere annoyances include silently
		501	dropping file descriptors, requiring a system call per change per file
		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
		505	0.1ms) and so on. The biggest issue is fork races, however - if a program
		506	forks then I<both> parent and child process have to recreate the epoll
		507	set, which can take considerable time (one syscall per file descriptor)
		508	and is of course hard to detect.
		509
		510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		511	but of course I<doesn't>, and epoll just loves to report events for
		512	totally I<different> file descriptors (even already closed ones, so
		513	one cannot even remove them from the set) than registered in the set
		514	(especially on SMP systems). Libev tries to counter these spurious
		515	notifications by employing an additional generation counter and comparing
		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...
389		526
390	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
391	will result in some caching, there is still a system call per such incident	528	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	529	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	531	file descriptors might not work very well if you register events for both
395		532	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		533
400	Best performance from this backend is achieved by not unregistering all	534	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	535	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	536	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	537	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	538	extra overhead. A fork can both result in spurious notifications as well
		539	as in libev having to destroy and recreate the epoll object, which can
		540	take considerable time and thus should be avoided.
		541
		542	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		543	faster than epoll for maybe up to a hundred file descriptors, depending on
		544	the usage. So sad.
405		545
406	While nominally embeddable in other event loops, this feature is broken in	546	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	547	all kernel versions tested so far.
408		548
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	549	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	550	C<EVBACKEND_POLL>.
411		551
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	552	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		553
414	Kqueue deserves special mention, as at the time of this writing, it was	554	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	555	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	556	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	557	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	558	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	559	without API changes to existing programs. For this reason it's not being
		560	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		561	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		562	system like NetBSD.
420		563
421	You still can embed kqueue into a normal poll or select backend and use it	564	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	565	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	566	the target platform). See C<ev_embed> watchers for more info.
424		567
425	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	572	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	573	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		574	cases
431		575
432	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
433		577
434	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	580	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	581	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	582	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	583	also broken on OS X)) and, did I mention it, using it only for sockets.
440		584
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	585	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	586	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	587	C<NOTE_EOF>.
444		588
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		597
454	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,
455	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)).
456		600
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	604	might perform better.
465		605
466	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	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.
470		620
471	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
472	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
473		623
474	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
475		625
476	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
477	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
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		629
480	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).
481		639
482	=back	640	=back
483		641
484	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,
485	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
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
487		645	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		646
516	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.
517		648
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	650	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
521		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
522	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
523		659
524	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	666	for example).
531		667
532	Note that certain global state, such as signal state, will not be freed by	668	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	669	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
535		671
536	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
537	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.
538	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>
539	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
540		680
541	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
542		682
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
553	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.
554		693
555	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
556	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
557	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).
558		700
559	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
560	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		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	...
563	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		715
572	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
573		717
574	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
575	otherwise.	719	otherwise.
576		720
577	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
578		722
579	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
580	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>
581	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
582		726
583	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
584	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
585	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.
586		745
587	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
588		747
589	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
590	use.	749	use.
…		…
599		758
600	=item ev_now_update (loop)	759	=item ev_now_update (loop)
601		760
602	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
605		764
606	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
607	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
608	the current time is a good idea.	767	the current time is a good idea.
609		768
610	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.
611		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
612	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
613		798
614	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
615	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
616	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>.
617		804
618	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
619	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.
620		808
621	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
622	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
623	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
624	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
625	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
626	beauty.	814	beauty.
627		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
628	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
629	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
630	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
631	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.
632		826
633	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
634	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	830	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
638	iteration of the loop.	832	iteration of the loop.
639		833
640	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
641	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
642	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
643	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
644		838
645	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):
646		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- 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.
650	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	852	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
658	- 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.
659	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
661	- 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.
662	- Queue all expired timers.	863	- Queue all expired timers.
663	- Queue all expired periodics.	864	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	866	- Queue all check watchers.
666	- 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).
667	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
668	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
669	- 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
670	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
671	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.
672		877
673	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
674	anymore.	879	anymore.
675		880
676	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
680		885
681	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
682		887
683	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
684	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
685	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
686	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.
687		892
688	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>.
689		894
690	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.
691		897
692	=item ev_ref (loop)	898	=item ev_ref (loop)
693		899
694	=item ev_unref (loop)	900	=item ev_unref (loop)
695		901
696	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
697	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
698	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.
699		905
700	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
701	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>
702	stopping it.	909	before stopping it.
703		910
704	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
705	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
706	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
707	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
708	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
709	(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
710	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).
711		920
712	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>
713	running when nothing else is active.	922	running when nothing else is active.
714		923
715	ev_signal exitsig;	924	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	927	ev_unref (loop);
719		928
720	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
721		930
722	ev_ref (loop);	931	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
743	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.
744		953
745	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
746	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,
747	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
748	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
749	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).
750		962
751	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
752	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		968
757	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
758	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
759	interactive servers (of course not for games), likewise for timeouts. It	971	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	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).
762		978
763	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	983	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	984	they fire on, say, one-second boundaries only.
769		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
770	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
771		1062
772	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
773	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
774	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1067	error and call C<abort ()>.
777		1068
778	This can be used to catch bugs inside libev itself: under normal	1069	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1073	=back
783		1074
784		1075
785	=head1 ANATOMY OF A WATCHER	1076	=head1 ANATOMY OF A WATCHER
786		1077
		1078	In the following description, uppercase C<TYPE> in names stands for the
		1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1080	watchers and C<ev_io_start> for I/O watchers.
		1081
787	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
788	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
789	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:
790		1086
791	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)
792	{	1088	{
793	ev_io_stop (w);	1089	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
795	}	1091	}
796		1092
797	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
		1094
798	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
		1096
799	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
		1100
802	ev_loop (loop, 0);	1101	ev_run (loop, 0);
803		1102
804	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
805	watcher structures (and it is usually a bad idea to do this on the stack,	1104	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1105	stack).
807		1106
		1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1109
808	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
809	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1114	and/or writable).
813		1115
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1117	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1118	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
818		1120
819	To make the watcher actually watch out for events, you have to start it	1121	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1122	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1123	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1124	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1125
824	As long as your watcher is active (has been started but not stopped) you	1126	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1127	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1128	reinitialise it or call its C<ev_TYPE_set> macro.
827		1129
828	Each and every callback receives the event loop pointer as first, the	1130	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1131	registered watcher structure as second, and a bitset of received events as
830	third argument.	1132	third argument.
831		1133
…		…
840	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
841		1143
842	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
843	writable.	1145	writable.
844		1146
845	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
846		1148
847	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
848		1150
849	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
850		1152
…		…
868		1170
869	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
870		1172
871	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
872		1174
873	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
874	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
875	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
876	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
877	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
878	(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
879	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
880		1182
881	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
882		1184
883	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.
884		1186
885	=item C<EV_FORK>	1187	=item C<EV_FORK>
886		1188
887	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
888	C<ev_fork>).	1190	C<ev_fork>).
889		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
		1195
890	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
891		1197
892	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>).
893		1204
894	=item C<EV_ERROR>	1205	=item C<EV_ERROR>
895		1206
896	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
897	happen because the watcher could not be properly started because libev	1208	happen because the watcher could not be properly started because libev
…		…
912		1223
913	=back	1224	=back
914		1225
915	=head2 GENERIC WATCHER FUNCTIONS	1226	=head2 GENERIC WATCHER FUNCTIONS
916		1227
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1228	=over 4
921		1229
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1230	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1231
924	This macro initialises the generic portion of a watcher. The contents	1232	This macro initialises the generic portion of a watcher. The contents
…		…
938		1246
939	ev_io w;	1247	ev_io w;
940	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1250
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1252
945	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
946	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
947	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
948	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
…		…
961		1269
962	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.
963		1271
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1273
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1275
968	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
970		1278
971	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
972	whole section.	1280	whole section.
973		1281
974	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
975		1283
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1285
978	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
979	the watcher was active or not).	1287	the watcher was active or not).
980		1288
981	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1315
1008	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
1009	(modulo threads).	1317	(modulo threads).
1010		1318
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1320
1013	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1014		1322
1015	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
1016	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>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1325	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1326	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1327	from being executed (except for C<ev_idle> watchers).
1020		1328
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1329	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1330	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1331
1029	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
1030	pending.	1333	pending.
1031		1334
		1335	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1336	fine, as long as you do not mind that the priority value you query might
		1337	or might not have been clamped to the valid range.
		1338
1032	The default priority used by watchers when no priority has been set is	1339	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1340	always C<0>, which is supposed to not be too high and not be too low :).
1034		1341
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1342	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1343	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1344
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1345	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1346
1041	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
1042	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
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1051		1357
1052	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
1053	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1054		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
1055	=back	1375	=back
1056		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1057		1379
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1059		1381
1060	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1061	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
1062	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
1063	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".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1386
1067	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)
1068	{	1512	{
1069	ev_io io;	1513	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1514	// are not yet ready to handle it.
1071	void *somedata;	1515	ev_io_stop (EV_A_ w);
1072	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);
1073	};	1521	}
1074		1522
1075	...	1523	static void
1076	struct my_io w;	1524	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1525	{
1084	struct my_io *w = (struct my_io *)w_;	1526	// actual processing
1085	...	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);
1086	}	1532	}
1087		1533
1088	More interesting and less C-conformant ways of casting your callback type	1534	// initialisation
1089	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);
1090		1538
1091	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
1092	embedded watchers:	1540	low-priority connections can not be locked out forever under load. This
1093		1541	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1542	during short periods of high load, while not completely locking out less
1095	{	1543	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1544
1123		1545
1124	=head1 WATCHER TYPES	1546	=head1 WATCHER TYPES
1125		1547
1126	This section describes each watcher in detail, but will not repeat	1548	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1575	required if you know what you are doing).
1154		1576
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1164	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
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1167		1584
1168	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
1169	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
1170	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
1171	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
1172	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
1173	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
1174	indefinitely.	1591	indefinitely.
1175		1592
1176	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1177		1594
…		…
1205		1622
1206	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		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
1210	=head3 The special problem of fork	1660	=head3 The special problem of fork
1211		1661
1212	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
1213	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
1214	it in the child.	1664	it in the child if you want to continue to use it in the child.
1215		1665
1216	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
1217	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
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1669
1221	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1222		1671
1223	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>:
1224	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
…		…
1227		1676
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1231		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.
1232		1719
1233	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1234		1721
1235	=over 4	1722	=over 4
1236		1723
…		…
1268	...	1755	...
1269	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1757	ev_io stdin_readable;
1271	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);
1272	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1274		1761
1275		1762
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1764
1278	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
…		…
1283	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
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1286		1773
1287	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
1288	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
1289	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).
1290		1781
1291	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1292		1783
1293	Many real-world problems invole some kind of time-out, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1786	you want to raise some error after a while.
1296		1787
1297	Here are some ways on how to handle this problem, from simple and	1788	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1789	inefficient to smart and efficient.
1299		1790
1300	In the following examples a 60 second activity timeout is assumed - a	1791	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1792	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1793	data or other life sign was received).
1303		1794
1304	=over 4	1795	=over 4
1305		1796
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1797	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1798
1308	This is the most obvious, but not the most simple way: In the beginning,	1799	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1800	start the watcher:
1310		1801
1311	ev_timer_init (timer, callback, 60., 0.);	1802	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1803	ev_timer_start (loop, timer);
1313		1804
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1805	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1806	and start it again:
1316		1807
1317	ev_timer_stop (loop, timer);	1808	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1809	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1810	ev_timer_start (loop, timer);
1320		1811
1321	This is relatively simple to implement, but means that each time there	1812	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1813	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1814	data structure and then add it again. Libev tries to be fast, but it's
		1815	still not a constant-time operation.
1324		1816
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1817	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1818
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1819	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1820	C<ev_timer_start>.
1329		1821
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1822	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1823	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1824	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1825	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1826	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1827
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1828	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1829	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1830	member and C<ev_timer_again>.
1338		1831
1339	At start:	1832	At start:
1340		1833
1341	ev_timer_init (timer, callback, 0., 60.);	1834	ev_init (timer, callback);
		1835	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1836	ev_timer_again (loop, timer);
1343		1837
1344	Each time you receive some data:	1838	Each time there is some activity:
1345		1839
1346	ev_timer_again (loop, timer);	1840	ev_timer_again (loop, timer);
1347		1841
1348	It is even possible to change the time-out on the fly:	1842	It is even possible to change the time-out on the fly, regardless of
		1843	whether the watcher is active or not:
1349		1844
1350	timer->repeat = 30.;	1845	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1846	ev_timer_again (loop, timer);
1352		1847
1353	This is slightly more efficient then stopping/starting the timer each time	1848	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1849	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1850	remove and re-insert the timer from/into its internal data structure.
		1851
		1852	It is, however, even simpler than the "obvious" way to do it.
1356		1853
1357	=item 3. Let the timer time out, but then re-arm it as required.	1854	=item 3. Let the timer time out, but then re-arm it as required.
1358		1855
1359	This method is more tricky, but usually most efficient: Most timeouts are	1856	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1857	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1858	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1859	associated activity resets.
1363		1860
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1863	within the callback:
1367		1864
		1865	ev_tstamp timeout = 60.;
1368	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1369		1868
1370	static void	1869	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1372	{	1871	{
1373	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1374	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1375		1874
1376	// if last_activity is older than now - timeout, we did time out	1875	// if negative, it means we the timeout already occured
1377	if (timeout < now)	1876	if (after < 0.)
1378	{	1877	{
1379	// timeout occured, take action	1878	// timeout occurred, take action
1380	}	1879	}
1381	else	1880	else
1382	{	1881	{
1383	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1384	// to fire in last_activity + 60.	1883	// activity. simply restart the timer to time out
1385	w->again = timeout - now;	1884	// after "after" seconds, which is the earliest time
		1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1386	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1387	}	1888	}
1388	}	1889	}
1389		1890
1390	To summarise the callback: first calculate the real time-out (defined as	1891	To summarise the callback: first calculate in how many seconds the
1391	"60 seconds after the last activity"), then check if that time has been	1892	timeout will occur (by calculating the absolute time when it would occur,
1392	reached, which means there was a real timeout. Otherwise the callback was	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1894	(EV_A)> from that).
1394	fire at that future time.
1395		1895
1396	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1397	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
1398		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
		1905
1399	This scheme causes more callback invocations (about one every 60 seconds),	1906	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1907	minus half the average time between activity), but virtually no calls to
		1908	libev to change the timeout.
1401		1909
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1910	To start the machinery, simply initialise the watcher and set
1403	then call the callback:	1911	C<last_activity> to the current time (meaning there was some activity just
		1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1404		1914
		1915	last_activity = ev_now (EV_A);
1405	ev_timer_init (timer, callback);	1916	ev_init (&timer, callback);
		1917	callback (EV_A_ &timer, 0);
		1918
		1919	When there is some activity, simply store the current time in
		1920	C<last_activity>, no libev calls at all:
		1921
		1922	if (activity detected)
1406	last_activity = ev_now (loop);	1923	last_activity = ev_now (EV_A);
1407	callback (loop, timer, EV_TIMEOUT);
1408		1924
1409	And when there is some activity, simply remember the time in	1925	When your timeout value changes, then the timeout can be changed by simply
1410	C<last_activity>:	1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
1411		1928
1412	last_actiivty = ev_now (loop);	1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1413		1932
1414	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1416		1935
		1936	=item 4. Wee, just use a double-linked list for your timeouts.
		1937
		1938	If there is not one request, but many thousands (millions...), all
		1939	employing some kind of timeout with the same timeout value, then one can
		1940	do even better:
		1941
		1942	When starting the timeout, calculate the timeout value and put the timeout
		1943	at the I<end> of the list.
		1944
		1945	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1946	the list is expected to fire (for example, using the technique #3).
		1947
		1948	When there is some activity, remove the timer from the list, recalculate
		1949	the timeout, append it to the end of the list again, and make sure to
		1950	update the C<ev_timer> if it was taken from the beginning of the list.
		1951
		1952	This way, one can manage an unlimited number of timeouts in O(1) time for
		1953	starting, stopping and updating the timers, at the expense of a major
		1954	complication, and having to use a constant timeout. The constant timeout
		1955	ensures that the list stays sorted.
		1956
1417	=back	1957	=back
1418		1958
		1959	So which method the best?
		1960
		1961	Method #2 is a simple no-brain-required solution that is adequate in most
		1962	situations. Method #3 requires a bit more thinking, but handles many cases
		1963	better, and isn't very complicated either. In most case, choosing either
		1964	one is fine, with #3 being better in typical situations.
		1965
		1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1967	rather complicated, but extremely efficient, something that really pays
		1968	off after the first million or so of active timers, i.e. it's usually
		1969	overkill :)
		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1419	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1420		2009
1421	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1422	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	2014	lots of events in one iteration.
1426		2015
1427	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		2023
1435	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	2026	()>.
1438		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
		2060
		2061	=head3 The special problems of suspended animation
		2062
		2063	When you leave the server world it is quite customary to hit machines that
		2064	can suspend/hibernate - what happens to the clocks during such a suspend?
		2065
		2066	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2067	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2068	to run until the system is suspended, but they will not advance while the
		2069	system is suspended. That means, on resume, it will be as if the program
		2070	was frozen for a few seconds, but the suspend time will not be counted
		2071	towards C<ev_timer> when a monotonic clock source is used. The real time
		2072	clock advanced as expected, but if it is used as sole clocksource, then a
		2073	long suspend would be detected as a time jump by libev, and timers would
		2074	be adjusted accordingly.
		2075
		2076	I would not be surprised to see different behaviour in different between
		2077	operating systems, OS versions or even different hardware.
		2078
		2079	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2080	time jump in the monotonic clocks and the realtime clock. If the program
		2081	is suspended for a very long time, and monotonic clock sources are in use,
		2082	then you can expect C<ev_timer>s to expire as the full suspension time
		2083	will be counted towards the timers. When no monotonic clock source is in
		2084	use, then libev will again assume a timejump and adjust accordingly.
		2085
		2086	It might be beneficial for this latter case to call C<ev_suspend>
		2087	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2088	deterministic behaviour in this case (you can do nothing against
		2089	C<SIGSTOP>).
		2090
1439	=head3 Watcher-Specific Functions and Data Members	2091	=head3 Watcher-Specific Functions and Data Members
1440		2092
1441	=over 4	2093	=over 4
1442		2094
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2095	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1456	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1457	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1458		2110
1459	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1460		2112
1461	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out, and restarts it again if it is
1462	repeating. The exact semantics are:	2114	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2115	timeout to the C<repeat> value and calling C<ev_timer_start>.
1463		2116
		2117	The exact semantics are as in the following rules, all of which will be
		2118	applied to the watcher:
		2119
		2120	=over 4
		2121
1464	If the timer is pending, its pending status is cleared.	2122	=item If the timer is pending, the pending status is always cleared.
1465		2123
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2124	=item If the timer is started but non-repeating, stop it (as if it timed
		2125	out, without invoking it).
1467		2126
1468	If the timer is repeating, either start it if necessary (with the	2127	=item If the timer is repeating, make the C<repeat> value the new timeout
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2128	and start the timer, if necessary.
1470		2129
		2130	=back
		2131
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2132	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	2133	usage example.
		2134
		2135	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2136
		2137	Returns the remaining time until a timer fires. If the timer is active,
		2138	then this time is relative to the current event loop time, otherwise it's
		2139	the timeout value currently configured.
		2140
		2141	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2142	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2143	will return C<4>. When the timer expires and is restarted, it will return
		2144	roughly C<7> (likely slightly less as callback invocation takes some time,
		2145	too), and so on.
1473		2146
1474	=item ev_tstamp repeat [read-write]	2147	=item ev_tstamp repeat [read-write]
1475		2148
1476	The current C<repeat> value. Will be used each time the watcher times out	2149	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2150	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2176	}
1504		2177
1505	ev_timer mytimer;	2178	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2179	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2180	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2181	ev_run (loop, 0);
1509		2182
1510	// and in some piece of code that gets executed on any "activity":	2183	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2184	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2185	ev_timer_again (&mytimer);
1513		2186
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2188	=head2 C<ev_periodic> - to cron or not to cron?
1516		2189
1517	Periodic watchers are also timers of a kind, but they are very versatile	2190	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2191	(and unfortunately a bit complex).
1519		2192
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2193	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2194	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2195	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2196	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2197	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2198	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2199
		2200	You can tell a periodic watcher to trigger after some specific point
		2201	in time: for example, if you tell a periodic watcher to trigger "in 10
		2202	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2203	not a delay) and then reset your system clock to January of the previous
		2204	year, then it will take a year or more to trigger the event (unlike an
		2205	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2206	it, as it uses a relative timeout).
		2207
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2208	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2209	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2210	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2211	those cannot react to time jumps.
1532		2212
1533	As with timers, the callback is guaranteed to be invoked only when the	2213	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2214	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2215	timers become ready during the same loop iteration then the ones with
		2216	earlier time-out values are invoked before ones with later time-out values
		2217	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2218
1537	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1538		2220
1539	=over 4	2221	=over 4
1540		2222
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2223	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2224
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2225	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2226
1545	Lots of arguments, lets sort it out... There are basically three modes of	2227	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2228	operation, and we will explain them from simplest to most complex:
1547		2229
1548	=over 4	2230	=over 4
1549		2231
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2232	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2233
1552	In this configuration the watcher triggers an event after the wall clock	2234	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2235	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2236	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2237	will be stopped and invoked when the system clock reaches or surpasses
		2238	this point in time.
1556		2239
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2240	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2241
1559	In this mode the watcher will always be scheduled to time out at the next	2242	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2243	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2244	negative) and then repeat, regardless of any time jumps. The C<offset>
		2245	argument is merely an offset into the C<interval> periods.
1562		2246
1563	This can be used to create timers that do not drift with respect to the	2247	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2248	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2249	hour, on the hour (with respect to UTC):
1566		2250
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2251	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2252
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2253	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2254	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2255	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2256	by 3600.
1573		2257
1574	Another way to think about it (for the mathematically inclined) is that	2258	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2259	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2260	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2261
1578	For numerical stability it is preferable that the C<at> value is near	2262	The C<interval> I<MUST> be positive, and for numerical stability, the
1579	C<ev_now ()> (the current time), but there is no range requirement for	2263	interval value should be higher than C<1/8192> (which is around 100
1580	this value, and in fact is often specified as zero.	2264	microseconds) and C<offset> should be higher than C<0> and should have
		2265	at most a similar magnitude as the current time (say, within a factor of
		2266	ten). Typical values for offset are, in fact, C<0> or something between
		2267	C<0> and C<interval>, which is also the recommended range.
1581		2268
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2269	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2270	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2271	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2272	millisecond (if the OS supports it and the machine is fast enough).
1586		2273
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2274	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2275
1589	In this mode the values for C<interval> and C<at> are both being	2276	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2277	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2278	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2279	current time as second argument.
1593		2280
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2281	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2282	or make ANY other event loop modifications whatsoever, unless explicitly
		2283	allowed by documentation here>.
1596		2284
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2285	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2286	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2287	only event loop modification you are allowed to do).
1600		2288
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2318	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2319	program when the crontabs have changed).
1632		2320
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2321	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2322
1635	When active, returns the absolute time that the watcher is supposed to	2323	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2324	to trigger next. This is not the same as the C<offset> argument to
		2325	C<ev_periodic_set>, but indeed works even in interval and manual
		2326	rescheduling modes.
1637		2327
1638	=item ev_tstamp offset [read-write]	2328	=item ev_tstamp offset [read-write]
1639		2329
1640	When repeating, this contains the offset value, otherwise this is the	2330	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2331	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2332	although libev might modify this value for better numerical stability).
1642		2333
1643	Can be modified any time, but changes only take effect when the periodic	2334	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2335	timer fires or C<ev_periodic_again> is being called.
1645		2336
1646	=item ev_tstamp interval [read-write]	2337	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2353	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2354	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2355	potentially a lot of jitter, but good long-term stability.
1665		2356
1666	static void	2357	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2358	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2359	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2360	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2361	}
1671		2362
1672	ev_periodic hourly_tick;	2363	ev_periodic hourly_tick;
…		…
1695		2386
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2387	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2388
1698	Signal watchers will trigger an event when the process receives a specific	2389	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2390	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2391	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2392	normal event processing, like any other event.
1702		2393
1703	If you want signals asynchronously, just use C<sigaction> as you would	2394	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2395	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2396	the signal. You can even use C<ev_async> from a signal handler to
		2397	synchronously wake up an event loop.
1706		2398
1707	You can configure as many watchers as you like per signal. Only when the	2399	You can configure as many watchers as you like for the same signal, but
		2400	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2401	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2402	C<SIGINT> in both the default loop and another loop at the same time. At
		2403	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2404
1708	first watcher gets started will libev actually register a signal handler	2405	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2406	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2407	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2408
1714	If possible and supported, libev will install its handlers with	2409	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2410	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2411	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2412	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2413	and unblock them in an C<ev_prepare> watcher.
		2414
		2415	=head3 The special problem of inheritance over fork/execve/pthread_create
		2416
		2417	Both the signal mask (C<sigprocmask>) and the signal disposition
		2418	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2419	stopping it again), that is, libev might or might not block the signal,
		2420	and might or might not set or restore the installed signal handler (but
		2421	see C<EVFLAG_NOSIGMASK>).
		2422
		2423	While this does not matter for the signal disposition (libev never
		2424	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2425	C<execve>), this matters for the signal mask: many programs do not expect
		2426	certain signals to be blocked.
		2427
		2428	This means that before calling C<exec> (from the child) you should reset
		2429	the signal mask to whatever "default" you expect (all clear is a good
		2430	choice usually).
		2431
		2432	The simplest way to ensure that the signal mask is reset in the child is
		2433	to install a fork handler with C<pthread_atfork> that resets it. That will
		2434	catch fork calls done by libraries (such as the libc) as well.
		2435
		2436	In current versions of libev, the signal will not be blocked indefinitely
		2437	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2438	the window of opportunity for problems, it will not go away, as libev
		2439	I<has> to modify the signal mask, at least temporarily.
		2440
		2441	So I can't stress this enough: I<If you do not reset your signal mask when
		2442	you expect it to be empty, you have a race condition in your code>. This
		2443	is not a libev-specific thing, this is true for most event libraries.
		2444
		2445	=head3 The special problem of threads signal handling
		2446
		2447	POSIX threads has problematic signal handling semantics, specifically,
		2448	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2449	threads in a process block signals, which is hard to achieve.
		2450
		2451	When you want to use sigwait (or mix libev signal handling with your own
		2452	for the same signals), you can tackle this problem by globally blocking
		2453	all signals before creating any threads (or creating them with a fully set
		2454	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2455	loops. Then designate one thread as "signal receiver thread" which handles
		2456	these signals. You can pass on any signals that libev might be interested
		2457	in by calling C<ev_feed_signal>.
1719		2458
1720	=head3 Watcher-Specific Functions and Data Members	2459	=head3 Watcher-Specific Functions and Data Members
1721		2460
1722	=over 4	2461	=over 4
1723		2462
…		…
1739	Example: Try to exit cleanly on SIGINT.	2478	Example: Try to exit cleanly on SIGINT.
1740		2479
1741	static void	2480	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2481	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2482	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2483	ev_break (loop, EVBREAK_ALL);
1745	}	2484	}
1746		2485
1747	ev_signal signal_watcher;	2486	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2487	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2488	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2494	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2495	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2496	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2497	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2498	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2499	but forking and registering a watcher a few event loop iterations later or
1761	not.	2500	in the next callback invocation is not.
1762		2501
1763	Only the default event loop is capable of handling signals, and therefore	2502	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2503	you can only register child watchers in the default event loop.
1765		2504
		2505	Due to some design glitches inside libev, child watchers will always be
		2506	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2507	libev)
		2508
1766	=head3 Process Interaction	2509	=head3 Process Interaction
1767		2510
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2511	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2512	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2513	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2515	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2516	children, even ones not watched.
1774		2517
1775	=head3 Overriding the Built-In Processing	2518	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2528	=head3 Stopping the Child Watcher
1786		2529
1787	Currently, the child watcher never gets stopped, even when the	2530	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2531	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2532	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2533	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2534	problem).
1791		2535
1792	=head3 Watcher-Specific Functions and Data Members	2536	=head3 Watcher-Specific Functions and Data Members
1793		2537
1794	=over 4	2538	=over 4
1795		2539
…		…
1852		2596
1853		2597
1854	=head2 C<ev_stat> - did the file attributes just change?	2598	=head2 C<ev_stat> - did the file attributes just change?
1855		2599
1856	This watches a file system path for attribute changes. That is, it calls	2600	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2601	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2602	and sees if it changed compared to the last time, invoking the callback if
		2603	it did.
1859		2604
1860	The path does not need to exist: changing from "path exists" to "path does	2605	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2606	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2607	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2608	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2609	least one) and all the other fields of the stat buffer having unspecified
		2610	contents.
1865		2611
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2612	The path I<must not> end in a slash or contain special components such as
		2613	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2614	your working directory changes, then the behaviour is undefined.
1868		2615
1869	Since there is no standard kernel interface to do this, the portable	2616	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2617	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2618	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2619	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2620	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2621	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2622	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2623	currently around C<0.1>, but that's usually overkill.
1877		2624
1878	This watcher type is not meant for massive numbers of stat watchers,	2625	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2626	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2627	resource-intensive.
1881		2628
1882	At the time of this writing, the only OS-specific interface implemented	2629	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2630	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2631	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2632	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2633
1887	=head3 ABI Issues (Largefile Support)	2634	=head3 ABI Issues (Largefile Support)
1888		2635
1889	Libev by default (unless the user overrides this) uses the default	2636	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2637	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2638	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2639	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2640	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2641	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2642	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2643	most noticeably displayed with ev_stat and large file support.
1897		2644
1898	The solution for this is to lobby your distribution maker to make large	2645	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2646	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2647	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2648	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2649	default compilation environment.
1903		2650
1904	=head3 Inotify and Kqueue	2651	=head3 Inotify and Kqueue
1905		2652
1906	When C<inotify (7)> support has been compiled into libev (generally	2653	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2654	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2655	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2656	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2657
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2658	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2659	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2660	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2661	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2662	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2663	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2664	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2665	xfs are fully working) libev usually gets away without polling.
1917		2666
1918	There is no support for kqueue, as apparently it cannot be used to	2667	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2668	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2669	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2670	etc. is difficult.
1922		2671
		2672	=head3 C<stat ()> is a synchronous operation
		2673
		2674	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2675	the process. The exception are C<ev_stat> watchers - those call C<stat
		2676	()>, which is a synchronous operation.
		2677
		2678	For local paths, this usually doesn't matter: unless the system is very
		2679	busy or the intervals between stat's are large, a stat call will be fast,
		2680	as the path data is usually in memory already (except when starting the
		2681	watcher).
		2682
		2683	For networked file systems, calling C<stat ()> can block an indefinite
		2684	time due to network issues, and even under good conditions, a stat call
		2685	often takes multiple milliseconds.
		2686
		2687	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2688	paths, although this is fully supported by libev.
		2689
1923	=head3 The special problem of stat time resolution	2690	=head3 The special problem of stat time resolution
1924		2691
1925	The C<stat ()> system call only supports full-second resolution portably, and	2692	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2693	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2694	still only support whole seconds.
1928		2695
1929	That means that, if the time is the only thing that changes, you can	2696	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2697	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2698	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2699	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2842
2076	=head3 Watcher-Specific Functions and Data Members	2843	=head3 Watcher-Specific Functions and Data Members
2077		2844
2078	=over 4	2845	=over 4
2079		2846
2080	=item ev_idle_init (ev_signal *, callback)	2847	=item ev_idle_init (ev_idle *, callback)
2081		2848
2082	Initialises and configures the idle watcher - it has no parameters of any	2849	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2850	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2851	believe me.
2085		2852
…		…
2098	// no longer anything immediate to do.	2865	// no longer anything immediate to do.
2099	}	2866	}
2100		2867
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2868	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2869	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2870	ev_idle_start (loop, idle_watcher);
2104		2871
2105		2872
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2873	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2874
2108	Prepare and check watchers are usually (but not always) used in pairs:	2875	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2876	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2877	afterwards.
2111		2878
2112	You I<must not> call C<ev_loop> or similar functions that enter	2879	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2880	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2881	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2882	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2883	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2884	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2968	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2969	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2970	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2971
2205	/* the callback is illegal, but won't be called as we stop during check */	2972	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2973	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2974	ev_timer_start (loop, &tw);
2208		2975
2209	// create one ev_io per pollfd	2976	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2977	for (int i = 0; i < nfd; ++i)
2211	{	2978	{
…		…
2285		3052
2286	if (timeout >= 0)	3053	if (timeout >= 0)
2287	// create/start timer	3054	// create/start timer
2288		3055
2289	// poll	3056	// poll
2290	ev_loop (EV_A_ 0);	3057	ev_run (EV_A_ 0);
2291		3058
2292	// stop timer again	3059	// stop timer again
2293	if (timeout >= 0)	3060	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	3061	ev_timer_stop (EV_A_ &to);
2295		3062
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	3091	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	3092	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	3093	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	3094	the rest in a second one, and embed the second one in the first.
2328		3095
2329	As long as the watcher is active, the callback will be invoked every time	3096	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	3097	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3098	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	3099	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	3100	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	3101	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		3102
2337	As long as the watcher is started it will automatically handle events. The	3103	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	3104	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		3105
2342	Also, there have not currently been made special provisions for forking:	3106	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3107	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	3108	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3109	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3110
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3111	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3112	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3113	portable one.
2351		3114
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	3140	if you do not want that, you need to temporarily stop the embed watcher).
2378		3141
2379	=item ev_embed_sweep (loop, ev_embed *)	3142	=item ev_embed_sweep (loop, ev_embed *)
2380		3143
2381	Make a single, non-blocking sweep over the embedded loop. This works	3144	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3145	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3146	appropriate way for embedded loops.
2384		3147
2385	=item struct ev_loop *other [read-only]	3148	=item struct ev_loop *other [read-only]
2386		3149
2387	The embedded event loop.	3150	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3208	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3209	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3210	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3211	handlers will be invoked, too, of course.
2449		3212
		3213	=head3 The special problem of life after fork - how is it possible?
		3214
		3215	Most uses of C<fork()> consist of forking, then some simple calls to set
		3216	up/change the process environment, followed by a call to C<exec()>. This
		3217	sequence should be handled by libev without any problems.
		3218
		3219	This changes when the application actually wants to do event handling
		3220	in the child, or both parent in child, in effect "continuing" after the
		3221	fork.
		3222
		3223	The default mode of operation (for libev, with application help to detect
		3224	forks) is to duplicate all the state in the child, as would be expected
		3225	when I<either> the parent I<or> the child process continues.
		3226
		3227	When both processes want to continue using libev, then this is usually the
		3228	wrong result. In that case, usually one process (typically the parent) is
		3229	supposed to continue with all watchers in place as before, while the other
		3230	process typically wants to start fresh, i.e. without any active watchers.
		3231
		3232	The cleanest and most efficient way to achieve that with libev is to
		3233	simply create a new event loop, which of course will be "empty", and
		3234	use that for new watchers. This has the advantage of not touching more
		3235	memory than necessary, and thus avoiding the copy-on-write, and the
		3236	disadvantage of having to use multiple event loops (which do not support
		3237	signal watchers).
		3238
		3239	When this is not possible, or you want to use the default loop for
		3240	other reasons, then in the process that wants to start "fresh", call
		3241	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3242	Destroying the default loop will "orphan" (not stop) all registered
		3243	watchers, so you have to be careful not to execute code that modifies
		3244	those watchers. Note also that in that case, you have to re-register any
		3245	signal watchers.
		3246
2450	=head3 Watcher-Specific Functions and Data Members	3247	=head3 Watcher-Specific Functions and Data Members
2451		3248
2452	=over 4	3249	=over 4
2453		3250
2454	=item ev_fork_init (ev_signal *, callback)	3251	=item ev_fork_init (ev_fork *, callback)
2455		3252
2456	Initialises and configures the fork watcher - it has no parameters of any	3253	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3254	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3255	really.
2459		3256
2460	=back	3257	=back
2461		3258
2462		3259
		3260	=head2 C<ev_cleanup> - even the best things end
		3261
		3262	Cleanup watchers are called just before the event loop is being destroyed
		3263	by a call to C<ev_loop_destroy>.
		3264
		3265	While there is no guarantee that the event loop gets destroyed, cleanup
		3266	watchers provide a convenient method to install cleanup hooks for your
		3267	program, worker threads and so on - you just to make sure to destroy the
		3268	loop when you want them to be invoked.
		3269
		3270	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3271	all other watchers, they do not keep a reference to the event loop (which
		3272	makes a lot of sense if you think about it). Like all other watchers, you
		3273	can call libev functions in the callback, except C<ev_cleanup_start>.
		3274
		3275	=head3 Watcher-Specific Functions and Data Members
		3276
		3277	=over 4
		3278
		3279	=item ev_cleanup_init (ev_cleanup *, callback)
		3280
		3281	Initialises and configures the cleanup watcher - it has no parameters of
		3282	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3283	pointless, I assure you.
		3284
		3285	=back
		3286
		3287	Example: Register an atexit handler to destroy the default loop, so any
		3288	cleanup functions are called.
		3289
		3290	static void
		3291	program_exits (void)
		3292	{
		3293	ev_loop_destroy (EV_DEFAULT_UC);
		3294	}
		3295
		3296	...
		3297	atexit (program_exits);
		3298
		3299
2463	=head2 C<ev_async> - how to wake up another event loop	3300	=head2 C<ev_async> - how to wake up an event loop
2464		3301
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3302	In general, you cannot use an C<ev_loop> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3303	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3304	loops - those are of course safe to use in different threads).
2468		3305
2469	Sometimes, however, you need to wake up another event loop you do not	3306	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3307	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3308	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3309	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3310
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3311	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3312	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3313	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3314	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2479		3315	of "global async watchers" by using a watcher on an otherwise unused
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3316	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2481	just the default loop.	3317	even without knowing which loop owns the signal.
2482		3318
2483	=head3 Queueing	3319	=head3 Queueing
2484		3320
2485	C<ev_async> does not support queueing of data in any way. The reason	3321	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3322	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3323	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3324	need elaborate support such as pthreads or unportable memory access
		3325	semantics.
2489		3326
2490	That means that if you want to queue data, you have to provide your own	3327	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3328	queue. But at least I can tell you how to implement locking around your
2492	queue:	3329	queue:
2493		3330
…		…
2571	=over 4	3408	=over 4
2572		3409
2573	=item ev_async_init (ev_async *, callback)	3410	=item ev_async_init (ev_async *, callback)
2574		3411
2575	Initialises and configures the async watcher - it has no parameters of any	3412	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3413	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3414	trust me.
2578		3415
2579	=item ev_async_send (loop, ev_async *)	3416	=item ev_async_send (loop, ev_async *)
2580		3417
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3418	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3419	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3420	returns.
		3421
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3422	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3423	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2585	section below on what exactly this means).	3424	embedding section below on what exactly this means).
2586		3425
2587	This call incurs the overhead of a system call only once per loop iteration,	3426	Note that, as with other watchers in libev, multiple events might get
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3427	compressed into a single callback invocation (another way to look at
2589	calls to C<ev_async_send>.	3428	this is that C<ev_async> watchers are level-triggered: they are set on
		3429	C<ev_async_send>, reset when the event loop detects that).
		3430
		3431	This call incurs the overhead of at most one extra system call per event
		3432	loop iteration, if the event loop is blocked, and no syscall at all if
		3433	the event loop (or your program) is processing events. That means that
		3434	repeated calls are basically free (there is no need to avoid calls for
		3435	performance reasons) and that the overhead becomes smaller (typically
		3436	zero) under load.
2590		3437
2591	=item bool = ev_async_pending (ev_async *)	3438	=item bool = ev_async_pending (ev_async *)
2592		3439
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3440	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3441	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3444	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3445	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3446	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3447	quickly check whether invoking the loop might be a good idea.
2601		3448
2602	Not that this does I<not> check whether the watcher itself is pending, only	3449	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3450	only whether it has been requested to make this watcher pending: there
		3451	is a time window between the event loop checking and resetting the async
		3452	notification, and the callback being invoked.
2604		3453
2605	=back	3454	=back
2606		3455
2607		3456
2608	=head1 OTHER FUNCTIONS	3457	=head1 OTHER FUNCTIONS
…		…
2625		3474
2626	If C<timeout> is less than 0, then no timeout watcher will be	3475	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3476	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3477	repeat = 0) will be started. C<0> is a valid timeout.
2629		3478
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3479	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3480	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3481	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3482	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3483	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3484	events precedence.
2636		3485
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3486	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3487
2639	static void stdin_ready (int revents, void *arg)	3488	static void stdin_ready (int revents, void *arg)
2640	{	3489	{
2641	if (revents & EV_READ)	3490	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3491	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3492	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3493	/* doh, nothing entered */;
2645	}	3494	}
2646		3495
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3496	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3497
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3498	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3499
2657	Feed an event on the given fd, as if a file descriptor backend detected	3500	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3501	the given events.
2659		3502
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3503	=item ev_feed_signal_event (loop, int signum)
2661		3504
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3505	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3506	which is async-safe.
2664		3507
2665	=back	3508	=back
		3509
		3510
		3511	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3512
		3513	This section explains some common idioms that are not immediately
		3514	obvious. Note that examples are sprinkled over the whole manual, and this
		3515	section only contains stuff that wouldn't fit anywhere else.
		3516
		3517	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3518
		3519	Each watcher has, by default, a C<void *data> member that you can read
		3520	or modify at any time: libev will completely ignore it. This can be used
		3521	to associate arbitrary data with your watcher. If you need more data and
		3522	don't want to allocate memory separately and store a pointer to it in that
		3523	data member, you can also "subclass" the watcher type and provide your own
		3524	data:
		3525
		3526	struct my_io
		3527	{
		3528	ev_io io;
		3529	int otherfd;
		3530	void *somedata;
		3531	struct whatever *mostinteresting;
		3532	};
		3533
		3534	...
		3535	struct my_io w;
		3536	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3537
		3538	And since your callback will be called with a pointer to the watcher, you
		3539	can cast it back to your own type:
		3540
		3541	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3542	{
		3543	struct my_io *w = (struct my_io *)w_;
		3544	...
		3545	}
		3546
		3547	More interesting and less C-conformant ways of casting your callback
		3548	function type instead have been omitted.
		3549
		3550	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3551
		3552	Another common scenario is to use some data structure with multiple
		3553	embedded watchers, in effect creating your own watcher that combines
		3554	multiple libev event sources into one "super-watcher":
		3555
		3556	struct my_biggy
		3557	{
		3558	int some_data;
		3559	ev_timer t1;
		3560	ev_timer t2;
		3561	}
		3562
		3563	In this case getting the pointer to C<my_biggy> is a bit more
		3564	complicated: Either you store the address of your C<my_biggy> struct in
		3565	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3566	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3567	real programmers):
		3568
		3569	#include <stddef.h>
		3570
		3571	static void
		3572	t1_cb (EV_P_ ev_timer *w, int revents)
		3573	{
		3574	struct my_biggy big = (struct my_biggy *)
		3575	(((char *)w) - offsetof (struct my_biggy, t1));
		3576	}
		3577
		3578	static void
		3579	t2_cb (EV_P_ ev_timer *w, int revents)
		3580	{
		3581	struct my_biggy big = (struct my_biggy *)
		3582	(((char *)w) - offsetof (struct my_biggy, t2));
		3583	}
		3584
		3585	=head2 AVOIDING FINISHING BEFORE RETURNING
		3586
		3587	Often you have structures like this in event-based programs:
		3588
		3589	callback ()
		3590	{
		3591	free (request);
		3592	}
		3593
		3594	request = start_new_request (..., callback);
		3595
		3596	The intent is to start some "lengthy" operation. The C<request> could be
		3597	used to cancel the operation, or do other things with it.
		3598
		3599	It's not uncommon to have code paths in C<start_new_request> that
		3600	immediately invoke the callback, for example, to report errors. Or you add
		3601	some caching layer that finds that it can skip the lengthy aspects of the
		3602	operation and simply invoke the callback with the result.
		3603
		3604	The problem here is that this will happen I<before> C<start_new_request>
		3605	has returned, so C<request> is not set.
		3606
		3607	Even if you pass the request by some safer means to the callback, you
		3608	might want to do something to the request after starting it, such as
		3609	canceling it, which probably isn't working so well when the callback has
		3610	already been invoked.
		3611
		3612	A common way around all these issues is to make sure that
		3613	C<start_new_request> I<always> returns before the callback is invoked. If
		3614	C<start_new_request> immediately knows the result, it can artificially
		3615	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3616	for example, or more sneakily, by reusing an existing (stopped) watcher
		3617	and pushing it into the pending queue:
		3618
		3619	ev_set_cb (watcher, callback);
		3620	ev_feed_event (EV_A_ watcher, 0);
		3621
		3622	This way, C<start_new_request> can safely return before the callback is
		3623	invoked, while not delaying callback invocation too much.
		3624
		3625	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3626
		3627	Often (especially in GUI toolkits) there are places where you have
		3628	I<modal> interaction, which is most easily implemented by recursively
		3629	invoking C<ev_run>.
		3630
		3631	This brings the problem of exiting - a callback might want to finish the
		3632	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3633	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3634	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3635	other combination: In these cases, C<ev_break> will not work alone.
		3636
		3637	The solution is to maintain "break this loop" variable for each C<ev_run>
		3638	invocation, and use a loop around C<ev_run> until the condition is
		3639	triggered, using C<EVRUN_ONCE>:
		3640
		3641	// main loop
		3642	int exit_main_loop = 0;
		3643
		3644	while (!exit_main_loop)
		3645	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3646
		3647	// in a modal watcher
		3648	int exit_nested_loop = 0;
		3649
		3650	while (!exit_nested_loop)
		3651	ev_run (EV_A_ EVRUN_ONCE);
		3652
		3653	To exit from any of these loops, just set the corresponding exit variable:
		3654
		3655	// exit modal loop
		3656	exit_nested_loop = 1;
		3657
		3658	// exit main program, after modal loop is finished
		3659	exit_main_loop = 1;
		3660
		3661	// exit both
		3662	exit_main_loop = exit_nested_loop = 1;
		3663
		3664	=head2 THREAD LOCKING EXAMPLE
		3665
		3666	Here is a fictitious example of how to run an event loop in a different
		3667	thread from where callbacks are being invoked and watchers are
		3668	created/added/removed.
		3669
		3670	For a real-world example, see the C<EV::Loop::Async> perl module,
		3671	which uses exactly this technique (which is suited for many high-level
		3672	languages).
		3673
		3674	The example uses a pthread mutex to protect the loop data, a condition
		3675	variable to wait for callback invocations, an async watcher to notify the
		3676	event loop thread and an unspecified mechanism to wake up the main thread.
		3677
		3678	First, you need to associate some data with the event loop:
		3679
		3680	typedef struct {
		3681	mutex_t lock; /* global loop lock */
		3682	ev_async async_w;
		3683	thread_t tid;
		3684	cond_t invoke_cv;
		3685	} userdata;
		3686
		3687	void prepare_loop (EV_P)
		3688	{
		3689	// for simplicity, we use a static userdata struct.
		3690	static userdata u;
		3691
		3692	ev_async_init (&u->async_w, async_cb);
		3693	ev_async_start (EV_A_ &u->async_w);
		3694
		3695	pthread_mutex_init (&u->lock, 0);
		3696	pthread_cond_init (&u->invoke_cv, 0);
		3697
		3698	// now associate this with the loop
		3699	ev_set_userdata (EV_A_ u);
		3700	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3701	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3702
		3703	// then create the thread running ev_run
		3704	pthread_create (&u->tid, 0, l_run, EV_A);
		3705	}
		3706
		3707	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3708	solely to wake up the event loop so it takes notice of any new watchers
		3709	that might have been added:
		3710
		3711	static void
		3712	async_cb (EV_P_ ev_async *w, int revents)
		3713	{
		3714	// just used for the side effects
		3715	}
		3716
		3717	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3718	protecting the loop data, respectively.
		3719
		3720	static void
		3721	l_release (EV_P)
		3722	{
		3723	userdata *u = ev_userdata (EV_A);
		3724	pthread_mutex_unlock (&u->lock);
		3725	}
		3726
		3727	static void
		3728	l_acquire (EV_P)
		3729	{
		3730	userdata *u = ev_userdata (EV_A);
		3731	pthread_mutex_lock (&u->lock);
		3732	}
		3733
		3734	The event loop thread first acquires the mutex, and then jumps straight
		3735	into C<ev_run>:
		3736
		3737	void *
		3738	l_run (void *thr_arg)
		3739	{
		3740	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3741
		3742	l_acquire (EV_A);
		3743	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3744	ev_run (EV_A_ 0);
		3745	l_release (EV_A);
		3746
		3747	return 0;
		3748	}
		3749
		3750	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3751	signal the main thread via some unspecified mechanism (signals? pipe
		3752	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3753	have been called (in a while loop because a) spurious wakeups are possible
		3754	and b) skipping inter-thread-communication when there are no pending
		3755	watchers is very beneficial):
		3756
		3757	static void
		3758	l_invoke (EV_P)
		3759	{
		3760	userdata *u = ev_userdata (EV_A);
		3761
		3762	while (ev_pending_count (EV_A))
		3763	{
		3764	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3765	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3766	}
		3767	}
		3768
		3769	Now, whenever the main thread gets told to invoke pending watchers, it
		3770	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3771	thread to continue:
		3772
		3773	static void
		3774	real_invoke_pending (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777
		3778	pthread_mutex_lock (&u->lock);
		3779	ev_invoke_pending (EV_A);
		3780	pthread_cond_signal (&u->invoke_cv);
		3781	pthread_mutex_unlock (&u->lock);
		3782	}
		3783
		3784	Whenever you want to start/stop a watcher or do other modifications to an
		3785	event loop, you will now have to lock:
		3786
		3787	ev_timer timeout_watcher;
		3788	userdata *u = ev_userdata (EV_A);
		3789
		3790	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3791
		3792	pthread_mutex_lock (&u->lock);
		3793	ev_timer_start (EV_A_ &timeout_watcher);
		3794	ev_async_send (EV_A_ &u->async_w);
		3795	pthread_mutex_unlock (&u->lock);
		3796
		3797	Note that sending the C<ev_async> watcher is required because otherwise
		3798	an event loop currently blocking in the kernel will have no knowledge
		3799	about the newly added timer. By waking up the loop it will pick up any new
		3800	watchers in the next event loop iteration.
		3801
		3802	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3803
		3804	While the overhead of a callback that e.g. schedules a thread is small, it
		3805	is still an overhead. If you embed libev, and your main usage is with some
		3806	kind of threads or coroutines, you might want to customise libev so that
		3807	doesn't need callbacks anymore.
		3808
		3809	Imagine you have coroutines that you can switch to using a function
		3810	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3811	and that due to some magic, the currently active coroutine is stored in a
		3812	global called C<current_coro>. Then you can build your own "wait for libev
		3813	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3814	the differing C<;> conventions):
		3815
		3816	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3817	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3818
		3819	That means instead of having a C callback function, you store the
		3820	coroutine to switch to in each watcher, and instead of having libev call
		3821	your callback, you instead have it switch to that coroutine.
		3822
		3823	A coroutine might now wait for an event with a function called
		3824	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3825	matter when, or whether the watcher is active or not when this function is
		3826	called):
		3827
		3828	void
		3829	wait_for_event (ev_watcher *w)
		3830	{
		3831	ev_cb_set (w) = current_coro;
		3832	switch_to (libev_coro);
		3833	}
		3834
		3835	That basically suspends the coroutine inside C<wait_for_event> and
		3836	continues the libev coroutine, which, when appropriate, switches back to
		3837	this or any other coroutine.
		3838
		3839	You can do similar tricks if you have, say, threads with an event queue -
		3840	instead of storing a coroutine, you store the queue object and instead of
		3841	switching to a coroutine, you push the watcher onto the queue and notify
		3842	any waiters.
		3843
		3844	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3845	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3846
		3847	// my_ev.h
		3848	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3849	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3850	#include "../libev/ev.h"
		3851
		3852	// my_ev.c
		3853	#define EV_H "my_ev.h"
		3854	#include "../libev/ev.c"
		3855
		3856	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3857	F<my_ev.c> into your project. When properly specifying include paths, you
		3858	can even use F<ev.h> as header file name directly.
2666		3859
2667		3860
2668	=head1 LIBEVENT EMULATION	3861	=head1 LIBEVENT EMULATION
2669		3862
2670	Libev offers a compatibility emulation layer for libevent. It cannot	3863	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	3864	emulate the internals of libevent, so here are some usage hints:
2672		3865
2673	=over 4	3866	=over 4
		3867
		3868	=item * Only the libevent-1.4.1-beta API is being emulated.
		3869
		3870	This was the newest libevent version available when libev was implemented,
		3871	and is still mostly unchanged in 2010.
2674		3872
2675	=item * Use it by including <event.h>, as usual.	3873	=item * Use it by including <event.h>, as usual.
2676		3874
2677	=item * The following members are fully supported: ev_base, ev_callback,	3875	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	3876	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3882	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3883	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3884	is an ev_pri field.
2687		3885
2688	=item * In libevent, the last base created gets the signals, in libev, the	3886	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3887	base that registered the signal gets the signals.
2690		3888
2691	=item * Other members are not supported.	3889	=item * Other members are not supported.
2692		3890
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3891	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3892	to use the libev header file and library.
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	3911	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	3912	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	3913	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	3914	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		3915
2718	Currently, functions, and static and non-static member functions can be	3916	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	3917	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	3918	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	3919	you need support for other types of functors please contact the author
2722	it).	3920	(preferably after implementing it).
2723		3921
2724	Here is a list of things available in the C<ev> namespace:	3922	Here is a list of things available in the C<ev> namespace:
2725		3923
2726	=over 4	3924	=over 4
2727		3925
…		…
2737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3935	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2738		3936
2739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3937	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2740	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3938	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2741	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3939	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2742	defines by many implementations.	3940	defined by many implementations.
2743		3941
2744	All of those classes have these methods:	3942	All of those classes have these methods:
2745		3943
2746	=over 4	3944	=over 4
2747		3945
2748	=item ev::TYPE::TYPE ()	3946	=item ev::TYPE::TYPE ()
2749		3947
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3948	=item ev::TYPE::TYPE (loop)
2751		3949
2752	=item ev::TYPE::~TYPE	3950	=item ev::TYPE::~TYPE
2753		3951
2754	The constructor (optionally) takes an event loop to associate the watcher	3952	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3953	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3985
2788	myclass obj;	3986	myclass obj;
2789	ev::io iow;	3987	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3988	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3989
		3990	=item w->set (object *)
		3991
		3992	This is a variation of a method callback - leaving out the method to call
		3993	will default the method to C<operator ()>, which makes it possible to use
		3994	functor objects without having to manually specify the C<operator ()> all
		3995	the time. Incidentally, you can then also leave out the template argument
		3996	list.
		3997
		3998	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3999	int revents)>.
		4000
		4001	See the method-C<set> above for more details.
		4002
		4003	Example: use a functor object as callback.
		4004
		4005	struct myfunctor
		4006	{
		4007	void operator() (ev::io &w, int revents)
		4008	{
		4009	...
		4010	}
		4011	}
		4012
		4013	myfunctor f;
		4014
		4015	ev::io w;
		4016	w.set (&f);
		4017
2792	=item w->set<function> (void *data = 0)	4018	=item w->set<function> (void *data = 0)
2793		4019
2794	Also sets a callback, but uses a static method or plain function as	4020	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	4021	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	4022	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	4028	Example: Use a plain function as callback.
2803		4029
2804	static void io_cb (ev::io &w, int revents) { }	4030	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	4031	iow.set <io_cb> ();
2806		4032
2807	=item w->set (struct ev_loop *)	4033	=item w->set (loop)
2808		4034
2809	Associates a different C<struct ev_loop> with this watcher. You can only	4035	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	4036	do this when the watcher is inactive (and not pending either).
2811		4037
2812	=item w->set ([arguments])	4038	=item w->set ([arguments])
2813		4039
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4040	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	4041	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	4042	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	4043	when reconfiguring it with this method.
2818		4044
2819	=item w->start ()	4045	=item w->start ()
2820		4046
2821	Starts the watcher. Note that there is no C<loop> argument, as the	4047	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	4048	constructor already stores the event loop.
2823		4049
		4050	=item w->start ([arguments])
		4051
		4052	Instead of calling C<set> and C<start> methods separately, it is often
		4053	convenient to wrap them in one call. Uses the same type of arguments as
		4054	the configure C<set> method of the watcher.
		4055
2824	=item w->stop ()	4056	=item w->stop ()
2825		4057
2826	Stops the watcher if it is active. Again, no C<loop> argument.	4058	Stops the watcher if it is active. Again, no C<loop> argument.
2827		4059
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4060	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		4072
2841	=back	4073	=back
2842		4074
2843	=back	4075	=back
2844		4076
2845	Example: Define a class with an IO and idle watcher, start one of them in	4077	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	4078	watchers in the constructor.
2847		4079
2848	class myclass	4080	class myclass
2849	{	4081	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	4082	ev::io io ; void io_cb (ev::io &w, int revents);
		4083	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4084	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		4085
2853	myclass (int fd)	4086	myclass (int fd)
2854	{	4087	{
2855	io .set <myclass, &myclass::io_cb > (this);	4088	io .set <myclass, &myclass::io_cb > (this);
		4089	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	4090	idle.set <myclass, &myclass::idle_cb> (this);
2857		4091
2858	io.start (fd, ev::READ);	4092	io.set (fd, ev::WRITE); // configure the watcher
		4093	io.start (); // start it whenever convenient
		4094
		4095	io2.start (fd, ev::READ); // set + start in one call
2859	}	4096	}
2860	};	4097	};
2861		4098
2862		4099
2863	=head1 OTHER LANGUAGE BINDINGS	4100	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	4119	L<http://software.schmorp.de/pkg/EV>.
2883		4120
2884	=item Python	4121	=item Python
2885		4122
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4123	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	4124	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		4125
2893	=item Ruby	4126	=item Ruby
2894		4127
2895	Tony Arcieri has written a ruby extension that offers access to a subset	4128	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	4129	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	4130	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	4131	L<http://rev.rubyforge.org/>.
2899		4132
		4133	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4134	makes rev work even on mingw.
		4135
		4136	=item Haskell
		4137
		4138	A haskell binding to libev is available at
		4139	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4140
2900	=item D	4141	=item D
2901		4142
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4143	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4144	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4145
		4146	=item Ocaml
		4147
		4148	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4149	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4150
		4151	=item Lua
		4152
		4153	Brian Maher has written a partial interface to libev for lua (at the
		4154	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4155	L<http://github.com/brimworks/lua-ev>.
2904		4156
2905	=back	4157	=back
2906		4158
2907		4159
2908	=head1 MACRO MAGIC	4160	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4174	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4175	C<EV_A_> is used when other arguments are following. Example:
2924		4176
2925	ev_unref (EV_A);	4177	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4178	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4179	ev_run (EV_A_ 0);
2928		4180
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4181	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4182	which is often provided by the following macro.
2931		4183
2932	=item C<EV_P>, C<EV_P_>	4184	=item C<EV_P>, C<EV_P_>
…		…
2945	suitable for use with C<EV_A>.	4197	suitable for use with C<EV_A>.
2946		4198
2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4199	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2948		4200
2949	Similar to the other two macros, this gives you the value of the default	4201	Similar to the other two macros, this gives you the value of the default
2950	loop, if multiple loops are supported ("ev loop default").	4202	loop, if multiple loops are supported ("ev loop default"). The default loop
		4203	will be initialised if it isn't already initialised.
		4204
		4205	For non-multiplicity builds, these macros do nothing, so you always have
		4206	to initialise the loop somewhere.
2951		4207
2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4208	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2953		4209
2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4210	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2955	default loop has been initialised (C<UC> == unchecked). Their behaviour	4211	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2972	}	4228	}
2973		4229
2974	ev_check check;	4230	ev_check check;
2975	ev_check_init (&check, check_cb);	4231	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4232	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4233	ev_run (EV_DEFAULT_ 0);
2978		4234
2979	=head1 EMBEDDING	4235	=head1 EMBEDDING
2980		4236
2981	Libev can (and often is) directly embedded into host	4237	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4238	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4265
3010	#define EV_STANDALONE 1	4266	#define EV_STANDALONE 1
3011	#include "ev.h"	4267	#include "ev.h"
3012		4268
3013	Both header files and implementation files can be compiled with a C++	4269	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4270	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4271	as a bug).
3016		4272
3017	You need the following files in your source tree, or in a directory	4273	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4274	in your include path (e.g. in libev/ when using -Ilibev):
3019		4275
…		…
3062	libev.m4	4318	libev.m4
3063		4319
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4320	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4321
3066	Libev can be configured via a variety of preprocessor symbols you have to	4322	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4323	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4324	the absence of autoconf is documented for every option.
		4325
		4326	Symbols marked with "(h)" do not change the ABI, and can have different
		4327	values when compiling libev vs. including F<ev.h>, so it is permissible
		4328	to redefine them before including F<ev.h> without breaking compatibility
		4329	to a compiled library. All other symbols change the ABI, which means all
		4330	users of libev and the libev code itself must be compiled with compatible
		4331	settings.
3069		4332
3070	=over 4	4333	=over 4
3071		4334
		4335	=item EV_COMPAT3 (h)
		4336
		4337	Backwards compatibility is a major concern for libev. This is why this
		4338	release of libev comes with wrappers for the functions and symbols that
		4339	have been renamed between libev version 3 and 4.
		4340
		4341	You can disable these wrappers (to test compatibility with future
		4342	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4343	sources. This has the additional advantage that you can drop the C<struct>
		4344	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4345	typedef in that case.
		4346
		4347	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4348	and in some even more future version the compatibility code will be
		4349	removed completely.
		4350
3072	=item EV_STANDALONE	4351	=item EV_STANDALONE (h)
3073		4352
3074	Must always be C<1> if you do not use autoconf configuration, which	4353	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4354	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4355	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4356	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4357	F<event.h> that are not directly supported by the libev core alone.
3079		4358
		4359	In standalone mode, libev will still try to automatically deduce the
		4360	configuration, but has to be more conservative.
		4361
		4362	=item EV_USE_FLOOR
		4363
		4364	If defined to be C<1>, libev will use the C<floor ()> function for its
		4365	periodic reschedule calculations, otherwise libev will fall back on a
		4366	portable (slower) implementation. If you enable this, you usually have to
		4367	link against libm or something equivalent. Enabling this when the C<floor>
		4368	function is not available will fail, so the safe default is to not enable
		4369	this.
		4370
3080	=item EV_USE_MONOTONIC	4371	=item EV_USE_MONOTONIC
3081		4372
3082	If defined to be C<1>, libev will try to detect the availability of the	4373	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4374	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4375	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4376	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4377	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4378	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4379	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4380
3090	=item EV_USE_REALTIME	4381	=item EV_USE_REALTIME
3091		4382
3092	If defined to be C<1>, libev will try to detect the availability of the	4383	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4384	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4385	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4386	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4387	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4388	correctness. See the note about libraries in the description of
		4389	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4390	C<EV_USE_CLOCK_SYSCALL>.
		4391
		4392	=item EV_USE_CLOCK_SYSCALL
		4393
		4394	If defined to be C<1>, libev will try to use a direct syscall instead
		4395	of calling the system-provided C<clock_gettime> function. This option
		4396	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4397	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4398	programs needlessly. Using a direct syscall is slightly slower (in
		4399	theory), because no optimised vdso implementation can be used, but avoids
		4400	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4401	higher, as it simplifies linking (no need for C<-lrt>).
3098		4402
3099	=item EV_USE_NANOSLEEP	4403	=item EV_USE_NANOSLEEP
3100		4404
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4405	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4406	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4422
3119	=item EV_SELECT_USE_FD_SET	4423	=item EV_SELECT_USE_FD_SET
3120		4424
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4425	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4426	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4427	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4428	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4429	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4430	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4431	configures the maximum size of the C<fd_set>.
3128		4432
3129	=item EV_SELECT_IS_WINSOCKET	4433	=item EV_SELECT_IS_WINSOCKET
3130		4434
3131	When defined to C<1>, the select backend will assume that	4435	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4436	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4438	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4439	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4440	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4441	on win32. Should not be defined on non-win32 platforms.
3138		4442
3139	=item EV_FD_TO_WIN32_HANDLE	4443	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4444
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4445	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4446	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4447	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4448	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4449	in which case they can provide this function to map fds to socket handles.
		4450
		4451	=item EV_WIN32_HANDLE_TO_FD(handle)
		4452
		4453	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4454	using the standard C<_open_osfhandle> function. For programs implementing
		4455	their own fd to handle mapping, overwriting this function makes it easier
		4456	to do so. This can be done by defining this macro to an appropriate value.
		4457
		4458	=item EV_WIN32_CLOSE_FD(fd)
		4459
		4460	If programs implement their own fd to handle mapping on win32, then this
		4461	macro can be used to override the C<close> function, useful to unregister
		4462	file descriptors again. Note that the replacement function has to close
		4463	the underlying OS handle.
3146		4464
3147	=item EV_USE_POLL	4465	=item EV_USE_POLL
3148		4466
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4467	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4468	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4507	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3190		4508
3191	=item EV_ATOMIC_T	4509	=item EV_ATOMIC_T
3192		4510
3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4511	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3194	access is atomic with respect to other threads or signal contexts. No such	4512	access is atomic and serialised with respect to other threads or signal
3195	type is easily found in the C language, so you can provide your own type	4513	contexts. No such type is easily found in the C language, so you can
3196	that you know is safe for your purposes. It is used both for signal handler "locking"	4514	provide your own type that you know is safe for your purposes. It is used
3197	as well as for signal and thread safety in C<ev_async> watchers.	4515	both for signal handler "locking" as well as for signal and thread safety
		4516	in C<ev_async> watchers.
3198		4517
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4518	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4519	(from F<signal.h>), which is usually good enough on most platforms,
		4520	although strictly speaking using a type that also implies a memory fence
		4521	is required.
3201		4522
3202	=item EV_H	4523	=item EV_H (h)
3203		4524
3204	The name of the F<ev.h> header file used to include it. The default if	4525	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4526	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4527	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4528
3208	=item EV_CONFIG_H	4529	=item EV_CONFIG_H (h)
3209		4530
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4531	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4532	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4533	C<EV_H>, above.
3213		4534
3214	=item EV_EVENT_H	4535	=item EV_EVENT_H (h)
3215		4536
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4537	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4538	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4539
3219	=item EV_PROTOTYPES	4540	=item EV_PROTOTYPES (h)
3220		4541
3221	If defined to be C<0>, then F<ev.h> will not define any function	4542	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4543	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4544	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4545	around libev functions.
…		…
3229	will have the C<struct ev_loop *> as first argument, and you can create	4550	will have the C<struct ev_loop *> as first argument, and you can create
3230	additional independent event loops. Otherwise there will be no support	4551	additional independent event loops. Otherwise there will be no support
3231	for multiple event loops and there is no first event loop pointer	4552	for multiple event loops and there is no first event loop pointer
3232	argument. Instead, all functions act on the single default loop.	4553	argument. Instead, all functions act on the single default loop.
3233		4554
		4555	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4556	default loop when multiplicity is switched off - you always have to
		4557	initialise the loop manually in this case.
		4558
3234	=item EV_MINPRI	4559	=item EV_MINPRI
3235		4560
3236	=item EV_MAXPRI	4561	=item EV_MAXPRI
3237		4562
3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4563	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3246	fine.	4571	fine.
3247		4572
3248	If your embedding application does not need any priorities, defining these	4573	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4574	both to C<0> will save some memory and CPU.
3250		4575
3251	=item EV_PERIODIC_ENABLE	4576	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4577	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4578	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4579
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4580	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4581	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4582	is not. Disabling watcher types mainly saves code size.
3256		4583
3257	=item EV_IDLE_ENABLE	4584	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4585
3286	If you need to shave off some kilobytes of code at the expense of some	4586	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4587	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4588	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4589	that can be enabled on the platform.
		4590
		4591	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4592	with some broad features you want) and then selectively re-enable
		4593	additional parts you want, for example if you want everything minimal,
		4594	but multiple event loop support, async and child watchers and the poll
		4595	backend, use this:
		4596
		4597	#define EV_FEATURES 0
		4598	#define EV_MULTIPLICITY 1
		4599	#define EV_USE_POLL 1
		4600	#define EV_CHILD_ENABLE 1
		4601	#define EV_ASYNC_ENABLE 1
		4602
		4603	The actual value is a bitset, it can be a combination of the following
		4604	values:
		4605
		4606	=over 4
		4607
		4608	=item C<1> - faster/larger code
		4609
		4610	Use larger code to speed up some operations.
		4611
		4612	Currently this is used to override some inlining decisions (enlarging the
		4613	code size by roughly 30% on amd64).
		4614
		4615	When optimising for size, use of compiler flags such as C<-Os> with
		4616	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4617	assertions.
		4618
		4619	=item C<2> - faster/larger data structures
		4620
		4621	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4622	hash table sizes and so on. This will usually further increase code size
		4623	and can additionally have an effect on the size of data structures at
		4624	runtime.
		4625
		4626	=item C<4> - full API configuration
		4627
		4628	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4629	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4630
		4631	=item C<8> - full API
		4632
		4633	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4634	details on which parts of the API are still available without this
		4635	feature, and do not complain if this subset changes over time.
		4636
		4637	=item C<16> - enable all optional watcher types
		4638
		4639	Enables all optional watcher types. If you want to selectively enable
		4640	only some watcher types other than I/O and timers (e.g. prepare,
		4641	embed, async, child...) you can enable them manually by defining
		4642	C<EV_watchertype_ENABLE> to C<1> instead.
		4643
		4644	=item C<32> - enable all backends
		4645
		4646	This enables all backends - without this feature, you need to enable at
		4647	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4648
		4649	=item C<64> - enable OS-specific "helper" APIs
		4650
		4651	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4652	default.
		4653
		4654	=back
		4655
		4656	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4657	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4658	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4659	watchers, timers and monotonic clock support.
		4660
		4661	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4662	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4663	your program might be left out as well - a binary starting a timer and an
		4664	I/O watcher then might come out at only 5Kb.
		4665
		4666	=item EV_API_STATIC
		4667
		4668	If this symbol is defined (by default it is not), then all identifiers
		4669	will have static linkage. This means that libev will not export any
		4670	identifiers, and you cannot link against libev anymore. This can be useful
		4671	when you embed libev, only want to use libev functions in a single file,
		4672	and do not want its identifiers to be visible.
		4673
		4674	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4675	wants to use libev.
		4676
		4677	This option only works when libev is compiled with a C compiler, as C++
		4678	doesn't support the required declaration syntax.
		4679
		4680	=item EV_AVOID_STDIO
		4681
		4682	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4683	functions (printf, scanf, perror etc.). This will increase the code size
		4684	somewhat, but if your program doesn't otherwise depend on stdio and your
		4685	libc allows it, this avoids linking in the stdio library which is quite
		4686	big.
		4687
		4688	Note that error messages might become less precise when this option is
		4689	enabled.
		4690
		4691	=item EV_NSIG
		4692
		4693	The highest supported signal number, +1 (or, the number of
		4694	signals): Normally, libev tries to deduce the maximum number of signals
		4695	automatically, but sometimes this fails, in which case it can be
		4696	specified. Also, using a lower number than detected (C<32> should be
		4697	good for about any system in existence) can save some memory, as libev
		4698	statically allocates some 12-24 bytes per signal number.
3290		4699
3291	=item EV_PID_HASHSIZE	4700	=item EV_PID_HASHSIZE
3292		4701
3293	C<ev_child> watchers use a small hash table to distribute workload by	4702	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4703	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4704	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4705	might want to increase this value (I<must> be a power of two).
3297		4706
3298	=item EV_INOTIFY_HASHSIZE	4707	=item EV_INOTIFY_HASHSIZE
3299		4708
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4709	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4710	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4711	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4712	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4713	power of two).
3305		4714
3306	=item EV_USE_4HEAP	4715	=item EV_USE_4HEAP
3307		4716
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4717	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4718	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4719	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4720	faster performance with many (thousands) of watchers.
3312		4721
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4722	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4723	will be C<0>.
3315		4724
3316	=item EV_HEAP_CACHE_AT	4725	=item EV_HEAP_CACHE_AT
3317		4726
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4727	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4728	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4729	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4730	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4731	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4732	noticeably with many (hundreds) of watchers.
3324		4733
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4734	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4735	will be C<0>.
3327		4736
3328	=item EV_VERIFY	4737	=item EV_VERIFY
3329		4738
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4739	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4740	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4741	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4742	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4743	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4744	verification code will be called very frequently, which will slow down
3336	libev considerably.	4745	libev considerably.
3337		4746
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4747	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4748	will be C<0>.
3340		4749
3341	=item EV_COMMON	4750	=item EV_COMMON
3342		4751
3343	By default, all watchers have a C<void *data> member. By redefining	4752	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4753	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4754	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4755	though, and it must be identical each time.
3347		4756
3348	For example, the perl EV module uses something like this:	4757	For example, the perl EV module uses something like this:
3349		4758
…		…
3402	file.	4811	file.
3403		4812
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4813	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4814	that everybody includes and which overrides some configure choices:
3406		4815
3407	#define EV_MINIMAL 1	4816	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4817	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4818	#define EV_PREPARE_ENABLE 1
		4819	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4820	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4821	#define EV_CHILD_ENABLE 1
		4822	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4823	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4824
3417	#include "ev++.h"	4825	#include "ev++.h"
3418		4826
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4827	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4828
3421	#include "ev_cpp.h"	4829	#include "ev_cpp.h"
3422	#include "ev.c"	4830	#include "ev.c"
3423		4831
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4832	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		4833
3426	=head2 THREADS AND COROUTINES	4834	=head2 THREADS AND COROUTINES
3427		4835
3428	=head3 THREADS	4836	=head3 THREADS
3429		4837
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4888	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4889	watcher callback into the event loop interested in the signal.
3482		4890
3483	=back	4891	=back
3484		4892
		4893	See also L<THREAD LOCKING EXAMPLE>.
		4894
3485	=head3 COROUTINES	4895	=head3 COROUTINES
3486		4896
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4897	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4898	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4899	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4900	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4901	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4902	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4903
3494	Care has been taken to ensure that libev does not keep local state inside	4904	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4905	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4906	they do not call any callbacks.
3497		4907
3498	=head2 COMPILER WARNINGS	4908	=head2 COMPILER WARNINGS
3499		4909
3500	Depending on your compiler and compiler settings, you might get no or a	4910	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4911	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4921	maintainable.
3512		4922
3513	And of course, some compiler warnings are just plain stupid, or simply	4923	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4924	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4925	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4926	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	4927	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4928	such buggy versions.
3519		4929
3520	While libev is written to generate as few warnings as possible,	4930	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	4931	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4945	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4946	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4947	==2274== still reachable: 256 bytes in 1 blocks.
3538		4948
3539	Then there is no memory leak, just as memory accounted to global variables	4949	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	4950	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4951
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4952	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4953	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	4954	although an acceptable workaround has been found here), or it might be
3545	confused.	4955	confused.
…		…
3557	I suggest using suppression lists.	4967	I suggest using suppression lists.
3558		4968
3559		4969
3560	=head1 PORTABILITY NOTES	4970	=head1 PORTABILITY NOTES
3561		4971
		4972	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4973
		4974	GNU/Linux is the only common platform that supports 64 bit file/large file
		4975	interfaces but I<disables> them by default.
		4976
		4977	That means that libev compiled in the default environment doesn't support
		4978	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4979
		4980	Unfortunately, many programs try to work around this GNU/Linux issue
		4981	by enabling the large file API, which makes them incompatible with the
		4982	standard libev compiled for their system.
		4983
		4984	Likewise, libev cannot enable the large file API itself as this would
		4985	suddenly make it incompatible to the default compile time environment,
		4986	i.e. all programs not using special compile switches.
		4987
		4988	=head2 OS/X AND DARWIN BUGS
		4989
		4990	The whole thing is a bug if you ask me - basically any system interface
		4991	you touch is broken, whether it is locales, poll, kqueue or even the
		4992	OpenGL drivers.
		4993
		4994	=head3 C<kqueue> is buggy
		4995
		4996	The kqueue syscall is broken in all known versions - most versions support
		4997	only sockets, many support pipes.
		4998
		4999	Libev tries to work around this by not using C<kqueue> by default on this
		5000	rotten platform, but of course you can still ask for it when creating a
		5001	loop - embedding a socket-only kqueue loop into a select-based one is
		5002	probably going to work well.
		5003
		5004	=head3 C<poll> is buggy
		5005
		5006	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5007	implementation by something calling C<kqueue> internally around the 10.5.6
		5008	release, so now C<kqueue> I<and> C<poll> are broken.
		5009
		5010	Libev tries to work around this by not using C<poll> by default on
		5011	this rotten platform, but of course you can still ask for it when creating
		5012	a loop.
		5013
		5014	=head3 C<select> is buggy
		5015
		5016	All that's left is C<select>, and of course Apple found a way to fuck this
		5017	one up as well: On OS/X, C<select> actively limits the number of file
		5018	descriptors you can pass in to 1024 - your program suddenly crashes when
		5019	you use more.
		5020
		5021	There is an undocumented "workaround" for this - defining
		5022	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5023	work on OS/X.
		5024
		5025	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5026
		5027	=head3 C<errno> reentrancy
		5028
		5029	The default compile environment on Solaris is unfortunately so
		5030	thread-unsafe that you can't even use components/libraries compiled
		5031	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5032	defined by default. A valid, if stupid, implementation choice.
		5033
		5034	If you want to use libev in threaded environments you have to make sure
		5035	it's compiled with C<_REENTRANT> defined.
		5036
		5037	=head3 Event port backend
		5038
		5039	The scalable event interface for Solaris is called "event
		5040	ports". Unfortunately, this mechanism is very buggy in all major
		5041	releases. If you run into high CPU usage, your program freezes or you get
		5042	a large number of spurious wakeups, make sure you have all the relevant
		5043	and latest kernel patches applied. No, I don't know which ones, but there
		5044	are multiple ones to apply, and afterwards, event ports actually work
		5045	great.
		5046
		5047	If you can't get it to work, you can try running the program by setting
		5048	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5049	C<select> backends.
		5050
		5051	=head2 AIX POLL BUG
		5052
		5053	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5054	this by trying to avoid the poll backend altogether (i.e. it's not even
		5055	compiled in), which normally isn't a big problem as C<select> works fine
		5056	with large bitsets on AIX, and AIX is dead anyway.
		5057
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5058	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5059
		5060	=head3 General issues
3563		5061
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5062	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	5063	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	5064	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5065	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	5066	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	5067	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5068	as every compiler comes with a slightly differently broken/incompatible
		5069	environment.
3570		5070
3571	Lifting these limitations would basically require the full	5071	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	5072	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	5073	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	5074	also that glib is the slowest event library known to man).
3575		5075
3576	There is no supported compilation method available on windows except	5076	There is no supported compilation method available on windows except
3577	embedding it into other applications.	5077	embedding it into other applications.
		5078
		5079	Sensible signal handling is officially unsupported by Microsoft - libev
		5080	tries its best, but under most conditions, signals will simply not work.
3578		5081
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	5082	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	5083	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	5084	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	5085	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	5090	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	5091	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	5092	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	5093	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	5094	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	5095	(due to Microsoft monopoly games).
3593		5096
3594	A typical way to use libev under windows is to embed it (see the embedding	5097	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	5098	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	5099	of F<ev.h>:
3597		5100
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	5107	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		5108
3606	#include "evwrap.h"	5109	#include "evwrap.h"
3607	#include "ev.c"	5110	#include "ev.c"
3608		5111
3609	=over 4
3610
3611	=item The winsocket select function	5112	=head3 The winsocket C<select> function
3612		5113
3613	The winsocket C<select> function doesn't follow POSIX in that it	5114	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	5115	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	5116	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	5117	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5126	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		5127
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	5128	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	5129	complexity in the O(n²) range when using win32.
3629		5130
3630	=item Limited number of file descriptors	5131	=head3 Limited number of file descriptors
3631		5132
3632	Windows has numerous arbitrary (and low) limits on things.	5133	Windows has numerous arbitrary (and low) limits on things.
3633		5134
3634	Early versions of winsocket's select only supported waiting for a maximum	5135	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	5136	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	5137	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	5138	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	5139	previous thread in each. Sounds great!).
3639		5140
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5141	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	5142	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	5143	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	5144	other interpreters do their own select emulation on windows).
3644		5145
3645	Another limit is the number of file descriptors in the Microsoft runtime	5146	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5147	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	5148	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5149	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	5150	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	5151	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	5152	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	5153	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	5154	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		5155
3659	=head2 PORTABILITY REQUIREMENTS	5156	=head2 PORTABILITY REQUIREMENTS
3660		5157
3661	In addition to a working ISO-C implementation and of course the	5158	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	5159	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	5166	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	5167	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	5168	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	5169	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	5170	calls them using an C<ev_watcher *> internally.
		5171
		5172	=item pointer accesses must be thread-atomic
		5173
		5174	Accessing a pointer value must be atomic, it must both be readable and
		5175	writable in one piece - this is the case on all current architectures.
3674		5176
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	5177	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		5178
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	5179	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5180	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3701	watchers.	5203	watchers.
3702		5204
3703	=item C<double> must hold a time value in seconds with enough accuracy	5205	=item C<double> must hold a time value in seconds with enough accuracy
3704		5206
3705	The type C<double> is used to represent timestamps. It is required to	5207	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5208	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5209	good enough for at least into the year 4000 with millisecond accuracy
		5210	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5211	implementations using IEEE 754, which is basically all existing ones.
		5212
		5213	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5214	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5215	is either obsolete or somebody patched it to use C<long double> or
		5216	something like that, just kidding).
3709		5217
3710	=back	5218	=back
3711		5219
3712	If you know of other additional requirements drop me a note.	5220	If you know of other additional requirements drop me a note.
3713		5221
…		…
3775	=item Processing ev_async_send: O(number_of_async_watchers)	5283	=item Processing ev_async_send: O(number_of_async_watchers)
3776		5284
3777	=item Processing signals: O(max_signal_number)	5285	=item Processing signals: O(max_signal_number)
3778		5286
3779	Sending involves a system call I<iff> there were no other C<ev_async_send>	5287	Sending involves a system call I<iff> there were no other C<ev_async_send>
3780	calls in the current loop iteration. Checking for async and signal events	5288	calls in the current loop iteration and the loop is currently
		5289	blocked. Checking for async and signal events involves iterating over all
3781	involves iterating over all running async watchers or all signal numbers.	5290	running async watchers or all signal numbers.
3782		5291
3783	=back	5292	=back
3784		5293
3785		5294
		5295	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5296
		5297	The major version 4 introduced some incompatible changes to the API.
		5298
		5299	At the moment, the C<ev.h> header file provides compatibility definitions
		5300	for all changes, so most programs should still compile. The compatibility
		5301	layer might be removed in later versions of libev, so better update to the
		5302	new API early than late.
		5303
		5304	=over 4
		5305
		5306	=item C<EV_COMPAT3> backwards compatibility mechanism
		5307
		5308	The backward compatibility mechanism can be controlled by
		5309	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5310	section.
		5311
		5312	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5313
		5314	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5315
		5316	ev_loop_destroy (EV_DEFAULT_UC);
		5317	ev_loop_fork (EV_DEFAULT);
		5318
		5319	=item function/symbol renames
		5320
		5321	A number of functions and symbols have been renamed:
		5322
		5323	ev_loop => ev_run
		5324	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5325	EVLOOP_ONESHOT => EVRUN_ONCE
		5326
		5327	ev_unloop => ev_break
		5328	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5329	EVUNLOOP_ONE => EVBREAK_ONE
		5330	EVUNLOOP_ALL => EVBREAK_ALL
		5331
		5332	EV_TIMEOUT => EV_TIMER
		5333
		5334	ev_loop_count => ev_iteration
		5335	ev_loop_depth => ev_depth
		5336	ev_loop_verify => ev_verify
		5337
		5338	Most functions working on C<struct ev_loop> objects don't have an
		5339	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5340	associated constants have been renamed to not collide with the C<struct
		5341	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5342	as all other watcher types. Note that C<ev_loop_fork> is still called
		5343	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5344	typedef.
		5345
		5346	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5347
		5348	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5349	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5350	and work, but the library code will of course be larger.
		5351
		5352	=back
		5353
		5354
		5355	=head1 GLOSSARY
		5356
		5357	=over 4
		5358
		5359	=item active
		5360
		5361	A watcher is active as long as it has been started and not yet stopped.
		5362	See L<WATCHER STATES> for details.
		5363
		5364	=item application
		5365
		5366	In this document, an application is whatever is using libev.
		5367
		5368	=item backend
		5369
		5370	The part of the code dealing with the operating system interfaces.
		5371
		5372	=item callback
		5373
		5374	The address of a function that is called when some event has been
		5375	detected. Callbacks are being passed the event loop, the watcher that
		5376	received the event, and the actual event bitset.
		5377
		5378	=item callback/watcher invocation
		5379
		5380	The act of calling the callback associated with a watcher.
		5381
		5382	=item event
		5383
		5384	A change of state of some external event, such as data now being available
		5385	for reading on a file descriptor, time having passed or simply not having
		5386	any other events happening anymore.
		5387
		5388	In libev, events are represented as single bits (such as C<EV_READ> or
		5389	C<EV_TIMER>).
		5390
		5391	=item event library
		5392
		5393	A software package implementing an event model and loop.
		5394
		5395	=item event loop
		5396
		5397	An entity that handles and processes external events and converts them
		5398	into callback invocations.
		5399
		5400	=item event model
		5401
		5402	The model used to describe how an event loop handles and processes
		5403	watchers and events.
		5404
		5405	=item pending
		5406
		5407	A watcher is pending as soon as the corresponding event has been
		5408	detected. See L<WATCHER STATES> for details.
		5409
		5410	=item real time
		5411
		5412	The physical time that is observed. It is apparently strictly monotonic :)
		5413
		5414	=item wall-clock time
		5415
		5416	The time and date as shown on clocks. Unlike real time, it can actually
		5417	be wrong and jump forwards and backwards, e.g. when you adjust your
		5418	clock.
		5419
		5420	=item watcher
		5421
		5422	A data structure that describes interest in certain events. Watchers need
		5423	to be started (attached to an event loop) before they can receive events.
		5424
		5425	=back
		5426
3786	=head1 AUTHOR	5427	=head1 AUTHOR
3787		5428
3788	Marc Lehmann <libev@schmorp.de>.	5429	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5430	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3789		5431

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