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…		…
8		8
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
		14	#include <stdio.h> // for puts
13		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;
…		…
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	// unloop 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 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	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	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	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	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(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	107	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	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	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	122	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	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	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	130	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	131	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	132	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	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
149		165
150	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
151		167
152	Returns the current time as libev would use it. Please note that the	168	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	169	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
155		172
156	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
157		174
158	Sleep for the given interval: The current thread will be blocked until	175	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	176	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	195	not a problem.
179		196
180	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
182		200
183	assert (("libev version mismatch",	201	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
186		204
…		…
197	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
199		217
200	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
201		219
202	Return the set of all backends compiled into this binary of libev and also	220	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	221	also recommended for this platform, meaning it will work for most file
		222	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	223	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	224	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	225	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.	226	probe for if you specify no backends explicitly.
208		227
209	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
210		229
211	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	231	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	232	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
216		235
217	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
218		237
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		239
…		…
274	...	293	...
275	ev_set_syserr_cb (fatal_error);	294	ev_set_syserr_cb (fatal_error);
276		295
277	=back	296	=back
278		297
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		299
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	302	libev 3 had an C<ev_loop> function colliding with the struct name).
284		303
285	The library knows two types of such loops, the I<default> loop, which	304	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	305	supports signals and child events, and dynamically created event loops
287	not.	306	which do not.
288		307
289	=over 4	308	=over 4
290		309
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		311
293	This will initialise the default event loop if it hasn't been initialised	312	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	313	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	314	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	315	C<ev_loop_new>.
		316
		317	If the default loop is already initialised then this function simply
		318	returns it (and ignores the flags. If that is troubling you, check
		319	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		320	flags, which should almost always be C<0>, unless the caller is also the
		321	one calling C<ev_run> or otherwise qualifies as "the main program".
297		322
298	If you don't know what event loop to use, use the one returned from this	323	If you don't know what event loop to use, use the one returned from this
299	function.	324	function (or via the C<EV_DEFAULT> macro).
300		325
301	Note that this function is I<not> thread-safe, so if you want to use it	326	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	327	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot bes hared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
304		330
305	The default loop is the only loop that can handle C<ev_signal> and	331	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	332	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	333	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	334	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	336
		337	Example: This is the most typical usage.
		338
		339	if (!ev_default_loop (0))
		340	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		341
		342	Example: Restrict libev to the select and poll backends, and do not allow
		343	environment settings to be taken into account:
		344
		345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		346
		347	Example: Use whatever libev has to offer, but make sure that kqueue is
		348	used if available (warning, breaks stuff, best use only with your own
		349	private event loop and only if you know the OS supports your types of
		350	fds):
		351
		352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
		353
		354	=item struct ev_loop *ev_loop_new (unsigned int flags)
		355
		356	This will create and initialise a new event loop object. If the loop
		357	could not be initialised, returns false.
		358
		359	Note that this function I<is> thread-safe, and one common way to use
		360	libev with threads is indeed to create one loop per thread, and using the
		361	default loop in the "main" or "initial" thread.
311		362
312	The flags argument can be used to specify special behaviour or specific	363	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	364	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		365
315	The following flags are supported:	366	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	381	useful to try out specific backends to test their performance, or to work
331	around bugs.	382	around bugs.
332		383
333	=item C<EVFLAG_FORKCHECK>	384	=item C<EVFLAG_FORKCHECK>
334		385
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	386	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	387	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		388
339	This works by calling C<getpid ()> on every iteration of the loop,	389	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	390	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	391	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	392	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	398	flag.
349		399
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	400	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	401	environment variable.
352		402
		403	=item C<EVFLAG_NOINOTIFY>
		404
		405	When this flag is specified, then libev will not attempt to use the
		406	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		407	testing, this flag can be useful to conserve inotify file descriptors, as
		408	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		409
		410	=item C<EVFLAG_SIGNALFD>
		411
		412	When this flag is specified, then libev will attempt to use the
		413	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		414	delivers signals synchronously, which makes it both faster and might make
		415	it possible to get the queued signal data. It can also simplify signal
		416	handling with threads, as long as you properly block signals in your
		417	threads that are not interested in handling them.
		418
		419	Signalfd will not be used by default as this changes your signal mask, and
		420	there are a lot of shoddy libraries and programs (glib's threadpool for
		421	example) that can't properly initialise their signal masks.
		422
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		424
355	This is your standard select(2) backend. Not I<completely> standard, as	425	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	426	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	427	but if that fails, expect a fairly low limit on the number of fds when
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	451	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	452	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		453
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	454	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		455
		456	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		457	kernels).
		458
386	For few fds, this backend is a bit little slower than poll and select,	459	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	460	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	461	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	462	epoll scales either O(1) or O(active_fds).
390		463
391	The epoll syscalls are the most misdesigned of the more advanced	464	The epoll mechanism deserves honorable mention as the most misdesigned
392	event mechanisms: probelsm include silently dropping events in some	465	of the more advanced event mechanisms: mere annoyances include silently
393	hard-to-detect cases, requiring a system call per fd change, no fork	466	dropping file descriptors, requiring a system call per change per file
394	support, problems with dup and so on.	467	descriptor (and unnecessary guessing of parameters), problems with dup and
		468	so on. The biggest issue is fork races, however - if a program forks then
		469	I<both> parent and child process have to recreate the epoll set, which can
		470	take considerable time (one syscall per file descriptor) and is of course
		471	hard to detect.
395		472
396	Epoll is also notoriously buggy - embedding epoll fds should work, but	473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
397	of course doesn't, and epoll just loves to report events for totally	474	of course I<doesn't>, and epoll just loves to report events for totally
398	I<different> file descriptors (even already closed ones, so one cannot	475	I<different> file descriptors (even already closed ones, so one cannot
399	even remove them from the set) than registered in the set (especially	476	even remove them from the set) than registered in the set (especially
400	on SMP systems). Libev tries to counter these spurious notifications by	477	on SMP systems). Libev tries to counter these spurious notifications by
401	employing an additional generation counter and comparing that against the	478	employing an additional generation counter and comparing that against the
402	events to filter out spurious ones.	479	events to filter out spurious ones, recreating the set when required. Last
		480	not least, it also refuses to work with some file descriptors which work
		481	perfectly fine with C<select> (files, many character devices...).
403		482
404	While stopping, setting and starting an I/O watcher in the same iteration	483	While stopping, setting and starting an I/O watcher in the same iteration
405	will result in some caching, there is still a system call per such incident	484	will result in some caching, there is still a system call per such
406	(because the fd could point to a different file description now), so its	485	incident (because the same I<file descriptor> could point to a different
407	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	486	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
408	very well if you register events for both fds.	487	file descriptors might not work very well if you register events for both
		488	file descriptors.
409		489
410	Best performance from this backend is achieved by not unregistering all	490	Best performance from this backend is achieved by not unregistering all
411	watchers for a file descriptor until it has been closed, if possible,	491	watchers for a file descriptor until it has been closed, if possible,
412	i.e. keep at least one watcher active per fd at all times. Stopping and	492	i.e. keep at least one watcher active per fd at all times. Stopping and
413	starting a watcher (without re-setting it) also usually doesn't cause	493	starting a watcher (without re-setting it) also usually doesn't cause
414	extra overhead.	494	extra overhead. A fork can both result in spurious notifications as well
		495	as in libev having to destroy and recreate the epoll object, which can
		496	take considerable time and thus should be avoided.
		497
		498	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		499	faster than epoll for maybe up to a hundred file descriptors, depending on
		500	the usage. So sad.
415		501
416	While nominally embeddable in other event loops, this feature is broken in	502	While nominally embeddable in other event loops, this feature is broken in
417	all kernel versions tested so far.	503	all kernel versions tested so far.
418		504
419	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	505	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
420	C<EVBACKEND_POLL>.	506	C<EVBACKEND_POLL>.
421		507
422	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	508	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
423		509
424	Kqueue deserves special mention, as at the time of this writing, it was	510	Kqueue deserves special mention, as at the time of this writing, it
425	broken on all BSDs except NetBSD (usually it doesn't work reliably with	511	was broken on all BSDs except NetBSD (usually it doesn't work reliably
426	anything but sockets and pipes, except on Darwin, where of course it's	512	with anything but sockets and pipes, except on Darwin, where of course
427	completely useless). For this reason it's not being "auto-detected" unless	513	it's completely useless). Unlike epoll, however, whose brokenness
428	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	514	is by design, these kqueue bugs can (and eventually will) be fixed
429	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	515	without API changes to existing programs. For this reason it's not being
		516	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		517	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		518	system like NetBSD.
430		519
431	You still can embed kqueue into a normal poll or select backend and use it	520	You still can embed kqueue into a normal poll or select backend and use it
432	only for sockets (after having made sure that sockets work with kqueue on	521	only for sockets (after having made sure that sockets work with kqueue on
433	the target platform). See C<ev_embed> watchers for more info.	522	the target platform). See C<ev_embed> watchers for more info.
434		523
435	It scales in the same way as the epoll backend, but the interface to the	524	It scales in the same way as the epoll backend, but the interface to the
436	kernel is more efficient (which says nothing about its actual speed, of	525	kernel is more efficient (which says nothing about its actual speed, of
437	course). While stopping, setting and starting an I/O watcher does never	526	course). While stopping, setting and starting an I/O watcher does never
438	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	527	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
439	two event changes per incident. Support for C<fork ()> is very bad and it	528	two event changes per incident. Support for C<fork ()> is very bad (but
440	drops fds silently in similarly hard-to-detect cases.	529	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		530	cases
441		531
442	This backend usually performs well under most conditions.	532	This backend usually performs well under most conditions.
443		533
444	While nominally embeddable in other event loops, this doesn't work	534	While nominally embeddable in other event loops, this doesn't work
445	everywhere, so you might need to test for this. And since it is broken	535	everywhere, so you might need to test for this. And since it is broken
446	almost everywhere, you should only use it when you have a lot of sockets	536	almost everywhere, you should only use it when you have a lot of sockets
447	(for which it usually works), by embedding it into another event loop	537	(for which it usually works), by embedding it into another event loop
448	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	538	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
449	using it only for sockets.	539	also broken on OS X)) and, did I mention it, using it only for sockets.
450		540
451	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	541	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
452	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	542	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
453	C<NOTE_EOF>.	543	C<NOTE_EOF>.
454		544
…		…
474	might perform better.	564	might perform better.
475		565
476	On the positive side, with the exception of the spurious readiness	566	On the positive side, with the exception of the spurious readiness
477	notifications, this backend actually performed fully to specification	567	notifications, this backend actually performed fully to specification
478	in all tests and is fully embeddable, which is a rare feat among the	568	in all tests and is fully embeddable, which is a rare feat among the
479	OS-specific backends.	569	OS-specific backends (I vastly prefer correctness over speed hacks).
480		570
481	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	571	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
482	C<EVBACKEND_POLL>.	572	C<EVBACKEND_POLL>.
483		573
484	=item C<EVBACKEND_ALL>	574	=item C<EVBACKEND_ALL>
…		…
489		579
490	It is definitely not recommended to use this flag.	580	It is definitely not recommended to use this flag.
491		581
492	=back	582	=back
493		583
494	If one or more of these are or'ed into the flags value, then only these	584	If one or more of the backend flags are or'ed into the flags value,
495	backends will be tried (in the reverse order as listed here). If none are	585	then only these backends will be tried (in the reverse order as listed
496	specified, all backends in C<ev_recommended_backends ()> will be tried.	586	here). If none are specified, all backends in C<ev_recommended_backends
497		587	()> will be tried.
498	Example: This is the most typical usage.
499
500	if (!ev_default_loop (0))
501	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
502
503	Example: Restrict libev to the select and poll backends, and do not allow
504	environment settings to be taken into account:
505
506	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
507
508	Example: Use whatever libev has to offer, but make sure that kqueue is
509	used if available (warning, breaks stuff, best use only with your own
510	private event loop and only if you know the OS supports your types of
511	fds):
512
513	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
514
515	=item struct ev_loop *ev_loop_new (unsigned int flags)
516
517	Similar to C<ev_default_loop>, but always creates a new event loop that is
518	always distinct from the default loop. Unlike the default loop, it cannot
519	handle signal and child watchers, and attempts to do so will be greeted by
520	undefined behaviour (or a failed assertion if assertions are enabled).
521
522	Note that this function I<is> thread-safe, and the recommended way to use
523	libev with threads is indeed to create one loop per thread, and using the
524	default loop in the "main" or "initial" thread.
525		588
526	Example: Try to create a event loop that uses epoll and nothing else.	589	Example: Try to create a event loop that uses epoll and nothing else.
527		590
528	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
529	if (!epoller)	592	if (!epoller)
530	fatal ("no epoll found here, maybe it hides under your chair");	593	fatal ("no epoll found here, maybe it hides under your chair");
531		594
532	=item ev_default_destroy ()	595	=item ev_loop_destroy (loop)
533		596
534	Destroys the default loop again (frees all memory and kernel state	597	Destroys an event loop object (frees all memory and kernel state
535	etc.). None of the active event watchers will be stopped in the normal	598	etc.). None of the active event watchers will be stopped in the normal
536	sense, so e.g. C<ev_is_active> might still return true. It is your	599	sense, so e.g. C<ev_is_active> might still return true. It is your
537	responsibility to either stop all watchers cleanly yourself I<before>	600	responsibility to either stop all watchers cleanly yourself I<before>
538	calling this function, or cope with the fact afterwards (which is usually	601	calling this function, or cope with the fact afterwards (which is usually
539	the easiest thing, you can just ignore the watchers and/or C<free ()> them	602	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
541		604
542	Note that certain global state, such as signal state (and installed signal	605	Note that certain global state, such as signal state (and installed signal
543	handlers), will not be freed by this function, and related watchers (such	606	handlers), will not be freed by this function, and related watchers (such
544	as signal and child watchers) would need to be stopped manually.	607	as signal and child watchers) would need to be stopped manually.
545		608
546	In general it is not advisable to call this function except in the	609	This function is normally used on loop objects allocated by
547	rare occasion where you really need to free e.g. the signal handling	610	C<ev_loop_new>, but it can also be used on the default loop returned by
		611	C<ev_default_loop>, in which case it is not thread-safe.
		612
		613	Note that it is not advisable to call this function on the default loop
		614	except in the rare occasion where you really need to free it's resources.
548	pipe fds. If you need dynamically allocated loops it is better to use	615	If you need dynamically allocated loops it is better to use C<ev_loop_new>
549	C<ev_loop_new> and C<ev_loop_destroy>).	616	and C<ev_loop_destroy>.
550		617
551	=item ev_loop_destroy (loop)	618	=item ev_loop_fork (loop)
552		619
553	Like C<ev_default_destroy>, but destroys an event loop created by an
554	earlier call to C<ev_loop_new>.
555
556	=item ev_default_fork ()
557
558	This function sets a flag that causes subsequent C<ev_loop> iterations	620	This function sets a flag that causes subsequent C<ev_run> iterations to
559	to reinitialise the kernel state for backends that have one. Despite the	621	reinitialise the kernel state for backends that have one. Despite the
560	name, you can call it anytime, but it makes most sense after forking, in	622	name, you can call it anytime, but it makes most sense after forking, in
561	the child process (or both child and parent, but that again makes little	623	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
562	sense). You I<must> call it in the child before using any of the libev	624	child before resuming or calling C<ev_run>.
563	functions, and it will only take effect at the next C<ev_loop> iteration.	625
		626	Again, you I<have> to call it on I<any> loop that you want to re-use after
		627	a fork, I<even if you do not plan to use the loop in the parent>. This is
		628	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		629	during fork.
564		630
565	On the other hand, you only need to call this function in the child	631	On the other hand, you only need to call this function in the child
566	process if and only if you want to use the event library in the child. If	632	process if and only if you want to use the event loop in the child. If
567	you just fork+exec, you don't have to call it at all.	633	you just fork+exec or create a new loop in the child, you don't have to
		634	call it at all (in fact, C<epoll> is so badly broken that it makes a
		635	difference, but libev will usually detect this case on its own and do a
		636	costly reset of the backend).
568		637
569	The function itself is quite fast and it's usually not a problem to call	638	The function itself is quite fast and it's usually not a problem to call
570	it just in case after a fork. To make this easy, the function will fit in	639	it just in case after a fork.
571	quite nicely into a call to C<pthread_atfork>:
572		640
		641	Example: Automate calling C<ev_loop_fork> on the default loop when
		642	using pthreads.
		643
		644	static void
		645	post_fork_child (void)
		646	{
		647	ev_loop_fork (EV_DEFAULT);
		648	}
		649
		650	...
573	pthread_atfork (0, 0, ev_default_fork);	651	pthread_atfork (0, 0, post_fork_child);
574
575	=item ev_loop_fork (loop)
576
577	Like C<ev_default_fork>, but acts on an event loop created by
578	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
579	after fork that you want to re-use in the child, and how you do this is
580	entirely your own problem.
581		652
582	=item int ev_is_default_loop (loop)	653	=item int ev_is_default_loop (loop)
583		654
584	Returns true when the given loop is, in fact, the default loop, and false	655	Returns true when the given loop is, in fact, the default loop, and false
585	otherwise.	656	otherwise.
586		657
587	=item unsigned int ev_loop_count (loop)	658	=item unsigned int ev_iteration (loop)
588		659
589	Returns the count of loop iterations for the loop, which is identical to	660	Returns the current iteration count for the event loop, which is identical
590	the number of times libev did poll for new events. It starts at C<0> and	661	to the number of times libev did poll for new events. It starts at C<0>
591	happily wraps around with enough iterations.	662	and happily wraps around with enough iterations.
592		663
593	This value can sometimes be useful as a generation counter of sorts (it	664	This value can sometimes be useful as a generation counter of sorts (it
594	"ticks" the number of loop iterations), as it roughly corresponds with	665	"ticks" the number of loop iterations), as it roughly corresponds with
595	C<ev_prepare> and C<ev_check> calls.	666	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		667	prepare and check phases.
		668
		669	=item unsigned int ev_depth (loop)
		670
		671	Returns the number of times C<ev_run> was entered minus the number of
		672	times C<ev_run> was exited, in other words, the recursion depth.
		673
		674	Outside C<ev_run>, this number is zero. In a callback, this number is
		675	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		676	in which case it is higher.
		677
		678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		679	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		680	ungentleman-like behaviour unless it's really convenient.
596		681
597	=item unsigned int ev_backend (loop)	682	=item unsigned int ev_backend (loop)
598		683
599	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	684	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
600	use.	685	use.
…		…
609		694
610	=item ev_now_update (loop)	695	=item ev_now_update (loop)
611		696
612	Establishes the current time by querying the kernel, updating the time	697	Establishes the current time by querying the kernel, updating the time
613	returned by C<ev_now ()> in the progress. This is a costly operation and	698	returned by C<ev_now ()> in the progress. This is a costly operation and
614	is usually done automatically within C<ev_loop ()>.	699	is usually done automatically within C<ev_run ()>.
615		700
616	This function is rarely useful, but when some event callback runs for a	701	This function is rarely useful, but when some event callback runs for a
617	very long time without entering the event loop, updating libev's idea of	702	very long time without entering the event loop, updating libev's idea of
618	the current time is a good idea.	703	the current time is a good idea.
619		704
620	See also "The special problem of time updates" in the C<ev_timer> section.	705	See also L<The special problem of time updates> in the C<ev_timer> section.
621		706
		707	=item ev_suspend (loop)
		708
		709	=item ev_resume (loop)
		710
		711	These two functions suspend and resume an event loop, for use when the
		712	loop is not used for a while and timeouts should not be processed.
		713
		714	A typical use case would be an interactive program such as a game: When
		715	the user presses C<^Z> to suspend the game and resumes it an hour later it
		716	would be best to handle timeouts as if no time had actually passed while
		717	the program was suspended. This can be achieved by calling C<ev_suspend>
		718	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		719	C<ev_resume> directly afterwards to resume timer processing.
		720
		721	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		722	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		723	will be rescheduled (that is, they will lose any events that would have
		724	occurred while suspended).
		725
		726	After calling C<ev_suspend> you B<must not> call I<any> function on the
		727	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		728	without a previous call to C<ev_suspend>.
		729
		730	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		731	event loop time (see C<ev_now_update>).
		732
622	=item ev_loop (loop, int flags)	733	=item ev_run (loop, int flags)
623		734
624	Finally, this is it, the event handler. This function usually is called	735	Finally, this is it, the event handler. This function usually is called
625	after you initialised all your watchers and you want to start handling	736	after you have initialised all your watchers and you want to start
626	events.	737	handling events. It will ask the operating system for any new events, call
		738	the watcher callbacks, an then repeat the whole process indefinitely: This
		739	is why event loops are called I<loops>.
627		740
628	If the flags argument is specified as C<0>, it will not return until	741	If the flags argument is specified as C<0>, it will keep handling events
629	either no event watchers are active anymore or C<ev_unloop> was called.	742	until either no event watchers are active anymore or C<ev_break> was
		743	called.
630		744
631	Please note that an explicit C<ev_unloop> is usually better than	745	Please note that an explicit C<ev_break> is usually better than
632	relying on all watchers to be stopped when deciding when a program has	746	relying on all watchers to be stopped when deciding when a program has
633	finished (especially in interactive programs), but having a program	747	finished (especially in interactive programs), but having a program
634	that automatically loops as long as it has to and no longer by virtue	748	that automatically loops as long as it has to and no longer by virtue
635	of relying on its watchers stopping correctly, that is truly a thing of	749	of relying on its watchers stopping correctly, that is truly a thing of
636	beauty.	750	beauty.
637		751
638	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	752	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
639	those events and any already outstanding ones, but will not block your	753	those events and any already outstanding ones, but will not wait and
640	process in case there are no events and will return after one iteration of	754	block your process in case there are no events and will return after one
641	the loop.	755	iteration of the loop. This is sometimes useful to poll and handle new
		756	events while doing lengthy calculations, to keep the program responsive.
642		757
643	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	758	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
644	necessary) and will handle those and any already outstanding ones. It	759	necessary) and will handle those and any already outstanding ones. It
645	will block your process until at least one new event arrives (which could	760	will block your process until at least one new event arrives (which could
646	be an event internal to libev itself, so there is no guarentee that a	761	be an event internal to libev itself, so there is no guarantee that a
647	user-registered callback will be called), and will return after one	762	user-registered callback will be called), and will return after one
648	iteration of the loop.	763	iteration of the loop.
649		764
650	This is useful if you are waiting for some external event in conjunction	765	This is useful if you are waiting for some external event in conjunction
651	with something not expressible using other libev watchers (i.e. "roll your	766	with something not expressible using other libev watchers (i.e. "roll your
652	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	767	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
653	usually a better approach for this kind of thing.	768	usually a better approach for this kind of thing.
654		769
655	Here are the gory details of what C<ev_loop> does:	770	Here are the gory details of what C<ev_run> does:
656		771
		772	- Increment loop depth.
		773	- Reset the ev_break status.
657	- Before the first iteration, call any pending watchers.	774	- Before the first iteration, call any pending watchers.
		775	LOOP:
658	* If EVFLAG_FORKCHECK was used, check for a fork.	776	- If EVFLAG_FORKCHECK was used, check for a fork.
659	- If a fork was detected (by any means), queue and call all fork watchers.	777	- If a fork was detected (by any means), queue and call all fork watchers.
660	- Queue and call all prepare watchers.	778	- Queue and call all prepare watchers.
		779	- If ev_break was called, goto FINISH.
661	- If we have been forked, detach and recreate the kernel state	780	- If we have been forked, detach and recreate the kernel state
662	as to not disturb the other process.	781	as to not disturb the other process.
663	- Update the kernel state with all outstanding changes.	782	- Update the kernel state with all outstanding changes.
664	- Update the "event loop time" (ev_now ()).	783	- Update the "event loop time" (ev_now ()).
665	- Calculate for how long to sleep or block, if at all	784	- Calculate for how long to sleep or block, if at all
666	(active idle watchers, EVLOOP_NONBLOCK or not having	785	(active idle watchers, EVRUN_NOWAIT or not having
667	any active watchers at all will result in not sleeping).	786	any active watchers at all will result in not sleeping).
668	- Sleep if the I/O and timer collect interval say so.	787	- Sleep if the I/O and timer collect interval say so.
		788	- Increment loop iteration counter.
669	- Block the process, waiting for any events.	789	- Block the process, waiting for any events.
670	- Queue all outstanding I/O (fd) events.	790	- Queue all outstanding I/O (fd) events.
671	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	791	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
672	- Queue all expired timers.	792	- Queue all expired timers.
673	- Queue all expired periodics.	793	- Queue all expired periodics.
674	- Unless any events are pending now, queue all idle watchers.	794	- Queue all idle watchers with priority higher than that of pending events.
675	- Queue all check watchers.	795	- Queue all check watchers.
676	- Call all queued watchers in reverse order (i.e. check watchers first).	796	- Call all queued watchers in reverse order (i.e. check watchers first).
677	Signals and child watchers are implemented as I/O watchers, and will	797	Signals and child watchers are implemented as I/O watchers, and will
678	be handled here by queueing them when their watcher gets executed.	798	be handled here by queueing them when their watcher gets executed.
679	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	799	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
680	were used, or there are no active watchers, return, otherwise	800	were used, or there are no active watchers, goto FINISH, otherwise
681	continue with step *.	801	continue with step LOOP.
		802	FINISH:
		803	- Reset the ev_break status iff it was EVBREAK_ONE.
		804	- Decrement the loop depth.
		805	- Return.
682		806
683	Example: Queue some jobs and then loop until no events are outstanding	807	Example: Queue some jobs and then loop until no events are outstanding
684	anymore.	808	anymore.
685		809
686	... queue jobs here, make sure they register event watchers as long	810	... queue jobs here, make sure they register event watchers as long
687	... as they still have work to do (even an idle watcher will do..)	811	... as they still have work to do (even an idle watcher will do..)
688	ev_loop (my_loop, 0);	812	ev_run (my_loop, 0);
689	... jobs done or somebody called unloop. yeah!	813	... jobs done or somebody called unloop. yeah!
690		814
691	=item ev_unloop (loop, how)	815	=item ev_break (loop, how)
692		816
693	Can be used to make a call to C<ev_loop> return early (but only after it	817	Can be used to make a call to C<ev_run> return early (but only after it
694	has processed all outstanding events). The C<how> argument must be either	818	has processed all outstanding events). The C<how> argument must be either
695	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	819	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
696	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	820	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
697		821
698	This "unloop state" will be cleared when entering C<ev_loop> again.	822	This "unloop state" will be cleared when entering C<ev_run> again.
699		823
700	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	824	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
701		825
702	=item ev_ref (loop)	826	=item ev_ref (loop)
703		827
704	=item ev_unref (loop)	828	=item ev_unref (loop)
705		829
706	Ref/unref can be used to add or remove a reference count on the event	830	Ref/unref can be used to add or remove a reference count on the event
707	loop: Every watcher keeps one reference, and as long as the reference	831	loop: Every watcher keeps one reference, and as long as the reference
708	count is nonzero, C<ev_loop> will not return on its own.	832	count is nonzero, C<ev_run> will not return on its own.
709		833
710	If you have a watcher you never unregister that should not keep C<ev_loop>	834	This is useful when you have a watcher that you never intend to
711	from returning, call ev_unref() after starting, and ev_ref() before	835	unregister, but that nevertheless should not keep C<ev_run> from
		836	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
712	stopping it.	837	before stopping it.
713		838
714	As an example, libev itself uses this for its internal signal pipe: It is	839	As an example, libev itself uses this for its internal signal pipe: It
715	not visible to the libev user and should not keep C<ev_loop> from exiting	840	is not visible to the libev user and should not keep C<ev_run> from
716	if no event watchers registered by it are active. It is also an excellent	841	exiting if no event watchers registered by it are active. It is also an
717	way to do this for generic recurring timers or from within third-party	842	excellent way to do this for generic recurring timers or from within
718	libraries. Just remember to I<unref after start> and I<ref before stop>	843	third-party libraries. Just remember to I<unref after start> and I<ref
719	(but only if the watcher wasn't active before, or was active before,	844	before stop> (but only if the watcher wasn't active before, or was active
720	respectively).	845	before, respectively. Note also that libev might stop watchers itself
		846	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		847	in the callback).
721		848
722	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	849	Example: Create a signal watcher, but keep it from keeping C<ev_run>
723	running when nothing else is active.	850	running when nothing else is active.
724		851
725	ev_signal exitsig;	852	ev_signal exitsig;
726	ev_signal_init (&exitsig, sig_cb, SIGINT);	853	ev_signal_init (&exitsig, sig_cb, SIGINT);
727	ev_signal_start (loop, &exitsig);	854	ev_signal_start (loop, &exitsig);
…		…
754		881
755	By setting a higher I<io collect interval> you allow libev to spend more	882	By setting a higher I<io collect interval> you allow libev to spend more
756	time collecting I/O events, so you can handle more events per iteration,	883	time collecting I/O events, so you can handle more events per iteration,
757	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	884	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
758	C<ev_timer>) will be not affected. Setting this to a non-null value will	885	C<ev_timer>) will be not affected. Setting this to a non-null value will
759	introduce an additional C<ev_sleep ()> call into most loop iterations.	886	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		887	sleep time ensures that libev will not poll for I/O events more often then
		888	once per this interval, on average.
760		889
761	Likewise, by setting a higher I<timeout collect interval> you allow libev	890	Likewise, by setting a higher I<timeout collect interval> you allow libev
762	to spend more time collecting timeouts, at the expense of increased	891	to spend more time collecting timeouts, at the expense of increased
763	latency/jitter/inexactness (the watcher callback will be called	892	latency/jitter/inexactness (the watcher callback will be called
764	later). C<ev_io> watchers will not be affected. Setting this to a non-null	893	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
766		895
767	Many (busy) programs can usually benefit by setting the I/O collect	896	Many (busy) programs can usually benefit by setting the I/O collect
768	interval to a value near C<0.1> or so, which is often enough for	897	interval to a value near C<0.1> or so, which is often enough for
769	interactive servers (of course not for games), likewise for timeouts. It	898	interactive servers (of course not for games), likewise for timeouts. It
770	usually doesn't make much sense to set it to a lower value than C<0.01>,	899	usually doesn't make much sense to set it to a lower value than C<0.01>,
771	as this approaches the timing granularity of most systems.	900	as this approaches the timing granularity of most systems. Note that if
		901	you do transactions with the outside world and you can't increase the
		902	parallelity, then this setting will limit your transaction rate (if you
		903	need to poll once per transaction and the I/O collect interval is 0.01,
		904	then you can't do more than 100 transactions per second).
772		905
773	Setting the I<timeout collect interval> can improve the opportunity for	906	Setting the I<timeout collect interval> can improve the opportunity for
774	saving power, as the program will "bundle" timer callback invocations that	907	saving power, as the program will "bundle" timer callback invocations that
775	are "near" in time together, by delaying some, thus reducing the number of	908	are "near" in time together, by delaying some, thus reducing the number of
776	times the process sleeps and wakes up again. Another useful technique to	909	times the process sleeps and wakes up again. Another useful technique to
777	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	910	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
778	they fire on, say, one-second boundaries only.	911	they fire on, say, one-second boundaries only.
779		912
		913	Example: we only need 0.1s timeout granularity, and we wish not to poll
		914	more often than 100 times per second:
		915
		916	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		917	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		918
		919	=item ev_invoke_pending (loop)
		920
		921	This call will simply invoke all pending watchers while resetting their
		922	pending state. Normally, C<ev_run> does this automatically when required,
		923	but when overriding the invoke callback this call comes handy. This
		924	function can be invoked from a watcher - this can be useful for example
		925	when you want to do some lengthy calculation and want to pass further
		926	event handling to another thread (you still have to make sure only one
		927	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		928
		929	=item int ev_pending_count (loop)
		930
		931	Returns the number of pending watchers - zero indicates that no watchers
		932	are pending.
		933
		934	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		935
		936	This overrides the invoke pending functionality of the loop: Instead of
		937	invoking all pending watchers when there are any, C<ev_run> will call
		938	this callback instead. This is useful, for example, when you want to
		939	invoke the actual watchers inside another context (another thread etc.).
		940
		941	If you want to reset the callback, use C<ev_invoke_pending> as new
		942	callback.
		943
		944	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		945
		946	Sometimes you want to share the same loop between multiple threads. This
		947	can be done relatively simply by putting mutex_lock/unlock calls around
		948	each call to a libev function.
		949
		950	However, C<ev_run> can run an indefinite time, so it is not feasible
		951	to wait for it to return. One way around this is to wake up the event
		952	loop via C<ev_break> and C<av_async_send>, another way is to set these
		953	I<release> and I<acquire> callbacks on the loop.
		954
		955	When set, then C<release> will be called just before the thread is
		956	suspended waiting for new events, and C<acquire> is called just
		957	afterwards.
		958
		959	Ideally, C<release> will just call your mutex_unlock function, and
		960	C<acquire> will just call the mutex_lock function again.
		961
		962	While event loop modifications are allowed between invocations of
		963	C<release> and C<acquire> (that's their only purpose after all), no
		964	modifications done will affect the event loop, i.e. adding watchers will
		965	have no effect on the set of file descriptors being watched, or the time
		966	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		967	to take note of any changes you made.
		968
		969	In theory, threads executing C<ev_run> will be async-cancel safe between
		970	invocations of C<release> and C<acquire>.
		971
		972	See also the locking example in the C<THREADS> section later in this
		973	document.
		974
		975	=item ev_set_userdata (loop, void *data)
		976
		977	=item ev_userdata (loop)
		978
		979	Set and retrieve a single C<void *> associated with a loop. When
		980	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		981	C<0.>
		982
		983	These two functions can be used to associate arbitrary data with a loop,
		984	and are intended solely for the C<invoke_pending_cb>, C<release> and
		985	C<acquire> callbacks described above, but of course can be (ab-)used for
		986	any other purpose as well.
		987
780	=item ev_loop_verify (loop)	988	=item ev_verify (loop)
781		989
782	This function only does something when C<EV_VERIFY> support has been	990	This function only does something when C<EV_VERIFY> support has been
783	compiled in, which is the default for non-minimal builds. It tries to go	991	compiled in, which is the default for non-minimal builds. It tries to go
784	through all internal structures and checks them for validity. If anything	992	through all internal structures and checks them for validity. If anything
785	is found to be inconsistent, it will print an error message to standard	993	is found to be inconsistent, it will print an error message to standard
…		…
796		1004
797	In the following description, uppercase C<TYPE> in names stands for the	1005	In the following description, uppercase C<TYPE> in names stands for the
798	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1006	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
799	watchers and C<ev_io_start> for I/O watchers.	1007	watchers and C<ev_io_start> for I/O watchers.
800		1008
801	A watcher is a structure that you create and register to record your	1009	A watcher is an opaque structure that you allocate and register to record
802	interest in some event. For instance, if you want to wait for STDIN to	1010	your interest in some event. To make a concrete example, imagine you want
803	become readable, you would create an C<ev_io> watcher for that:	1011	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1012	for that:
804		1013
805	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1014	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
806	{	1015	{
807	ev_io_stop (w);	1016	ev_io_stop (w);
808	ev_unloop (loop, EVUNLOOP_ALL);	1017	ev_break (loop, EVBREAK_ALL);
809	}	1018	}
810		1019
811	struct ev_loop *loop = ev_default_loop (0);	1020	struct ev_loop *loop = ev_default_loop (0);
812		1021
813	ev_io stdin_watcher;	1022	ev_io stdin_watcher;
814		1023
815	ev_init (&stdin_watcher, my_cb);	1024	ev_init (&stdin_watcher, my_cb);
816	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1025	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
817	ev_io_start (loop, &stdin_watcher);	1026	ev_io_start (loop, &stdin_watcher);
818		1027
819	ev_loop (loop, 0);	1028	ev_run (loop, 0);
820		1029
821	As you can see, you are responsible for allocating the memory for your	1030	As you can see, you are responsible for allocating the memory for your
822	watcher structures (and it is I<usually> a bad idea to do this on the	1031	watcher structures (and it is I<usually> a bad idea to do this on the
823	stack).	1032	stack).
824		1033
825	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1034	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
826	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1035	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
827		1036
828	Each watcher structure must be initialised by a call to C<ev_init	1037	Each watcher structure must be initialised by a call to C<ev_init (watcher
829	(watcher *, callback)>, which expects a callback to be provided. This	1038	*, callback)>, which expects a callback to be provided. This callback is
830	callback gets invoked each time the event occurs (or, in the case of I/O	1039	invoked each time the event occurs (or, in the case of I/O watchers, each
831	watchers, each time the event loop detects that the file descriptor given	1040	time the event loop detects that the file descriptor given is readable
832	is readable and/or writable).	1041	and/or writable).
833		1042
834	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1043	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
835	macro to configure it, with arguments specific to the watcher type. There	1044	macro to configure it, with arguments specific to the watcher type. There
836	is also a macro to combine initialisation and setting in one call: C<<	1045	is also a macro to combine initialisation and setting in one call: C<<
837	ev_TYPE_init (watcher *, callback, ...) >>.	1046	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
860	=item C<EV_WRITE>	1069	=item C<EV_WRITE>
861		1070
862	The file descriptor in the C<ev_io> watcher has become readable and/or	1071	The file descriptor in the C<ev_io> watcher has become readable and/or
863	writable.	1072	writable.
864		1073
865	=item C<EV_TIMEOUT>	1074	=item C<EV_TIMER>
866		1075
867	The C<ev_timer> watcher has timed out.	1076	The C<ev_timer> watcher has timed out.
868		1077
869	=item C<EV_PERIODIC>	1078	=item C<EV_PERIODIC>
870		1079
…		…
888		1097
889	=item C<EV_PREPARE>	1098	=item C<EV_PREPARE>
890		1099
891	=item C<EV_CHECK>	1100	=item C<EV_CHECK>
892		1101
893	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1102	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
894	to gather new events, and all C<ev_check> watchers are invoked just after	1103	to gather new events, and all C<ev_check> watchers are invoked just after
895	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1104	C<ev_run> has gathered them, but before it invokes any callbacks for any
896	received events. Callbacks of both watcher types can start and stop as	1105	received events. Callbacks of both watcher types can start and stop as
897	many watchers as they want, and all of them will be taken into account	1106	many watchers as they want, and all of them will be taken into account
898	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1107	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
899	C<ev_loop> from blocking).	1108	C<ev_run> from blocking).
900		1109
901	=item C<EV_EMBED>	1110	=item C<EV_EMBED>
902		1111
903	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1112	The embedded event loop specified in the C<ev_embed> watcher needs attention.
904		1113
…		…
908	C<ev_fork>).	1117	C<ev_fork>).
909		1118
910	=item C<EV_ASYNC>	1119	=item C<EV_ASYNC>
911		1120
912	The given async watcher has been asynchronously notified (see C<ev_async>).	1121	The given async watcher has been asynchronously notified (see C<ev_async>).
		1122
		1123	=item C<EV_CUSTOM>
		1124
		1125	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1126	by libev users to signal watchers (e.g. via C<ev_feed_event>).
913		1127
914	=item C<EV_ERROR>	1128	=item C<EV_ERROR>
915		1129
916	An unspecified error has occurred, the watcher has been stopped. This might	1130	An unspecified error has occurred, the watcher has been stopped. This might
917	happen because the watcher could not be properly started because libev	1131	happen because the watcher could not be properly started because libev
…		…
930	programs, though, as the fd could already be closed and reused for another	1144	programs, though, as the fd could already be closed and reused for another
931	thing, so beware.	1145	thing, so beware.
932		1146
933	=back	1147	=back
934		1148
		1149	=head2 WATCHER STATES
		1150
		1151	There are various watcher states mentioned throughout this manual -
		1152	active, pending and so on. In this section these states and the rules to
		1153	transition between them will be described in more detail - and while these
		1154	rules might look complicated, they usually do "the right thing".
		1155
		1156	=over 4
		1157
		1158	=item initialiased
		1159
		1160	Before a watcher can be registered with the event looop it has to be
		1161	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1162	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1163
		1164	In this state it is simply some block of memory that is suitable for use
		1165	in an event loop. It can be moved around, freed, reused etc. at will.
		1166
		1167	=item started/running/active
		1168
		1169	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1170	property of the event loop, and is actively waiting for events. While in
		1171	this state it cannot be accessed (except in a few documented ways), moved,
		1172	freed or anything else - the only legal thing is to keep a pointer to it,
		1173	and call libev functions on it that are documented to work on active watchers.
		1174
		1175	=item pending
		1176
		1177	If a watcher is active and libev determines that an event it is interested
		1178	in has occurred (such as a timer expiring), it will become pending. It will
		1179	stay in this pending state until either it is stopped or its callback is
		1180	about to be invoked, so it is not normally pending inside the watcher
		1181	callback.
		1182
		1183	The watcher might or might not be active while it is pending (for example,
		1184	an expired non-repeating timer can be pending but no longer active). If it
		1185	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1186	but it is still property of the event loop at this time, so cannot be
		1187	moved, freed or reused. And if it is active the rules described in the
		1188	previous item still apply.
		1189
		1190	It is also possible to feed an event on a watcher that is not active (e.g.
		1191	via C<ev_feed_event>), in which case it becomes pending without being
		1192	active.
		1193
		1194	=item stopped
		1195
		1196	A watcher can be stopped implicitly by libev (in which case it might still
		1197	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1198	latter will clear any pending state the watcher might be in, regardless
		1199	of whether it was active or not, so stopping a watcher explicitly before
		1200	freeing it is often a good idea.
		1201
		1202	While stopped (and not pending) the watcher is essentially in the
		1203	initialised state, that is it can be reused, moved, modified in any way
		1204	you wish.
		1205
		1206	=back
		1207
935	=head2 GENERIC WATCHER FUNCTIONS	1208	=head2 GENERIC WATCHER FUNCTIONS
936		1209
937	=over 4	1210	=over 4
938		1211
939	=item C<ev_init> (ev_TYPE *watcher, callback)	1212	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
955		1228
956	ev_io w;	1229	ev_io w;
957	ev_init (&w, my_cb);	1230	ev_init (&w, my_cb);
958	ev_io_set (&w, STDIN_FILENO, EV_READ);	1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
959		1232
960	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
961		1234
962	This macro initialises the type-specific parts of a watcher. You need to	1235	This macro initialises the type-specific parts of a watcher. You need to
963	call C<ev_init> at least once before you call this macro, but you can	1236	call C<ev_init> at least once before you call this macro, but you can
964	call C<ev_TYPE_set> any number of times. You must not, however, call this	1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
965	macro on a watcher that is active (it can be pending, however, which is a	1238	macro on a watcher that is active (it can be pending, however, which is a
…		…
978		1251
979	Example: Initialise and set an C<ev_io> watcher in one step.	1252	Example: Initialise and set an C<ev_io> watcher in one step.
980		1253
981	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
982		1255
983	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
984		1257
985	Starts (activates) the given watcher. Only active watchers will receive	1258	Starts (activates) the given watcher. Only active watchers will receive
986	events. If the watcher is already active nothing will happen.	1259	events. If the watcher is already active nothing will happen.
987		1260
988	Example: Start the C<ev_io> watcher that is being abused as example in this	1261	Example: Start the C<ev_io> watcher that is being abused as example in this
989	whole section.	1262	whole section.
990		1263
991	ev_io_start (EV_DEFAULT_UC, &w);	1264	ev_io_start (EV_DEFAULT_UC, &w);
992		1265
993	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
994		1267
995	Stops the given watcher if active, and clears the pending status (whether	1268	Stops the given watcher if active, and clears the pending status (whether
996	the watcher was active or not).	1269	the watcher was active or not).
997		1270
998	It is possible that stopped watchers are pending - for example,	1271	It is possible that stopped watchers are pending - for example,
…		…
1023	=item ev_cb_set (ev_TYPE *watcher, callback)	1296	=item ev_cb_set (ev_TYPE *watcher, callback)
1024		1297
1025	Change the callback. You can change the callback at virtually any time	1298	Change the callback. You can change the callback at virtually any time
1026	(modulo threads).	1299	(modulo threads).
1027		1300
1028	=item ev_set_priority (ev_TYPE *watcher, priority)	1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1029		1302
1030	=item int ev_priority (ev_TYPE *watcher)	1303	=item int ev_priority (ev_TYPE *watcher)
1031		1304
1032	Set and query the priority of the watcher. The priority is a small	1305	Set and query the priority of the watcher. The priority is a small
1033	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1034	(default: C<-2>). Pending watchers with higher priority will be invoked	1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1035	before watchers with lower priority, but priority will not keep watchers	1308	before watchers with lower priority, but priority will not keep watchers
1036	from being executed (except for C<ev_idle> watchers).	1309	from being executed (except for C<ev_idle> watchers).
1037		1310
1038	This means that priorities are I<only> used for ordering callback
1039	invocation after new events have been received. This is useful, for
1040	example, to reduce latency after idling, or more often, to bind two
1041	watchers on the same event and make sure one is called first.
1042
1043	If you need to suppress invocation when higher priority events are pending	1311	If you need to suppress invocation when higher priority events are pending
1044	you need to look at C<ev_idle> watchers, which provide this functionality.	1312	you need to look at C<ev_idle> watchers, which provide this functionality.
1045		1313
1046	You I<must not> change the priority of a watcher as long as it is active or	1314	You I<must not> change the priority of a watcher as long as it is active or
1047	pending.	1315	pending.
1048
1049	The default priority used by watchers when no priority has been set is
1050	always C<0>, which is supposed to not be too high and not be too low :).
1051		1316
1052	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1053	fine, as long as you do not mind that the priority value you query might	1318	fine, as long as you do not mind that the priority value you query might
1054	or might not have been clamped to the valid range.	1319	or might not have been clamped to the valid range.
		1320
		1321	The default priority used by watchers when no priority has been set is
		1322	always C<0>, which is supposed to not be too high and not be too low :).
		1323
		1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1325	priorities.
1055		1326
1056	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1057		1328
1058	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1059	C<loop> nor C<revents> need to be valid as long as the watcher callback	1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1066	returns its C<revents> bitset (as if its callback was invoked). If the	1337	returns its C<revents> bitset (as if its callback was invoked). If the
1067	watcher isn't pending it does nothing and returns C<0>.	1338	watcher isn't pending it does nothing and returns C<0>.
1068		1339
1069	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1070	callback to be invoked, which can be accomplished with this function.	1341	callback to be invoked, which can be accomplished with this function.
		1342
		1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1344
		1345	Feeds the given event set into the event loop, as if the specified event
		1346	had happened for the specified watcher (which must be a pointer to an
		1347	initialised but not necessarily started event watcher). Obviously you must
		1348	not free the watcher as long as it has pending events.
		1349
		1350	Stopping the watcher, letting libev invoke it, or calling
		1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1352	not started in the first place.
		1353
		1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1355	functions that do not need a watcher.
1071		1356
1072	=back	1357	=back
1073		1358
1074		1359
1075	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1124	#include <stddef.h>	1409	#include <stddef.h>
1125		1410
1126	static void	1411	static void
1127	t1_cb (EV_P_ ev_timer *w, int revents)	1412	t1_cb (EV_P_ ev_timer *w, int revents)
1128	{	1413	{
1129	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1130	(((char *)w) - offsetof (struct my_biggy, t1));	1415	(((char *)w) - offsetof (struct my_biggy, t1));
1131	}	1416	}
1132		1417
1133	static void	1418	static void
1134	t2_cb (EV_P_ ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1135	{	1420	{
1136	struct my_biggy big = (struct my_biggy *	1421	struct my_biggy big = (struct my_biggy *)
1137	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1138	}	1423	}
		1424
		1425	=head2 WATCHER PRIORITY MODELS
		1426
		1427	Many event loops support I<watcher priorities>, which are usually small
		1428	integers that influence the ordering of event callback invocation
		1429	between watchers in some way, all else being equal.
		1430
		1431	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1432	description for the more technical details such as the actual priority
		1433	range.
		1434
		1435	There are two common ways how these these priorities are being interpreted
		1436	by event loops:
		1437
		1438	In the more common lock-out model, higher priorities "lock out" invocation
		1439	of lower priority watchers, which means as long as higher priority
		1440	watchers receive events, lower priority watchers are not being invoked.
		1441
		1442	The less common only-for-ordering model uses priorities solely to order
		1443	callback invocation within a single event loop iteration: Higher priority
		1444	watchers are invoked before lower priority ones, but they all get invoked
		1445	before polling for new events.
		1446
		1447	Libev uses the second (only-for-ordering) model for all its watchers
		1448	except for idle watchers (which use the lock-out model).
		1449
		1450	The rationale behind this is that implementing the lock-out model for
		1451	watchers is not well supported by most kernel interfaces, and most event
		1452	libraries will just poll for the same events again and again as long as
		1453	their callbacks have not been executed, which is very inefficient in the
		1454	common case of one high-priority watcher locking out a mass of lower
		1455	priority ones.
		1456
		1457	Static (ordering) priorities are most useful when you have two or more
		1458	watchers handling the same resource: a typical usage example is having an
		1459	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1460	timeouts. Under load, data might be received while the program handles
		1461	other jobs, but since timers normally get invoked first, the timeout
		1462	handler will be executed before checking for data. In that case, giving
		1463	the timer a lower priority than the I/O watcher ensures that I/O will be
		1464	handled first even under adverse conditions (which is usually, but not
		1465	always, what you want).
		1466
		1467	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1468	will only be executed when no same or higher priority watchers have
		1469	received events, they can be used to implement the "lock-out" model when
		1470	required.
		1471
		1472	For example, to emulate how many other event libraries handle priorities,
		1473	you can associate an C<ev_idle> watcher to each such watcher, and in
		1474	the normal watcher callback, you just start the idle watcher. The real
		1475	processing is done in the idle watcher callback. This causes libev to
		1476	continuously poll and process kernel event data for the watcher, but when
		1477	the lock-out case is known to be rare (which in turn is rare :), this is
		1478	workable.
		1479
		1480	Usually, however, the lock-out model implemented that way will perform
		1481	miserably under the type of load it was designed to handle. In that case,
		1482	it might be preferable to stop the real watcher before starting the
		1483	idle watcher, so the kernel will not have to process the event in case
		1484	the actual processing will be delayed for considerable time.
		1485
		1486	Here is an example of an I/O watcher that should run at a strictly lower
		1487	priority than the default, and which should only process data when no
		1488	other events are pending:
		1489
		1490	ev_idle idle; // actual processing watcher
		1491	ev_io io; // actual event watcher
		1492
		1493	static void
		1494	io_cb (EV_P_ ev_io *w, int revents)
		1495	{
		1496	// stop the I/O watcher, we received the event, but
		1497	// are not yet ready to handle it.
		1498	ev_io_stop (EV_A_ w);
		1499
		1500	// start the idle watcher to handle the actual event.
		1501	// it will not be executed as long as other watchers
		1502	// with the default priority are receiving events.
		1503	ev_idle_start (EV_A_ &idle);
		1504	}
		1505
		1506	static void
		1507	idle_cb (EV_P_ ev_idle *w, int revents)
		1508	{
		1509	// actual processing
		1510	read (STDIN_FILENO, ...);
		1511
		1512	// have to start the I/O watcher again, as
		1513	// we have handled the event
		1514	ev_io_start (EV_P_ &io);
		1515	}
		1516
		1517	// initialisation
		1518	ev_idle_init (&idle, idle_cb);
		1519	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1520	ev_io_start (EV_DEFAULT_ &io);
		1521
		1522	In the "real" world, it might also be beneficial to start a timer, so that
		1523	low-priority connections can not be locked out forever under load. This
		1524	enables your program to keep a lower latency for important connections
		1525	during short periods of high load, while not completely locking out less
		1526	important ones.
1139		1527
1140		1528
1141	=head1 WATCHER TYPES	1529	=head1 WATCHER TYPES
1142		1530
1143	This section describes each watcher in detail, but will not repeat	1531	This section describes each watcher in detail, but will not repeat
…		…
1169	descriptors to non-blocking mode is also usually a good idea (but not	1557	descriptors to non-blocking mode is also usually a good idea (but not
1170	required if you know what you are doing).	1558	required if you know what you are doing).
1171		1559
1172	If you cannot use non-blocking mode, then force the use of a	1560	If you cannot use non-blocking mode, then force the use of a
1173	known-to-be-good backend (at the time of this writing, this includes only	1561	known-to-be-good backend (at the time of this writing, this includes only
1174	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1563	descriptors for which non-blocking operation makes no sense (such as
		1564	files) - libev doesn't guarantee any specific behaviour in that case.
1175		1565
1176	Another thing you have to watch out for is that it is quite easy to	1566	Another thing you have to watch out for is that it is quite easy to
1177	receive "spurious" readiness notifications, that is your callback might	1567	receive "spurious" readiness notifications, that is your callback might
1178	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1568	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1179	because there is no data. Not only are some backends known to create a	1569	because there is no data. Not only are some backends known to create a
…		…
1244		1634
1245	So when you encounter spurious, unexplained daemon exits, make sure you	1635	So when you encounter spurious, unexplained daemon exits, make sure you
1246	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1636	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1247	somewhere, as that would have given you a big clue).	1637	somewhere, as that would have given you a big clue).
1248		1638
		1639	=head3 The special problem of accept()ing when you can't
		1640
		1641	Many implementations of the POSIX C<accept> function (for example,
		1642	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1643	connection from the pending queue in all error cases.
		1644
		1645	For example, larger servers often run out of file descriptors (because
		1646	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1647	rejecting the connection, leading to libev signalling readiness on
		1648	the next iteration again (the connection still exists after all), and
		1649	typically causing the program to loop at 100% CPU usage.
		1650
		1651	Unfortunately, the set of errors that cause this issue differs between
		1652	operating systems, there is usually little the app can do to remedy the
		1653	situation, and no known thread-safe method of removing the connection to
		1654	cope with overload is known (to me).
		1655
		1656	One of the easiest ways to handle this situation is to just ignore it
		1657	- when the program encounters an overload, it will just loop until the
		1658	situation is over. While this is a form of busy waiting, no OS offers an
		1659	event-based way to handle this situation, so it's the best one can do.
		1660
		1661	A better way to handle the situation is to log any errors other than
		1662	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1663	messages, and continue as usual, which at least gives the user an idea of
		1664	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1665	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1666	usage.
		1667
		1668	If your program is single-threaded, then you could also keep a dummy file
		1669	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1670	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1671	close that fd, and create a new dummy fd. This will gracefully refuse
		1672	clients under typical overload conditions.
		1673
		1674	The last way to handle it is to simply log the error and C<exit>, as
		1675	is often done with C<malloc> failures, but this results in an easy
		1676	opportunity for a DoS attack.
1249		1677
1250	=head3 Watcher-Specific Functions	1678	=head3 Watcher-Specific Functions
1251		1679
1252	=over 4	1680	=over 4
1253		1681
…		…
1285	...	1713	...
1286	struct ev_loop *loop = ev_default_init (0);	1714	struct ev_loop *loop = ev_default_init (0);
1287	ev_io stdin_readable;	1715	ev_io stdin_readable;
1288	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1716	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1289	ev_io_start (loop, &stdin_readable);	1717	ev_io_start (loop, &stdin_readable);
1290	ev_loop (loop, 0);	1718	ev_run (loop, 0);
1291		1719
1292		1720
1293	=head2 C<ev_timer> - relative and optionally repeating timeouts	1721	=head2 C<ev_timer> - relative and optionally repeating timeouts
1294		1722
1295	Timer watchers are simple relative timers that generate an event after a	1723	Timer watchers are simple relative timers that generate an event after a
…		…
1300	year, it will still time out after (roughly) one hour. "Roughly" because	1728	year, it will still time out after (roughly) one hour. "Roughly" because
1301	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1302	monotonic clock option helps a lot here).	1730	monotonic clock option helps a lot here).
1303		1731
1304	The callback is guaranteed to be invoked only I<after> its timeout has	1732	The callback is guaranteed to be invoked only I<after> its timeout has
1305	passed, but if multiple timers become ready during the same loop iteration	1733	passed (not I<at>, so on systems with very low-resolution clocks this
1306	then order of execution is undefined.	1734	might introduce a small delay). If multiple timers become ready during the
		1735	same loop iteration then the ones with earlier time-out values are invoked
		1736	before ones of the same priority with later time-out values (but this is
		1737	no longer true when a callback calls C<ev_run> recursively).
1307		1738
1308	=head3 Be smart about timeouts	1739	=head3 Be smart about timeouts
1309		1740
1310	Many real-world problems involve some kind of timeout, usually for error	1741	Many real-world problems involve some kind of timeout, usually for error
1311	recovery. A typical example is an HTTP request - if the other side hangs,	1742	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1355	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1786	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1356	member and C<ev_timer_again>.	1787	member and C<ev_timer_again>.
1357		1788
1358	At start:	1789	At start:
1359		1790
1360	ev_timer_init (timer, callback);	1791	ev_init (timer, callback);
1361	timer->repeat = 60.;	1792	timer->repeat = 60.;
1362	ev_timer_again (loop, timer);	1793	ev_timer_again (loop, timer);
1363		1794
1364	Each time there is some activity:	1795	Each time there is some activity:
1365		1796
…		…
1397	ev_tstamp timeout = last_activity + 60.;	1828	ev_tstamp timeout = last_activity + 60.;
1398		1829
1399	// if last_activity + 60. is older than now, we did time out	1830	// if last_activity + 60. is older than now, we did time out
1400	if (timeout < now)	1831	if (timeout < now)
1401	{	1832	{
1402	// timeout occured, take action	1833	// timeout occurred, take action
1403	}	1834	}
1404	else	1835	else
1405	{	1836	{
1406	// callback was invoked, but there was some activity, re-arm	1837	// callback was invoked, but there was some activity, re-arm
1407	// the watcher to fire in last_activity + 60, which is	1838	// the watcher to fire in last_activity + 60, which is
1408	// guaranteed to be in the future, so "again" is positive:	1839	// guaranteed to be in the future, so "again" is positive:
1409	w->again = timeout - now;	1840	w->repeat = timeout - now;
1410	ev_timer_again (EV_A_ w);	1841	ev_timer_again (EV_A_ w);
1411	}	1842	}
1412	}	1843	}
1413		1844
1414	To summarise the callback: first calculate the real timeout (defined	1845	To summarise the callback: first calculate the real timeout (defined
…		…
1427		1858
1428	To start the timer, simply initialise the watcher and set C<last_activity>	1859	To start the timer, simply initialise the watcher and set C<last_activity>
1429	to the current time (meaning we just have some activity :), then call the	1860	to the current time (meaning we just have some activity :), then call the
1430	callback, which will "do the right thing" and start the timer:	1861	callback, which will "do the right thing" and start the timer:
1431		1862
1432	ev_timer_init (timer, callback);	1863	ev_init (timer, callback);
1433	last_activity = ev_now (loop);	1864	last_activity = ev_now (loop);
1434	callback (loop, timer, EV_TIMEOUT);	1865	callback (loop, timer, EV_TIMER);
1435		1866
1436	And when there is some activity, simply store the current time in	1867	And when there is some activity, simply store the current time in
1437	C<last_activity>, no libev calls at all:	1868	C<last_activity>, no libev calls at all:
1438		1869
1439	last_actiivty = ev_now (loop);	1870	last_activity = ev_now (loop);
1440		1871
1441	This technique is slightly more complex, but in most cases where the	1872	This technique is slightly more complex, but in most cases where the
1442	time-out is unlikely to be triggered, much more efficient.	1873	time-out is unlikely to be triggered, much more efficient.
1443		1874
1444	Changing the timeout is trivial as well (if it isn't hard-coded in the	1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1482		1913
1483	=head3 The special problem of time updates	1914	=head3 The special problem of time updates
1484		1915
1485	Establishing the current time is a costly operation (it usually takes at	1916	Establishing the current time is a costly operation (it usually takes at
1486	least two system calls): EV therefore updates its idea of the current	1917	least two system calls): EV therefore updates its idea of the current
1487	time only before and after C<ev_loop> collects new events, which causes a	1918	time only before and after C<ev_run> collects new events, which causes a
1488	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1919	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1489	lots of events in one iteration.	1920	lots of events in one iteration.
1490		1921
1491	The relative timeouts are calculated relative to the C<ev_now ()>	1922	The relative timeouts are calculated relative to the C<ev_now ()>
1492	time. This is usually the right thing as this timestamp refers to the time	1923	time. This is usually the right thing as this timestamp refers to the time
…		…
1498		1929
1499	If the event loop is suspended for a long time, you can also force an	1930	If the event loop is suspended for a long time, you can also force an
1500	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1931	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1501	()>.	1932	()>.
1502		1933
		1934	=head3 The special problems of suspended animation
		1935
		1936	When you leave the server world it is quite customary to hit machines that
		1937	can suspend/hibernate - what happens to the clocks during such a suspend?
		1938
		1939	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1940	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1941	to run until the system is suspended, but they will not advance while the
		1942	system is suspended. That means, on resume, it will be as if the program
		1943	was frozen for a few seconds, but the suspend time will not be counted
		1944	towards C<ev_timer> when a monotonic clock source is used. The real time
		1945	clock advanced as expected, but if it is used as sole clocksource, then a
		1946	long suspend would be detected as a time jump by libev, and timers would
		1947	be adjusted accordingly.
		1948
		1949	I would not be surprised to see different behaviour in different between
		1950	operating systems, OS versions or even different hardware.
		1951
		1952	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1953	time jump in the monotonic clocks and the realtime clock. If the program
		1954	is suspended for a very long time, and monotonic clock sources are in use,
		1955	then you can expect C<ev_timer>s to expire as the full suspension time
		1956	will be counted towards the timers. When no monotonic clock source is in
		1957	use, then libev will again assume a timejump and adjust accordingly.
		1958
		1959	It might be beneficial for this latter case to call C<ev_suspend>
		1960	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1961	deterministic behaviour in this case (you can do nothing against
		1962	C<SIGSTOP>).
		1963
1503	=head3 Watcher-Specific Functions and Data Members	1964	=head3 Watcher-Specific Functions and Data Members
1504		1965
1505	=over 4	1966	=over 4
1506		1967
1507	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1968	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1530	If the timer is started but non-repeating, stop it (as if it timed out).	1991	If the timer is started but non-repeating, stop it (as if it timed out).
1531		1992
1532	If the timer is repeating, either start it if necessary (with the	1993	If the timer is repeating, either start it if necessary (with the
1533	C<repeat> value), or reset the running timer to the C<repeat> value.	1994	C<repeat> value), or reset the running timer to the C<repeat> value.
1534		1995
1535	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1996	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1536	usage example.	1997	usage example.
		1998
		1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2000
		2001	Returns the remaining time until a timer fires. If the timer is active,
		2002	then this time is relative to the current event loop time, otherwise it's
		2003	the timeout value currently configured.
		2004
		2005	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2006	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2007	will return C<4>. When the timer expires and is restarted, it will return
		2008	roughly C<7> (likely slightly less as callback invocation takes some time,
		2009	too), and so on.
1537		2010
1538	=item ev_tstamp repeat [read-write]	2011	=item ev_tstamp repeat [read-write]
1539		2012
1540	The current C<repeat> value. Will be used each time the watcher times out	2013	The current C<repeat> value. Will be used each time the watcher times out
1541	or C<ev_timer_again> is called, and determines the next timeout (if any),	2014	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1567	}	2040	}
1568		2041
1569	ev_timer mytimer;	2042	ev_timer mytimer;
1570	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2043	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1571	ev_timer_again (&mytimer); /* start timer */	2044	ev_timer_again (&mytimer); /* start timer */
1572	ev_loop (loop, 0);	2045	ev_run (loop, 0);
1573		2046
1574	// and in some piece of code that gets executed on any "activity":	2047	// and in some piece of code that gets executed on any "activity":
1575	// reset the timeout to start ticking again at 10 seconds	2048	// reset the timeout to start ticking again at 10 seconds
1576	ev_timer_again (&mytimer);	2049	ev_timer_again (&mytimer);
1577		2050
…		…
1579	=head2 C<ev_periodic> - to cron or not to cron?	2052	=head2 C<ev_periodic> - to cron or not to cron?
1580		2053
1581	Periodic watchers are also timers of a kind, but they are very versatile	2054	Periodic watchers are also timers of a kind, but they are very versatile
1582	(and unfortunately a bit complex).	2055	(and unfortunately a bit complex).
1583		2056
1584	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2057	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1585	but on wall clock time (absolute time). You can tell a periodic watcher	2058	relative time, the physical time that passes) but on wall clock time
1586	to trigger after some specific point in time. For example, if you tell a	2059	(absolute time, the thing you can read on your calender or clock). The
1587	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2060	difference is that wall clock time can run faster or slower than real
1588	+ 10.>, that is, an absolute time not a delay) and then reset your system	2061	time, and time jumps are not uncommon (e.g. when you adjust your
1589	clock to January of the previous year, then it will take more than year	2062	wrist-watch).
1590	to trigger the event (unlike an C<ev_timer>, which would still trigger
1591	roughly 10 seconds later as it uses a relative timeout).
1592		2063
		2064	You can tell a periodic watcher to trigger after some specific point
		2065	in time: for example, if you tell a periodic watcher to trigger "in 10
		2066	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2067	not a delay) and then reset your system clock to January of the previous
		2068	year, then it will take a year or more to trigger the event (unlike an
		2069	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2070	it, as it uses a relative timeout).
		2071
1593	C<ev_periodic>s can also be used to implement vastly more complex timers,	2072	C<ev_periodic> watchers can also be used to implement vastly more complex
1594	such as triggering an event on each "midnight, local time", or other	2073	timers, such as triggering an event on each "midnight, local time", or
1595	complicated rules.	2074	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2075	those cannot react to time jumps.
1596		2076
1597	As with timers, the callback is guaranteed to be invoked only when the	2077	As with timers, the callback is guaranteed to be invoked only when the
1598	time (C<at>) has passed, but if multiple periodic timers become ready	2078	point in time where it is supposed to trigger has passed. If multiple
1599	during the same loop iteration, then order of execution is undefined.	2079	timers become ready during the same loop iteration then the ones with
		2080	earlier time-out values are invoked before ones with later time-out values
		2081	(but this is no longer true when a callback calls C<ev_run> recursively).
1600		2082
1601	=head3 Watcher-Specific Functions and Data Members	2083	=head3 Watcher-Specific Functions and Data Members
1602		2084
1603	=over 4	2085	=over 4
1604		2086
1605	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2087	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1606		2088
1607	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2089	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1608		2090
1609	Lots of arguments, lets sort it out... There are basically three modes of	2091	Lots of arguments, let's sort it out... There are basically three modes of
1610	operation, and we will explain them from simplest to most complex:	2092	operation, and we will explain them from simplest to most complex:
1611		2093
1612	=over 4	2094	=over 4
1613		2095
1614	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2096	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1615		2097
1616	In this configuration the watcher triggers an event after the wall clock	2098	In this configuration the watcher triggers an event after the wall clock
1617	time C<at> has passed. It will not repeat and will not adjust when a time	2099	time C<offset> has passed. It will not repeat and will not adjust when a
1618	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2100	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1619	only run when the system clock reaches or surpasses this time.	2101	will be stopped and invoked when the system clock reaches or surpasses
		2102	this point in time.
1620		2103
1621	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2104	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1622		2105
1623	In this mode the watcher will always be scheduled to time out at the next	2106	In this mode the watcher will always be scheduled to time out at the next
1624	C<at + N * interval> time (for some integer N, which can also be negative)	2107	C<offset + N * interval> time (for some integer N, which can also be
1625	and then repeat, regardless of any time jumps.	2108	negative) and then repeat, regardless of any time jumps. The C<offset>
		2109	argument is merely an offset into the C<interval> periods.
1626		2110
1627	This can be used to create timers that do not drift with respect to the	2111	This can be used to create timers that do not drift with respect to the
1628	system clock, for example, here is a C<ev_periodic> that triggers each	2112	system clock, for example, here is an C<ev_periodic> that triggers each
1629	hour, on the hour:	2113	hour, on the hour (with respect to UTC):
1630		2114
1631	ev_periodic_set (&periodic, 0., 3600., 0);	2115	ev_periodic_set (&periodic, 0., 3600., 0);
1632		2116
1633	This doesn't mean there will always be 3600 seconds in between triggers,	2117	This doesn't mean there will always be 3600 seconds in between triggers,
1634	but only that the callback will be called when the system time shows a	2118	but only that the callback will be called when the system time shows a
1635	full hour (UTC), or more correctly, when the system time is evenly divisible	2119	full hour (UTC), or more correctly, when the system time is evenly divisible
1636	by 3600.	2120	by 3600.
1637		2121
1638	Another way to think about it (for the mathematically inclined) is that	2122	Another way to think about it (for the mathematically inclined) is that
1639	C<ev_periodic> will try to run the callback in this mode at the next possible	2123	C<ev_periodic> will try to run the callback in this mode at the next possible
1640	time where C<time = at (mod interval)>, regardless of any time jumps.	2124	time where C<time = offset (mod interval)>, regardless of any time jumps.
1641		2125
1642	For numerical stability it is preferable that the C<at> value is near	2126	For numerical stability it is preferable that the C<offset> value is near
1643	C<ev_now ()> (the current time), but there is no range requirement for	2127	C<ev_now ()> (the current time), but there is no range requirement for
1644	this value, and in fact is often specified as zero.	2128	this value, and in fact is often specified as zero.
1645		2129
1646	Note also that there is an upper limit to how often a timer can fire (CPU	2130	Note also that there is an upper limit to how often a timer can fire (CPU
1647	speed for example), so if C<interval> is very small then timing stability	2131	speed for example), so if C<interval> is very small then timing stability
1648	will of course deteriorate. Libev itself tries to be exact to be about one	2132	will of course deteriorate. Libev itself tries to be exact to be about one
1649	millisecond (if the OS supports it and the machine is fast enough).	2133	millisecond (if the OS supports it and the machine is fast enough).
1650		2134
1651	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2135	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1652		2136
1653	In this mode the values for C<interval> and C<at> are both being	2137	In this mode the values for C<interval> and C<offset> are both being
1654	ignored. Instead, each time the periodic watcher gets scheduled, the	2138	ignored. Instead, each time the periodic watcher gets scheduled, the
1655	reschedule callback will be called with the watcher as first, and the	2139	reschedule callback will be called with the watcher as first, and the
1656	current time as second argument.	2140	current time as second argument.
1657		2141
1658	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2142	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1659	ever, or make ANY event loop modifications whatsoever>.	2143	or make ANY other event loop modifications whatsoever, unless explicitly
		2144	allowed by documentation here>.
1660		2145
1661	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2146	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1662	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2147	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1663	only event loop modification you are allowed to do).	2148	only event loop modification you are allowed to do).
1664		2149
…		…
1694	a different time than the last time it was called (e.g. in a crond like	2179	a different time than the last time it was called (e.g. in a crond like
1695	program when the crontabs have changed).	2180	program when the crontabs have changed).
1696		2181
1697	=item ev_tstamp ev_periodic_at (ev_periodic *)	2182	=item ev_tstamp ev_periodic_at (ev_periodic *)
1698		2183
1699	When active, returns the absolute time that the watcher is supposed to	2184	When active, returns the absolute time that the watcher is supposed
1700	trigger next.	2185	to trigger next. This is not the same as the C<offset> argument to
		2186	C<ev_periodic_set>, but indeed works even in interval and manual
		2187	rescheduling modes.
1701		2188
1702	=item ev_tstamp offset [read-write]	2189	=item ev_tstamp offset [read-write]
1703		2190
1704	When repeating, this contains the offset value, otherwise this is the	2191	When repeating, this contains the offset value, otherwise this is the
1705	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2192	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2193	although libev might modify this value for better numerical stability).
1706		2194
1707	Can be modified any time, but changes only take effect when the periodic	2195	Can be modified any time, but changes only take effect when the periodic
1708	timer fires or C<ev_periodic_again> is being called.	2196	timer fires or C<ev_periodic_again> is being called.
1709		2197
1710	=item ev_tstamp interval [read-write]	2198	=item ev_tstamp interval [read-write]
…		…
1726	Example: Call a callback every hour, or, more precisely, whenever the	2214	Example: Call a callback every hour, or, more precisely, whenever the
1727	system time is divisible by 3600. The callback invocation times have	2215	system time is divisible by 3600. The callback invocation times have
1728	potentially a lot of jitter, but good long-term stability.	2216	potentially a lot of jitter, but good long-term stability.
1729		2217
1730	static void	2218	static void
1731	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2219	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1732	{	2220	{
1733	... its now a full hour (UTC, or TAI or whatever your clock follows)	2221	... its now a full hour (UTC, or TAI or whatever your clock follows)
1734	}	2222	}
1735		2223
1736	ev_periodic hourly_tick;	2224	ev_periodic hourly_tick;
…		…
1762	Signal watchers will trigger an event when the process receives a specific	2250	Signal watchers will trigger an event when the process receives a specific
1763	signal one or more times. Even though signals are very asynchronous, libev	2251	signal one or more times. Even though signals are very asynchronous, libev
1764	will try it's best to deliver signals synchronously, i.e. as part of the	2252	will try it's best to deliver signals synchronously, i.e. as part of the
1765	normal event processing, like any other event.	2253	normal event processing, like any other event.
1766		2254
1767	If you want signals asynchronously, just use C<sigaction> as you would	2255	If you want signals to be delivered truly asynchronously, just use
1768	do without libev and forget about sharing the signal. You can even use	2256	C<sigaction> as you would do without libev and forget about sharing
1769	C<ev_async> from a signal handler to synchronously wake up an event loop.	2257	the signal. You can even use C<ev_async> from a signal handler to
		2258	synchronously wake up an event loop.
1770		2259
1771	You can configure as many watchers as you like per signal. Only when the	2260	You can configure as many watchers as you like for the same signal, but
		2261	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2262	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2263	C<SIGINT> in both the default loop and another loop at the same time. At
		2264	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2265
1772	first watcher gets started will libev actually register a signal handler	2266	When the first watcher gets started will libev actually register something
1773	with the kernel (thus it coexists with your own signal handlers as long as	2267	with the kernel (thus it coexists with your own signal handlers as long as
1774	you don't register any with libev for the same signal). Similarly, when	2268	you don't register any with libev for the same signal).
1775	the last signal watcher for a signal is stopped, libev will reset the
1776	signal handler to SIG_DFL (regardless of what it was set to before).
1777		2269
1778	If possible and supported, libev will install its handlers with	2270	If possible and supported, libev will install its handlers with
1779	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2271	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1780	interrupted. If you have a problem with system calls getting interrupted by	2272	not be unduly interrupted. If you have a problem with system calls getting
1781	signals you can block all signals in an C<ev_check> watcher and unblock	2273	interrupted by signals you can block all signals in an C<ev_check> watcher
1782	them in an C<ev_prepare> watcher.	2274	and unblock them in an C<ev_prepare> watcher.
		2275
		2276	=head3 The special problem of inheritance over fork/execve/pthread_create
		2277
		2278	Both the signal mask (C<sigprocmask>) and the signal disposition
		2279	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2280	stopping it again), that is, libev might or might not block the signal,
		2281	and might or might not set or restore the installed signal handler.
		2282
		2283	While this does not matter for the signal disposition (libev never
		2284	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2285	C<execve>), this matters for the signal mask: many programs do not expect
		2286	certain signals to be blocked.
		2287
		2288	This means that before calling C<exec> (from the child) you should reset
		2289	the signal mask to whatever "default" you expect (all clear is a good
		2290	choice usually).
		2291
		2292	The simplest way to ensure that the signal mask is reset in the child is
		2293	to install a fork handler with C<pthread_atfork> that resets it. That will
		2294	catch fork calls done by libraries (such as the libc) as well.
		2295
		2296	In current versions of libev, the signal will not be blocked indefinitely
		2297	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2298	the window of opportunity for problems, it will not go away, as libev
		2299	I<has> to modify the signal mask, at least temporarily.
		2300
		2301	So I can't stress this enough: I<If you do not reset your signal mask when
		2302	you expect it to be empty, you have a race condition in your code>. This
		2303	is not a libev-specific thing, this is true for most event libraries.
1783		2304
1784	=head3 Watcher-Specific Functions and Data Members	2305	=head3 Watcher-Specific Functions and Data Members
1785		2306
1786	=over 4	2307	=over 4
1787		2308
…		…
1803	Example: Try to exit cleanly on SIGINT.	2324	Example: Try to exit cleanly on SIGINT.
1804		2325
1805	static void	2326	static void
1806	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2327	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1807	{	2328	{
1808	ev_unloop (loop, EVUNLOOP_ALL);	2329	ev_break (loop, EVBREAK_ALL);
1809	}	2330	}
1810		2331
1811	ev_signal signal_watcher;	2332	ev_signal signal_watcher;
1812	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2333	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1813	ev_signal_start (loop, &signal_watcher);	2334	ev_signal_start (loop, &signal_watcher);
…		…
1819	some child status changes (most typically when a child of yours dies or	2340	some child status changes (most typically when a child of yours dies or
1820	exits). It is permissible to install a child watcher I<after> the child	2341	exits). It is permissible to install a child watcher I<after> the child
1821	has been forked (which implies it might have already exited), as long	2342	has been forked (which implies it might have already exited), as long
1822	as the event loop isn't entered (or is continued from a watcher), i.e.,	2343	as the event loop isn't entered (or is continued from a watcher), i.e.,
1823	forking and then immediately registering a watcher for the child is fine,	2344	forking and then immediately registering a watcher for the child is fine,
1824	but forking and registering a watcher a few event loop iterations later is	2345	but forking and registering a watcher a few event loop iterations later or
1825	not.	2346	in the next callback invocation is not.
1826		2347
1827	Only the default event loop is capable of handling signals, and therefore	2348	Only the default event loop is capable of handling signals, and therefore
1828	you can only register child watchers in the default event loop.	2349	you can only register child watchers in the default event loop.
1829		2350
		2351	Due to some design glitches inside libev, child watchers will always be
		2352	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2353	libev)
		2354
1830	=head3 Process Interaction	2355	=head3 Process Interaction
1831		2356
1832	Libev grabs C<SIGCHLD> as soon as the default event loop is	2357	Libev grabs C<SIGCHLD> as soon as the default event loop is
1833	initialised. This is necessary to guarantee proper behaviour even if	2358	initialised. This is necessary to guarantee proper behaviour even if the
1834	the first child watcher is started after the child exits. The occurrence	2359	first child watcher is started after the child exits. The occurrence
1835	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2360	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1836	synchronously as part of the event loop processing. Libev always reaps all	2361	synchronously as part of the event loop processing. Libev always reaps all
1837	children, even ones not watched.	2362	children, even ones not watched.
1838		2363
1839	=head3 Overriding the Built-In Processing	2364	=head3 Overriding the Built-In Processing
…		…
1849	=head3 Stopping the Child Watcher	2374	=head3 Stopping the Child Watcher
1850		2375
1851	Currently, the child watcher never gets stopped, even when the	2376	Currently, the child watcher never gets stopped, even when the
1852	child terminates, so normally one needs to stop the watcher in the	2377	child terminates, so normally one needs to stop the watcher in the
1853	callback. Future versions of libev might stop the watcher automatically	2378	callback. Future versions of libev might stop the watcher automatically
1854	when a child exit is detected.	2379	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2380	problem).
1855		2381
1856	=head3 Watcher-Specific Functions and Data Members	2382	=head3 Watcher-Specific Functions and Data Members
1857		2383
1858	=over 4	2384	=over 4
1859		2385
…		…
1916		2442
1917		2443
1918	=head2 C<ev_stat> - did the file attributes just change?	2444	=head2 C<ev_stat> - did the file attributes just change?
1919		2445
1920	This watches a file system path for attribute changes. That is, it calls	2446	This watches a file system path for attribute changes. That is, it calls
1921	C<stat> regularly (or when the OS says it changed) and sees if it changed	2447	C<stat> on that path in regular intervals (or when the OS says it changed)
1922	compared to the last time, invoking the callback if it did.	2448	and sees if it changed compared to the last time, invoking the callback if
		2449	it did.
1923		2450
1924	The path does not need to exist: changing from "path exists" to "path does	2451	The path does not need to exist: changing from "path exists" to "path does
1925	not exist" is a status change like any other. The condition "path does	2452	not exist" is a status change like any other. The condition "path does not
1926	not exist" is signified by the C<st_nlink> field being zero (which is	2453	exist" (or more correctly "path cannot be stat'ed") is signified by the
1927	otherwise always forced to be at least one) and all the other fields of	2454	C<st_nlink> field being zero (which is otherwise always forced to be at
1928	the stat buffer having unspecified contents.	2455	least one) and all the other fields of the stat buffer having unspecified
		2456	contents.
1929		2457
1930	The path I<should> be absolute and I<must not> end in a slash. If it is	2458	The path I<must not> end in a slash or contain special components such as
		2459	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1931	relative and your working directory changes, the behaviour is undefined.	2460	your working directory changes, then the behaviour is undefined.
1932		2461
1933	Since there is no standard kernel interface to do this, the portable	2462	Since there is no portable change notification interface available, the
1934	implementation simply calls C<stat (2)> regularly on the path to see if	2463	portable implementation simply calls C<stat(2)> regularly on the path
1935	it changed somehow. You can specify a recommended polling interval for	2464	to see if it changed somehow. You can specify a recommended polling
1936	this case. If you specify a polling interval of C<0> (highly recommended!)	2465	interval for this case. If you specify a polling interval of C<0> (highly
1937	then a I<suitable, unspecified default> value will be used (which	2466	recommended!) then a I<suitable, unspecified default> value will be used
1938	you can expect to be around five seconds, although this might change	2467	(which you can expect to be around five seconds, although this might
1939	dynamically). Libev will also impose a minimum interval which is currently	2468	change dynamically). Libev will also impose a minimum interval which is
1940	around C<0.1>, but thats usually overkill.	2469	currently around C<0.1>, but that's usually overkill.
1941		2470
1942	This watcher type is not meant for massive numbers of stat watchers,	2471	This watcher type is not meant for massive numbers of stat watchers,
1943	as even with OS-supported change notifications, this can be	2472	as even with OS-supported change notifications, this can be
1944	resource-intensive.	2473	resource-intensive.
1945		2474
1946	At the time of this writing, the only OS-specific interface implemented	2475	At the time of this writing, the only OS-specific interface implemented
1947	is the Linux inotify interface (implementing kqueue support is left as	2476	is the Linux inotify interface (implementing kqueue support is left as an
1948	an exercise for the reader. Note, however, that the author sees no way	2477	exercise for the reader. Note, however, that the author sees no way of
1949	of implementing C<ev_stat> semantics with kqueue).	2478	implementing C<ev_stat> semantics with kqueue, except as a hint).
1950		2479
1951	=head3 ABI Issues (Largefile Support)	2480	=head3 ABI Issues (Largefile Support)
1952		2481
1953	Libev by default (unless the user overrides this) uses the default	2482	Libev by default (unless the user overrides this) uses the default
1954	compilation environment, which means that on systems with large file	2483	compilation environment, which means that on systems with large file
1955	support disabled by default, you get the 32 bit version of the stat	2484	support disabled by default, you get the 32 bit version of the stat
1956	structure. When using the library from programs that change the ABI to	2485	structure. When using the library from programs that change the ABI to
1957	use 64 bit file offsets the programs will fail. In that case you have to	2486	use 64 bit file offsets the programs will fail. In that case you have to
1958	compile libev with the same flags to get binary compatibility. This is	2487	compile libev with the same flags to get binary compatibility. This is
1959	obviously the case with any flags that change the ABI, but the problem is	2488	obviously the case with any flags that change the ABI, but the problem is
1960	most noticeably disabled with ev_stat and large file support.	2489	most noticeably displayed with ev_stat and large file support.
1961		2490
1962	The solution for this is to lobby your distribution maker to make large	2491	The solution for this is to lobby your distribution maker to make large
1963	file interfaces available by default (as e.g. FreeBSD does) and not	2492	file interfaces available by default (as e.g. FreeBSD does) and not
1964	optional. Libev cannot simply switch on large file support because it has	2493	optional. Libev cannot simply switch on large file support because it has
1965	to exchange stat structures with application programs compiled using the	2494	to exchange stat structures with application programs compiled using the
1966	default compilation environment.	2495	default compilation environment.
1967		2496
1968	=head3 Inotify and Kqueue	2497	=head3 Inotify and Kqueue
1969		2498
1970	When C<inotify (7)> support has been compiled into libev (generally	2499	When C<inotify (7)> support has been compiled into libev and present at
1971	only available with Linux 2.6.25 or above due to bugs in earlier	2500	runtime, it will be used to speed up change detection where possible. The
1972	implementations) and present at runtime, it will be used to speed up	2501	inotify descriptor will be created lazily when the first C<ev_stat>
1973	change detection where possible. The inotify descriptor will be created	2502	watcher is being started.
1974	lazily when the first C<ev_stat> watcher is being started.
1975		2503
1976	Inotify presence does not change the semantics of C<ev_stat> watchers	2504	Inotify presence does not change the semantics of C<ev_stat> watchers
1977	except that changes might be detected earlier, and in some cases, to avoid	2505	except that changes might be detected earlier, and in some cases, to avoid
1978	making regular C<stat> calls. Even in the presence of inotify support	2506	making regular C<stat> calls. Even in the presence of inotify support
1979	there are many cases where libev has to resort to regular C<stat> polling,	2507	there are many cases where libev has to resort to regular C<stat> polling,
1980	but as long as the path exists, libev usually gets away without polling.	2508	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2509	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2510	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2511	xfs are fully working) libev usually gets away without polling.
1981		2512
1982	There is no support for kqueue, as apparently it cannot be used to	2513	There is no support for kqueue, as apparently it cannot be used to
1983	implement this functionality, due to the requirement of having a file	2514	implement this functionality, due to the requirement of having a file
1984	descriptor open on the object at all times, and detecting renames, unlinks	2515	descriptor open on the object at all times, and detecting renames, unlinks
1985	etc. is difficult.	2516	etc. is difficult.
1986		2517
		2518	=head3 C<stat ()> is a synchronous operation
		2519
		2520	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2521	the process. The exception are C<ev_stat> watchers - those call C<stat
		2522	()>, which is a synchronous operation.
		2523
		2524	For local paths, this usually doesn't matter: unless the system is very
		2525	busy or the intervals between stat's are large, a stat call will be fast,
		2526	as the path data is usually in memory already (except when starting the
		2527	watcher).
		2528
		2529	For networked file systems, calling C<stat ()> can block an indefinite
		2530	time due to network issues, and even under good conditions, a stat call
		2531	often takes multiple milliseconds.
		2532
		2533	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2534	paths, although this is fully supported by libev.
		2535
1987	=head3 The special problem of stat time resolution	2536	=head3 The special problem of stat time resolution
1988		2537
1989	The C<stat ()> system call only supports full-second resolution portably, and	2538	The C<stat ()> system call only supports full-second resolution portably,
1990	even on systems where the resolution is higher, most file systems still	2539	and even on systems where the resolution is higher, most file systems
1991	only support whole seconds.	2540	still only support whole seconds.
1992		2541
1993	That means that, if the time is the only thing that changes, you can	2542	That means that, if the time is the only thing that changes, you can
1994	easily miss updates: on the first update, C<ev_stat> detects a change and	2543	easily miss updates: on the first update, C<ev_stat> detects a change and
1995	calls your callback, which does something. When there is another update	2544	calls your callback, which does something. When there is another update
1996	within the same second, C<ev_stat> will be unable to detect unless the	2545	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2139		2688
2140	=head3 Watcher-Specific Functions and Data Members	2689	=head3 Watcher-Specific Functions and Data Members
2141		2690
2142	=over 4	2691	=over 4
2143		2692
2144	=item ev_idle_init (ev_signal *, callback)	2693	=item ev_idle_init (ev_idle *, callback)
2145		2694
2146	Initialises and configures the idle watcher - it has no parameters of any	2695	Initialises and configures the idle watcher - it has no parameters of any
2147	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2696	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2148	believe me.	2697	believe me.
2149		2698
…		…
2162	// no longer anything immediate to do.	2711	// no longer anything immediate to do.
2163	}	2712	}
2164		2713
2165	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2714	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2166	ev_idle_init (idle_watcher, idle_cb);	2715	ev_idle_init (idle_watcher, idle_cb);
2167	ev_idle_start (loop, idle_cb);	2716	ev_idle_start (loop, idle_watcher);
2168		2717
2169		2718
2170	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2719	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2171		2720
2172	Prepare and check watchers are usually (but not always) used in pairs:	2721	Prepare and check watchers are usually (but not always) used in pairs:
2173	prepare watchers get invoked before the process blocks and check watchers	2722	prepare watchers get invoked before the process blocks and check watchers
2174	afterwards.	2723	afterwards.
2175		2724
2176	You I<must not> call C<ev_loop> or similar functions that enter	2725	You I<must not> call C<ev_run> or similar functions that enter
2177	the current event loop from either C<ev_prepare> or C<ev_check>	2726	the current event loop from either C<ev_prepare> or C<ev_check>
2178	watchers. Other loops than the current one are fine, however. The	2727	watchers. Other loops than the current one are fine, however. The
2179	rationale behind this is that you do not need to check for recursion in	2728	rationale behind this is that you do not need to check for recursion in
2180	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2729	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2181	C<ev_check> so if you have one watcher of each kind they will always be	2730	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2265	struct pollfd fds [nfd];	2814	struct pollfd fds [nfd];
2266	// actual code will need to loop here and realloc etc.	2815	// actual code will need to loop here and realloc etc.
2267	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2816	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2268		2817
2269	/* the callback is illegal, but won't be called as we stop during check */	2818	/* the callback is illegal, but won't be called as we stop during check */
2270	ev_timer_init (&tw, 0, timeout * 1e-3);	2819	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2271	ev_timer_start (loop, &tw);	2820	ev_timer_start (loop, &tw);
2272		2821
2273	// create one ev_io per pollfd	2822	// create one ev_io per pollfd
2274	for (int i = 0; i < nfd; ++i)	2823	for (int i = 0; i < nfd; ++i)
2275	{	2824	{
…		…
2349		2898
2350	if (timeout >= 0)	2899	if (timeout >= 0)
2351	// create/start timer	2900	// create/start timer
2352		2901
2353	// poll	2902	// poll
2354	ev_loop (EV_A_ 0);	2903	ev_run (EV_A_ 0);
2355		2904
2356	// stop timer again	2905	// stop timer again
2357	if (timeout >= 0)	2906	if (timeout >= 0)
2358	ev_timer_stop (EV_A_ &to);	2907	ev_timer_stop (EV_A_ &to);
2359		2908
…		…
2388	some fds have to be watched and handled very quickly (with low latency),	2937	some fds have to be watched and handled very quickly (with low latency),
2389	and even priorities and idle watchers might have too much overhead. In	2938	and even priorities and idle watchers might have too much overhead. In
2390	this case you would put all the high priority stuff in one loop and all	2939	this case you would put all the high priority stuff in one loop and all
2391	the rest in a second one, and embed the second one in the first.	2940	the rest in a second one, and embed the second one in the first.
2392		2941
2393	As long as the watcher is active, the callback will be invoked every time	2942	As long as the watcher is active, the callback will be invoked every
2394	there might be events pending in the embedded loop. The callback must then	2943	time there might be events pending in the embedded loop. The callback
2395	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2944	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2396	their callbacks (you could also start an idle watcher to give the embedded	2945	sweep and invoke their callbacks (the callback doesn't need to invoke the
2397	loop strictly lower priority for example). You can also set the callback	2946	C<ev_embed_sweep> function directly, it could also start an idle watcher
2398	to C<0>, in which case the embed watcher will automatically execute the	2947	to give the embedded loop strictly lower priority for example).
2399	embedded loop sweep.
2400		2948
2401	As long as the watcher is started it will automatically handle events. The	2949	You can also set the callback to C<0>, in which case the embed watcher
2402	callback will be invoked whenever some events have been handled. You can	2950	will automatically execute the embedded loop sweep whenever necessary.
2403	set the callback to C<0> to avoid having to specify one if you are not
2404	interested in that.
2405		2951
2406	Also, there have not currently been made special provisions for forking:	2952	Fork detection will be handled transparently while the C<ev_embed> watcher
2407	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2953	is active, i.e., the embedded loop will automatically be forked when the
2408	but you will also have to stop and restart any C<ev_embed> watchers	2954	embedding loop forks. In other cases, the user is responsible for calling
2409	yourself - but you can use a fork watcher to handle this automatically,	2955	C<ev_loop_fork> on the embedded loop.
2410	and future versions of libev might do just that.
2411		2956
2412	Unfortunately, not all backends are embeddable: only the ones returned by	2957	Unfortunately, not all backends are embeddable: only the ones returned by
2413	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2958	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2414	portable one.	2959	portable one.
2415		2960
…		…
2441	if you do not want that, you need to temporarily stop the embed watcher).	2986	if you do not want that, you need to temporarily stop the embed watcher).
2442		2987
2443	=item ev_embed_sweep (loop, ev_embed *)	2988	=item ev_embed_sweep (loop, ev_embed *)
2444		2989
2445	Make a single, non-blocking sweep over the embedded loop. This works	2990	Make a single, non-blocking sweep over the embedded loop. This works
2446	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2991	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2447	appropriate way for embedded loops.	2992	appropriate way for embedded loops.
2448		2993
2449	=item struct ev_loop *other [read-only]	2994	=item struct ev_loop *other [read-only]
2450		2995
2451	The embedded event loop.	2996	The embedded event loop.
…		…
2509	event loop blocks next and before C<ev_check> watchers are being called,	3054	event loop blocks next and before C<ev_check> watchers are being called,
2510	and only in the child after the fork. If whoever good citizen calling	3055	and only in the child after the fork. If whoever good citizen calling
2511	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3056	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2512	handlers will be invoked, too, of course.	3057	handlers will be invoked, too, of course.
2513		3058
		3059	=head3 The special problem of life after fork - how is it possible?
		3060
		3061	Most uses of C<fork()> consist of forking, then some simple calls to set
		3062	up/change the process environment, followed by a call to C<exec()>. This
		3063	sequence should be handled by libev without any problems.
		3064
		3065	This changes when the application actually wants to do event handling
		3066	in the child, or both parent in child, in effect "continuing" after the
		3067	fork.
		3068
		3069	The default mode of operation (for libev, with application help to detect
		3070	forks) is to duplicate all the state in the child, as would be expected
		3071	when I<either> the parent I<or> the child process continues.
		3072
		3073	When both processes want to continue using libev, then this is usually the
		3074	wrong result. In that case, usually one process (typically the parent) is
		3075	supposed to continue with all watchers in place as before, while the other
		3076	process typically wants to start fresh, i.e. without any active watchers.
		3077
		3078	The cleanest and most efficient way to achieve that with libev is to
		3079	simply create a new event loop, which of course will be "empty", and
		3080	use that for new watchers. This has the advantage of not touching more
		3081	memory than necessary, and thus avoiding the copy-on-write, and the
		3082	disadvantage of having to use multiple event loops (which do not support
		3083	signal watchers).
		3084
		3085	When this is not possible, or you want to use the default loop for
		3086	other reasons, then in the process that wants to start "fresh", call
		3087	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3088	Destroying the default loop will "orphan" (not stop) all registered
		3089	watchers, so you have to be careful not to execute code that modifies
		3090	those watchers. Note also that in that case, you have to re-register any
		3091	signal watchers.
		3092
2514	=head3 Watcher-Specific Functions and Data Members	3093	=head3 Watcher-Specific Functions and Data Members
2515		3094
2516	=over 4	3095	=over 4
2517		3096
2518	=item ev_fork_init (ev_signal *, callback)	3097	=item ev_fork_init (ev_signal *, callback)
…		…
2522	believe me.	3101	believe me.
2523		3102
2524	=back	3103	=back
2525		3104
2526		3105
2527	=head2 C<ev_async> - how to wake up another event loop	3106	=head2 C<ev_async> - how to wake up an event loop
2528		3107
2529	In general, you cannot use an C<ev_loop> from multiple threads or other	3108	In general, you cannot use an C<ev_run> from multiple threads or other
2530	asynchronous sources such as signal handlers (as opposed to multiple event	3109	asynchronous sources such as signal handlers (as opposed to multiple event
2531	loops - those are of course safe to use in different threads).	3110	loops - those are of course safe to use in different threads).
2532		3111
2533	Sometimes, however, you need to wake up another event loop you do not	3112	Sometimes, however, you need to wake up an event loop you do not control,
2534	control, for example because it belongs to another thread. This is what	3113	for example because it belongs to another thread. This is what C<ev_async>
2535	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3114	watchers do: as long as the C<ev_async> watcher is active, you can signal
2536	can signal it by calling C<ev_async_send>, which is thread- and signal	3115	it by calling C<ev_async_send>, which is thread- and signal safe.
2537	safe.
2538		3116
2539	This functionality is very similar to C<ev_signal> watchers, as signals,	3117	This functionality is very similar to C<ev_signal> watchers, as signals,
2540	too, are asynchronous in nature, and signals, too, will be compressed	3118	too, are asynchronous in nature, and signals, too, will be compressed
2541	(i.e. the number of callback invocations may be less than the number of	3119	(i.e. the number of callback invocations may be less than the number of
2542	C<ev_async_sent> calls).	3120	C<ev_async_sent> calls).
…		…
2547	=head3 Queueing	3125	=head3 Queueing
2548		3126
2549	C<ev_async> does not support queueing of data in any way. The reason	3127	C<ev_async> does not support queueing of data in any way. The reason
2550	is that the author does not know of a simple (or any) algorithm for a	3128	is that the author does not know of a simple (or any) algorithm for a
2551	multiple-writer-single-reader queue that works in all cases and doesn't	3129	multiple-writer-single-reader queue that works in all cases and doesn't
2552	need elaborate support such as pthreads.	3130	need elaborate support such as pthreads or unportable memory access
		3131	semantics.
2553		3132
2554	That means that if you want to queue data, you have to provide your own	3133	That means that if you want to queue data, you have to provide your own
2555	queue. But at least I can tell you how to implement locking around your	3134	queue. But at least I can tell you how to implement locking around your
2556	queue:	3135	queue:
2557		3136
…		…
2635	=over 4	3214	=over 4
2636		3215
2637	=item ev_async_init (ev_async *, callback)	3216	=item ev_async_init (ev_async *, callback)
2638		3217
2639	Initialises and configures the async watcher - it has no parameters of any	3218	Initialises and configures the async watcher - it has no parameters of any
2640	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3219	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2641	trust me.	3220	trust me.
2642		3221
2643	=item ev_async_send (loop, ev_async *)	3222	=item ev_async_send (loop, ev_async *)
2644		3223
2645	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3224	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2646	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3225	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2647	C<ev_feed_event>, this call is safe to do from other threads, signal or	3226	C<ev_feed_event>, this call is safe to do from other threads, signal or
2648	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3227	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2649	section below on what exactly this means).	3228	section below on what exactly this means).
2650		3229
		3230	Note that, as with other watchers in libev, multiple events might get
		3231	compressed into a single callback invocation (another way to look at this
		3232	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3233	reset when the event loop detects that).
		3234
2651	This call incurs the overhead of a system call only once per loop iteration,	3235	This call incurs the overhead of a system call only once per event loop
2652	so while the overhead might be noticeable, it doesn't apply to repeated	3236	iteration, so while the overhead might be noticeable, it doesn't apply to
2653	calls to C<ev_async_send>.	3237	repeated calls to C<ev_async_send> for the same event loop.
2654		3238
2655	=item bool = ev_async_pending (ev_async *)	3239	=item bool = ev_async_pending (ev_async *)
2656		3240
2657	Returns a non-zero value when C<ev_async_send> has been called on the	3241	Returns a non-zero value when C<ev_async_send> has been called on the
2658	watcher but the event has not yet been processed (or even noted) by the	3242	watcher but the event has not yet been processed (or even noted) by the
…		…
2661	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3245	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2662	the loop iterates next and checks for the watcher to have become active,	3246	the loop iterates next and checks for the watcher to have become active,
2663	it will reset the flag again. C<ev_async_pending> can be used to very	3247	it will reset the flag again. C<ev_async_pending> can be used to very
2664	quickly check whether invoking the loop might be a good idea.	3248	quickly check whether invoking the loop might be a good idea.
2665		3249
2666	Not that this does I<not> check whether the watcher itself is pending, only	3250	Not that this does I<not> check whether the watcher itself is pending,
2667	whether it has been requested to make this watcher pending.	3251	only whether it has been requested to make this watcher pending: there
		3252	is a time window between the event loop checking and resetting the async
		3253	notification, and the callback being invoked.
2668		3254
2669	=back	3255	=back
2670		3256
2671		3257
2672	=head1 OTHER FUNCTIONS	3258	=head1 OTHER FUNCTIONS
…		…
2689		3275
2690	If C<timeout> is less than 0, then no timeout watcher will be	3276	If C<timeout> is less than 0, then no timeout watcher will be
2691	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3277	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2692	repeat = 0) will be started. C<0> is a valid timeout.	3278	repeat = 0) will be started. C<0> is a valid timeout.
2693		3279
2694	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3280	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2695	passed an C<revents> set like normal event callbacks (a combination of	3281	passed an C<revents> set like normal event callbacks (a combination of
2696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3282	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2697	value passed to C<ev_once>. Note that it is possible to receive I<both>	3283	value passed to C<ev_once>. Note that it is possible to receive I<both>
2698	a timeout and an io event at the same time - you probably should give io	3284	a timeout and an io event at the same time - you probably should give io
2699	events precedence.	3285	events precedence.
2700		3286
2701	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3287	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2702		3288
2703	static void stdin_ready (int revents, void *arg)	3289	static void stdin_ready (int revents, void *arg)
2704	{	3290	{
2705	if (revents & EV_READ)	3291	if (revents & EV_READ)
2706	/* stdin might have data for us, joy! */;	3292	/* stdin might have data for us, joy! */;
2707	else if (revents & EV_TIMEOUT)	3293	else if (revents & EV_TIMER)
2708	/* doh, nothing entered */;	3294	/* doh, nothing entered */;
2709	}	3295	}
2710		3296
2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2712		3298
2713	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2714
2715	Feeds the given event set into the event loop, as if the specified event
2716	had happened for the specified watcher (which must be a pointer to an
2717	initialised but not necessarily started event watcher).
2718
2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3299	=item ev_feed_fd_event (loop, int fd, int revents)
2720		3300
2721	Feed an event on the given fd, as if a file descriptor backend detected	3301	Feed an event on the given fd, as if a file descriptor backend detected
2722	the given events it.	3302	the given events it.
2723		3303
2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3304	=item ev_feed_signal_event (loop, int signum)
2725		3305
2726	Feed an event as if the given signal occurred (C<loop> must be the default	3306	Feed an event as if the given signal occurred (C<loop> must be the default
2727	loop!).	3307	loop!).
2728		3308
2729	=back	3309	=back
…		…
2809		3389
2810	=over 4	3390	=over 4
2811		3391
2812	=item ev::TYPE::TYPE ()	3392	=item ev::TYPE::TYPE ()
2813		3393
2814	=item ev::TYPE::TYPE (struct ev_loop *)	3394	=item ev::TYPE::TYPE (loop)
2815		3395
2816	=item ev::TYPE::~TYPE	3396	=item ev::TYPE::~TYPE
2817		3397
2818	The constructor (optionally) takes an event loop to associate the watcher	3398	The constructor (optionally) takes an event loop to associate the watcher
2819	with. If it is omitted, it will use C<EV_DEFAULT>.	3399	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2851		3431
2852	myclass obj;	3432	myclass obj;
2853	ev::io iow;	3433	ev::io iow;
2854	iow.set <myclass, &myclass::io_cb> (&obj);	3434	iow.set <myclass, &myclass::io_cb> (&obj);
2855		3435
		3436	=item w->set (object *)
		3437
		3438	This is a variation of a method callback - leaving out the method to call
		3439	will default the method to C<operator ()>, which makes it possible to use
		3440	functor objects without having to manually specify the C<operator ()> all
		3441	the time. Incidentally, you can then also leave out the template argument
		3442	list.
		3443
		3444	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3445	int revents)>.
		3446
		3447	See the method-C<set> above for more details.
		3448
		3449	Example: use a functor object as callback.
		3450
		3451	struct myfunctor
		3452	{
		3453	void operator() (ev::io &w, int revents)
		3454	{
		3455	...
		3456	}
		3457	}
		3458
		3459	myfunctor f;
		3460
		3461	ev::io w;
		3462	w.set (&f);
		3463
2856	=item w->set<function> (void *data = 0)	3464	=item w->set<function> (void *data = 0)
2857		3465
2858	Also sets a callback, but uses a static method or plain function as	3466	Also sets a callback, but uses a static method or plain function as
2859	callback. The optional C<data> argument will be stored in the watcher's	3467	callback. The optional C<data> argument will be stored in the watcher's
2860	C<data> member and is free for you to use.	3468	C<data> member and is free for you to use.
…		…
2866	Example: Use a plain function as callback.	3474	Example: Use a plain function as callback.
2867		3475
2868	static void io_cb (ev::io &w, int revents) { }	3476	static void io_cb (ev::io &w, int revents) { }
2869	iow.set <io_cb> ();	3477	iow.set <io_cb> ();
2870		3478
2871	=item w->set (struct ev_loop *)	3479	=item w->set (loop)
2872		3480
2873	Associates a different C<struct ev_loop> with this watcher. You can only	3481	Associates a different C<struct ev_loop> with this watcher. You can only
2874	do this when the watcher is inactive (and not pending either).	3482	do this when the watcher is inactive (and not pending either).
2875		3483
2876	=item w->set ([arguments])	3484	=item w->set ([arguments])
2877		3485
2878	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3486	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2879	called at least once. Unlike the C counterpart, an active watcher gets	3487	method or a suitable start method must be called at least once. Unlike the
2880	automatically stopped and restarted when reconfiguring it with this	3488	C counterpart, an active watcher gets automatically stopped and restarted
2881	method.	3489	when reconfiguring it with this method.
2882		3490
2883	=item w->start ()	3491	=item w->start ()
2884		3492
2885	Starts the watcher. Note that there is no C<loop> argument, as the	3493	Starts the watcher. Note that there is no C<loop> argument, as the
2886	constructor already stores the event loop.	3494	constructor already stores the event loop.
2887		3495
		3496	=item w->start ([arguments])
		3497
		3498	Instead of calling C<set> and C<start> methods separately, it is often
		3499	convenient to wrap them in one call. Uses the same type of arguments as
		3500	the configure C<set> method of the watcher.
		3501
2888	=item w->stop ()	3502	=item w->stop ()
2889		3503
2890	Stops the watcher if it is active. Again, no C<loop> argument.	3504	Stops the watcher if it is active. Again, no C<loop> argument.
2891		3505
2892	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3506	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2904		3518
2905	=back	3519	=back
2906		3520
2907	=back	3521	=back
2908		3522
2909	Example: Define a class with an IO and idle watcher, start one of them in	3523	Example: Define a class with two I/O and idle watchers, start the I/O
2910	the constructor.	3524	watchers in the constructor.
2911		3525
2912	class myclass	3526	class myclass
2913	{	3527	{
2914	ev::io io ; void io_cb (ev::io &w, int revents);	3528	ev::io io ; void io_cb (ev::io &w, int revents);
		3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2915	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2916		3531
2917	myclass (int fd)	3532	myclass (int fd)
2918	{	3533	{
2919	io .set <myclass, &myclass::io_cb > (this);	3534	io .set <myclass, &myclass::io_cb > (this);
		3535	io2 .set <myclass, &myclass::io2_cb > (this);
2920	idle.set <myclass, &myclass::idle_cb> (this);	3536	idle.set <myclass, &myclass::idle_cb> (this);
2921		3537
2922	io.start (fd, ev::READ);	3538	io.set (fd, ev::WRITE); // configure the watcher
		3539	io.start (); // start it whenever convenient
		3540
		3541	io2.start (fd, ev::READ); // set + start in one call
2923	}	3542	}
2924	};	3543	};
2925		3544
2926		3545
2927	=head1 OTHER LANGUAGE BINDINGS	3546	=head1 OTHER LANGUAGE BINDINGS
…		…
2946	L<http://software.schmorp.de/pkg/EV>.	3565	L<http://software.schmorp.de/pkg/EV>.
2947		3566
2948	=item Python	3567	=item Python
2949		3568
2950	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3569	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2951	seems to be quite complete and well-documented. Note, however, that the	3570	seems to be quite complete and well-documented.
2952	patch they require for libev is outright dangerous as it breaks the ABI
2953	for everybody else, and therefore, should never be applied in an installed
2954	libev (if python requires an incompatible ABI then it needs to embed
2955	libev).
2956		3571
2957	=item Ruby	3572	=item Ruby
2958		3573
2959	Tony Arcieri has written a ruby extension that offers access to a subset	3574	Tony Arcieri has written a ruby extension that offers access to a subset
2960	of the libev API and adds file handle abstractions, asynchronous DNS and	3575	of the libev API and adds file handle abstractions, asynchronous DNS and
2961	more on top of it. It can be found via gem servers. Its homepage is at	3576	more on top of it. It can be found via gem servers. Its homepage is at
2962	L<http://rev.rubyforge.org/>.	3577	L<http://rev.rubyforge.org/>.
2963		3578
		3579	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3580	makes rev work even on mingw.
		3581
		3582	=item Haskell
		3583
		3584	A haskell binding to libev is available at
		3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3586
2964	=item D	3587	=item D
2965		3588
2966	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3589	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2968		3591
2969	=item Ocaml	3592	=item Ocaml
2970		3593
2971	Erkki Seppala has written Ocaml bindings for libev, to be found at	3594	Erkki Seppala has written Ocaml bindings for libev, to be found at
2972	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3596
		3597	=item Lua
		3598
		3599	Brian Maher has written a partial interface to libev for lua (at the
		3600	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3601	L<http://github.com/brimworks/lua-ev>.
2973		3602
2974	=back	3603	=back
2975		3604
2976		3605
2977	=head1 MACRO MAGIC	3606	=head1 MACRO MAGIC
…		…
2991	loop argument"). The C<EV_A> form is used when this is the sole argument,	3620	loop argument"). The C<EV_A> form is used when this is the sole argument,
2992	C<EV_A_> is used when other arguments are following. Example:	3621	C<EV_A_> is used when other arguments are following. Example:
2993		3622
2994	ev_unref (EV_A);	3623	ev_unref (EV_A);
2995	ev_timer_add (EV_A_ watcher);	3624	ev_timer_add (EV_A_ watcher);
2996	ev_loop (EV_A_ 0);	3625	ev_run (EV_A_ 0);
2997		3626
2998	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3627	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2999	which is often provided by the following macro.	3628	which is often provided by the following macro.
3000		3629
3001	=item C<EV_P>, C<EV_P_>	3630	=item C<EV_P>, C<EV_P_>
…		…
3041	}	3670	}
3042		3671
3043	ev_check check;	3672	ev_check check;
3044	ev_check_init (&check, check_cb);	3673	ev_check_init (&check, check_cb);
3045	ev_check_start (EV_DEFAULT_ &check);	3674	ev_check_start (EV_DEFAULT_ &check);
3046	ev_loop (EV_DEFAULT_ 0);	3675	ev_run (EV_DEFAULT_ 0);
3047		3676
3048	=head1 EMBEDDING	3677	=head1 EMBEDDING
3049		3678
3050	Libev can (and often is) directly embedded into host	3679	Libev can (and often is) directly embedded into host
3051	applications. Examples of applications that embed it include the Deliantra	3680	applications. Examples of applications that embed it include the Deliantra
…		…
3078		3707
3079	#define EV_STANDALONE 1	3708	#define EV_STANDALONE 1
3080	#include "ev.h"	3709	#include "ev.h"
3081		3710
3082	Both header files and implementation files can be compiled with a C++	3711	Both header files and implementation files can be compiled with a C++
3083	compiler (at least, thats a stated goal, and breakage will be treated	3712	compiler (at least, that's a stated goal, and breakage will be treated
3084	as a bug).	3713	as a bug).
3085		3714
3086	You need the following files in your source tree, or in a directory	3715	You need the following files in your source tree, or in a directory
3087	in your include path (e.g. in libev/ when using -Ilibev):	3716	in your include path (e.g. in libev/ when using -Ilibev):
3088		3717
…		…
3131	libev.m4	3760	libev.m4
3132		3761
3133	=head2 PREPROCESSOR SYMBOLS/MACROS	3762	=head2 PREPROCESSOR SYMBOLS/MACROS
3134		3763
3135	Libev can be configured via a variety of preprocessor symbols you have to	3764	Libev can be configured via a variety of preprocessor symbols you have to
3136	define before including any of its files. The default in the absence of	3765	define before including (or compiling) any of its files. The default in
3137	autoconf is documented for every option.	3766	the absence of autoconf is documented for every option.
		3767
		3768	Symbols marked with "(h)" do not change the ABI, and can have different
		3769	values when compiling libev vs. including F<ev.h>, so it is permissible
		3770	to redefine them before including F<ev.h> without breaking compatibility
		3771	to a compiled library. All other symbols change the ABI, which means all
		3772	users of libev and the libev code itself must be compiled with compatible
		3773	settings.
3138		3774
3139	=over 4	3775	=over 4
3140		3776
		3777	=item EV_COMPAT3 (h)
		3778
		3779	Backwards compatibility is a major concern for libev. This is why this
		3780	release of libev comes with wrappers for the functions and symbols that
		3781	have been renamed between libev version 3 and 4.
		3782
		3783	You can disable these wrappers (to test compatibility with future
		3784	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3785	sources. This has the additional advantage that you can drop the C<struct>
		3786	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3787	typedef in that case.
		3788
		3789	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3790	and in some even more future version the compatibility code will be
		3791	removed completely.
		3792
3141	=item EV_STANDALONE	3793	=item EV_STANDALONE (h)
3142		3794
3143	Must always be C<1> if you do not use autoconf configuration, which	3795	Must always be C<1> if you do not use autoconf configuration, which
3144	keeps libev from including F<config.h>, and it also defines dummy	3796	keeps libev from including F<config.h>, and it also defines dummy
3145	implementations for some libevent functions (such as logging, which is not	3797	implementations for some libevent functions (such as logging, which is not
3146	supported). It will also not define any of the structs usually found in	3798	supported). It will also not define any of the structs usually found in
3147	F<event.h> that are not directly supported by the libev core alone.	3799	F<event.h> that are not directly supported by the libev core alone.
3148		3800
		3801	In standalone mode, libev will still try to automatically deduce the
		3802	configuration, but has to be more conservative.
		3803
3149	=item EV_USE_MONOTONIC	3804	=item EV_USE_MONOTONIC
3150		3805
3151	If defined to be C<1>, libev will try to detect the availability of the	3806	If defined to be C<1>, libev will try to detect the availability of the
3152	monotonic clock option at both compile time and runtime. Otherwise no use	3807	monotonic clock option at both compile time and runtime. Otherwise no
3153	of the monotonic clock option will be attempted. If you enable this, you	3808	use of the monotonic clock option will be attempted. If you enable this,
3154	usually have to link against librt or something similar. Enabling it when	3809	you usually have to link against librt or something similar. Enabling it
3155	the functionality isn't available is safe, though, although you have	3810	when the functionality isn't available is safe, though, although you have
3156	to make sure you link against any libraries where the C<clock_gettime>	3811	to make sure you link against any libraries where the C<clock_gettime>
3157	function is hiding in (often F<-lrt>).	3812	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3158		3813
3159	=item EV_USE_REALTIME	3814	=item EV_USE_REALTIME
3160		3815
3161	If defined to be C<1>, libev will try to detect the availability of the	3816	If defined to be C<1>, libev will try to detect the availability of the
3162	real-time clock option at compile time (and assume its availability at	3817	real-time clock option at compile time (and assume its availability
3163	runtime if successful). Otherwise no use of the real-time clock option will	3818	at runtime if successful). Otherwise no use of the real-time clock
3164	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3819	option will be attempted. This effectively replaces C<gettimeofday>
3165	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3820	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3166	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3821	correctness. See the note about libraries in the description of
		3822	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3823	C<EV_USE_CLOCK_SYSCALL>.
		3824
		3825	=item EV_USE_CLOCK_SYSCALL
		3826
		3827	If defined to be C<1>, libev will try to use a direct syscall instead
		3828	of calling the system-provided C<clock_gettime> function. This option
		3829	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3830	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3831	programs needlessly. Using a direct syscall is slightly slower (in
		3832	theory), because no optimised vdso implementation can be used, but avoids
		3833	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3834	higher, as it simplifies linking (no need for C<-lrt>).
3167		3835
3168	=item EV_USE_NANOSLEEP	3836	=item EV_USE_NANOSLEEP
3169		3837
3170	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3838	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3171	and will use it for delays. Otherwise it will use C<select ()>.	3839	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3187		3855
3188	=item EV_SELECT_USE_FD_SET	3856	=item EV_SELECT_USE_FD_SET
3189		3857
3190	If defined to C<1>, then the select backend will use the system C<fd_set>	3858	If defined to C<1>, then the select backend will use the system C<fd_set>
3191	structure. This is useful if libev doesn't compile due to a missing	3859	structure. This is useful if libev doesn't compile due to a missing
3192	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3860	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3193	exotic systems. This usually limits the range of file descriptors to some	3861	on exotic systems. This usually limits the range of file descriptors to
3194	low limit such as 1024 or might have other limitations (winsocket only	3862	some low limit such as 1024 or might have other limitations (winsocket
3195	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3863	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3196	influence the size of the C<fd_set> used.	3864	configures the maximum size of the C<fd_set>.
3197		3865
3198	=item EV_SELECT_IS_WINSOCKET	3866	=item EV_SELECT_IS_WINSOCKET
3199		3867
3200	When defined to C<1>, the select backend will assume that	3868	When defined to C<1>, the select backend will assume that
3201	select/socket/connect etc. don't understand file descriptors but	3869	select/socket/connect etc. don't understand file descriptors but
…		…
3203	be used is the winsock select). This means that it will call	3871	be used is the winsock select). This means that it will call
3204	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3872	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3205	it is assumed that all these functions actually work on fds, even	3873	it is assumed that all these functions actually work on fds, even
3206	on win32. Should not be defined on non-win32 platforms.	3874	on win32. Should not be defined on non-win32 platforms.
3207		3875
3208	=item EV_FD_TO_WIN32_HANDLE	3876	=item EV_FD_TO_WIN32_HANDLE(fd)
3209		3877
3210	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3878	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3211	file descriptors to socket handles. When not defining this symbol (the	3879	file descriptors to socket handles. When not defining this symbol (the
3212	default), then libev will call C<_get_osfhandle>, which is usually	3880	default), then libev will call C<_get_osfhandle>, which is usually
3213	correct. In some cases, programs use their own file descriptor management,	3881	correct. In some cases, programs use their own file descriptor management,
3214	in which case they can provide this function to map fds to socket handles.	3882	in which case they can provide this function to map fds to socket handles.
		3883
		3884	=item EV_WIN32_HANDLE_TO_FD(handle)
		3885
		3886	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3887	using the standard C<_open_osfhandle> function. For programs implementing
		3888	their own fd to handle mapping, overwriting this function makes it easier
		3889	to do so. This can be done by defining this macro to an appropriate value.
		3890
		3891	=item EV_WIN32_CLOSE_FD(fd)
		3892
		3893	If programs implement their own fd to handle mapping on win32, then this
		3894	macro can be used to override the C<close> function, useful to unregister
		3895	file descriptors again. Note that the replacement function has to close
		3896	the underlying OS handle.
3215		3897
3216	=item EV_USE_POLL	3898	=item EV_USE_POLL
3217		3899
3218	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3900	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3219	backend. Otherwise it will be enabled on non-win32 platforms. It	3901	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3266	as well as for signal and thread safety in C<ev_async> watchers.	3948	as well as for signal and thread safety in C<ev_async> watchers.
3267		3949
3268	In the absence of this define, libev will use C<sig_atomic_t volatile>	3950	In the absence of this define, libev will use C<sig_atomic_t volatile>
3269	(from F<signal.h>), which is usually good enough on most platforms.	3951	(from F<signal.h>), which is usually good enough on most platforms.
3270		3952
3271	=item EV_H	3953	=item EV_H (h)
3272		3954
3273	The name of the F<ev.h> header file used to include it. The default if	3955	The name of the F<ev.h> header file used to include it. The default if
3274	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3956	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3275	used to virtually rename the F<ev.h> header file in case of conflicts.	3957	used to virtually rename the F<ev.h> header file in case of conflicts.
3276		3958
3277	=item EV_CONFIG_H	3959	=item EV_CONFIG_H (h)
3278		3960
3279	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3961	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3280	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3962	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3281	C<EV_H>, above.	3963	C<EV_H>, above.
3282		3964
3283	=item EV_EVENT_H	3965	=item EV_EVENT_H (h)
3284		3966
3285	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3967	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3286	of how the F<event.h> header can be found, the default is C<"event.h">.	3968	of how the F<event.h> header can be found, the default is C<"event.h">.
3287		3969
3288	=item EV_PROTOTYPES	3970	=item EV_PROTOTYPES (h)
3289		3971
3290	If defined to be C<0>, then F<ev.h> will not define any function	3972	If defined to be C<0>, then F<ev.h> will not define any function
3291	prototypes, but still define all the structs and other symbols. This is	3973	prototypes, but still define all the structs and other symbols. This is
3292	occasionally useful if you want to provide your own wrapper functions	3974	occasionally useful if you want to provide your own wrapper functions
3293	around libev functions.	3975	around libev functions.
…		…
3315	fine.	3997	fine.
3316		3998
3317	If your embedding application does not need any priorities, defining these	3999	If your embedding application does not need any priorities, defining these
3318	both to C<0> will save some memory and CPU.	4000	both to C<0> will save some memory and CPU.
3319		4001
3320	=item EV_PERIODIC_ENABLE	4002	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4003	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4004	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3321		4005
3322	If undefined or defined to be C<1>, then periodic timers are supported. If	4006	If undefined or defined to be C<1> (and the platform supports it), then
3323	defined to be C<0>, then they are not. Disabling them saves a few kB of	4007	the respective watcher type is supported. If defined to be C<0>, then it
3324	code.	4008	is not. Disabling watcher types mainly saves code size.
3325		4009
3326	=item EV_IDLE_ENABLE	4010	=item EV_FEATURES
3327
3328	If undefined or defined to be C<1>, then idle watchers are supported. If
3329	defined to be C<0>, then they are not. Disabling them saves a few kB of
3330	code.
3331
3332	=item EV_EMBED_ENABLE
3333
3334	If undefined or defined to be C<1>, then embed watchers are supported. If
3335	defined to be C<0>, then they are not. Embed watchers rely on most other
3336	watcher types, which therefore must not be disabled.
3337
3338	=item EV_STAT_ENABLE
3339
3340	If undefined or defined to be C<1>, then stat watchers are supported. If
3341	defined to be C<0>, then they are not.
3342
3343	=item EV_FORK_ENABLE
3344
3345	If undefined or defined to be C<1>, then fork watchers are supported. If
3346	defined to be C<0>, then they are not.
3347
3348	=item EV_ASYNC_ENABLE
3349
3350	If undefined or defined to be C<1>, then async watchers are supported. If
3351	defined to be C<0>, then they are not.
3352
3353	=item EV_MINIMAL
3354		4011
3355	If you need to shave off some kilobytes of code at the expense of some	4012	If you need to shave off some kilobytes of code at the expense of some
3356	speed, define this symbol to C<1>. Currently this is used to override some	4013	speed (but with the full API), you can define this symbol to request
3357	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4014	certain subsets of functionality. The default is to enable all features
3358	much smaller 2-heap for timer management over the default 4-heap.	4015	that can be enabled on the platform.
		4016
		4017	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4018	with some broad features you want) and then selectively re-enable
		4019	additional parts you want, for example if you want everything minimal,
		4020	but multiple event loop support, async and child watchers and the poll
		4021	backend, use this:
		4022
		4023	#define EV_FEATURES 0
		4024	#define EV_MULTIPLICITY 1
		4025	#define EV_USE_POLL 1
		4026	#define EV_CHILD_ENABLE 1
		4027	#define EV_ASYNC_ENABLE 1
		4028
		4029	The actual value is a bitset, it can be a combination of the following
		4030	values:
		4031
		4032	=over 4
		4033
		4034	=item C<1> - faster/larger code
		4035
		4036	Use larger code to speed up some operations.
		4037
		4038	Currently this is used to override some inlining decisions (enlarging the
		4039	code size by roughly 30% on amd64).
		4040
		4041	When optimising for size, use of compiler flags such as C<-Os> with
		4042	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4043	assertions.
		4044
		4045	=item C<2> - faster/larger data structures
		4046
		4047	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4048	hash table sizes and so on. This will usually further increase code size
		4049	and can additionally have an effect on the size of data structures at
		4050	runtime.
		4051
		4052	=item C<4> - full API configuration
		4053
		4054	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4055	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4056
		4057	=item C<8> - full API
		4058
		4059	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4060	details on which parts of the API are still available without this
		4061	feature, and do not complain if this subset changes over time.
		4062
		4063	=item C<16> - enable all optional watcher types
		4064
		4065	Enables all optional watcher types. If you want to selectively enable
		4066	only some watcher types other than I/O and timers (e.g. prepare,
		4067	embed, async, child...) you can enable them manually by defining
		4068	C<EV_watchertype_ENABLE> to C<1> instead.
		4069
		4070	=item C<32> - enable all backends
		4071
		4072	This enables all backends - without this feature, you need to enable at
		4073	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4074
		4075	=item C<64> - enable OS-specific "helper" APIs
		4076
		4077	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4078	default.
		4079
		4080	=back
		4081
		4082	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4083	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4084	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4085	watchers, timers and monotonic clock support.
		4086
		4087	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4088	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4089	your program might be left out as well - a binary starting a timer and an
		4090	I/O watcher then might come out at only 5Kb.
		4091
		4092	=item EV_AVOID_STDIO
		4093
		4094	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4095	functions (printf, scanf, perror etc.). This will increase the code size
		4096	somewhat, but if your program doesn't otherwise depend on stdio and your
		4097	libc allows it, this avoids linking in the stdio library which is quite
		4098	big.
		4099
		4100	Note that error messages might become less precise when this option is
		4101	enabled.
		4102
		4103	=item EV_NSIG
		4104
		4105	The highest supported signal number, +1 (or, the number of
		4106	signals): Normally, libev tries to deduce the maximum number of signals
		4107	automatically, but sometimes this fails, in which case it can be
		4108	specified. Also, using a lower number than detected (C<32> should be
		4109	good for about any system in existence) can save some memory, as libev
		4110	statically allocates some 12-24 bytes per signal number.
3359		4111
3360	=item EV_PID_HASHSIZE	4112	=item EV_PID_HASHSIZE
3361		4113
3362	C<ev_child> watchers use a small hash table to distribute workload by	4114	C<ev_child> watchers use a small hash table to distribute workload by
3363	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4115	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3364	than enough. If you need to manage thousands of children you might want to	4116	usually more than enough. If you need to manage thousands of children you
3365	increase this value (I<must> be a power of two).	4117	might want to increase this value (I<must> be a power of two).
3366		4118
3367	=item EV_INOTIFY_HASHSIZE	4119	=item EV_INOTIFY_HASHSIZE
3368		4120
3369	C<ev_stat> watchers use a small hash table to distribute workload by	4121	C<ev_stat> watchers use a small hash table to distribute workload by
3370	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4122	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3371	usually more than enough. If you need to manage thousands of C<ev_stat>	4123	disabled), usually more than enough. If you need to manage thousands of
3372	watchers you might want to increase this value (I<must> be a power of	4124	C<ev_stat> watchers you might want to increase this value (I<must> be a
3373	two).	4125	power of two).
3374		4126
3375	=item EV_USE_4HEAP	4127	=item EV_USE_4HEAP
3376		4128
3377	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4129	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3378	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4130	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3379	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4131	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3380	faster performance with many (thousands) of watchers.	4132	faster performance with many (thousands) of watchers.
3381		4133
3382	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4134	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3383	(disabled).	4135	will be C<0>.
3384		4136
3385	=item EV_HEAP_CACHE_AT	4137	=item EV_HEAP_CACHE_AT
3386		4138
3387	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4139	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3388	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4140	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3389	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4141	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3390	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4142	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3391	but avoids random read accesses on heap changes. This improves performance	4143	but avoids random read accesses on heap changes. This improves performance
3392	noticeably with many (hundreds) of watchers.	4144	noticeably with many (hundreds) of watchers.
3393		4145
3394	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4146	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3395	(disabled).	4147	will be C<0>.
3396		4148
3397	=item EV_VERIFY	4149	=item EV_VERIFY
3398		4150
3399	Controls how much internal verification (see C<ev_loop_verify ()>) will	4151	Controls how much internal verification (see C<ev_verify ()>) will
3400	be done: If set to C<0>, no internal verification code will be compiled	4152	be done: If set to C<0>, no internal verification code will be compiled
3401	in. If set to C<1>, then verification code will be compiled in, but not	4153	in. If set to C<1>, then verification code will be compiled in, but not
3402	called. If set to C<2>, then the internal verification code will be	4154	called. If set to C<2>, then the internal verification code will be
3403	called once per loop, which can slow down libev. If set to C<3>, then the	4155	called once per loop, which can slow down libev. If set to C<3>, then the
3404	verification code will be called very frequently, which will slow down	4156	verification code will be called very frequently, which will slow down
3405	libev considerably.	4157	libev considerably.
3406		4158
3407	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4159	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3408	C<0>.	4160	will be C<0>.
3409		4161
3410	=item EV_COMMON	4162	=item EV_COMMON
3411		4163
3412	By default, all watchers have a C<void *data> member. By redefining	4164	By default, all watchers have a C<void *data> member. By redefining
3413	this macro to a something else you can include more and other types of	4165	this macro to something else you can include more and other types of
3414	members. You have to define it each time you include one of the files,	4166	members. You have to define it each time you include one of the files,
3415	though, and it must be identical each time.	4167	though, and it must be identical each time.
3416		4168
3417	For example, the perl EV module uses something like this:	4169	For example, the perl EV module uses something like this:
3418		4170
…		…
3471	file.	4223	file.
3472		4224
3473	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4225	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3474	that everybody includes and which overrides some configure choices:	4226	that everybody includes and which overrides some configure choices:
3475		4227
3476	#define EV_MINIMAL 1	4228	#define EV_FEATURES 8
3477	#define EV_USE_POLL 0	4229	#define EV_USE_SELECT 1
3478	#define EV_MULTIPLICITY 0
3479	#define EV_PERIODIC_ENABLE 0	4230	#define EV_PREPARE_ENABLE 1
		4231	#define EV_IDLE_ENABLE 1
3480	#define EV_STAT_ENABLE 0	4232	#define EV_SIGNAL_ENABLE 1
3481	#define EV_FORK_ENABLE 0	4233	#define EV_CHILD_ENABLE 1
		4234	#define EV_USE_STDEXCEPT 0
3482	#define EV_CONFIG_H <config.h>	4235	#define EV_CONFIG_H <config.h>
3483	#define EV_MINPRI 0
3484	#define EV_MAXPRI 0
3485		4236
3486	#include "ev++.h"	4237	#include "ev++.h"
3487		4238
3488	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4239	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3489		4240
…		…
3549	default loop and triggering an C<ev_async> watcher from the default loop	4300	default loop and triggering an C<ev_async> watcher from the default loop
3550	watcher callback into the event loop interested in the signal.	4301	watcher callback into the event loop interested in the signal.
3551		4302
3552	=back	4303	=back
3553		4304
		4305	=head4 THREAD LOCKING EXAMPLE
		4306
		4307	Here is a fictitious example of how to run an event loop in a different
		4308	thread than where callbacks are being invoked and watchers are
		4309	created/added/removed.
		4310
		4311	For a real-world example, see the C<EV::Loop::Async> perl module,
		4312	which uses exactly this technique (which is suited for many high-level
		4313	languages).
		4314
		4315	The example uses a pthread mutex to protect the loop data, a condition
		4316	variable to wait for callback invocations, an async watcher to notify the
		4317	event loop thread and an unspecified mechanism to wake up the main thread.
		4318
		4319	First, you need to associate some data with the event loop:
		4320
		4321	typedef struct {
		4322	mutex_t lock; /* global loop lock */
		4323	ev_async async_w;
		4324	thread_t tid;
		4325	cond_t invoke_cv;
		4326	} userdata;
		4327
		4328	void prepare_loop (EV_P)
		4329	{
		4330	// for simplicity, we use a static userdata struct.
		4331	static userdata u;
		4332
		4333	ev_async_init (&u->async_w, async_cb);
		4334	ev_async_start (EV_A_ &u->async_w);
		4335
		4336	pthread_mutex_init (&u->lock, 0);
		4337	pthread_cond_init (&u->invoke_cv, 0);
		4338
		4339	// now associate this with the loop
		4340	ev_set_userdata (EV_A_ u);
		4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4343
		4344	// then create the thread running ev_loop
		4345	pthread_create (&u->tid, 0, l_run, EV_A);
		4346	}
		4347
		4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4349	solely to wake up the event loop so it takes notice of any new watchers
		4350	that might have been added:
		4351
		4352	static void
		4353	async_cb (EV_P_ ev_async *w, int revents)
		4354	{
		4355	// just used for the side effects
		4356	}
		4357
		4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4359	protecting the loop data, respectively.
		4360
		4361	static void
		4362	l_release (EV_P)
		4363	{
		4364	userdata *u = ev_userdata (EV_A);
		4365	pthread_mutex_unlock (&u->lock);
		4366	}
		4367
		4368	static void
		4369	l_acquire (EV_P)
		4370	{
		4371	userdata *u = ev_userdata (EV_A);
		4372	pthread_mutex_lock (&u->lock);
		4373	}
		4374
		4375	The event loop thread first acquires the mutex, and then jumps straight
		4376	into C<ev_run>:
		4377
		4378	void *
		4379	l_run (void *thr_arg)
		4380	{
		4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4382
		4383	l_acquire (EV_A);
		4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4385	ev_run (EV_A_ 0);
		4386	l_release (EV_A);
		4387
		4388	return 0;
		4389	}
		4390
		4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4392	signal the main thread via some unspecified mechanism (signals? pipe
		4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4394	have been called (in a while loop because a) spurious wakeups are possible
		4395	and b) skipping inter-thread-communication when there are no pending
		4396	watchers is very beneficial):
		4397
		4398	static void
		4399	l_invoke (EV_P)
		4400	{
		4401	userdata *u = ev_userdata (EV_A);
		4402
		4403	while (ev_pending_count (EV_A))
		4404	{
		4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4407	}
		4408	}
		4409
		4410	Now, whenever the main thread gets told to invoke pending watchers, it
		4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4412	thread to continue:
		4413
		4414	static void
		4415	real_invoke_pending (EV_P)
		4416	{
		4417	userdata *u = ev_userdata (EV_A);
		4418
		4419	pthread_mutex_lock (&u->lock);
		4420	ev_invoke_pending (EV_A);
		4421	pthread_cond_signal (&u->invoke_cv);
		4422	pthread_mutex_unlock (&u->lock);
		4423	}
		4424
		4425	Whenever you want to start/stop a watcher or do other modifications to an
		4426	event loop, you will now have to lock:
		4427
		4428	ev_timer timeout_watcher;
		4429	userdata *u = ev_userdata (EV_A);
		4430
		4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4432
		4433	pthread_mutex_lock (&u->lock);
		4434	ev_timer_start (EV_A_ &timeout_watcher);
		4435	ev_async_send (EV_A_ &u->async_w);
		4436	pthread_mutex_unlock (&u->lock);
		4437
		4438	Note that sending the C<ev_async> watcher is required because otherwise
		4439	an event loop currently blocking in the kernel will have no knowledge
		4440	about the newly added timer. By waking up the loop it will pick up any new
		4441	watchers in the next event loop iteration.
		4442
3554	=head3 COROUTINES	4443	=head3 COROUTINES
3555		4444
3556	Libev is very accommodating to coroutines ("cooperative threads"):	4445	Libev is very accommodating to coroutines ("cooperative threads"):
3557	libev fully supports nesting calls to its functions from different	4446	libev fully supports nesting calls to its functions from different
3558	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4447	coroutines (e.g. you can call C<ev_run> on the same loop from two
3559	different coroutines, and switch freely between both coroutines running the	4448	different coroutines, and switch freely between both coroutines running
3560	loop, as long as you don't confuse yourself). The only exception is that	4449	the loop, as long as you don't confuse yourself). The only exception is
3561	you must not do this from C<ev_periodic> reschedule callbacks.	4450	that you must not do this from C<ev_periodic> reschedule callbacks.
3562		4451
3563	Care has been taken to ensure that libev does not keep local state inside	4452	Care has been taken to ensure that libev does not keep local state inside
3564	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4453	C<ev_run>, and other calls do not usually allow for coroutine switches as
3565	they do not clal any callbacks.	4454	they do not call any callbacks.
3566		4455
3567	=head2 COMPILER WARNINGS	4456	=head2 COMPILER WARNINGS
3568		4457
3569	Depending on your compiler and compiler settings, you might get no or a	4458	Depending on your compiler and compiler settings, you might get no or a
3570	lot of warnings when compiling libev code. Some people are apparently	4459	lot of warnings when compiling libev code. Some people are apparently
…		…
3580	maintainable.	4469	maintainable.
3581		4470
3582	And of course, some compiler warnings are just plain stupid, or simply	4471	And of course, some compiler warnings are just plain stupid, or simply
3583	wrong (because they don't actually warn about the condition their message	4472	wrong (because they don't actually warn about the condition their message
3584	seems to warn about). For example, certain older gcc versions had some	4473	seems to warn about). For example, certain older gcc versions had some
3585	warnings that resulted an extreme number of false positives. These have	4474	warnings that resulted in an extreme number of false positives. These have
3586	been fixed, but some people still insist on making code warn-free with	4475	been fixed, but some people still insist on making code warn-free with
3587	such buggy versions.	4476	such buggy versions.
3588		4477
3589	While libev is written to generate as few warnings as possible,	4478	While libev is written to generate as few warnings as possible,
3590	"warn-free" code is not a goal, and it is recommended not to build libev	4479	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3604	==2274== definitely lost: 0 bytes in 0 blocks.	4493	==2274== definitely lost: 0 bytes in 0 blocks.
3605	==2274== possibly lost: 0 bytes in 0 blocks.	4494	==2274== possibly lost: 0 bytes in 0 blocks.
3606	==2274== still reachable: 256 bytes in 1 blocks.	4495	==2274== still reachable: 256 bytes in 1 blocks.
3607		4496
3608	Then there is no memory leak, just as memory accounted to global variables	4497	Then there is no memory leak, just as memory accounted to global variables
3609	is not a memleak - the memory is still being refernced, and didn't leak.	4498	is not a memleak - the memory is still being referenced, and didn't leak.
3610		4499
3611	Similarly, under some circumstances, valgrind might report kernel bugs	4500	Similarly, under some circumstances, valgrind might report kernel bugs
3612	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4501	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3613	although an acceptable workaround has been found here), or it might be	4502	although an acceptable workaround has been found here), or it might be
3614	confused.	4503	confused.
…		…
3626	I suggest using suppression lists.	4515	I suggest using suppression lists.
3627		4516
3628		4517
3629	=head1 PORTABILITY NOTES	4518	=head1 PORTABILITY NOTES
3630		4519
		4520	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4521
		4522	GNU/Linux is the only common platform that supports 64 bit file/large file
		4523	interfaces but I<disables> them by default.
		4524
		4525	That means that libev compiled in the default environment doesn't support
		4526	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4527
		4528	Unfortunately, many programs try to work around this GNU/Linux issue
		4529	by enabling the large file API, which makes them incompatible with the
		4530	standard libev compiled for their system.
		4531
		4532	Likewise, libev cannot enable the large file API itself as this would
		4533	suddenly make it incompatible to the default compile time environment,
		4534	i.e. all programs not using special compile switches.
		4535
		4536	=head2 OS/X AND DARWIN BUGS
		4537
		4538	The whole thing is a bug if you ask me - basically any system interface
		4539	you touch is broken, whether it is locales, poll, kqueue or even the
		4540	OpenGL drivers.
		4541
		4542	=head3 C<kqueue> is buggy
		4543
		4544	The kqueue syscall is broken in all known versions - most versions support
		4545	only sockets, many support pipes.
		4546
		4547	Libev tries to work around this by not using C<kqueue> by default on this
		4548	rotten platform, but of course you can still ask for it when creating a
		4549	loop - embedding a socket-only kqueue loop into a select-based one is
		4550	probably going to work well.
		4551
		4552	=head3 C<poll> is buggy
		4553
		4554	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4555	implementation by something calling C<kqueue> internally around the 10.5.6
		4556	release, so now C<kqueue> I<and> C<poll> are broken.
		4557
		4558	Libev tries to work around this by not using C<poll> by default on
		4559	this rotten platform, but of course you can still ask for it when creating
		4560	a loop.
		4561
		4562	=head3 C<select> is buggy
		4563
		4564	All that's left is C<select>, and of course Apple found a way to fuck this
		4565	one up as well: On OS/X, C<select> actively limits the number of file
		4566	descriptors you can pass in to 1024 - your program suddenly crashes when
		4567	you use more.
		4568
		4569	There is an undocumented "workaround" for this - defining
		4570	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4571	work on OS/X.
		4572
		4573	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4574
		4575	=head3 C<errno> reentrancy
		4576
		4577	The default compile environment on Solaris is unfortunately so
		4578	thread-unsafe that you can't even use components/libraries compiled
		4579	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4580	defined by default. A valid, if stupid, implementation choice.
		4581
		4582	If you want to use libev in threaded environments you have to make sure
		4583	it's compiled with C<_REENTRANT> defined.
		4584
		4585	=head3 Event port backend
		4586
		4587	The scalable event interface for Solaris is called "event
		4588	ports". Unfortunately, this mechanism is very buggy in all major
		4589	releases. If you run into high CPU usage, your program freezes or you get
		4590	a large number of spurious wakeups, make sure you have all the relevant
		4591	and latest kernel patches applied. No, I don't know which ones, but there
		4592	are multiple ones to apply, and afterwards, event ports actually work
		4593	great.
		4594
		4595	If you can't get it to work, you can try running the program by setting
		4596	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4597	C<select> backends.
		4598
		4599	=head2 AIX POLL BUG
		4600
		4601	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4602	this by trying to avoid the poll backend altogether (i.e. it's not even
		4603	compiled in), which normally isn't a big problem as C<select> works fine
		4604	with large bitsets on AIX, and AIX is dead anyway.
		4605
3631	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4606	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4607
		4608	=head3 General issues
3632		4609
3633	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3634	requires, and its I/O model is fundamentally incompatible with the POSIX	4611	requires, and its I/O model is fundamentally incompatible with the POSIX
3635	model. Libev still offers limited functionality on this platform in	4612	model. Libev still offers limited functionality on this platform in
3636	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3637	descriptors. This only applies when using Win32 natively, not when using	4614	descriptors. This only applies when using Win32 natively, not when using
3638	e.g. cygwin.	4615	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4616	as every compielr comes with a slightly differently broken/incompatible
		4617	environment.
3639		4618
3640	Lifting these limitations would basically require the full	4619	Lifting these limitations would basically require the full
3641	re-implementation of the I/O system. If you are into these kinds of	4620	re-implementation of the I/O system. If you are into this kind of thing,
3642	things, then note that glib does exactly that for you in a very portable	4621	then note that glib does exactly that for you in a very portable way (note
3643	way (note also that glib is the slowest event library known to man).	4622	also that glib is the slowest event library known to man).
3644		4623
3645	There is no supported compilation method available on windows except	4624	There is no supported compilation method available on windows except
3646	embedding it into other applications.	4625	embedding it into other applications.
		4626
		4627	Sensible signal handling is officially unsupported by Microsoft - libev
		4628	tries its best, but under most conditions, signals will simply not work.
3647		4629
3648	Not a libev limitation but worth mentioning: windows apparently doesn't	4630	Not a libev limitation but worth mentioning: windows apparently doesn't
3649	accept large writes: instead of resulting in a partial write, windows will	4631	accept large writes: instead of resulting in a partial write, windows will
3650	either accept everything or return C<ENOBUFS> if the buffer is too large,	4632	either accept everything or return C<ENOBUFS> if the buffer is too large,
3651	so make sure you only write small amounts into your sockets (less than a	4633	so make sure you only write small amounts into your sockets (less than a
…		…
3656	the abysmal performance of winsockets, using a large number of sockets	4638	the abysmal performance of winsockets, using a large number of sockets
3657	is not recommended (and not reasonable). If your program needs to use	4639	is not recommended (and not reasonable). If your program needs to use
3658	more than a hundred or so sockets, then likely it needs to use a totally	4640	more than a hundred or so sockets, then likely it needs to use a totally
3659	different implementation for windows, as libev offers the POSIX readiness	4641	different implementation for windows, as libev offers the POSIX readiness
3660	notification model, which cannot be implemented efficiently on windows	4642	notification model, which cannot be implemented efficiently on windows
3661	(Microsoft monopoly games).	4643	(due to Microsoft monopoly games).
3662		4644
3663	A typical way to use libev under windows is to embed it (see the embedding	4645	A typical way to use libev under windows is to embed it (see the embedding
3664	section for details) and use the following F<evwrap.h> header file instead	4646	section for details) and use the following F<evwrap.h> header file instead
3665	of F<ev.h>:	4647	of F<ev.h>:
3666		4648
…		…
3673	you do I<not> compile the F<ev.c> or any other embedded source files!):	4655	you do I<not> compile the F<ev.c> or any other embedded source files!):
3674		4656
3675	#include "evwrap.h"	4657	#include "evwrap.h"
3676	#include "ev.c"	4658	#include "ev.c"
3677		4659
3678	=over 4
3679
3680	=item The winsocket select function	4660	=head3 The winsocket C<select> function
3681		4661
3682	The winsocket C<select> function doesn't follow POSIX in that it	4662	The winsocket C<select> function doesn't follow POSIX in that it
3683	requires socket I<handles> and not socket I<file descriptors> (it is	4663	requires socket I<handles> and not socket I<file descriptors> (it is
3684	also extremely buggy). This makes select very inefficient, and also	4664	also extremely buggy). This makes select very inefficient, and also
3685	requires a mapping from file descriptors to socket handles (the Microsoft	4665	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3694	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4674	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3695		4675
3696	Note that winsockets handling of fd sets is O(n), so you can easily get a	4676	Note that winsockets handling of fd sets is O(n), so you can easily get a
3697	complexity in the O(n²) range when using win32.	4677	complexity in the O(n²) range when using win32.
3698		4678
3699	=item Limited number of file descriptors	4679	=head3 Limited number of file descriptors
3700		4680
3701	Windows has numerous arbitrary (and low) limits on things.	4681	Windows has numerous arbitrary (and low) limits on things.
3702		4682
3703	Early versions of winsocket's select only supported waiting for a maximum	4683	Early versions of winsocket's select only supported waiting for a maximum
3704	of C<64> handles (probably owning to the fact that all windows kernels	4684	of C<64> handles (probably owning to the fact that all windows kernels
3705	can only wait for C<64> things at the same time internally; Microsoft	4685	can only wait for C<64> things at the same time internally; Microsoft
3706	recommends spawning a chain of threads and wait for 63 handles and the	4686	recommends spawning a chain of threads and wait for 63 handles and the
3707	previous thread in each. Great).	4687	previous thread in each. Sounds great!).
3708		4688
3709	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4689	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3710	to some high number (e.g. C<2048>) before compiling the winsocket select	4690	to some high number (e.g. C<2048>) before compiling the winsocket select
3711	call (which might be in libev or elsewhere, for example, perl does its own	4691	call (which might be in libev or elsewhere, for example, perl and many
3712	select emulation on windows).	4692	other interpreters do their own select emulation on windows).
3713		4693
3714	Another limit is the number of file descriptors in the Microsoft runtime	4694	Another limit is the number of file descriptors in the Microsoft runtime
3715	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4695	libraries, which by default is C<64> (there must be a hidden I<64>
3716	or something like this inside Microsoft). You can increase this by calling	4696	fetish or something like this inside Microsoft). You can increase this
3717	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4697	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3718	arbitrary limit), but is broken in many versions of the Microsoft runtime	4698	(another arbitrary limit), but is broken in many versions of the Microsoft
3719	libraries.
3720
3721	This might get you to about C<512> or C<2048> sockets (depending on	4699	runtime libraries. This might get you to about C<512> or C<2048> sockets
3722	windows version and/or the phase of the moon). To get more, you need to	4700	(depending on windows version and/or the phase of the moon). To get more,
3723	wrap all I/O functions and provide your own fd management, but the cost of	4701	you need to wrap all I/O functions and provide your own fd management, but
3724	calling select (O(n²)) will likely make this unworkable.	4702	the cost of calling select (O(n²)) will likely make this unworkable.
3725
3726	=back
3727		4703
3728	=head2 PORTABILITY REQUIREMENTS	4704	=head2 PORTABILITY REQUIREMENTS
3729		4705
3730	In addition to a working ISO-C implementation and of course the	4706	In addition to a working ISO-C implementation and of course the
3731	backend-specific APIs, libev relies on a few additional extensions:	4707	backend-specific APIs, libev relies on a few additional extensions:
…		…
3770	watchers.	4746	watchers.
3771		4747
3772	=item C<double> must hold a time value in seconds with enough accuracy	4748	=item C<double> must hold a time value in seconds with enough accuracy
3773		4749
3774	The type C<double> is used to represent timestamps. It is required to	4750	The type C<double> is used to represent timestamps. It is required to
3775	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4751	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3776	enough for at least into the year 4000. This requirement is fulfilled by	4752	good enough for at least into the year 4000 with millisecond accuracy
		4753	(the design goal for libev). This requirement is overfulfilled by
3777	implementations implementing IEEE 754 (basically all existing ones).	4754	implementations using IEEE 754, which is basically all existing ones. With
		4755	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3778		4756
3779	=back	4757	=back
3780		4758
3781	If you know of other additional requirements drop me a note.	4759	If you know of other additional requirements drop me a note.
3782		4760
…		…
3850	involves iterating over all running async watchers or all signal numbers.	4828	involves iterating over all running async watchers or all signal numbers.
3851		4829
3852	=back	4830	=back
3853		4831
3854		4832
		4833	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4834
		4835	The major version 4 introduced some minor incompatible changes to the API.
		4836
		4837	At the moment, the C<ev.h> header file tries to implement superficial
		4838	compatibility, so most programs should still compile. Those might be
		4839	removed in later versions of libev, so better update early than late.
		4840
		4841	=over 4
		4842
		4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4844
		4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4846
		4847	ev_loop_destroy (EV_DEFAULT);
		4848	ev_loop_fork (EV_DEFAULT);
		4849
		4850	=item function/symbol renames
		4851
		4852	A number of functions and symbols have been renamed:
		4853
		4854	ev_loop => ev_run
		4855	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4856	EVLOOP_ONESHOT => EVRUN_ONCE
		4857
		4858	ev_unloop => ev_break
		4859	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4860	EVUNLOOP_ONE => EVBREAK_ONE
		4861	EVUNLOOP_ALL => EVBREAK_ALL
		4862
		4863	EV_TIMEOUT => EV_TIMER
		4864
		4865	ev_loop_count => ev_iteration
		4866	ev_loop_depth => ev_depth
		4867	ev_loop_verify => ev_verify
		4868
		4869	Most functions working on C<struct ev_loop> objects don't have an
		4870	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4871	associated constants have been renamed to not collide with the C<struct
		4872	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4873	as all other watcher types. Note that C<ev_loop_fork> is still called
		4874	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4875	typedef.
		4876
		4877	=item C<EV_COMPAT3> backwards compatibility mechanism
		4878
		4879	The backward compatibility mechanism can be controlled by
		4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4881	section.
		4882
		4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4884
		4885	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4887	and work, but the library code will of course be larger.
		4888
		4889	=back
		4890
		4891
		4892	=head1 GLOSSARY
		4893
		4894	=over 4
		4895
		4896	=item active
		4897
		4898	A watcher is active as long as it has been started and not yet stopped.
		4899	See L<WATCHER STATES> for details.
		4900
		4901	=item application
		4902
		4903	In this document, an application is whatever is using libev.
		4904
		4905	=item backend
		4906
		4907	The part of the code dealing with the operating system interfaces.
		4908
		4909	=item callback
		4910
		4911	The address of a function that is called when some event has been
		4912	detected. Callbacks are being passed the event loop, the watcher that
		4913	received the event, and the actual event bitset.
		4914
		4915	=item callback/watcher invocation
		4916
		4917	The act of calling the callback associated with a watcher.
		4918
		4919	=item event
		4920
		4921	A change of state of some external event, such as data now being available
		4922	for reading on a file descriptor, time having passed or simply not having
		4923	any other events happening anymore.
		4924
		4925	In libev, events are represented as single bits (such as C<EV_READ> or
		4926	C<EV_TIMER>).
		4927
		4928	=item event library
		4929
		4930	A software package implementing an event model and loop.
		4931
		4932	=item event loop
		4933
		4934	An entity that handles and processes external events and converts them
		4935	into callback invocations.
		4936
		4937	=item event model
		4938
		4939	The model used to describe how an event loop handles and processes
		4940	watchers and events.
		4941
		4942	=item pending
		4943
		4944	A watcher is pending as soon as the corresponding event has been
		4945	detected. See L<WATCHER STATES> for details.
		4946
		4947	=item real time
		4948
		4949	The physical time that is observed. It is apparently strictly monotonic :)
		4950
		4951	=item wall-clock time
		4952
		4953	The time and date as shown on clocks. Unlike real time, it can actually
		4954	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4955	clock.
		4956
		4957	=item watcher
		4958
		4959	A data structure that describes interest in certain events. Watchers need
		4960	to be started (attached to an event loop) before they can receive events.
		4961
		4962	=back
		4963
3855	=head1 AUTHOR	4964	=head1 AUTHOR
3856		4965
3857	Marc Lehmann <libev@schmorp.de>.	4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3858		4967

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