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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
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_ struct 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	struct 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
…		…
108	name C<loop> (which is always of type C<struct 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 library knows two	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	302	libev 3 had an C<ev_loop> function colliding with the struct name).
		303
		304	The library knows two types of such loops, the I<default> loop, which
		305	supports signals and child events, and dynamically created event loops
		306	which do not.
284		307
285	=over 4	308	=over 4
286		309
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		311
289	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
290	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
291	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
292	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".
293		322
294	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
295	function.	324	function (or via the C<EV_DEFAULT> macro).
296		325
297	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
298	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
299	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).
300		330
301	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,
302	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
303	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
304	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
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	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.
307		362
308	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
309	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>).
310		365
311	The following flags are supported:	366	The following flags are supported:
…		…
326	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
327	around bugs.	382	around bugs.
328		383
329	=item C<EVFLAG_FORKCHECK>	384	=item C<EVFLAG_FORKCHECK>
330		385
331	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
332	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.
333	enabling this flag.
334		388
335	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,
336	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
337	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
338	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
…		…
344	flag.	398	flag.
345		399
346	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>
347	environment variable.	401	environment variable.
348		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
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		424
351	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
352	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,
353	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
…		…
377	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
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	452	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		453
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	454	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		455
		456	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		457	kernels).
		458
382	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,
383	but it scales phenomenally better. While poll and select usually scale	460	but it scales phenomenally better. While poll and select usually scale
384	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),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	462	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	463
387	cases and requiring a system call per fd change, no fork support and bad	464	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	465	of the more advanced event mechanisms: mere annoyances include silently
		466	dropping file descriptors, requiring a system call per change per file
		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.
		472
		473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		474	of course I<doesn't>, and epoll just loves to report events for totally
		475	I<different> file descriptors (even already closed ones, so one cannot
		476	even remove them from the set) than registered in the set (especially
		477	on SMP systems). Libev tries to counter these spurious notifications by
		478	employing an additional generation counter and comparing that against the
		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...).
389		482
390	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
391	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
392	(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
393	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
394	very well if you register events for both fds.	487	file descriptors might not work very well if you register events for both
395		488	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		489
400	Best performance from this backend is achieved by not unregistering all	490	Best performance from this backend is achieved by not unregistering all
401	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,
402	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
403	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
404	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.
405		501
406	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
407	all kernel versions tested so far.	503	all kernel versions tested so far.
408		504
409	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
410	C<EVBACKEND_POLL>.	506	C<EVBACKEND_POLL>.
411		507
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	508	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		509
414	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
415	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
416	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
417	completely useless). For this reason it's not being "auto-detected" unless	513	it's completely useless). Unlike epoll, however, whose brokenness
418	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
419	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.
420		519
421	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
422	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
423	the target platform). See C<ev_embed> watchers for more info.	522	the target platform). See C<ev_embed> watchers for more info.
424		523
425	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
426	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
427	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
428	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
429	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
430	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
431		531
432	This backend usually performs well under most conditions.	532	This backend usually performs well under most conditions.
433		533
434	While nominally embeddable in other event loops, this doesn't work	534	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	535	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	536	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	537	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	538	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	539	also broken on OS X)) and, did I mention it, using it only for sockets.
440		540
441	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
442	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
443	C<NOTE_EOF>.	543	C<NOTE_EOF>.
444		544
…		…
464	might perform better.	564	might perform better.
465		565
466	On the positive side, with the exception of the spurious readiness	566	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	567	notifications, this backend actually performed fully to specification
468	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
469	OS-specific backends.	569	OS-specific backends (I vastly prefer correctness over speed hacks).
470		570
471	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
472	C<EVBACKEND_POLL>.	572	C<EVBACKEND_POLL>.
473		573
474	=item C<EVBACKEND_ALL>	574	=item C<EVBACKEND_ALL>
…		…
479		579
480	It is definitely not recommended to use this flag.	580	It is definitely not recommended to use this flag.
481		581
482	=back	582	=back
483		583
484	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,
485	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
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	586	here). If none are specified, all backends in C<ev_recommended_backends
487		587	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		588
516	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.
517		590
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	592	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	593	fatal ("no epoll found here, maybe it hides under your chair");
521		594
522	=item ev_default_destroy ()	595	=item ev_loop_destroy (loop)
523		596
524	Destroys the default loop again (frees all memory and kernel state	597	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	598	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	599	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	600	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	603	for example).
531		604
532	Note that certain global state, such as signal state, will not be freed by	605	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	606	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	607	as signal and child watchers) would need to be stopped manually.
535		608
536	In general it is not advisable to call this function except in the	609	This function is normally used on loop objects allocated by
537	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.
538	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>
539	C<ev_loop_new> and C<ev_loop_destroy>).	616	and C<ev_loop_destroy>.
540		617
541	=item ev_loop_destroy (loop)	618	=item ev_loop_fork (loop)
542		619
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	620	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	621	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	622	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	623	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	624	child before resuming or calling C<ev_run>.
553	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.
554		630
555	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
556	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
557	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).
558		637
559	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
560	it just in case after a fork. To make this easy, the function will fit in	639	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		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	...
563	pthread_atfork (0, 0, ev_default_fork);	651	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		652
572	=item int ev_is_default_loop (loop)	653	=item int ev_is_default_loop (loop)
573		654
574	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
575	otherwise.	656	otherwise.
576		657
577	=item unsigned int ev_loop_count (loop)	658	=item unsigned int ev_iteration (loop)
578		659
579	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
580	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>
581	happily wraps around with enough iterations.	662	and happily wraps around with enough iterations.
582		663
583	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
584	"ticks" the number of loop iterations), as it roughly corresponds with	665	"ticks" the number of loop iterations), as it roughly corresponds with
585	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.
586		681
587	=item unsigned int ev_backend (loop)	682	=item unsigned int ev_backend (loop)
588		683
589	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
590	use.	685	use.
…		…
599		694
600	=item ev_now_update (loop)	695	=item ev_now_update (loop)
601		696
602	Establishes the current time by querying the kernel, updating the time	697	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	698	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	699	is usually done automatically within C<ev_run ()>.
605		700
606	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
607	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
608	the current time is a good idea.	703	the current time is a good idea.
609		704
610	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.
611		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
612	=item ev_loop (loop, int flags)	733	=item ev_run (loop, int flags)
613		734
614	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
615	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
616	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>.
617		740
618	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
619	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.
620		744
621	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
622	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
623	finished (especially in interactive programs), but having a program	747	finished (especially in interactive programs), but having a program
624	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
625	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
626	beauty.	750	beauty.
627		751
628	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
629	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
630	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
631	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.
632		757
633	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
634	necessary) and will handle those and any already outstanding ones. It	759	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	760	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	761	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	762	user-registered callback will be called), and will return after one
638	iteration of the loop.	763	iteration of the loop.
639		764
640	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
641	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
642	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
643	usually a better approach for this kind of thing.	768	usually a better approach for this kind of thing.
644		769
645	Here are the gory details of what C<ev_loop> does:	770	Here are the gory details of what C<ev_run> does:
646		771
		772	- Increment loop depth.
		773	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	774	- Before the first iteration, call any pending watchers.
		775	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	776	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- 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.
650	- Queue and call all prepare watchers.	778	- Queue and call all prepare watchers.
		779	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	780	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	781	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	782	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	783	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	784	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	785	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	786	any active watchers at all will result in not sleeping).
658	- 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.
659	- Block the process, waiting for any events.	789	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	790	- Queue all outstanding I/O (fd) events.
661	- 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.
662	- Queue all expired timers.	792	- Queue all expired timers.
663	- Queue all expired periodics.	793	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	794	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	795	- Queue all check watchers.
666	- 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).
667	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
668	be handled here by queueing them when their watcher gets executed.	798	be handled here by queueing them when their watcher gets executed.
669	- 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
670	were used, or there are no active watchers, return, otherwise	800	were used, or there are no active watchers, goto FINISH, otherwise
671	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.
672		806
673	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
674	anymore.	808	anymore.
675		809
676	... queue jobs here, make sure they register event watchers as long	810	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	811	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	812	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	813	... jobs done or somebody called unloop. yeah!
680		814
681	=item ev_unloop (loop, how)	815	=item ev_break (loop, how)
682		816
683	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
684	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
685	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
686	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.
687		821
688	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.
		823
		824	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
689		825
690	=item ev_ref (loop)	826	=item ev_ref (loop)
691		827
692	=item ev_unref (loop)	828	=item ev_unref (loop)
693		829
694	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
695	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
696	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.
697		833
698	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
699	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>
700	stopping it.	837	before stopping it.
701		838
702	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
703	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
704	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
705	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
706	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
707	(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
708	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).
709		848
710	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>
711	running when nothing else is active.	850	running when nothing else is active.
712		851
713	struct ev_signal exitsig;	852	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	853	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	854	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	855	evf_unref (loop);
717		856
718	Example: For some weird reason, unregister the above signal handler again.	857	Example: For some weird reason, unregister the above signal handler again.
…		…
742		881
743	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
744	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,
745	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
746	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
747	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.
748		889
749	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
750	to spend more time collecting timeouts, at the expense of increased	891	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	892	latency/jitter/inexactness (the watcher callback will be called
752	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
…		…
754		895
755	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
756	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
757	interactive servers (of course not for games), likewise for timeouts. It	898	interactive servers (of course not for games), likewise for timeouts. It
758	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>,
759	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).
760		905
761	Setting the I<timeout collect interval> can improve the opportunity for	906	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	907	saving power, as the program will "bundle" timer callback invocations that
763	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
764	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
765	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
766	they fire on, say, one-second boundaries only.	911	they fire on, say, one-second boundaries only.
767		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
768	=item ev_loop_verify (loop)	988	=item ev_verify (loop)
769		989
770	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
771	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
772	through all internal structures and checks them for validity. If anything	992	through all internal structures and checks them for validity. If anything
773	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
774	error and call C<abort ()>.	994	error and call C<abort ()>.
775		995
776	This can be used to catch bugs inside libev itself: under normal	996	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	1000	=back
781		1001
782		1002
783	=head1 ANATOMY OF A WATCHER	1003	=head1 ANATOMY OF A WATCHER
784		1004
		1005	In the following description, uppercase C<TYPE> in names stands for the
		1006	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1007	watchers and C<ev_io_start> for I/O watchers.
		1008
785	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
786	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
787	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:
788		1013
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1014	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	1015	{
791	ev_io_stop (w);	1016	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	1017	ev_break (loop, EVBREAK_ALL);
793	}	1018	}
794		1019
795	struct ev_loop *loop = ev_default_loop (0);	1020	struct ev_loop *loop = ev_default_loop (0);
		1021
796	struct ev_io stdin_watcher;	1022	ev_io stdin_watcher;
		1023
797	ev_init (&stdin_watcher, my_cb);	1024	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1025	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	1026	ev_io_start (loop, &stdin_watcher);
		1027
800	ev_loop (loop, 0);	1028	ev_run (loop, 0);
801		1029
802	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
803	watcher structures (and it is usually a bad idea to do this on the stack,	1031	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	1032	stack).
805		1033
		1034	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1035	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1036
806	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
807	(watcher *, callback)>, which expects a callback to be provided. This	1038	*, callback)>, which expects a callback to be provided. This callback is
808	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
809	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
810	is readable and/or writable).	1041	and/or writable).
811		1042
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1043	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1044	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1045	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1046	ev_TYPE_init (watcher *, callback, ...) >>.
816		1047
817	To make the watcher actually watch out for events, you have to start it	1048	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1049	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1050	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1051	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1052
822	As long as your watcher is active (has been started but not stopped) you	1053	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1054	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1055	reinitialise it or call its C<ev_TYPE_set> macro.
825		1056
826	Each and every callback receives the event loop pointer as first, the	1057	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1058	registered watcher structure as second, and a bitset of received events as
828	third argument.	1059	third argument.
829		1060
…		…
838	=item C<EV_WRITE>	1069	=item C<EV_WRITE>
839		1070
840	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
841	writable.	1072	writable.
842		1073
843	=item C<EV_TIMEOUT>	1074	=item C<EV_TIMER>
844		1075
845	The C<ev_timer> watcher has timed out.	1076	The C<ev_timer> watcher has timed out.
846		1077
847	=item C<EV_PERIODIC>	1078	=item C<EV_PERIODIC>
848		1079
…		…
866		1097
867	=item C<EV_PREPARE>	1098	=item C<EV_PREPARE>
868		1099
869	=item C<EV_CHECK>	1100	=item C<EV_CHECK>
870		1101
871	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
872	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
873	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
874	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
875	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
876	(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
877	C<ev_loop> from blocking).	1108	C<ev_run> from blocking).
878		1109
879	=item C<EV_EMBED>	1110	=item C<EV_EMBED>
880		1111
881	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.
882		1113
…		…
886	C<ev_fork>).	1117	C<ev_fork>).
887		1118
888	=item C<EV_ASYNC>	1119	=item C<EV_ASYNC>
889		1120
890	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>).
891		1127
892	=item C<EV_ERROR>	1128	=item C<EV_ERROR>
893		1129
894	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
895	happen because the watcher could not be properly started because libev	1131	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1132	ran out of memory, a file descriptor was found to be closed or any other
		1133	problem. Libev considers these application bugs.
		1134
897	problem. You best act on it by reporting the problem and somehow coping	1135	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1136	watcher being stopped. Note that well-written programs should not receive
		1137	an error ever, so when your watcher receives it, this usually indicates a
		1138	bug in your program.
899		1139
900	Libev will usually signal a few "dummy" events together with an error, for	1140	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1141	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1142	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1143	the error from read() or write(). This will not work in multi-threaded
904	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
905	thing, so beware.	1145	thing, so beware.
906		1146
907	=back	1147	=back
908		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
909	=head2 GENERIC WATCHER FUNCTIONS	1208	=head2 GENERIC WATCHER FUNCTIONS
910
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913		1209
914	=over 4	1210	=over 4
915		1211
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1212	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1213
…		…
923	which rolls both calls into one.	1219	which rolls both calls into one.
924		1220
925	You can reinitialise a watcher at any time as long as it has been stopped	1221	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1222	(or never started) and there are no pending events outstanding.
927		1223
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1225	int revents)>.
930		1226
931	Example: Initialise an C<ev_io> watcher in two steps.	1227	Example: Initialise an C<ev_io> watcher in two steps.
932		1228
933	ev_io w;	1229	ev_io w;
934	ev_init (&w, my_cb);	1230	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1232
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1234
939	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
940	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
941	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
942	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
…		…
955		1251
956	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.
957		1253
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1255
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1257
962	Starts (activates) the given watcher. Only active watchers will receive	1258	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1259	events. If the watcher is already active nothing will happen.
964		1260
965	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
966	whole section.	1262	whole section.
967		1263
968	ev_io_start (EV_DEFAULT_UC, &w);	1264	ev_io_start (EV_DEFAULT_UC, &w);
969		1265
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1267
972	Stops the given watcher again (if active) and clears the pending	1268	Stops the given watcher if active, and clears the pending status (whether
		1269	the watcher was active or not).
		1270
973	status. It is possible that stopped watchers are pending (for example,	1271	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1272	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1274	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1276
979	=item bool ev_is_active (ev_TYPE *watcher)	1277	=item bool ev_is_active (ev_TYPE *watcher)
980		1278
981	Returns a true value iff the watcher is active (i.e. it has been started	1279	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1280	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1296	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1297
1000	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
1001	(modulo threads).	1299	(modulo threads).
1002		1300
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1302
1005	=item int ev_priority (ev_TYPE *watcher)	1303	=item int ev_priority (ev_TYPE *watcher)
1006		1304
1007	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
1008	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>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1308	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1309	from being executed (except for C<ev_idle> watchers).
1012		1310
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	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
1019	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.
1020		1313
1021	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
1022	pending.	1315	pending.
1023		1316
		1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1318	fine, as long as you do not mind that the priority value you query might
		1319	or might not have been clamped to the valid range.
		1320
1024	The default priority used by watchers when no priority has been set is	1321	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1322	always C<0>, which is supposed to not be too high and not be too low :).
1026		1323
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1325	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1326
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1328
1033	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
1034	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
…		…
1041	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
1042	watcher isn't pending it does nothing and returns C<0>.	1338	watcher isn't pending it does nothing and returns C<0>.
1043		1339
1044	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
1045	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.
1046		1356
1047	=back	1357	=back
1048		1358
1049		1359
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1366	member, you can also "subclass" the watcher type and provide your own
1057	data:	1367	data:
1058		1368
1059	struct my_io	1369	struct my_io
1060	{	1370	{
1061	struct ev_io io;	1371	ev_io io;
1062	int otherfd;	1372	int otherfd;
1063	void *somedata;	1373	void *somedata;
1064	struct whatever *mostinteresting;	1374	struct whatever *mostinteresting;
1065	};	1375	};
1066		1376
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1380
1071	And since your callback will be called with a pointer to the watcher, you	1381	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1382	can cast it back to your own type:
1073		1383
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1385	{
1076	struct my_io *w = (struct my_io *)w_;	1386	struct my_io *w = (struct my_io *)w_;
1077	...	1387	...
1078	}	1388	}
1079		1389
…		…
1097	programmers):	1407	programmers):
1098		1408
1099	#include <stddef.h>	1409	#include <stddef.h>
1100		1410
1101	static void	1411	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1412	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1413	{
1104	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1415	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1416	}
1107		1417
1108	static void	1418	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1420	{
1111	struct my_biggy big = (struct my_biggy *	1421	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	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.
1114		1527
1115		1528
1116	=head1 WATCHER TYPES	1529	=head1 WATCHER TYPES
1117		1530
1118	This section describes each watcher in detail, but will not repeat	1531	This section describes each watcher in detail, but will not repeat
…		…
1144	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
1145	required if you know what you are doing).	1558	required if you know what you are doing).
1146		1559
1147	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
1148	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
1149	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.
1150		1565
1151	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
1152	receive "spurious" readiness notifications, that is your callback might	1567	receive "spurious" readiness notifications, that is your callback might
1153	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
1154	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
…		…
1219		1634
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1635	So when you encounter spurious, unexplained daemon exits, make sure you
1221	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
1222	somewhere, as that would have given you a big clue).	1637	somewhere, as that would have given you a big clue).
1223		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.
1224		1677
1225	=head3 Watcher-Specific Functions	1678	=head3 Watcher-Specific Functions
1226		1679
1227	=over 4	1680	=over 4
1228		1681
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1702	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1703	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1704	attempt to read a whole line in the callback.
1252		1705
1253	static void	1706	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1707	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1708	{
1256	ev_io_stop (loop, w);	1709	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1710	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1711	}
1259		1712
1260	...	1713	...
1261	struct ev_loop *loop = ev_default_init (0);	1714	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1715	ev_io stdin_readable;
1263	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);
1264	ev_io_start (loop, &stdin_readable);	1717	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1718	ev_run (loop, 0);
1266		1719
1267		1720
1268	=head2 C<ev_timer> - relative and optionally repeating timeouts	1721	=head2 C<ev_timer> - relative and optionally repeating timeouts
1269		1722
1270	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
…		…
1275	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
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1730	monotonic clock option helps a lot here).
1278		1731
1279	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
1280	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
1281	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).
		1738
		1739	=head3 Be smart about timeouts
		1740
		1741	Many real-world problems involve some kind of timeout, usually for error
		1742	recovery. A typical example is an HTTP request - if the other side hangs,
		1743	you want to raise some error after a while.
		1744
		1745	What follows are some ways to handle this problem, from obvious and
		1746	inefficient to smart and efficient.
		1747
		1748	In the following, a 60 second activity timeout is assumed - a timeout that
		1749	gets reset to 60 seconds each time there is activity (e.g. each time some
		1750	data or other life sign was received).
		1751
		1752	=over 4
		1753
		1754	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1755
		1756	This is the most obvious, but not the most simple way: In the beginning,
		1757	start the watcher:
		1758
		1759	ev_timer_init (timer, callback, 60., 0.);
		1760	ev_timer_start (loop, timer);
		1761
		1762	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1763	and start it again:
		1764
		1765	ev_timer_stop (loop, timer);
		1766	ev_timer_set (timer, 60., 0.);
		1767	ev_timer_start (loop, timer);
		1768
		1769	This is relatively simple to implement, but means that each time there is
		1770	some activity, libev will first have to remove the timer from its internal
		1771	data structure and then add it again. Libev tries to be fast, but it's
		1772	still not a constant-time operation.
		1773
		1774	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1775
		1776	This is the easiest way, and involves using C<ev_timer_again> instead of
		1777	C<ev_timer_start>.
		1778
		1779	To implement this, configure an C<ev_timer> with a C<repeat> value
		1780	of C<60> and then call C<ev_timer_again> at start and each time you
		1781	successfully read or write some data. If you go into an idle state where
		1782	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1783	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1784
		1785	That means you can ignore both the C<ev_timer_start> function and the
		1786	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1787	member and C<ev_timer_again>.
		1788
		1789	At start:
		1790
		1791	ev_init (timer, callback);
		1792	timer->repeat = 60.;
		1793	ev_timer_again (loop, timer);
		1794
		1795	Each time there is some activity:
		1796
		1797	ev_timer_again (loop, timer);
		1798
		1799	It is even possible to change the time-out on the fly, regardless of
		1800	whether the watcher is active or not:
		1801
		1802	timer->repeat = 30.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	This is slightly more efficient then stopping/starting the timer each time
		1806	you want to modify its timeout value, as libev does not have to completely
		1807	remove and re-insert the timer from/into its internal data structure.
		1808
		1809	It is, however, even simpler than the "obvious" way to do it.
		1810
		1811	=item 3. Let the timer time out, but then re-arm it as required.
		1812
		1813	This method is more tricky, but usually most efficient: Most timeouts are
		1814	relatively long compared to the intervals between other activity - in
		1815	our example, within 60 seconds, there are usually many I/O events with
		1816	associated activity resets.
		1817
		1818	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1819	but remember the time of last activity, and check for a real timeout only
		1820	within the callback:
		1821
		1822	ev_tstamp last_activity; // time of last activity
		1823
		1824	static void
		1825	callback (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_tstamp now = ev_now (EV_A);
		1828	ev_tstamp timeout = last_activity + 60.;
		1829
		1830	// if last_activity + 60. is older than now, we did time out
		1831	if (timeout < now)
		1832	{
		1833	// timeout occurred, take action
		1834	}
		1835	else
		1836	{
		1837	// callback was invoked, but there was some activity, re-arm
		1838	// the watcher to fire in last_activity + 60, which is
		1839	// guaranteed to be in the future, so "again" is positive:
		1840	w->repeat = timeout - now;
		1841	ev_timer_again (EV_A_ w);
		1842	}
		1843	}
		1844
		1845	To summarise the callback: first calculate the real timeout (defined
		1846	as "60 seconds after the last activity"), then check if that time has
		1847	been reached, which means something I<did>, in fact, time out. Otherwise
		1848	the callback was invoked too early (C<timeout> is in the future), so
		1849	re-schedule the timer to fire at that future time, to see if maybe we have
		1850	a timeout then.
		1851
		1852	Note how C<ev_timer_again> is used, taking advantage of the
		1853	C<ev_timer_again> optimisation when the timer is already running.
		1854
		1855	This scheme causes more callback invocations (about one every 60 seconds
		1856	minus half the average time between activity), but virtually no calls to
		1857	libev to change the timeout.
		1858
		1859	To start the timer, simply initialise the watcher and set C<last_activity>
		1860	to the current time (meaning we just have some activity :), then call the
		1861	callback, which will "do the right thing" and start the timer:
		1862
		1863	ev_init (timer, callback);
		1864	last_activity = ev_now (loop);
		1865	callback (loop, timer, EV_TIMER);
		1866
		1867	And when there is some activity, simply store the current time in
		1868	C<last_activity>, no libev calls at all:
		1869
		1870	last_activity = ev_now (loop);
		1871
		1872	This technique is slightly more complex, but in most cases where the
		1873	time-out is unlikely to be triggered, much more efficient.
		1874
		1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1876	callback :) - just change the timeout and invoke the callback, which will
		1877	fix things for you.
		1878
		1879	=item 4. Wee, just use a double-linked list for your timeouts.
		1880
		1881	If there is not one request, but many thousands (millions...), all
		1882	employing some kind of timeout with the same timeout value, then one can
		1883	do even better:
		1884
		1885	When starting the timeout, calculate the timeout value and put the timeout
		1886	at the I<end> of the list.
		1887
		1888	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1889	the list is expected to fire (for example, using the technique #3).
		1890
		1891	When there is some activity, remove the timer from the list, recalculate
		1892	the timeout, append it to the end of the list again, and make sure to
		1893	update the C<ev_timer> if it was taken from the beginning of the list.
		1894
		1895	This way, one can manage an unlimited number of timeouts in O(1) time for
		1896	starting, stopping and updating the timers, at the expense of a major
		1897	complication, and having to use a constant timeout. The constant timeout
		1898	ensures that the list stays sorted.
		1899
		1900	=back
		1901
		1902	So which method the best?
		1903
		1904	Method #2 is a simple no-brain-required solution that is adequate in most
		1905	situations. Method #3 requires a bit more thinking, but handles many cases
		1906	better, and isn't very complicated either. In most case, choosing either
		1907	one is fine, with #3 being better in typical situations.
		1908
		1909	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1910	rather complicated, but extremely efficient, something that really pays
		1911	off after the first million or so of active timers, i.e. it's usually
		1912	overkill :)
1282		1913
1283	=head3 The special problem of time updates	1914	=head3 The special problem of time updates
1284		1915
1285	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
1286	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
1287	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
1288	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
1289	lots of events in one iteration.	1920	lots of events in one iteration.
1290		1921
1291	The relative timeouts are calculated relative to the C<ev_now ()>	1922	The relative timeouts are calculated relative to the C<ev_now ()>
1292	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
…		…
1298		1929
1299	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
1300	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
1301	()>.	1932	()>.
1302		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
1303	=head3 Watcher-Specific Functions and Data Members	1964	=head3 Watcher-Specific Functions and Data Members
1304		1965
1305	=over 4	1966	=over 4
1306		1967
1307	=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)
…		…
1330	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).
1331		1992
1332	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
1333	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.
1334		1995
1335	This sounds a bit complicated, but here is a useful and typical	1996	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1997	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		1998
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		2000
1348	ev_timer_init (timer, callback, 0., 5.);	2001	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	2002	then this time is relative to the current event loop time, otherwise it's
1350	...	2003	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		2004
1357	This is more slightly efficient then stopping/starting the timer each time	2005	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	2006	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		2007	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	2008	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	2009	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		2010
1366	=item ev_tstamp repeat [read-write]	2011	=item ev_tstamp repeat [read-write]
1367		2012
1368	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
1369	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),
…		…
1374	=head3 Examples	2019	=head3 Examples
1375		2020
1376	Example: Create a timer that fires after 60 seconds.	2021	Example: Create a timer that fires after 60 seconds.
1377		2022
1378	static void	2023	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2024	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	2025	{
1381	.. one minute over, w is actually stopped right here	2026	.. one minute over, w is actually stopped right here
1382	}	2027	}
1383		2028
1384	struct ev_timer mytimer;	2029	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2030	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	2031	ev_timer_start (loop, &mytimer);
1387		2032
1388	Example: Create a timeout timer that times out after 10 seconds of	2033	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	2034	inactivity.
1390		2035
1391	static void	2036	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2037	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	2038	{
1394	.. ten seconds without any activity	2039	.. ten seconds without any activity
1395	}	2040	}
1396		2041
1397	struct ev_timer mytimer;	2042	ev_timer mytimer;
1398	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 */
1399	ev_timer_again (&mytimer); /* start timer */	2044	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	2045	ev_run (loop, 0);
1401		2046
1402	// 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":
1403	// reset the timeout to start ticking again at 10 seconds	2048	// reset the timeout to start ticking again at 10 seconds
1404	ev_timer_again (&mytimer);	2049	ev_timer_again (&mytimer);
1405		2050
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	2052	=head2 C<ev_periodic> - to cron or not to cron?
1408		2053
1409	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
1410	(and unfortunately a bit complex).	2055	(and unfortunately a bit complex).
1411		2056
1412	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
1413	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
1414	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
1415	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
1416	+ 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
1417	clock to January of the previous year, then it will take more than year	2062	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		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
1421	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
1422	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
1423	complicated rules.	2074	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2075	those cannot react to time jumps.
1424		2076
1425	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
1426	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
1427	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).
1428		2082
1429	=head3 Watcher-Specific Functions and Data Members	2083	=head3 Watcher-Specific Functions and Data Members
1430		2084
1431	=over 4	2085	=over 4
1432		2086
1433	=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)
1434		2088
1435	=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)
1436		2090
1437	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
1438	operation, and we will explain them from simplest to most complex:	2092	operation, and we will explain them from simplest to most complex:
1439		2093
1440	=over 4	2094	=over 4
1441		2095
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2096	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2097
1444	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
1445	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
1446	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
1447	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.
1448		2103
1449	=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)
1450		2105
1451	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
1452	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
1453	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.
1454		2110
1455	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
1456	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
1457	hour, on the hour:	2113	hour, on the hour (with respect to UTC):
1458		2114
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2115	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2116
1461	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,
1462	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
1463	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
1464	by 3600.	2120	by 3600.
1465		2121
1466	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
1467	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
1468	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.
1469		2125
1470	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
1471	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
1472	this value, and in fact is often specified as zero.	2128	this value, and in fact is often specified as zero.
1473		2129
1474	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
1475	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
1476	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
1477	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).
1478		2134
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2135	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2136
1481	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
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2138	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	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
1484	current time as second argument.	2140	current time as second argument.
1485		2141
1486	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,
1487	ever, or make ANY event loop modifications whatsoever>.	2143	or make ANY other event loop modifications whatsoever, unless explicitly
		2144	allowed by documentation here>.
1488		2145
1489	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
1490	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
1491	only event loop modification you are allowed to do).	2148	only event loop modification you are allowed to do).
1492		2149
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2150	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2151	*w, ev_tstamp now)>, e.g.:
1495		2152
		2153	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2154	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2155	{
1498	return now + 60.;	2156	return now + 60.;
1499	}	2157	}
1500		2158
1501	It must return the next time to trigger, based on the passed time value	2159	It must return the next time to trigger, based on the passed time value
…		…
1521	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
1522	program when the crontabs have changed).	2180	program when the crontabs have changed).
1523		2181
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2182	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2183
1526	When active, returns the absolute time that the watcher is supposed to	2184	When active, returns the absolute time that the watcher is supposed
1527	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.
1528		2188
1529	=item ev_tstamp offset [read-write]	2189	=item ev_tstamp offset [read-write]
1530		2190
1531	When repeating, this contains the offset value, otherwise this is the	2191	When repeating, this contains the offset value, otherwise this is the
1532	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).
1533		2194
1534	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
1535	timer fires or C<ev_periodic_again> is being called.	2196	timer fires or C<ev_periodic_again> is being called.
1536		2197
1537	=item ev_tstamp interval [read-write]	2198	=item ev_tstamp interval [read-write]
1538		2199
1539	The current interval value. Can be modified any time, but changes only	2200	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2201	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2202	called.
1542		2203
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2204	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2205
1545	The current reschedule callback, or C<0>, if this functionality is	2206	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2207	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2208	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2209
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2214	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2215	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2216	potentially a lot of jitter, but good long-term stability.
1556		2217
1557	static void	2218	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2219	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1559	{	2220	{
1560	... 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)
1561	}	2222	}
1562		2223
1563	struct ev_periodic hourly_tick;	2224	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2225	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2226	ev_periodic_start (loop, &hourly_tick);
1566		2227
1567	Example: The same as above, but use a reschedule callback to do it:	2228	Example: The same as above, but use a reschedule callback to do it:
1568		2229
1569	#include <math.h>	2230	#include <math.h>
1570		2231
1571	static ev_tstamp	2232	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2233	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2234	{
1574	return now + (3600. - fmod (now, 3600.));	2235	return now + (3600. - fmod (now, 3600.));
1575	}	2236	}
1576		2237
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2238	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2239
1579	Example: Call a callback every hour, starting now:	2240	Example: Call a callback every hour, starting now:
1580		2241
1581	struct ev_periodic hourly_tick;	2242	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2243	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2244	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2245	ev_periodic_start (loop, &hourly_tick);
1585		2246
1586		2247
…		…
1589	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
1590	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
1591	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
1592	normal event processing, like any other event.	2253	normal event processing, like any other event.
1593		2254
1594	If you want signals asynchronously, just use C<sigaction> as you would	2255	If you want signals to be delivered truly asynchronously, just use
1595	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
1596	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.
1597		2259
1598	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
1599	first watcher gets started will libev actually register a signal handler	2266	When the first watcher gets started will libev actually register something
1600	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
1601	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).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2269
1605	If possible and supported, libev will install its handlers with	2270	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2271	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	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
1608	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
1609	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.
1610		2304
1611	=head3 Watcher-Specific Functions and Data Members	2305	=head3 Watcher-Specific Functions and Data Members
1612		2306
1613	=over 4	2307	=over 4
1614		2308
…		…
1628	=head3 Examples	2322	=head3 Examples
1629		2323
1630	Example: Try to exit cleanly on SIGINT.	2324	Example: Try to exit cleanly on SIGINT.
1631		2325
1632	static void	2326	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2327	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2328	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2329	ev_break (loop, EVBREAK_ALL);
1636	}	2330	}
1637		2331
1638	struct ev_signal signal_watcher;	2332	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2333	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &signal_watcher);	2334	ev_signal_start (loop, &signal_watcher);
1641		2335
1642		2336
1643	=head2 C<ev_child> - watch out for process status changes	2337	=head2 C<ev_child> - watch out for process status changes
…		…
1646	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
1647	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
1648	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
1649	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.,
1650	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,
1651	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
1652	not.	2346	in the next callback invocation is not.
1653		2347
1654	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
1655	you can only register child watchers in the default event loop.	2349	you can only register child watchers in the default event loop.
1656		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
1657	=head3 Process Interaction	2355	=head3 Process Interaction
1658		2356
1659	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
1660	initialised. This is necessary to guarantee proper behaviour even if	2358	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2359	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2360	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	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
1664	children, even ones not watched.	2362	children, even ones not watched.
1665		2363
1666	=head3 Overriding the Built-In Processing	2364	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2374	=head3 Stopping the Child Watcher
1677		2375
1678	Currently, the child watcher never gets stopped, even when the	2376	Currently, the child watcher never gets stopped, even when the
1679	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
1680	callback. Future versions of libev might stop the watcher automatically	2378	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2379	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2380	problem).
1682		2381
1683	=head3 Watcher-Specific Functions and Data Members	2382	=head3 Watcher-Specific Functions and Data Members
1684		2383
1685	=over 4	2384	=over 4
1686		2385
…		…
1718	its completion.	2417	its completion.
1719		2418
1720	ev_child cw;	2419	ev_child cw;
1721		2420
1722	static void	2421	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2422	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2423	{
1725	ev_child_stop (EV_A_ w);	2424	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2425	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2426	}
1728		2427
…		…
1743		2442
1744		2443
1745	=head2 C<ev_stat> - did the file attributes just change?	2444	=head2 C<ev_stat> - did the file attributes just change?
1746		2445
1747	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
1748	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)
1749	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.
1750		2450
1751	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
1752	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
1753	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
1754	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
1755	the stat buffer having unspecified contents.	2455	least one) and all the other fields of the stat buffer having unspecified
		2456	contents.
1756		2457
1757	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
1758	relative and your working directory changes, the behaviour is undefined.	2460	your working directory changes, then the behaviour is undefined.
1759		2461
1760	Since there is no standard kernel interface to do this, the portable	2462	Since there is no portable change notification interface available, the
1761	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
1762	it changed somehow. You can specify a recommended polling interval for	2464	to see if it changed somehow. You can specify a recommended polling
1763	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
1764	then a I<suitable, unspecified default> value will be used (which	2466	recommended!) then a I<suitable, unspecified default> value will be used
1765	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
1766	dynamically). Libev will also impose a minimum interval which is currently	2468	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2469	currently around C<0.1>, but that's usually overkill.
1768		2470
1769	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,
1770	as even with OS-supported change notifications, this can be	2472	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2473	resource-intensive.
1772		2474
1773	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
1774	is the Linux inotify interface (implementing kqueue support is left as	2476	is the Linux inotify interface (implementing kqueue support is left as an
1775	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
1776	of implementing C<ev_stat> semantics with kqueue).	2478	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2479
1778	=head3 ABI Issues (Largefile Support)	2480	=head3 ABI Issues (Largefile Support)
1779		2481
1780	Libev by default (unless the user overrides this) uses the default	2482	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2483	compilation environment, which means that on systems with large file
1782	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
1783	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
1784	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
1785	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
1786	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
1787	most noticeably disabled with ev_stat and large file support.	2489	most noticeably displayed with ev_stat and large file support.
1788		2490
1789	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
1790	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
1791	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
1792	to exchange stat structures with application programs compiled using the	2494	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2495	default compilation environment.
1794		2496
1795	=head3 Inotify and Kqueue	2497	=head3 Inotify and Kqueue
1796		2498
1797	When C<inotify (7)> support has been compiled into libev (generally only	2499	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2500	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2501	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2502	watcher is being started.
1801		2503
1802	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
1803	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
1804	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
1805	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,
1806	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.
1807		2512
1808	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
1809	implement this functionality, due to the requirement of having a file	2514	implement this functionality, due to the requirement of having a file
1810	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
1811	etc. is difficult.	2516	etc. is difficult.
1812		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
1813	=head3 The special problem of stat time resolution	2536	=head3 The special problem of stat time resolution
1814		2537
1815	The C<stat ()> system call only supports full-second resolution portably, and	2538	The C<stat ()> system call only supports full-second resolution portably,
1816	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
1817	only support whole seconds.	2540	still only support whole seconds.
1818		2541
1819	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
1820	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
1821	calls your callback, which does something. When there is another update	2544	calls your callback, which does something. When there is another update
1822	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
…		…
1965		2688
1966	=head3 Watcher-Specific Functions and Data Members	2689	=head3 Watcher-Specific Functions and Data Members
1967		2690
1968	=over 4	2691	=over 4
1969		2692
1970	=item ev_idle_init (ev_signal *, callback)	2693	=item ev_idle_init (ev_idle *, callback)
1971		2694
1972	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
1973	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,
1974	believe me.	2697	believe me.
1975		2698
…		…
1979		2702
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2703	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2704	callback, free it. Also, use no error checking, as usual.
1982		2705
1983	static void	2706	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2707	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2708	{
1986	free (w);	2709	free (w);
1987	// now do something you wanted to do when the program has	2710	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2711	// no longer anything immediate to do.
1989	}	2712	}
1990		2713
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2714	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2715	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2716	ev_idle_start (loop, idle_watcher);
1994		2717
1995		2718
1996	=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!
1997		2720
1998	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:
1999	prepare watchers get invoked before the process blocks and check watchers	2722	prepare watchers get invoked before the process blocks and check watchers
2000	afterwards.	2723	afterwards.
2001		2724
2002	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
2003	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>
2004	watchers. Other loops than the current one are fine, however. The	2727	watchers. Other loops than the current one are fine, however. The
2005	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
2006	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,
2007	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
…		…
2077		2800
2078	static ev_io iow [nfd];	2801	static ev_io iow [nfd];
2079	static ev_timer tw;	2802	static ev_timer tw;
2080		2803
2081	static void	2804	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2805	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2806	{
2084	}	2807	}
2085		2808
2086	// create io watchers for each fd and a timer before blocking	2809	// create io watchers for each fd and a timer before blocking
2087	static void	2810	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2811	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2812	{
2090	int timeout = 3600000;	2813	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2814	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2815	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2816	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2817
2095	/* 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 */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2819	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2820	ev_timer_start (loop, &tw);
2098		2821
2099	// create one ev_io per pollfd	2822	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2823	for (int i = 0; i < nfd; ++i)
2101	{	2824	{
…		…
2108	}	2831	}
2109	}	2832	}
2110		2833
2111	// stop all watchers after blocking	2834	// stop all watchers after blocking
2112	static void	2835	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2836	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2837	{
2115	ev_timer_stop (loop, &tw);	2838	ev_timer_stop (loop, &tw);
2116		2839
2117	for (int i = 0; i < nfd; ++i)	2840	for (int i = 0; i < nfd; ++i)
2118	{	2841	{
…		…
2175		2898
2176	if (timeout >= 0)	2899	if (timeout >= 0)
2177	// create/start timer	2900	// create/start timer
2178		2901
2179	// poll	2902	// poll
2180	ev_loop (EV_A_ 0);	2903	ev_run (EV_A_ 0);
2181		2904
2182	// stop timer again	2905	// stop timer again
2183	if (timeout >= 0)	2906	if (timeout >= 0)
2184	ev_timer_stop (EV_A_ &to);	2907	ev_timer_stop (EV_A_ &to);
2185		2908
…		…
2214	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),
2215	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
2216	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
2217	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.
2218		2941
2219	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
2220	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
2221	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
2222	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
2223	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
2224	to C<0>, in which case the embed watcher will automatically execute the	2947	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2948
2227	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
2228	callback will be invoked whenever some events have been handled. You can	2950	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2951
2232	Also, there have not currently been made special provisions for forking:	2952	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	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
2234	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
2235	yourself - but you can use a fork watcher to handle this automatically,	2955	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2956
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2957	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2958	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2959	portable one.
2241		2960
…		…
2267	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).
2268		2987
2269	=item ev_embed_sweep (loop, ev_embed *)	2988	=item ev_embed_sweep (loop, ev_embed *)
2270		2989
2271	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
2272	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
2273	appropriate way for embedded loops.	2992	appropriate way for embedded loops.
2274		2993
2275	=item struct ev_loop *other [read-only]	2994	=item struct ev_loop *other [read-only]
2276		2995
2277	The embedded event loop.	2996	The embedded event loop.
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3005	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	3006	used).
2288		3007
2289	struct ev_loop *loop_hi = ev_default_init (0);	3008	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	3009	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	3010	ev_embed embed;
2292		3011
2293	// see if there is a chance of getting one that works	3012	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	3013	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3014	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3015	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	3029	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3030	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		3031
2313	struct ev_loop *loop = ev_default_init (0);	3032	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	3033	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	3034	ev_embed embed;
2316		3035
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3036	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3037	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	3038	{
2320	ev_embed_init (&embed, 0, loop_socket);	3039	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	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,
2336	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
2337	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
2338	handlers will be invoked, too, of course.	3057	handlers will be invoked, too, of course.
2339		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
2340	=head3 Watcher-Specific Functions and Data Members	3093	=head3 Watcher-Specific Functions and Data Members
2341		3094
2342	=over 4	3095	=over 4
2343		3096
2344	=item ev_fork_init (ev_signal *, callback)	3097	=item ev_fork_init (ev_signal *, callback)
…		…
2348	believe me.	3101	believe me.
2349		3102
2350	=back	3103	=back
2351		3104
2352		3105
2353	=head2 C<ev_async> - how to wake up another event loop	3106	=head2 C<ev_async> - how to wake up an event loop
2354		3107
2355	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
2356	asynchronous sources such as signal handlers (as opposed to multiple event	3109	asynchronous sources such as signal handlers (as opposed to multiple event
2357	loops - those are of course safe to use in different threads).	3110	loops - those are of course safe to use in different threads).
2358		3111
2359	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,
2360	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>
2361	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
2362	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.
2363	safe.
2364		3116
2365	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,
2366	too, are asynchronous in nature, and signals, too, will be compressed	3118	too, are asynchronous in nature, and signals, too, will be compressed
2367	(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
2368	C<ev_async_sent> calls).	3120	C<ev_async_sent> calls).
…		…
2373	=head3 Queueing	3125	=head3 Queueing
2374		3126
2375	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
2376	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
2377	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
2378	need elaborate support such as pthreads.	3130	need elaborate support such as pthreads or unportable memory access
		3131	semantics.
2379		3132
2380	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
2381	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
2382	queue:	3135	queue:
2383		3136
2384	=over 4	3137	=over 4
2385		3138
2386	=item queueing from a signal handler context	3139	=item queueing from a signal handler context
2387		3140
2388	To implement race-free queueing, you simply add to the queue in the signal	3141	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3142	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	3143	an example that does that for some fictitious SIGUSR1 handler:
2391		3144
2392	static ev_async mysig;	3145	static ev_async mysig;
2393		3146
2394	static void	3147	static void
2395	sigusr1_handler (void)	3148	sigusr1_handler (void)
…		…
2461	=over 4	3214	=over 4
2462		3215
2463	=item ev_async_init (ev_async *, callback)	3216	=item ev_async_init (ev_async *, callback)
2464		3217
2465	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
2466	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,
2467	trust me.	3220	trust me.
2468		3221
2469	=item ev_async_send (loop, ev_async *)	3222	=item ev_async_send (loop, ev_async *)
2470		3223
2471	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
2472	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
2473	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
2474	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
2475	section below on what exactly this means).	3228	section below on what exactly this means).
2476		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
2477	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
2478	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
2479	calls to C<ev_async_send>.	3237	repeated calls to C<ev_async_send> for the same event loop.
2480		3238
2481	=item bool = ev_async_pending (ev_async *)	3239	=item bool = ev_async_pending (ev_async *)
2482		3240
2483	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
2484	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
…		…
2487	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
2488	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,
2489	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
2490	quickly check whether invoking the loop might be a good idea.	3248	quickly check whether invoking the loop might be a good idea.
2491		3249
2492	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,
2493	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.
2494		3254
2495	=back	3255	=back
2496		3256
2497		3257
2498	=head1 OTHER FUNCTIONS	3258	=head1 OTHER FUNCTIONS
…		…
2502	=over 4	3262	=over 4
2503		3263
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3264	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		3265
2506	This function combines a simple timer and an I/O watcher, calls your	3266	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	3267	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	3268	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	3269	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	3270	more watchers yourself.
2511		3271
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	3272	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3273	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	3274	the given C<fd> and C<events> set will be created and started.
2515		3275
2516	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
2517	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
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3278	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		3279
2521	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
2522	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
2523	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>
2524	value passed to C<ev_once>:	3283	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3284	a timeout and an io event at the same time - you probably should give io
		3285	events precedence.
		3286
		3287	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		3288
2526	static void stdin_ready (int revents, void *arg)	3289	static void stdin_ready (int revents, void *arg)
2527	{	3290	{
		3291	if (revents & EV_READ)
		3292	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	3293	else if (revents & EV_TIMER)
2529	/* doh, nothing entered */;	3294	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	3295	}
2533		3296
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		3298
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
2537
2538	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).
2541
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3299	=item ev_feed_fd_event (loop, int fd, int revents)
2543		3300
2544	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
2545	the given events it.	3302	the given events it.
2546		3303
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	3304	=item ev_feed_signal_event (loop, int signum)
2548		3305
2549	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
2550	loop!).	3307	loop!).
2551		3308
2552	=back	3309	=back
…		…
2632		3389
2633	=over 4	3390	=over 4
2634		3391
2635	=item ev::TYPE::TYPE ()	3392	=item ev::TYPE::TYPE ()
2636		3393
2637	=item ev::TYPE::TYPE (struct ev_loop *)	3394	=item ev::TYPE::TYPE (loop)
2638		3395
2639	=item ev::TYPE::~TYPE	3396	=item ev::TYPE::~TYPE
2640		3397
2641	The constructor (optionally) takes an event loop to associate the watcher	3398	The constructor (optionally) takes an event loop to associate the watcher
2642	with. If it is omitted, it will use C<EV_DEFAULT>.	3399	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2674		3431
2675	myclass obj;	3432	myclass obj;
2676	ev::io iow;	3433	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3434	iow.set <myclass, &myclass::io_cb> (&obj);
2678		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
2679	=item w->set<function> (void *data = 0)	3464	=item w->set<function> (void *data = 0)
2680		3465
2681	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
2682	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
2683	C<data> member and is free for you to use.	3468	C<data> member and is free for you to use.
…		…
2689	Example: Use a plain function as callback.	3474	Example: Use a plain function as callback.
2690		3475
2691	static void io_cb (ev::io &w, int revents) { }	3476	static void io_cb (ev::io &w, int revents) { }
2692	iow.set <io_cb> ();	3477	iow.set <io_cb> ();
2693		3478
2694	=item w->set (struct ev_loop *)	3479	=item w->set (loop)
2695		3480
2696	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
2697	do this when the watcher is inactive (and not pending either).	3482	do this when the watcher is inactive (and not pending either).
2698		3483
2699	=item w->set ([arguments])	3484	=item w->set ([arguments])
2700		3485
2701	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
2702	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
2703	automatically stopped and restarted when reconfiguring it with this	3488	C counterpart, an active watcher gets automatically stopped and restarted
2704	method.	3489	when reconfiguring it with this method.
2705		3490
2706	=item w->start ()	3491	=item w->start ()
2707		3492
2708	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
2709	constructor already stores the event loop.	3494	constructor already stores the event loop.
2710		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
2711	=item w->stop ()	3502	=item w->stop ()
2712		3503
2713	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.
2714		3505
2715	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3506	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2727		3518
2728	=back	3519	=back
2729		3520
2730	=back	3521	=back
2731		3522
2732	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
2733	the constructor.	3524	watchers in the constructor.
2734		3525
2735	class myclass	3526	class myclass
2736	{	3527	{
2737	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);
2738	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2739		3531
2740	myclass (int fd)	3532	myclass (int fd)
2741	{	3533	{
2742	io .set <myclass, &myclass::io_cb > (this);	3534	io .set <myclass, &myclass::io_cb > (this);
		3535	io2 .set <myclass, &myclass::io2_cb > (this);
2743	idle.set <myclass, &myclass::idle_cb> (this);	3536	idle.set <myclass, &myclass::idle_cb> (this);
2744		3537
2745	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
2746	}	3542	}
2747	};	3543	};
2748		3544
2749		3545
2750	=head1 OTHER LANGUAGE BINDINGS	3546	=head1 OTHER LANGUAGE BINDINGS
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3565	L<http://software.schmorp.de/pkg/EV>.
2770		3566
2771	=item Python	3567	=item Python
2772		3568
2773	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
2774	seems to be quite complete and well-documented. Note, however, that the	3570	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3571
2780	=item Ruby	3572	=item Ruby
2781		3573
2782	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
2783	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
2784	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
2785	L<http://rev.rubyforge.org/>.	3577	L<http://rev.rubyforge.org/>.
2786		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
2787	=item D	3587	=item D
2788		3588
2789	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
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3591
		3592	=item Ocaml
		3593
		3594	Erkki Seppala has written Ocaml bindings for libev, to be found at
		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>.
2791		3602
2792	=back	3603	=back
2793		3604
2794		3605
2795	=head1 MACRO MAGIC	3606	=head1 MACRO MAGIC
…		…
2809	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,
2810	C<EV_A_> is used when other arguments are following. Example:	3621	C<EV_A_> is used when other arguments are following. Example:
2811		3622
2812	ev_unref (EV_A);	3623	ev_unref (EV_A);
2813	ev_timer_add (EV_A_ watcher);	3624	ev_timer_add (EV_A_ watcher);
2814	ev_loop (EV_A_ 0);	3625	ev_run (EV_A_ 0);
2815		3626
2816	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,
2817	which is often provided by the following macro.	3628	which is often provided by the following macro.
2818		3629
2819	=item C<EV_P>, C<EV_P_>	3630	=item C<EV_P>, C<EV_P_>
…		…
2859	}	3670	}
2860		3671
2861	ev_check check;	3672	ev_check check;
2862	ev_check_init (&check, check_cb);	3673	ev_check_init (&check, check_cb);
2863	ev_check_start (EV_DEFAULT_ &check);	3674	ev_check_start (EV_DEFAULT_ &check);
2864	ev_loop (EV_DEFAULT_ 0);	3675	ev_run (EV_DEFAULT_ 0);
2865		3676
2866	=head1 EMBEDDING	3677	=head1 EMBEDDING
2867		3678
2868	Libev can (and often is) directly embedded into host	3679	Libev can (and often is) directly embedded into host
2869	applications. Examples of applications that embed it include the Deliantra	3680	applications. Examples of applications that embed it include the Deliantra
…		…
2896		3707
2897	#define EV_STANDALONE 1	3708	#define EV_STANDALONE 1
2898	#include "ev.h"	3709	#include "ev.h"
2899		3710
2900	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++
2901	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
2902	as a bug).	3713	as a bug).
2903		3714
2904	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
2905	in your include path (e.g. in libev/ when using -Ilibev):	3716	in your include path (e.g. in libev/ when using -Ilibev):
2906		3717
…		…
2949	libev.m4	3760	libev.m4
2950		3761
2951	=head2 PREPROCESSOR SYMBOLS/MACROS	3762	=head2 PREPROCESSOR SYMBOLS/MACROS
2952		3763
2953	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
2954	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
2955	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.
2956		3774
2957	=over 4	3775	=over 4
2958		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
2959	=item EV_STANDALONE	3793	=item EV_STANDALONE (h)
2960		3794
2961	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
2962	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
2963	implementations for some libevent functions (such as logging, which is not	3797	implementations for some libevent functions (such as logging, which is not
2964	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
2965	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.
2966		3800
		3801	In standalone mode, libev will still try to automatically deduce the
		3802	configuration, but has to be more conservative.
		3803
2967	=item EV_USE_MONOTONIC	3804	=item EV_USE_MONOTONIC
2968		3805
2969	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
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3807	monotonic clock option at both compile time and runtime. Otherwise no
2971	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,
2972	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
2973	the functionality isn't available is safe, though, although you have	3810	when the functionality isn't available is safe, though, although you have
2974	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>
2975	function is hiding in (often F<-lrt>).	3812	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3813
2977	=item EV_USE_REALTIME	3814	=item EV_USE_REALTIME
2978		3815
2979	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
2980	real-time clock option at compile time (and assume its availability at	3817	real-time clock option at compile time (and assume its availability
2981	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
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3819	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3820	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	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>).
2985		3835
2986	=item EV_USE_NANOSLEEP	3836	=item EV_USE_NANOSLEEP
2987		3837
2988	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
2989	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 ()>.
…		…
3005		3855
3006	=item EV_SELECT_USE_FD_SET	3856	=item EV_SELECT_USE_FD_SET
3007		3857
3008	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>
3009	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
3010	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
3011	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
3012	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
3013	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,
3014	influence the size of the C<fd_set> used.	3864	configures the maximum size of the C<fd_set>.
3015		3865
3016	=item EV_SELECT_IS_WINSOCKET	3866	=item EV_SELECT_IS_WINSOCKET
3017		3867
3018	When defined to C<1>, the select backend will assume that	3868	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3869	select/socket/connect etc. don't understand file descriptors but
…		…
3021	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
3022	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,
3023	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
3024	on win32. Should not be defined on non-win32 platforms.	3874	on win32. Should not be defined on non-win32 platforms.
3025		3875
3026	=item EV_FD_TO_WIN32_HANDLE	3876	=item EV_FD_TO_WIN32_HANDLE(fd)
3027		3877
3028	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
3029	file descriptors to socket handles. When not defining this symbol (the	3879	file descriptors to socket handles. When not defining this symbol (the
3030	default), then libev will call C<_get_osfhandle>, which is usually	3880	default), then libev will call C<_get_osfhandle>, which is usually
3031	correct. In some cases, programs use their own file descriptor management,	3881	correct. In some cases, programs use their own file descriptor management,
3032	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.
3033		3897
3034	=item EV_USE_POLL	3898	=item EV_USE_POLL
3035		3899
3036	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)
3037	backend. Otherwise it will be enabled on non-win32 platforms. It	3901	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3084	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.
3085		3949
3086	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>
3087	(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.
3088		3952
3089	=item EV_H	3953	=item EV_H (h)
3090		3954
3091	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
3092	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
3093	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.
3094		3958
3095	=item EV_CONFIG_H	3959	=item EV_CONFIG_H (h)
3096		3960
3097	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
3098	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
3099	C<EV_H>, above.	3963	C<EV_H>, above.
3100		3964
3101	=item EV_EVENT_H	3965	=item EV_EVENT_H (h)
3102		3966
3103	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
3104	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">.
3105		3969
3106	=item EV_PROTOTYPES	3970	=item EV_PROTOTYPES (h)
3107		3971
3108	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
3109	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
3110	occasionally useful if you want to provide your own wrapper functions	3974	occasionally useful if you want to provide your own wrapper functions
3111	around libev functions.	3975	around libev functions.
…		…
3133	fine.	3997	fine.
3134		3998
3135	If your embedding application does not need any priorities, defining these	3999	If your embedding application does not need any priorities, defining these
3136	both to C<0> will save some memory and CPU.	4000	both to C<0> will save some memory and CPU.
3137		4001
3138	=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.
3139		4005
3140	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
3141	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
3142	code.	4008	is not. Disabling watcher types mainly saves code size.
3143		4009
3144	=item EV_IDLE_ENABLE	4010	=item EV_FEATURES
3145
3146	If undefined or defined to be C<1>, then idle watchers are supported. If
3147	defined to be C<0>, then they are not. Disabling them saves a few kB of
3148	code.
3149
3150	=item EV_EMBED_ENABLE
3151
3152	If undefined or defined to be C<1>, then embed watchers are supported. If
3153	defined to be C<0>, then they are not. Embed watchers rely on most other
3154	watcher types, which therefore must not be disabled.
3155
3156	=item EV_STAT_ENABLE
3157
3158	If undefined or defined to be C<1>, then stat watchers are supported. If
3159	defined to be C<0>, then they are not.
3160
3161	=item EV_FORK_ENABLE
3162
3163	If undefined or defined to be C<1>, then fork watchers are supported. If
3164	defined to be C<0>, then they are not.
3165
3166	=item EV_ASYNC_ENABLE
3167
3168	If undefined or defined to be C<1>, then async watchers are supported. If
3169	defined to be C<0>, then they are not.
3170
3171	=item EV_MINIMAL
3172		4011
3173	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
3174	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
3175	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
3176	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.
3177		4111
3178	=item EV_PID_HASHSIZE	4112	=item EV_PID_HASHSIZE
3179		4113
3180	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
3181	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),
3182	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
3183	increase this value (I<must> be a power of two).	4117	might want to increase this value (I<must> be a power of two).
3184		4118
3185	=item EV_INOTIFY_HASHSIZE	4119	=item EV_INOTIFY_HASHSIZE
3186		4120
3187	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
3188	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>
3189	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
3190	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
3191	two).	4125	power of two).
3192		4126
3193	=item EV_USE_4HEAP	4127	=item EV_USE_4HEAP
3194		4128
3195	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
3196	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
3197	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
3198	faster performance with many (thousands) of watchers.	4132	faster performance with many (thousands) of watchers.
3199		4133
3200	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
3201	(disabled).	4135	will be C<0>.
3202		4136
3203	=item EV_HEAP_CACHE_AT	4137	=item EV_HEAP_CACHE_AT
3204		4138
3205	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
3206	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
3207	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>),
3208	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,
3209	but avoids random read accesses on heap changes. This improves performance	4143	but avoids random read accesses on heap changes. This improves performance
3210	noticeably with many (hundreds) of watchers.	4144	noticeably with many (hundreds) of watchers.
3211		4145
3212	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
3213	(disabled).	4147	will be C<0>.
3214		4148
3215	=item EV_VERIFY	4149	=item EV_VERIFY
3216		4150
3217	Controls how much internal verification (see C<ev_loop_verify ()>) will	4151	Controls how much internal verification (see C<ev_verify ()>) will
3218	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
3219	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
3220	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
3221	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
3222	verification code will be called very frequently, which will slow down	4156	verification code will be called very frequently, which will slow down
3223	libev considerably.	4157	libev considerably.
3224		4158
3225	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
3226	C<0>.	4160	will be C<0>.
3227		4161
3228	=item EV_COMMON	4162	=item EV_COMMON
3229		4163
3230	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
3231	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
3232	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,
3233	though, and it must be identical each time.	4167	though, and it must be identical each time.
3234		4168
3235	For example, the perl EV module uses something like this:	4169	For example, the perl EV module uses something like this:
3236		4170
…		…
3289	file.	4223	file.
3290		4224
3291	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
3292	that everybody includes and which overrides some configure choices:	4226	that everybody includes and which overrides some configure choices:
3293		4227
3294	#define EV_MINIMAL 1	4228	#define EV_FEATURES 8
3295	#define EV_USE_POLL 0	4229	#define EV_USE_SELECT 1
3296	#define EV_MULTIPLICITY 0
3297	#define EV_PERIODIC_ENABLE 0	4230	#define EV_PREPARE_ENABLE 1
		4231	#define EV_IDLE_ENABLE 1
3298	#define EV_STAT_ENABLE 0	4232	#define EV_SIGNAL_ENABLE 1
3299	#define EV_FORK_ENABLE 0	4233	#define EV_CHILD_ENABLE 1
		4234	#define EV_USE_STDEXCEPT 0
3300	#define EV_CONFIG_H <config.h>	4235	#define EV_CONFIG_H <config.h>
3301	#define EV_MINPRI 0
3302	#define EV_MAXPRI 0
3303		4236
3304	#include "ev++.h"	4237	#include "ev++.h"
3305		4238
3306	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:
3307		4240
3308	#include "ev_cpp.h"	4241	#include "ev_cpp.h"
3309	#include "ev.c"	4242	#include "ev.c"
3310		4243
		4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3311		4245
3312	=head1 THREADS AND COROUTINES	4246	=head2 THREADS AND COROUTINES
3313		4247
3314	=head2 THREADS	4248	=head3 THREADS
3315		4249
3316	All libev functions are reentrant and thread-safe unless explicitly	4250	All libev functions are reentrant and thread-safe unless explicitly
3317	documented otherwise, but it uses no locking itself. This means that you	4251	documented otherwise, but libev implements no locking itself. This means
3318	can use as many loops as you want in parallel, as long as there are no	4252	that you can use as many loops as you want in parallel, as long as there
3319	concurrent calls into any libev function with the same loop parameter	4253	are no concurrent calls into any libev function with the same loop
3320	(C<ev_default_*> calls have an implicit default loop parameter, of	4254	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3321	course): libev guarantees that different event loops share no data	4255	of course): libev guarantees that different event loops share no data
3322	structures that need any locking.	4256	structures that need any locking.
3323		4257
3324	Or to put it differently: calls with different loop parameters can be done	4258	Or to put it differently: calls with different loop parameters can be done
3325	concurrently from multiple threads, calls with the same loop parameter	4259	concurrently from multiple threads, calls with the same loop parameter
3326	must be done serially (but can be done from different threads, as long as	4260	must be done serially (but can be done from different threads, as long as
…		…
3366	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
3367	watcher callback into the event loop interested in the signal.	4301	watcher callback into the event loop interested in the signal.
3368		4302
3369	=back	4303	=back
3370		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
3371	=head2 COROUTINES	4443	=head3 COROUTINES
3372		4444
3373	Libev is much more accommodating to coroutines ("cooperative threads"):	4445	Libev is very accommodating to coroutines ("cooperative threads"):
3374	libev fully supports nesting calls to it's functions from different	4446	libev fully supports nesting calls to its functions from different
3375	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
3376	different coroutines and switch freely between both coroutines running the	4448	different coroutines, and switch freely between both coroutines running
3377	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
3378	you must not do this from C<ev_periodic> reschedule callbacks.	4450	that you must not do this from C<ev_periodic> reschedule callbacks.
3379		4451
3380	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
3381	C<ev_loop>, and other calls do not usually allow coroutine switches.	4453	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4454	they do not call any callbacks.
3382		4455
		4456	=head2 COMPILER WARNINGS
3383		4457
3384	=head1 COMPLEXITIES	4458	Depending on your compiler and compiler settings, you might get no or a
		4459	lot of warnings when compiling libev code. Some people are apparently
		4460	scared by this.
3385		4461
3386	In this section the complexities of (many of) the algorithms used inside	4462	However, these are unavoidable for many reasons. For one, each compiler
3387	libev will be explained. For complexity discussions about backends see the	4463	has different warnings, and each user has different tastes regarding
3388	documentation for C<ev_default_init>.	4464	warning options. "Warn-free" code therefore cannot be a goal except when
		4465	targeting a specific compiler and compiler-version.
3389		4466
3390	All of the following are about amortised time: If an array needs to be	4467	Another reason is that some compiler warnings require elaborate
3391	extended, libev needs to realloc and move the whole array, but this	4468	workarounds, or other changes to the code that make it less clear and less
3392	happens asymptotically never with higher number of elements, so O(1) might	4469	maintainable.
3393	mean it might do a lengthy realloc operation in rare cases, but on average
3394	it is much faster and asymptotically approaches constant time.
3395		4470
3396	=over 4	4471	And of course, some compiler warnings are just plain stupid, or simply
		4472	wrong (because they don't actually warn about the condition their message
		4473	seems to warn about). For example, certain older gcc versions had some
		4474	warnings that resulted in an extreme number of false positives. These have
		4475	been fixed, but some people still insist on making code warn-free with
		4476	such buggy versions.
3397		4477
3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4478	While libev is written to generate as few warnings as possible,
		4479	"warn-free" code is not a goal, and it is recommended not to build libev
		4480	with any compiler warnings enabled unless you are prepared to cope with
		4481	them (e.g. by ignoring them). Remember that warnings are just that:
		4482	warnings, not errors, or proof of bugs.
3399		4483
3400	This means that, when you have a watcher that triggers in one hour and
3401	there are 100 watchers that would trigger before that then inserting will
3402	have to skip roughly seven (C<ld 100>) of these watchers.
3403		4484
3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4485	=head2 VALGRIND
3405		4486
3406	That means that changing a timer costs less than removing/adding them	4487	Valgrind has a special section here because it is a popular tool that is
3407	as only the relative motion in the event queue has to be paid for.	4488	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3408		4489
3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4490	If you think you found a bug (memory leak, uninitialised data access etc.)
		4491	in libev, then check twice: If valgrind reports something like:
3410		4492
3411	These just add the watcher into an array or at the head of a list.	4493	==2274== definitely lost: 0 bytes in 0 blocks.
		4494	==2274== possibly lost: 0 bytes in 0 blocks.
		4495	==2274== still reachable: 256 bytes in 1 blocks.
3412		4496
3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4497	Then there is no memory leak, just as memory accounted to global variables
		4498	is not a memleak - the memory is still being referenced, and didn't leak.
3414		4499
3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4500	Similarly, under some circumstances, valgrind might report kernel bugs
		4501	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4502	although an acceptable workaround has been found here), or it might be
		4503	confused.
3416		4504
3417	These watchers are stored in lists then need to be walked to find the	4505	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3418	correct watcher to remove. The lists are usually short (you don't usually	4506	make it into some kind of religion.
3419	have many watchers waiting for the same fd or signal).
3420		4507
3421	=item Finding the next timer in each loop iteration: O(1)	4508	If you are unsure about something, feel free to contact the mailing list
		4509	with the full valgrind report and an explanation on why you think this
		4510	is a bug in libev (best check the archives, too :). However, don't be
		4511	annoyed when you get a brisk "this is no bug" answer and take the chance
		4512	of learning how to interpret valgrind properly.
3422		4513
3423	By virtue of using a binary or 4-heap, the next timer is always found at a	4514	If you need, for some reason, empty reports from valgrind for your project
3424	fixed position in the storage array.	4515	I suggest using suppression lists.
3425		4516
3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3427		4517
3428	A change means an I/O watcher gets started or stopped, which requires	4518	=head1 PORTABILITY NOTES
3429	libev to recalculate its status (and possibly tell the kernel, depending
3430	on backend and whether C<ev_io_set> was used).
3431		4519
3432	=item Activating one watcher (putting it into the pending state): O(1)	4520	=head2 GNU/LINUX 32 BIT LIMITATIONS
3433		4521
3434	=item Priority handling: O(number_of_priorities)	4522	GNU/Linux is the only common platform that supports 64 bit file/large file
		4523	interfaces but I<disables> them by default.
3435		4524
3436	Priorities are implemented by allocating some space for each	4525	That means that libev compiled in the default environment doesn't support
3437	priority. When doing priority-based operations, libev usually has to	4526	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3438	linearly search all the priorities, but starting/stopping and activating
3439	watchers becomes O(1) with respect to priority handling.
3440		4527
3441	=item Sending an ev_async: O(1)	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.
3442		4531
3443	=item Processing ev_async_send: O(number_of_async_watchers)	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.
3444		4535
3445	=item Processing signals: O(max_signal_number)	4536	=head2 OS/X AND DARWIN BUGS
3446		4537
3447	Sending involves a system call I<iff> there were no other C<ev_async_send>	4538	The whole thing is a bug if you ask me - basically any system interface
3448	calls in the current loop iteration. Checking for async and signal events	4539	you touch is broken, whether it is locales, poll, kqueue or even the
3449	involves iterating over all running async watchers or all signal numbers.	4540	OpenGL drivers.
3450		4541
3451	=back	4542	=head3 C<kqueue> is buggy
3452		4543
		4544	The kqueue syscall is broken in all known versions - most versions support
		4545	only sockets, many support pipes.
3453		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
3454	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4606	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4607
		4608	=head3 General issues
3455		4609
3456	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
3457	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
3458	model. Libev still offers limited functionality on this platform in	4612	model. Libev still offers limited functionality on this platform in
3459	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
3460	descriptors. This only applies when using Win32 natively, not when using	4614	descriptors. This only applies when using Win32 natively, not when using
3461	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.
3462		4618
3463	Lifting these limitations would basically require the full	4619	Lifting these limitations would basically require the full
3464	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,
3465	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
3466	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).
3467		4623
3468	There is no supported compilation method available on windows except	4624	There is no supported compilation method available on windows except
3469	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.
3470		4629
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	4630	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	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
3473	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,
3474	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
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	4638	the abysmal performance of winsockets, using a large number of sockets
3480	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
3481	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
3482	different implementation for windows, as libev offers the POSIX readiness	4641	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	4642	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	4643	(due to Microsoft monopoly games).
3485		4644
3486	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
3487	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
3488	of F<ev.h>:	4647	of F<ev.h>:
3489		4648
…		…
3496	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!):
3497		4656
3498	#include "evwrap.h"	4657	#include "evwrap.h"
3499	#include "ev.c"	4658	#include "ev.c"
3500		4659
3501	=over 4
3502
3503	=item The winsocket select function	4660	=head3 The winsocket C<select> function
3504		4661
3505	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
3506	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
3507	also extremely buggy). This makes select very inefficient, and also	4664	also extremely buggy). This makes select very inefficient, and also
3508	requires a mapping from file descriptors to socket handles (the Microsoft	4665	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3517	#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 */
3518		4675
3519	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
3520	complexity in the O(n²) range when using win32.	4677	complexity in the O(n²) range when using win32.
3521		4678
3522	=item Limited number of file descriptors	4679	=head3 Limited number of file descriptors
3523		4680
3524	Windows has numerous arbitrary (and low) limits on things.	4681	Windows has numerous arbitrary (and low) limits on things.
3525		4682
3526	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
3527	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
3528	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
3529	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
3530	previous thread in each. Great).	4687	previous thread in each. Sounds great!).
3531		4688
3532	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>
3533	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
3534	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
3535	select emulation on windows).	4692	other interpreters do their own select emulation on windows).
3536		4693
3537	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
3538	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>
3539	or something like this inside Microsoft). You can increase this by calling	4696	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4697	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	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
3542	libraries.
3543
3544	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
3545	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,
3546	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
3547	calling select (O(n²)) will likely make this unworkable.	4702	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4703
3549	=back
3550
3551
3552	=head1 PORTABILITY REQUIREMENTS	4704	=head2 PORTABILITY REQUIREMENTS
3553		4705
3554	In addition to a working ISO-C implementation, libev relies on a few	4706	In addition to a working ISO-C implementation and of course the
3555	additional extensions:	4707	backend-specific APIs, libev relies on a few additional extensions:
3556		4708
3557	=over 4	4709	=over 4
3558		4710
3559	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4711	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3560	calling conventions regardless of C<ev_watcher_type *>.	4712	calling conventions regardless of C<ev_watcher_type *>.
…		…
3585	except the initial one, and run the default loop in the initial thread as	4737	except the initial one, and run the default loop in the initial thread as
3586	well.	4738	well.
3587		4739
3588	=item C<long> must be large enough for common memory allocation sizes	4740	=item C<long> must be large enough for common memory allocation sizes
3589		4741
3590	To improve portability and simplify using libev, libev uses C<long>	4742	To improve portability and simplify its API, libev uses C<long> internally
3591	internally instead of C<size_t> when allocating its data structures. On	4743	instead of C<size_t> when allocating its data structures. On non-POSIX
3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4744	systems (Microsoft...) this might be unexpectedly low, but is still at
3593	is still at least 31 bits everywhere, which is enough for hundreds of	4745	least 31 bits everywhere, which is enough for hundreds of millions of
3594	millions of watchers.	4746	watchers.
3595		4747
3596	=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
3597		4749
3598	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
3599	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
3600	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
3601	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.
3602		4756
3603	=back	4757	=back
3604		4758
3605	If you know of other additional requirements drop me a note.	4759	If you know of other additional requirements drop me a note.
3606		4760
3607		4761
3608	=head1 COMPILER WARNINGS	4762	=head1 ALGORITHMIC COMPLEXITIES
3609		4763
3610	Depending on your compiler and compiler settings, you might get no or a	4764	In this section the complexities of (many of) the algorithms used inside
3611	lot of warnings when compiling libev code. Some people are apparently	4765	libev will be documented. For complexity discussions about backends see
3612	scared by this.	4766	the documentation for C<ev_default_init>.
3613		4767
3614	However, these are unavoidable for many reasons. For one, each compiler	4768	All of the following are about amortised time: If an array needs to be
3615	has different warnings, and each user has different tastes regarding	4769	extended, libev needs to realloc and move the whole array, but this
3616	warning options. "Warn-free" code therefore cannot be a goal except when	4770	happens asymptotically rarer with higher number of elements, so O(1) might
3617	targeting a specific compiler and compiler-version.	4771	mean that libev does a lengthy realloc operation in rare cases, but on
		4772	average it is much faster and asymptotically approaches constant time.
3618		4773
3619	Another reason is that some compiler warnings require elaborate	4774	=over 4
3620	workarounds, or other changes to the code that make it less clear and less
3621	maintainable.
3622		4775
3623	And of course, some compiler warnings are just plain stupid, or simply	4776	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3624	wrong (because they don't actually warn about the condition their message
3625	seems to warn about).
3626		4777
3627	While libev is written to generate as few warnings as possible,	4778	This means that, when you have a watcher that triggers in one hour and
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4779	there are 100 watchers that would trigger before that, then inserting will
3629	with any compiler warnings enabled unless you are prepared to cope with	4780	have to skip roughly seven (C<ld 100>) of these watchers.
3630	them (e.g. by ignoring them). Remember that warnings are just that:
3631	warnings, not errors, or proof of bugs.
3632		4781
		4782	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3633		4783
3634	=head1 VALGRIND	4784	That means that changing a timer costs less than removing/adding them,
		4785	as only the relative motion in the event queue has to be paid for.
3635		4786
3636	Valgrind has a special section here because it is a popular tool that is	4787	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3637	highly useful, but valgrind reports are very hard to interpret.
3638		4788
3639	If you think you found a bug (memory leak, uninitialised data access etc.)	4789	These just add the watcher into an array or at the head of a list.
3640	in libev, then check twice: If valgrind reports something like:
3641		4790
3642	==2274== definitely lost: 0 bytes in 0 blocks.	4791	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3643	==2274== possibly lost: 0 bytes in 0 blocks.
3644	==2274== still reachable: 256 bytes in 1 blocks.
3645		4792
3646	Then there is no memory leak. Similarly, under some circumstances,	4793	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3647	valgrind might report kernel bugs as if it were a bug in libev, or it
3648	might be confused (it is a very good tool, but only a tool).
3649		4794
3650	If you are unsure about something, feel free to contact the mailing list	4795	These watchers are stored in lists, so they need to be walked to find the
3651	with the full valgrind report and an explanation on why you think this is	4796	correct watcher to remove. The lists are usually short (you don't usually
3652	a bug in libev. However, don't be annoyed when you get a brisk "this is	4797	have many watchers waiting for the same fd or signal: one is typical, two
3653	no bug" answer and take the chance of learning how to interpret valgrind	4798	is rare).
3654	properly.
3655		4799
3656	If you need, for some reason, empty reports from valgrind for your project	4800	=item Finding the next timer in each loop iteration: O(1)
3657	I suggest using suppression lists.
3658		4801
		4802	By virtue of using a binary or 4-heap, the next timer is always found at a
		4803	fixed position in the storage array.
		4804
		4805	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4806
		4807	A change means an I/O watcher gets started or stopped, which requires
		4808	libev to recalculate its status (and possibly tell the kernel, depending
		4809	on backend and whether C<ev_io_set> was used).
		4810
		4811	=item Activating one watcher (putting it into the pending state): O(1)
		4812
		4813	=item Priority handling: O(number_of_priorities)
		4814
		4815	Priorities are implemented by allocating some space for each
		4816	priority. When doing priority-based operations, libev usually has to
		4817	linearly search all the priorities, but starting/stopping and activating
		4818	watchers becomes O(1) with respect to priority handling.
		4819
		4820	=item Sending an ev_async: O(1)
		4821
		4822	=item Processing ev_async_send: O(number_of_async_watchers)
		4823
		4824	=item Processing signals: O(max_signal_number)
		4825
		4826	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4827	calls in the current loop iteration. Checking for async and signal events
		4828	involves iterating over all running async watchers or all signal numbers.
		4829
		4830	=back
		4831
		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
3659		4963
3660	=head1 AUTHOR	4964	=head1 AUTHOR
3661		4965
3662	Marc Lehmann <libev@schmorp.de>.	4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3663		4967

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