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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// 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 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	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	229	also recommended for this platform, meaning it will work for most file
		230	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	231	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	232	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	233	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.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	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	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<ev_loop *>. The library knows two	308	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	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	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	321	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	322	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).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	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,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	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	340	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	341	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	342	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	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
307		363
308	The flags argument can be used to specify special behaviour or specific	364	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>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	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	388	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		389
335	This works by calling C<getpid ()> on every iteration of the loop,	390	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	391	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	392	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	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	399	flag.
345		400
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	402	environment variable.
348		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	This is your standard select(2) backend. Not I<completely> standard, as	426	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,	427	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	428	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	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		454
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
382	For few fds, this backend is a bit little slower than poll and select,	460	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	461	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),	462	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	463	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	464
387	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup and
		469	so on. The biggest issue is fork races, however - if a program forks then
		470	I<both> parent and child process have to recreate the epoll set, which can
		471	take considerable time (one syscall per file descriptor) and is of course
		472	hard to detect.
		473
		474	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		475	of course I<doesn't>, and epoll just loves to report events for totally
		476	I<different> file descriptors (even already closed ones, so one cannot
		477	even remove them from the set) than registered in the set (especially
		478	on SMP systems). Libev tries to counter these spurious notifications by
		479	employing an additional generation counter and comparing that against the
		480	events to filter out spurious ones, recreating the set when required. Last
		481	not least, it also refuses to work with some file descriptors which work
		482	perfectly fine with C<select> (files, many character devices...).
389		483
390	While stopping, setting and starting an I/O watcher in the same iteration	484	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	485	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	486	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	487	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	488	file descriptors might not work very well if you register events for both
395		489	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		490
400	Best performance from this backend is achieved by not unregistering all	491	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	492	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	493	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	494	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	495	extra overhead. A fork can both result in spurious notifications as well
		496	as in libev having to destroy and recreate the epoll object, which can
		497	take considerable time and thus should be avoided.
		498
		499	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		500	faster than epoll for maybe up to a hundred file descriptors, depending on
		501	the usage. So sad.
405		502
406	While nominally embeddable in other event loops, this feature is broken in	503	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	504	all kernel versions tested so far.
408		505
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	506	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	507	C<EVBACKEND_POLL>.
411		508
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	509	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		510
414	Kqueue deserves special mention, as at the time of this writing, it was	511	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	512	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	513	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	514	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	515	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.	516	without API changes to existing programs. For this reason it's not being
		517	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		518	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		519	system like NetBSD.
420		520
421	You still can embed kqueue into a normal poll or select backend and use it	521	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	522	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.	523	the target platform). See C<ev_embed> watchers for more info.
424		524
425	It scales in the same way as the epoll backend, but the interface to the	525	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	526	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	527	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	528	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	529	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	530	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		531	cases
431		532
432	This backend usually performs well under most conditions.	533	This backend usually performs well under most conditions.
433		534
434	While nominally embeddable in other event loops, this doesn't work	535	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	536	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	537	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	538	(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,	539	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	540	also broken on OS X)) and, did I mention it, using it only for sockets.
440		541
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	542	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	543	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	544	C<NOTE_EOF>.
444		545
…		…
464	might perform better.	565	might perform better.
465		566
466	On the positive side, with the exception of the spurious readiness	567	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	568	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	569	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	570	OS-specific backends (I vastly prefer correctness over speed hacks).
470		571
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	572	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	573	C<EVBACKEND_POLL>.
473		574
474	=item C<EVBACKEND_ALL>	575	=item C<EVBACKEND_ALL>
…		…
479		580
480	It is definitely not recommended to use this flag.	581	It is definitely not recommended to use this flag.
481		582
482	=back	583	=back
483		584
484	If one or more of these are or'ed into the flags value, then only these	585	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	586	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.	587	here). If none are specified, all backends in C<ev_recommended_backends
487		588	()> 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		589
516	Example: Try to create a event loop that uses epoll and nothing else.	590	Example: Try to create a event loop that uses epoll and nothing else.
517		591
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	592	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	593	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	594	fatal ("no epoll found here, maybe it hides under your chair");
521		595
		596	Example: Use whatever libev has to offer, but make sure that kqueue is
		597	used if available.
		598
		599	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		600
522	=item ev_default_destroy ()	601	=item ev_loop_destroy (loop)
523		602
524	Destroys the default loop again (frees all memory and kernel state	603	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	604	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	605	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>	606	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	607	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	608	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	609	for example).
531		610
532	Note that certain global state, such as signal state, will not be freed by	611	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	612	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	613	as signal and child watchers) would need to be stopped manually.
535		614
536	In general it is not advisable to call this function except in the	615	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	616	C<ev_loop_new>, but it can also be used on the default loop returned by
		617	C<ev_default_loop>, in which case it is not thread-safe.
		618
		619	Note that it is not advisable to call this function on the default loop
		620	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	621	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>).	622	and C<ev_loop_destroy>.
540		623
541	=item ev_loop_destroy (loop)	624	=item ev_loop_fork (loop)
542		625
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	626	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	627	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	628	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	629	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	630	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	631
		632	Again, you I<have> to call it on I<any> loop that you want to re-use after
		633	a fork, I<even if you do not plan to use the loop in the parent>. This is
		634	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		635	during fork.
554		636
555	On the other hand, you only need to call this function in the child	637	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	638	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.	639	you just fork+exec or create a new loop in the child, you don't have to
		640	call it at all (in fact, C<epoll> is so badly broken that it makes a
		641	difference, but libev will usually detect this case on its own and do a
		642	costly reset of the backend).
558		643
559	The function itself is quite fast and it's usually not a problem to call	644	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	645	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		646
		647	Example: Automate calling C<ev_loop_fork> on the default loop when
		648	using pthreads.
		649
		650	static void
		651	post_fork_child (void)
		652	{
		653	ev_loop_fork (EV_DEFAULT);
		654	}
		655
		656	...
563	pthread_atfork (0, 0, ev_default_fork);	657	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		658
572	=item int ev_is_default_loop (loop)	659	=item int ev_is_default_loop (loop)
573		660
574	Returns true when the given loop is, in fact, the default loop, and false	661	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	662	otherwise.
576		663
577	=item unsigned int ev_loop_count (loop)	664	=item unsigned int ev_iteration (loop)
578		665
579	Returns the count of loop iterations for the loop, which is identical to	666	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	667	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	668	and happily wraps around with enough iterations.
582		669
583	This value can sometimes be useful as a generation counter of sorts (it	670	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	671	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	672	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		673	prepare and check phases.
		674
		675	=item unsigned int ev_depth (loop)
		676
		677	Returns the number of times C<ev_run> was entered minus the number of
		678	times C<ev_run> was exited, in other words, the recursion depth.
		679
		680	Outside C<ev_run>, this number is zero. In a callback, this number is
		681	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		682	in which case it is higher.
		683
		684	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		685	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		686	ungentleman-like behaviour unless it's really convenient.
586		687
587	=item unsigned int ev_backend (loop)	688	=item unsigned int ev_backend (loop)
588		689
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	690	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	691	use.
…		…
599		700
600	=item ev_now_update (loop)	701	=item ev_now_update (loop)
601		702
602	Establishes the current time by querying the kernel, updating the time	703	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	704	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	705	is usually done automatically within C<ev_run ()>.
605		706
606	This function is rarely useful, but when some event callback runs for a	707	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	708	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	709	the current time is a good idea.
609		710
610	See also "The special problem of time updates" in the C<ev_timer> section.	711	See also L<The special problem of time updates> in the C<ev_timer> section.
611		712
		713	=item ev_suspend (loop)
		714
		715	=item ev_resume (loop)
		716
		717	These two functions suspend and resume an event loop, for use when the
		718	loop is not used for a while and timeouts should not be processed.
		719
		720	A typical use case would be an interactive program such as a game: When
		721	the user presses C<^Z> to suspend the game and resumes it an hour later it
		722	would be best to handle timeouts as if no time had actually passed while
		723	the program was suspended. This can be achieved by calling C<ev_suspend>
		724	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		725	C<ev_resume> directly afterwards to resume timer processing.
		726
		727	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		728	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		729	will be rescheduled (that is, they will lose any events that would have
		730	occurred while suspended).
		731
		732	After calling C<ev_suspend> you B<must not> call I<any> function on the
		733	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		734	without a previous call to C<ev_suspend>.
		735
		736	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		737	event loop time (see C<ev_now_update>).
		738
612	=item ev_loop (loop, int flags)	739	=item ev_run (loop, int flags)
613		740
614	Finally, this is it, the event handler. This function usually is called	741	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	742	after you have initialised all your watchers and you want to start
616	events.	743	handling events. It will ask the operating system for any new events, call
		744	the watcher callbacks, an then repeat the whole process indefinitely: This
		745	is why event loops are called I<loops>.
617		746
618	If the flags argument is specified as C<0>, it will not return until	747	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.	748	until either no event watchers are active anymore or C<ev_break> was
		749	called.
620		750
621	Please note that an explicit C<ev_unloop> is usually better than	751	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	752	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	753	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	754	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	755	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	756	beauty.
627		757
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	758	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	759	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	760	block your process in case there are no events and will return after one
631	the loop.	761	iteration of the loop. This is sometimes useful to poll and handle new
		762	events while doing lengthy calculations, to keep the program responsive.
632		763
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	764	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	765	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	766	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	767	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	768	user-registered callback will be called), and will return after one
638	iteration of the loop.	769	iteration of the loop.
639		770
640	This is useful if you are waiting for some external event in conjunction	771	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	772	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	773	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.	774	usually a better approach for this kind of thing.
644		775
645	Here are the gory details of what C<ev_loop> does:	776	Here are the gory details of what C<ev_run> does:
646		777
		778	- Increment loop depth.
		779	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	780	- Before the first iteration, call any pending watchers.
		781	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	782	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	783	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	784	- Queue and call all prepare watchers.
		785	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	786	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	787	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	788	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	789	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	790	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	791	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	792	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	793	- Sleep if the I/O and timer collect interval say so.
		794	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	795	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	796	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	797	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	798	- Queue all expired timers.
663	- Queue all expired periodics.	799	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	800	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	801	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	802	- 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	803	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	804	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	805	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	806	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	807	continue with step LOOP.
		808	FINISH:
		809	- Reset the ev_break status iff it was EVBREAK_ONE.
		810	- Decrement the loop depth.
		811	- Return.
672		812
673	Example: Queue some jobs and then loop until no events are outstanding	813	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	814	anymore.
675		815
676	... queue jobs here, make sure they register event watchers as long	816	... 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..)	817	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	818	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	819	... jobs done or somebody called unloop. yeah!
680		820
681	=item ev_unloop (loop, how)	821	=item ev_break (loop, how)
682		822
683	Can be used to make a call to C<ev_loop> return early (but only after it	823	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	824	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	825	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.	826	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		827
688	This "unloop state" will be cleared when entering C<ev_loop> again.	828	This "break state" will be cleared when entering C<ev_run> again.
689		829
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	830	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
691		831
692	=item ev_ref (loop)	832	=item ev_ref (loop)
693		833
694	=item ev_unref (loop)	834	=item ev_unref (loop)
695		835
696	Ref/unref can be used to add or remove a reference count on the event	836	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	837	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	838	count is nonzero, C<ev_run> will not return on its own.
699		839
700	If you have a watcher you never unregister that should not keep C<ev_loop>	840	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	841	unregister, but that nevertheless should not keep C<ev_run> from
		842	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	843	before stopping it.
703		844
704	As an example, libev itself uses this for its internal signal pipe: It is	845	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	846	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	847	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	848	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	849	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	850	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	851	before, respectively. Note also that libev might stop watchers itself
		852	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		853	in the callback).
711		854
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	855	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	856	running when nothing else is active.
714		857
715	ev_signal exitsig;	858	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	859	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	860	ev_signal_start (loop, &exitsig);
…		…
744		887
745	By setting a higher I<io collect interval> you allow libev to spend more	888	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	889	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	890	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	891	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	892	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		893	sleep time ensures that libev will not poll for I/O events more often then
		894	once per this interval, on average.
750		895
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	896	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	897	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	898	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	899	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		901
757	Many (busy) programs can usually benefit by setting the I/O collect	902	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	903	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	904	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	905	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	906	as this approaches the timing granularity of most systems. Note that if
		907	you do transactions with the outside world and you can't increase the
		908	parallelity, then this setting will limit your transaction rate (if you
		909	need to poll once per transaction and the I/O collect interval is 0.01,
		910	then you can't do more than 100 transactions per second).
762		911
763	Setting the I<timeout collect interval> can improve the opportunity for	912	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	913	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	914	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	915	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	916	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	917	they fire on, say, one-second boundaries only.
769		918
		919	Example: we only need 0.1s timeout granularity, and we wish not to poll
		920	more often than 100 times per second:
		921
		922	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		923	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		924
		925	=item ev_invoke_pending (loop)
		926
		927	This call will simply invoke all pending watchers while resetting their
		928	pending state. Normally, C<ev_run> does this automatically when required,
		929	but when overriding the invoke callback this call comes handy. This
		930	function can be invoked from a watcher - this can be useful for example
		931	when you want to do some lengthy calculation and want to pass further
		932	event handling to another thread (you still have to make sure only one
		933	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		934
		935	=item int ev_pending_count (loop)
		936
		937	Returns the number of pending watchers - zero indicates that no watchers
		938	are pending.
		939
		940	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		941
		942	This overrides the invoke pending functionality of the loop: Instead of
		943	invoking all pending watchers when there are any, C<ev_run> will call
		944	this callback instead. This is useful, for example, when you want to
		945	invoke the actual watchers inside another context (another thread etc.).
		946
		947	If you want to reset the callback, use C<ev_invoke_pending> as new
		948	callback.
		949
		950	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		951
		952	Sometimes you want to share the same loop between multiple threads. This
		953	can be done relatively simply by putting mutex_lock/unlock calls around
		954	each call to a libev function.
		955
		956	However, C<ev_run> can run an indefinite time, so it is not feasible
		957	to wait for it to return. One way around this is to wake up the event
		958	loop via C<ev_break> and C<av_async_send>, another way is to set these
		959	I<release> and I<acquire> callbacks on the loop.
		960
		961	When set, then C<release> will be called just before the thread is
		962	suspended waiting for new events, and C<acquire> is called just
		963	afterwards.
		964
		965	Ideally, C<release> will just call your mutex_unlock function, and
		966	C<acquire> will just call the mutex_lock function again.
		967
		968	While event loop modifications are allowed between invocations of
		969	C<release> and C<acquire> (that's their only purpose after all), no
		970	modifications done will affect the event loop, i.e. adding watchers will
		971	have no effect on the set of file descriptors being watched, or the time
		972	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		973	to take note of any changes you made.
		974
		975	In theory, threads executing C<ev_run> will be async-cancel safe between
		976	invocations of C<release> and C<acquire>.
		977
		978	See also the locking example in the C<THREADS> section later in this
		979	document.
		980
		981	=item ev_set_userdata (loop, void *data)
		982
		983	=item ev_userdata (loop)
		984
		985	Set and retrieve a single C<void *> associated with a loop. When
		986	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		987	C<0.>
		988
		989	These two functions can be used to associate arbitrary data with a loop,
		990	and are intended solely for the C<invoke_pending_cb>, C<release> and
		991	C<acquire> callbacks described above, but of course can be (ab-)used for
		992	any other purpose as well.
		993
770	=item ev_loop_verify (loop)	994	=item ev_verify (loop)
771		995
772	This function only does something when C<EV_VERIFY> support has been	996	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	997	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	998	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	999	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1000	error and call C<abort ()>.
777		1001
778	This can be used to catch bugs inside libev itself: under normal	1002	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1006	=back
783		1007
784		1008
785	=head1 ANATOMY OF A WATCHER	1009	=head1 ANATOMY OF A WATCHER
786		1010
		1011	In the following description, uppercase C<TYPE> in names stands for the
		1012	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1013	watchers and C<ev_io_start> for I/O watchers.
		1014
787	A watcher is a structure that you create and register to record your	1015	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1016	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1017	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1018	for that:
790		1019
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1020	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1021	{
793	ev_io_stop (w);	1022	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1023	ev_break (loop, EVBREAK_ALL);
795	}	1024	}
796		1025
797	struct ev_loop *loop = ev_default_loop (0);	1026	struct ev_loop *loop = ev_default_loop (0);
		1027
798	ev_io stdin_watcher;	1028	ev_io stdin_watcher;
		1029
799	ev_init (&stdin_watcher, my_cb);	1030	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1031	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1032	ev_io_start (loop, &stdin_watcher);
		1033
802	ev_loop (loop, 0);	1034	ev_run (loop, 0);
803		1035
804	As you can see, you are responsible for allocating the memory for your	1036	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1037	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1038	stack).
807		1039
		1040	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1041	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1042
808	Each watcher structure must be initialised by a call to C<ev_init	1043	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1044	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1045	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1046	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1047	and/or writable).
813		1048
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1049	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1050	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1051	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1052	ev_TYPE_init (watcher *, callback, ...) >>.
818		1053
819	To make the watcher actually watch out for events, you have to start it	1054	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1055	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1056	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1057	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1058
824	As long as your watcher is active (has been started but not stopped) you	1059	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1060	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1061	reinitialise it or call its C<ev_TYPE_set> macro.
827		1062
828	Each and every callback receives the event loop pointer as first, the	1063	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1064	registered watcher structure as second, and a bitset of received events as
830	third argument.	1065	third argument.
831		1066
…		…
840	=item C<EV_WRITE>	1075	=item C<EV_WRITE>
841		1076
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1077	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1078	writable.
844		1079
845	=item C<EV_TIMEOUT>	1080	=item C<EV_TIMER>
846		1081
847	The C<ev_timer> watcher has timed out.	1082	The C<ev_timer> watcher has timed out.
848		1083
849	=item C<EV_PERIODIC>	1084	=item C<EV_PERIODIC>
850		1085
…		…
868		1103
869	=item C<EV_PREPARE>	1104	=item C<EV_PREPARE>
870		1105
871	=item C<EV_CHECK>	1106	=item C<EV_CHECK>
872		1107
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1108	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
874	to gather new events, and all C<ev_check> watchers are invoked just after	1109	to gather new events, and all C<ev_check> watchers are invoked just after
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1110	C<ev_run> has gathered them, but before it invokes any callbacks for any
876	received events. Callbacks of both watcher types can start and stop as	1111	received events. Callbacks of both watcher types can start and stop as
877	many watchers as they want, and all of them will be taken into account	1112	many watchers as they want, and all of them will be taken into account
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1113	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
879	C<ev_loop> from blocking).	1114	C<ev_run> from blocking).
880		1115
881	=item C<EV_EMBED>	1116	=item C<EV_EMBED>
882		1117
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1118	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1119
885	=item C<EV_FORK>	1120	=item C<EV_FORK>
886		1121
887	The event loop has been resumed in the child process after fork (see	1122	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1123	C<ev_fork>).
889		1124
		1125	=item C<EV_CLEANUP>
		1126
		1127	The event loop is about to be destroyed (see C<ev_cleanup>).
		1128
890	=item C<EV_ASYNC>	1129	=item C<EV_ASYNC>
891		1130
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1131	The given async watcher has been asynchronously notified (see C<ev_async>).
		1132
		1133	=item C<EV_CUSTOM>
		1134
		1135	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1136	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1137
894	=item C<EV_ERROR>	1138	=item C<EV_ERROR>
895		1139
896	An unspecified error has occurred, the watcher has been stopped. This might	1140	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1141	happen because the watcher could not be properly started because libev
…		…
912		1156
913	=back	1157	=back
914		1158
915	=head2 GENERIC WATCHER FUNCTIONS	1159	=head2 GENERIC WATCHER FUNCTIONS
916		1160
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1161	=over 4
921		1162
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1163	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1164
924	This macro initialises the generic portion of a watcher. The contents	1165	This macro initialises the generic portion of a watcher. The contents
…		…
938		1179
939	ev_io w;	1180	ev_io w;
940	ev_init (&w, my_cb);	1181	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1182	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1183
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1184	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1185
945	This macro initialises the type-specific parts of a watcher. You need to	1186	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1187	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1188	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1189	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1202
962	Example: Initialise and set an C<ev_io> watcher in one step.	1203	Example: Initialise and set an C<ev_io> watcher in one step.
963		1204
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1205	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1206
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1207	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1208
968	Starts (activates) the given watcher. Only active watchers will receive	1209	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1210	events. If the watcher is already active nothing will happen.
970		1211
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1212	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1213	whole section.
973		1214
974	ev_io_start (EV_DEFAULT_UC, &w);	1215	ev_io_start (EV_DEFAULT_UC, &w);
975		1216
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1217	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1218
978	Stops the given watcher if active, and clears the pending status (whether	1219	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1220	the watcher was active or not).
980		1221
981	It is possible that stopped watchers are pending - for example,	1222	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1247	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1248
1008	Change the callback. You can change the callback at virtually any time	1249	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1250	(modulo threads).
1010		1251
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1252	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1253
1013	=item int ev_priority (ev_TYPE *watcher)	1254	=item int ev_priority (ev_TYPE *watcher)
1014		1255
1015	Set and query the priority of the watcher. The priority is a small	1256	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1257	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1258	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1259	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1260	from being executed (except for C<ev_idle> watchers).
1020		1261
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1262	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1263	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1264
1029	You I<must not> change the priority of a watcher as long as it is active or	1265	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1266	pending.
1031		1267
		1268	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1269	fine, as long as you do not mind that the priority value you query might
		1270	or might not have been clamped to the valid range.
		1271
1032	The default priority used by watchers when no priority has been set is	1272	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1273	always C<0>, which is supposed to not be too high and not be too low :).
1034		1274
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1275	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1276	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1277
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1278	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1279
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1280	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1281	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1289	watcher isn't pending it does nothing and returns C<0>.
1051		1290
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1291	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1292	callback to be invoked, which can be accomplished with this function.
1054		1293
		1294	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1295
		1296	Feeds the given event set into the event loop, as if the specified event
		1297	had happened for the specified watcher (which must be a pointer to an
		1298	initialised but not necessarily started event watcher). Obviously you must
		1299	not free the watcher as long as it has pending events.
		1300
		1301	Stopping the watcher, letting libev invoke it, or calling
		1302	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1303	not started in the first place.
		1304
		1305	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1306	functions that do not need a watcher.
		1307
1055	=back	1308	=back
1056
1057		1309
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1310	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1059		1311
1060	Each watcher has, by default, a member C<void *data> that you can change	1312	Each watcher has, by default, a member C<void *data> that you can change
1061	and read at any time: libev will completely ignore it. This can be used	1313	and read at any time: libev will completely ignore it. This can be used
…		…
1107	#include <stddef.h>	1359	#include <stddef.h>
1108		1360
1109	static void	1361	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)	1362	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1363	{
1112	struct my_biggy big = (struct my_biggy *	1364	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1365	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1366	}
1115		1367
1116	static void	1368	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)	1369	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1370	{
1119	struct my_biggy big = (struct my_biggy *	1371	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1372	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1373	}
		1374
		1375	=head2 WATCHER STATES
		1376
		1377	There are various watcher states mentioned throughout this manual -
		1378	active, pending and so on. In this section these states and the rules to
		1379	transition between them will be described in more detail - and while these
		1380	rules might look complicated, they usually do "the right thing".
		1381
		1382	=over 4
		1383
		1384	=item initialiased
		1385
		1386	Before a watcher can be registered with the event looop it has to be
		1387	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1388	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1389
		1390	In this state it is simply some block of memory that is suitable for use
		1391	in an event loop. It can be moved around, freed, reused etc. at will.
		1392
		1393	=item started/running/active
		1394
		1395	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1396	property of the event loop, and is actively waiting for events. While in
		1397	this state it cannot be accessed (except in a few documented ways), moved,
		1398	freed or anything else - the only legal thing is to keep a pointer to it,
		1399	and call libev functions on it that are documented to work on active watchers.
		1400
		1401	=item pending
		1402
		1403	If a watcher is active and libev determines that an event it is interested
		1404	in has occurred (such as a timer expiring), it will become pending. It will
		1405	stay in this pending state until either it is stopped or its callback is
		1406	about to be invoked, so it is not normally pending inside the watcher
		1407	callback.
		1408
		1409	The watcher might or might not be active while it is pending (for example,
		1410	an expired non-repeating timer can be pending but no longer active). If it
		1411	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1412	but it is still property of the event loop at this time, so cannot be
		1413	moved, freed or reused. And if it is active the rules described in the
		1414	previous item still apply.
		1415
		1416	It is also possible to feed an event on a watcher that is not active (e.g.
		1417	via C<ev_feed_event>), in which case it becomes pending without being
		1418	active.
		1419
		1420	=item stopped
		1421
		1422	A watcher can be stopped implicitly by libev (in which case it might still
		1423	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1424	latter will clear any pending state the watcher might be in, regardless
		1425	of whether it was active or not, so stopping a watcher explicitly before
		1426	freeing it is often a good idea.
		1427
		1428	While stopped (and not pending) the watcher is essentially in the
		1429	initialised state, that is it can be reused, moved, modified in any way
		1430	you wish.
		1431
		1432	=back
		1433
		1434	=head2 WATCHER PRIORITY MODELS
		1435
		1436	Many event loops support I<watcher priorities>, which are usually small
		1437	integers that influence the ordering of event callback invocation
		1438	between watchers in some way, all else being equal.
		1439
		1440	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1441	description for the more technical details such as the actual priority
		1442	range.
		1443
		1444	There are two common ways how these these priorities are being interpreted
		1445	by event loops:
		1446
		1447	In the more common lock-out model, higher priorities "lock out" invocation
		1448	of lower priority watchers, which means as long as higher priority
		1449	watchers receive events, lower priority watchers are not being invoked.
		1450
		1451	The less common only-for-ordering model uses priorities solely to order
		1452	callback invocation within a single event loop iteration: Higher priority
		1453	watchers are invoked before lower priority ones, but they all get invoked
		1454	before polling for new events.
		1455
		1456	Libev uses the second (only-for-ordering) model for all its watchers
		1457	except for idle watchers (which use the lock-out model).
		1458
		1459	The rationale behind this is that implementing the lock-out model for
		1460	watchers is not well supported by most kernel interfaces, and most event
		1461	libraries will just poll for the same events again and again as long as
		1462	their callbacks have not been executed, which is very inefficient in the
		1463	common case of one high-priority watcher locking out a mass of lower
		1464	priority ones.
		1465
		1466	Static (ordering) priorities are most useful when you have two or more
		1467	watchers handling the same resource: a typical usage example is having an
		1468	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1469	timeouts. Under load, data might be received while the program handles
		1470	other jobs, but since timers normally get invoked first, the timeout
		1471	handler will be executed before checking for data. In that case, giving
		1472	the timer a lower priority than the I/O watcher ensures that I/O will be
		1473	handled first even under adverse conditions (which is usually, but not
		1474	always, what you want).
		1475
		1476	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1477	will only be executed when no same or higher priority watchers have
		1478	received events, they can be used to implement the "lock-out" model when
		1479	required.
		1480
		1481	For example, to emulate how many other event libraries handle priorities,
		1482	you can associate an C<ev_idle> watcher to each such watcher, and in
		1483	the normal watcher callback, you just start the idle watcher. The real
		1484	processing is done in the idle watcher callback. This causes libev to
		1485	continuously poll and process kernel event data for the watcher, but when
		1486	the lock-out case is known to be rare (which in turn is rare :), this is
		1487	workable.
		1488
		1489	Usually, however, the lock-out model implemented that way will perform
		1490	miserably under the type of load it was designed to handle. In that case,
		1491	it might be preferable to stop the real watcher before starting the
		1492	idle watcher, so the kernel will not have to process the event in case
		1493	the actual processing will be delayed for considerable time.
		1494
		1495	Here is an example of an I/O watcher that should run at a strictly lower
		1496	priority than the default, and which should only process data when no
		1497	other events are pending:
		1498
		1499	ev_idle idle; // actual processing watcher
		1500	ev_io io; // actual event watcher
		1501
		1502	static void
		1503	io_cb (EV_P_ ev_io *w, int revents)
		1504	{
		1505	// stop the I/O watcher, we received the event, but
		1506	// are not yet ready to handle it.
		1507	ev_io_stop (EV_A_ w);
		1508
		1509	// start the idle watcher to handle the actual event.
		1510	// it will not be executed as long as other watchers
		1511	// with the default priority are receiving events.
		1512	ev_idle_start (EV_A_ &idle);
		1513	}
		1514
		1515	static void
		1516	idle_cb (EV_P_ ev_idle *w, int revents)
		1517	{
		1518	// actual processing
		1519	read (STDIN_FILENO, ...);
		1520
		1521	// have to start the I/O watcher again, as
		1522	// we have handled the event
		1523	ev_io_start (EV_P_ &io);
		1524	}
		1525
		1526	// initialisation
		1527	ev_idle_init (&idle, idle_cb);
		1528	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1529	ev_io_start (EV_DEFAULT_ &io);
		1530
		1531	In the "real" world, it might also be beneficial to start a timer, so that
		1532	low-priority connections can not be locked out forever under load. This
		1533	enables your program to keep a lower latency for important connections
		1534	during short periods of high load, while not completely locking out less
		1535	important ones.
1122		1536
1123		1537
1124	=head1 WATCHER TYPES	1538	=head1 WATCHER TYPES
1125		1539
1126	This section describes each watcher in detail, but will not repeat	1540	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1566	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1567	required if you know what you are doing).
1154		1568
1155	If you cannot use non-blocking mode, then force the use of a	1569	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1570	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1571	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1572	descriptors for which non-blocking operation makes no sense (such as
		1573	files) - libev doesn't guarantee any specific behaviour in that case.
1158		1574
1159	Another thing you have to watch out for is that it is quite easy to	1575	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1576	receive "spurious" readiness notifications, that is your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1577	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1578	because there is no data. Not only are some backends known to create a
…		…
1227		1643
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1644	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1645	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1646	somewhere, as that would have given you a big clue).
1231		1647
		1648	=head3 The special problem of accept()ing when you can't
		1649
		1650	Many implementations of the POSIX C<accept> function (for example,
		1651	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1652	connection from the pending queue in all error cases.
		1653
		1654	For example, larger servers often run out of file descriptors (because
		1655	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1656	rejecting the connection, leading to libev signalling readiness on
		1657	the next iteration again (the connection still exists after all), and
		1658	typically causing the program to loop at 100% CPU usage.
		1659
		1660	Unfortunately, the set of errors that cause this issue differs between
		1661	operating systems, there is usually little the app can do to remedy the
		1662	situation, and no known thread-safe method of removing the connection to
		1663	cope with overload is known (to me).
		1664
		1665	One of the easiest ways to handle this situation is to just ignore it
		1666	- when the program encounters an overload, it will just loop until the
		1667	situation is over. While this is a form of busy waiting, no OS offers an
		1668	event-based way to handle this situation, so it's the best one can do.
		1669
		1670	A better way to handle the situation is to log any errors other than
		1671	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1672	messages, and continue as usual, which at least gives the user an idea of
		1673	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1674	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1675	usage.
		1676
		1677	If your program is single-threaded, then you could also keep a dummy file
		1678	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1679	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1680	close that fd, and create a new dummy fd. This will gracefully refuse
		1681	clients under typical overload conditions.
		1682
		1683	The last way to handle it is to simply log the error and C<exit>, as
		1684	is often done with C<malloc> failures, but this results in an easy
		1685	opportunity for a DoS attack.
1232		1686
1233	=head3 Watcher-Specific Functions	1687	=head3 Watcher-Specific Functions
1234		1688
1235	=over 4	1689	=over 4
1236		1690
…		…
1268	...	1722	...
1269	struct ev_loop *loop = ev_default_init (0);	1723	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1724	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1725	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1726	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1727	ev_run (loop, 0);
1274		1728
1275		1729
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1730	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1731
1278	Timer watchers are simple relative timers that generate an event after a	1732	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1737	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1738	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1739	monotonic clock option helps a lot here).
1286		1740
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1741	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1742	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1743	might introduce a small delay). If multiple timers become ready during the
		1744	same loop iteration then the ones with earlier time-out values are invoked
		1745	before ones of the same priority with later time-out values (but this is
		1746	no longer true when a callback calls C<ev_run> recursively).
1290		1747
1291	=head3 Be smart about timeouts	1748	=head3 Be smart about timeouts
1292		1749
1293	Many real-world problems invole some kind of time-out, usually for error	1750	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1751	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1752	you want to raise some error after a while.
1296		1753
1297	Here are some ways on how to handle this problem, from simple and	1754	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1755	inefficient to smart and efficient.
1299		1756
1300	In the following examples a 60 second activity timeout is assumed - a	1757	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1758	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1759	data or other life sign was received).
1303		1760
1304	=over 4	1761	=over 4
1305		1762
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1763	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1764
1308	This is the most obvious, but not the most simple way: In the beginning,	1765	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1766	start the watcher:
1310		1767
1311	ev_timer_init (timer, callback, 60., 0.);	1768	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1769	ev_timer_start (loop, timer);
1313		1770
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1771	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1772	and start it again:
1316		1773
1317	ev_timer_stop (loop, timer);	1774	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1775	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1776	ev_timer_start (loop, timer);
1320		1777
1321	This is relatively simple to implement, but means that each time there	1778	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1779	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1780	data structure and then add it again. Libev tries to be fast, but it's
		1781	still not a constant-time operation.
1324		1782
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1783	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1784
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1785	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1786	C<ev_timer_start>.
1329		1787
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1788	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1789	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1790	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1791	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1792	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1793
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1794	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1795	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1796	member and C<ev_timer_again>.
1338		1797
1339	At start:	1798	At start:
1340		1799
1341	ev_timer_init (timer, callback, 0., 60.);	1800	ev_init (timer, callback);
		1801	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1802	ev_timer_again (loop, timer);
1343		1803
1344	Each time you receive some data:	1804	Each time there is some activity:
1345		1805
1346	ev_timer_again (loop, timer);	1806	ev_timer_again (loop, timer);
1347		1807
1348	It is even possible to change the time-out on the fly:	1808	It is even possible to change the time-out on the fly, regardless of
		1809	whether the watcher is active or not:
1349		1810
1350	timer->repeat = 30.;	1811	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1812	ev_timer_again (loop, timer);
1352		1813
1353	This is slightly more efficient then stopping/starting the timer each time	1814	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1815	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1816	remove and re-insert the timer from/into its internal data structure.
		1817
		1818	It is, however, even simpler than the "obvious" way to do it.
1356		1819
1357	=item 3. Let the timer time out, but then re-arm it as required.	1820	=item 3. Let the timer time out, but then re-arm it as required.
1358		1821
1359	This method is more tricky, but usually most efficient: Most timeouts are	1822	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1823	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1824	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1825	associated activity resets.
1363		1826
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1827	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1828	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1829	within the callback:
1367		1830
1368	ev_tstamp last_activity; // time of last activity	1831	ev_tstamp last_activity; // time of last activity
1369		1832
1370	static void	1833	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1834	callback (EV_P_ ev_timer *w, int revents)
1372	{	1835	{
1373	ev_tstamp now = ev_now (EV_A);	1836	ev_tstamp now = ev_now (EV_A);
1374	ev_tstamp timeout = last_activity + 60.;	1837	ev_tstamp timeout = last_activity + 60.;
1375		1838
1376	// if last_activity is older than now - timeout, we did time out	1839	// if last_activity + 60. is older than now, we did time out
1377	if (timeout < now)	1840	if (timeout < now)
1378	{	1841	{
1379	// timeout occured, take action	1842	// timeout occurred, take action
1380	}	1843	}
1381	else	1844	else
1382	{	1845	{
1383	// callback was invoked, but there was some activity, re-arm	1846	// callback was invoked, but there was some activity, re-arm
1384	// to fire in last_activity + 60.	1847	// the watcher to fire in last_activity + 60, which is
		1848	// guaranteed to be in the future, so "again" is positive:
1385	w->again = timeout - now;	1849	w->repeat = timeout - now;
1386	ev_timer_again (EV_A_ w);	1850	ev_timer_again (EV_A_ w);
1387	}	1851	}
1388	}	1852	}
1389		1853
1390	To summarise the callback: first calculate the real time-out (defined as	1854	To summarise the callback: first calculate the real timeout (defined
1391	"60 seconds after the last activity"), then check if that time has been	1855	as "60 seconds after the last activity"), then check if that time has
1392	reached, which means there was a real timeout. Otherwise the callback was	1856	been reached, which means something I<did>, in fact, time out. Otherwise
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1857	the callback was invoked too early (C<timeout> is in the future), so
1394	fire at that future time.	1858	re-schedule the timer to fire at that future time, to see if maybe we have
		1859	a timeout then.
1395		1860
1396	Note how C<ev_timer_again> is used, taking advantage of the	1861	Note how C<ev_timer_again> is used, taking advantage of the
1397	C<ev_timer_again> optimisation when the timer is already running.	1862	C<ev_timer_again> optimisation when the timer is already running.
1398		1863
1399	This scheme causes more callback invocations (about one every 60 seconds),	1864	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1865	minus half the average time between activity), but virtually no calls to
		1866	libev to change the timeout.
1401		1867
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1868	To start the timer, simply initialise the watcher and set C<last_activity>
1403	then call the callback:	1869	to the current time (meaning we just have some activity :), then call the
		1870	callback, which will "do the right thing" and start the timer:
1404		1871
1405	ev_timer_init (timer, callback);	1872	ev_init (timer, callback);
1406	last_activity = ev_now (loop);	1873	last_activity = ev_now (loop);
1407	callback (loop, timer, EV_TIMEOUT);	1874	callback (loop, timer, EV_TIMER);
1408		1875
1409	And when there is some activity, simply remember the time in	1876	And when there is some activity, simply store the current time in
1410	C<last_activity>:	1877	C<last_activity>, no libev calls at all:
1411		1878
1412	last_actiivty = ev_now (loop);	1879	last_activity = ev_now (loop);
1413		1880
1414	This technique is slightly more complex, but in most cases where the	1881	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1882	time-out is unlikely to be triggered, much more efficient.
1416		1883
		1884	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1885	callback :) - just change the timeout and invoke the callback, which will
		1886	fix things for you.
		1887
		1888	=item 4. Wee, just use a double-linked list for your timeouts.
		1889
		1890	If there is not one request, but many thousands (millions...), all
		1891	employing some kind of timeout with the same timeout value, then one can
		1892	do even better:
		1893
		1894	When starting the timeout, calculate the timeout value and put the timeout
		1895	at the I<end> of the list.
		1896
		1897	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1898	the list is expected to fire (for example, using the technique #3).
		1899
		1900	When there is some activity, remove the timer from the list, recalculate
		1901	the timeout, append it to the end of the list again, and make sure to
		1902	update the C<ev_timer> if it was taken from the beginning of the list.
		1903
		1904	This way, one can manage an unlimited number of timeouts in O(1) time for
		1905	starting, stopping and updating the timers, at the expense of a major
		1906	complication, and having to use a constant timeout. The constant timeout
		1907	ensures that the list stays sorted.
		1908
1417	=back	1909	=back
		1910
		1911	So which method the best?
		1912
		1913	Method #2 is a simple no-brain-required solution that is adequate in most
		1914	situations. Method #3 requires a bit more thinking, but handles many cases
		1915	better, and isn't very complicated either. In most case, choosing either
		1916	one is fine, with #3 being better in typical situations.
		1917
		1918	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1919	rather complicated, but extremely efficient, something that really pays
		1920	off after the first million or so of active timers, i.e. it's usually
		1921	overkill :)
1418		1922
1419	=head3 The special problem of time updates	1923	=head3 The special problem of time updates
1420		1924
1421	Establishing the current time is a costly operation (it usually takes at	1925	Establishing the current time is a costly operation (it usually takes at
1422	least two system calls): EV therefore updates its idea of the current	1926	least two system calls): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	1927	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1928	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	1929	lots of events in one iteration.
1426		1930
1427	The relative timeouts are calculated relative to the C<ev_now ()>	1931	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	1932	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		1938
1435	If the event loop is suspended for a long time, you can also force an	1939	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1940	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	1941	()>.
1438		1942
		1943	=head3 The special problems of suspended animation
		1944
		1945	When you leave the server world it is quite customary to hit machines that
		1946	can suspend/hibernate - what happens to the clocks during such a suspend?
		1947
		1948	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1949	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1950	to run until the system is suspended, but they will not advance while the
		1951	system is suspended. That means, on resume, it will be as if the program
		1952	was frozen for a few seconds, but the suspend time will not be counted
		1953	towards C<ev_timer> when a monotonic clock source is used. The real time
		1954	clock advanced as expected, but if it is used as sole clocksource, then a
		1955	long suspend would be detected as a time jump by libev, and timers would
		1956	be adjusted accordingly.
		1957
		1958	I would not be surprised to see different behaviour in different between
		1959	operating systems, OS versions or even different hardware.
		1960
		1961	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1962	time jump in the monotonic clocks and the realtime clock. If the program
		1963	is suspended for a very long time, and monotonic clock sources are in use,
		1964	then you can expect C<ev_timer>s to expire as the full suspension time
		1965	will be counted towards the timers. When no monotonic clock source is in
		1966	use, then libev will again assume a timejump and adjust accordingly.
		1967
		1968	It might be beneficial for this latter case to call C<ev_suspend>
		1969	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1970	deterministic behaviour in this case (you can do nothing against
		1971	C<SIGSTOP>).
		1972
1439	=head3 Watcher-Specific Functions and Data Members	1973	=head3 Watcher-Specific Functions and Data Members
1440		1974
1441	=over 4	1975	=over 4
1442		1976
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2000	If the timer is started but non-repeating, stop it (as if it timed out).
1467		2001
1468	If the timer is repeating, either start it if necessary (with the	2002	If the timer is repeating, either start it if necessary (with the
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2003	C<repeat> value), or reset the running timer to the C<repeat> value.
1470		2004
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2005	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	2006	usage example.
		2007
		2008	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2009
		2010	Returns the remaining time until a timer fires. If the timer is active,
		2011	then this time is relative to the current event loop time, otherwise it's
		2012	the timeout value currently configured.
		2013
		2014	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2015	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2016	will return C<4>. When the timer expires and is restarted, it will return
		2017	roughly C<7> (likely slightly less as callback invocation takes some time,
		2018	too), and so on.
1473		2019
1474	=item ev_tstamp repeat [read-write]	2020	=item ev_tstamp repeat [read-write]
1475		2021
1476	The current C<repeat> value. Will be used each time the watcher times out	2022	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2023	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2049	}
1504		2050
1505	ev_timer mytimer;	2051	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2052	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2053	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2054	ev_run (loop, 0);
1509		2055
1510	// and in some piece of code that gets executed on any "activity":	2056	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2057	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2058	ev_timer_again (&mytimer);
1513		2059
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2061	=head2 C<ev_periodic> - to cron or not to cron?
1516		2062
1517	Periodic watchers are also timers of a kind, but they are very versatile	2063	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2064	(and unfortunately a bit complex).
1519		2065
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2066	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2067	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2068	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2069	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2070	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2071	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2072
		2073	You can tell a periodic watcher to trigger after some specific point
		2074	in time: for example, if you tell a periodic watcher to trigger "in 10
		2075	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2076	not a delay) and then reset your system clock to January of the previous
		2077	year, then it will take a year or more to trigger the event (unlike an
		2078	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2079	it, as it uses a relative timeout).
		2080
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2081	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2082	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2083	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2084	those cannot react to time jumps.
1532		2085
1533	As with timers, the callback is guaranteed to be invoked only when the	2086	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2087	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2088	timers become ready during the same loop iteration then the ones with
		2089	earlier time-out values are invoked before ones with later time-out values
		2090	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2091
1537	=head3 Watcher-Specific Functions and Data Members	2092	=head3 Watcher-Specific Functions and Data Members
1538		2093
1539	=over 4	2094	=over 4
1540		2095
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2096	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2097
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2098	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2099
1545	Lots of arguments, lets sort it out... There are basically three modes of	2100	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2101	operation, and we will explain them from simplest to most complex:
1547		2102
1548	=over 4	2103	=over 4
1549		2104
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2105	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2106
1552	In this configuration the watcher triggers an event after the wall clock	2107	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2108	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2109	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2110	will be stopped and invoked when the system clock reaches or surpasses
		2111	this point in time.
1556		2112
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2113	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2114
1559	In this mode the watcher will always be scheduled to time out at the next	2115	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2116	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2117	negative) and then repeat, regardless of any time jumps. The C<offset>
		2118	argument is merely an offset into the C<interval> periods.
1562		2119
1563	This can be used to create timers that do not drift with respect to the	2120	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2121	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2122	hour, on the hour (with respect to UTC):
1566		2123
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2124	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2125
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2126	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2127	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2128	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2129	by 3600.
1573		2130
1574	Another way to think about it (for the mathematically inclined) is that	2131	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2132	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2133	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2134
1578	For numerical stability it is preferable that the C<at> value is near	2135	For numerical stability it is preferable that the C<offset> value is near
1579	C<ev_now ()> (the current time), but there is no range requirement for	2136	C<ev_now ()> (the current time), but there is no range requirement for
1580	this value, and in fact is often specified as zero.	2137	this value, and in fact is often specified as zero.
1581		2138
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2139	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2140	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2141	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2142	millisecond (if the OS supports it and the machine is fast enough).
1586		2143
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2144	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2145
1589	In this mode the values for C<interval> and C<at> are both being	2146	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2147	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2148	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2149	current time as second argument.
1593		2150
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2151	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2152	or make ANY other event loop modifications whatsoever, unless explicitly
		2153	allowed by documentation here>.
1596		2154
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2155	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2156	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2157	only event loop modification you are allowed to do).
1600		2158
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2188	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2189	program when the crontabs have changed).
1632		2190
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2191	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2192
1635	When active, returns the absolute time that the watcher is supposed to	2193	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2194	to trigger next. This is not the same as the C<offset> argument to
		2195	C<ev_periodic_set>, but indeed works even in interval and manual
		2196	rescheduling modes.
1637		2197
1638	=item ev_tstamp offset [read-write]	2198	=item ev_tstamp offset [read-write]
1639		2199
1640	When repeating, this contains the offset value, otherwise this is the	2200	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2201	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2202	although libev might modify this value for better numerical stability).
1642		2203
1643	Can be modified any time, but changes only take effect when the periodic	2204	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2205	timer fires or C<ev_periodic_again> is being called.
1645		2206
1646	=item ev_tstamp interval [read-write]	2207	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2223	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2224	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2225	potentially a lot of jitter, but good long-term stability.
1665		2226
1666	static void	2227	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2228	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2229	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2230	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2231	}
1671		2232
1672	ev_periodic hourly_tick;	2233	ev_periodic hourly_tick;
…		…
1698	Signal watchers will trigger an event when the process receives a specific	2259	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2260	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2261	will try it's best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2262	normal event processing, like any other event.
1702		2263
1703	If you want signals asynchronously, just use C<sigaction> as you would	2264	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2265	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2266	the signal. You can even use C<ev_async> from a signal handler to
		2267	synchronously wake up an event loop.
1706		2268
1707	You can configure as many watchers as you like per signal. Only when the	2269	You can configure as many watchers as you like for the same signal, but
		2270	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2271	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2272	C<SIGINT> in both the default loop and another loop at the same time. At
		2273	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2274
1708	first watcher gets started will libev actually register a signal handler	2275	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2276	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2277	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2278
1714	If possible and supported, libev will install its handlers with	2279	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2280	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2281	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2282	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2283	and unblock them in an C<ev_prepare> watcher.
		2284
		2285	=head3 The special problem of inheritance over fork/execve/pthread_create
		2286
		2287	Both the signal mask (C<sigprocmask>) and the signal disposition
		2288	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2289	stopping it again), that is, libev might or might not block the signal,
		2290	and might or might not set or restore the installed signal handler.
		2291
		2292	While this does not matter for the signal disposition (libev never
		2293	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2294	C<execve>), this matters for the signal mask: many programs do not expect
		2295	certain signals to be blocked.
		2296
		2297	This means that before calling C<exec> (from the child) you should reset
		2298	the signal mask to whatever "default" you expect (all clear is a good
		2299	choice usually).
		2300
		2301	The simplest way to ensure that the signal mask is reset in the child is
		2302	to install a fork handler with C<pthread_atfork> that resets it. That will
		2303	catch fork calls done by libraries (such as the libc) as well.
		2304
		2305	In current versions of libev, the signal will not be blocked indefinitely
		2306	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2307	the window of opportunity for problems, it will not go away, as libev
		2308	I<has> to modify the signal mask, at least temporarily.
		2309
		2310	So I can't stress this enough: I<If you do not reset your signal mask when
		2311	you expect it to be empty, you have a race condition in your code>. This
		2312	is not a libev-specific thing, this is true for most event libraries.
1719		2313
1720	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1721		2315
1722	=over 4	2316	=over 4
1723		2317
…		…
1739	Example: Try to exit cleanly on SIGINT.	2333	Example: Try to exit cleanly on SIGINT.
1740		2334
1741	static void	2335	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2336	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2337	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2338	ev_break (loop, EVBREAK_ALL);
1745	}	2339	}
1746		2340
1747	ev_signal signal_watcher;	2341	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2342	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2343	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2349	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2350	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2351	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2352	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2353	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2354	but forking and registering a watcher a few event loop iterations later or
1761	not.	2355	in the next callback invocation is not.
1762		2356
1763	Only the default event loop is capable of handling signals, and therefore	2357	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2358	you can only register child watchers in the default event loop.
1765		2359
		2360	Due to some design glitches inside libev, child watchers will always be
		2361	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2362	libev)
		2363
1766	=head3 Process Interaction	2364	=head3 Process Interaction
1767		2365
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2366	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2367	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2368	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2369	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2370	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2371	children, even ones not watched.
1774		2372
1775	=head3 Overriding the Built-In Processing	2373	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2383	=head3 Stopping the Child Watcher
1786		2384
1787	Currently, the child watcher never gets stopped, even when the	2385	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2386	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2387	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2388	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2389	problem).
1791		2390
1792	=head3 Watcher-Specific Functions and Data Members	2391	=head3 Watcher-Specific Functions and Data Members
1793		2392
1794	=over 4	2393	=over 4
1795		2394
…		…
1852		2451
1853		2452
1854	=head2 C<ev_stat> - did the file attributes just change?	2453	=head2 C<ev_stat> - did the file attributes just change?
1855		2454
1856	This watches a file system path for attribute changes. That is, it calls	2455	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2456	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2457	and sees if it changed compared to the last time, invoking the callback if
		2458	it did.
1859		2459
1860	The path does not need to exist: changing from "path exists" to "path does	2460	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2461	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2462	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2463	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2464	least one) and all the other fields of the stat buffer having unspecified
		2465	contents.
1865		2466
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2467	The path I<must not> end in a slash or contain special components such as
		2468	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2469	your working directory changes, then the behaviour is undefined.
1868		2470
1869	Since there is no standard kernel interface to do this, the portable	2471	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2472	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2473	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2474	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2475	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2476	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2477	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2478	currently around C<0.1>, but that's usually overkill.
1877		2479
1878	This watcher type is not meant for massive numbers of stat watchers,	2480	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2481	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2482	resource-intensive.
1881		2483
1882	At the time of this writing, the only OS-specific interface implemented	2484	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2485	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2486	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2487	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2488
1887	=head3 ABI Issues (Largefile Support)	2489	=head3 ABI Issues (Largefile Support)
1888		2490
1889	Libev by default (unless the user overrides this) uses the default	2491	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2492	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2493	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2494	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2495	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2496	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2497	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2498	most noticeably displayed with ev_stat and large file support.
1897		2499
1898	The solution for this is to lobby your distribution maker to make large	2500	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2501	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2502	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2503	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2504	default compilation environment.
1903		2505
1904	=head3 Inotify and Kqueue	2506	=head3 Inotify and Kqueue
1905		2507
1906	When C<inotify (7)> support has been compiled into libev (generally	2508	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2509	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2510	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2511	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2512
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2513	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2514	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2515	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2516	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2517	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2518	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2519	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2520	xfs are fully working) libev usually gets away without polling.
1917		2521
1918	There is no support for kqueue, as apparently it cannot be used to	2522	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2523	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2524	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2525	etc. is difficult.
1922		2526
		2527	=head3 C<stat ()> is a synchronous operation
		2528
		2529	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2530	the process. The exception are C<ev_stat> watchers - those call C<stat
		2531	()>, which is a synchronous operation.
		2532
		2533	For local paths, this usually doesn't matter: unless the system is very
		2534	busy or the intervals between stat's are large, a stat call will be fast,
		2535	as the path data is usually in memory already (except when starting the
		2536	watcher).
		2537
		2538	For networked file systems, calling C<stat ()> can block an indefinite
		2539	time due to network issues, and even under good conditions, a stat call
		2540	often takes multiple milliseconds.
		2541
		2542	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2543	paths, although this is fully supported by libev.
		2544
1923	=head3 The special problem of stat time resolution	2545	=head3 The special problem of stat time resolution
1924		2546
1925	The C<stat ()> system call only supports full-second resolution portably, and	2547	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2548	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2549	still only support whole seconds.
1928		2550
1929	That means that, if the time is the only thing that changes, you can	2551	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2552	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2553	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2554	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2697
2076	=head3 Watcher-Specific Functions and Data Members	2698	=head3 Watcher-Specific Functions and Data Members
2077		2699
2078	=over 4	2700	=over 4
2079		2701
2080	=item ev_idle_init (ev_signal *, callback)	2702	=item ev_idle_init (ev_idle *, callback)
2081		2703
2082	Initialises and configures the idle watcher - it has no parameters of any	2704	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2705	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2706	believe me.
2085		2707
…		…
2098	// no longer anything immediate to do.	2720	// no longer anything immediate to do.
2099	}	2721	}
2100		2722
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2723	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2724	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2725	ev_idle_start (loop, idle_watcher);
2104		2726
2105		2727
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2728	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2729
2108	Prepare and check watchers are usually (but not always) used in pairs:	2730	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2731	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2732	afterwards.
2111		2733
2112	You I<must not> call C<ev_loop> or similar functions that enter	2734	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2735	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2736	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2737	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2738	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2739	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2823	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2824	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2825	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2826
2205	/* the callback is illegal, but won't be called as we stop during check */	2827	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2828	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2829	ev_timer_start (loop, &tw);
2208		2830
2209	// create one ev_io per pollfd	2831	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2832	for (int i = 0; i < nfd; ++i)
2211	{	2833	{
…		…
2285		2907
2286	if (timeout >= 0)	2908	if (timeout >= 0)
2287	// create/start timer	2909	// create/start timer
2288		2910
2289	// poll	2911	// poll
2290	ev_loop (EV_A_ 0);	2912	ev_run (EV_A_ 0);
2291		2913
2292	// stop timer again	2914	// stop timer again
2293	if (timeout >= 0)	2915	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	2916	ev_timer_stop (EV_A_ &to);
2295		2917
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	2946	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	2947	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	2948	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	2949	the rest in a second one, and embed the second one in the first.
2328		2950
2329	As long as the watcher is active, the callback will be invoked every time	2951	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	2952	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2953	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	2954	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	2955	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	2956	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		2957
2337	As long as the watcher is started it will automatically handle events. The	2958	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	2959	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		2960
2342	Also, there have not currently been made special provisions for forking:	2961	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2962	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	2963	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	2964	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		2965
2348	Unfortunately, not all backends are embeddable: only the ones returned by	2966	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2967	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	2968	portable one.
2351		2969
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	2995	if you do not want that, you need to temporarily stop the embed watcher).
2378		2996
2379	=item ev_embed_sweep (loop, ev_embed *)	2997	=item ev_embed_sweep (loop, ev_embed *)
2380		2998
2381	Make a single, non-blocking sweep over the embedded loop. This works	2999	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3000	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3001	appropriate way for embedded loops.
2384		3002
2385	=item struct ev_loop *other [read-only]	3003	=item struct ev_loop *other [read-only]
2386		3004
2387	The embedded event loop.	3005	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3063	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3064	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3065	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3066	handlers will be invoked, too, of course.
2449		3067
		3068	=head3 The special problem of life after fork - how is it possible?
		3069
		3070	Most uses of C<fork()> consist of forking, then some simple calls to set
		3071	up/change the process environment, followed by a call to C<exec()>. This
		3072	sequence should be handled by libev without any problems.
		3073
		3074	This changes when the application actually wants to do event handling
		3075	in the child, or both parent in child, in effect "continuing" after the
		3076	fork.
		3077
		3078	The default mode of operation (for libev, with application help to detect
		3079	forks) is to duplicate all the state in the child, as would be expected
		3080	when I<either> the parent I<or> the child process continues.
		3081
		3082	When both processes want to continue using libev, then this is usually the
		3083	wrong result. In that case, usually one process (typically the parent) is
		3084	supposed to continue with all watchers in place as before, while the other
		3085	process typically wants to start fresh, i.e. without any active watchers.
		3086
		3087	The cleanest and most efficient way to achieve that with libev is to
		3088	simply create a new event loop, which of course will be "empty", and
		3089	use that for new watchers. This has the advantage of not touching more
		3090	memory than necessary, and thus avoiding the copy-on-write, and the
		3091	disadvantage of having to use multiple event loops (which do not support
		3092	signal watchers).
		3093
		3094	When this is not possible, or you want to use the default loop for
		3095	other reasons, then in the process that wants to start "fresh", call
		3096	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3097	Destroying the default loop will "orphan" (not stop) all registered
		3098	watchers, so you have to be careful not to execute code that modifies
		3099	those watchers. Note also that in that case, you have to re-register any
		3100	signal watchers.
		3101
2450	=head3 Watcher-Specific Functions and Data Members	3102	=head3 Watcher-Specific Functions and Data Members
2451		3103
2452	=over 4	3104	=over 4
2453		3105
2454	=item ev_fork_init (ev_signal *, callback)	3106	=item ev_fork_init (ev_fork *, callback)
2455		3107
2456	Initialises and configures the fork watcher - it has no parameters of any	3108	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3109	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3110	really.
2459		3111
2460	=back	3112	=back
2461		3113
2462		3114
		3115	=head2 C<ev_cleanup> - even the best things end
		3116
		3117	Cleanup watchers are called just before the event loop is being destroyed
		3118	by a call to C<ev_loop_destroy>.
		3119
		3120	While there is no guarantee that the event loop gets destroyed, cleanup
		3121	watchers provide a convenient method to install cleanup hooks for your
		3122	program, worker threads and so on - you just to make sure to destroy the
		3123	loop when you want them to be invoked.
		3124
		3125	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3126	all other watchers, they do not keep a reference to the event loop (which
		3127	makes a lot of sense if you think about it). Like all other watchers, you
		3128	can call libev functions in the callback, except C<ev_cleanup_start>.
		3129
		3130	=head3 Watcher-Specific Functions and Data Members
		3131
		3132	=over 4
		3133
		3134	=item ev_cleanup_init (ev_cleanup *, callback)
		3135
		3136	Initialises and configures the cleanup watcher - it has no parameters of
		3137	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3138	pointless, I assure you.
		3139
		3140	=back
		3141
		3142	Example: Register an atexit handler to destroy the default loop, so any
		3143	cleanup functions are called.
		3144
		3145	static void
		3146	program_exits (void)
		3147	{
		3148	ev_loop_destroy (EV_DEFAULT_UC);
		3149	}
		3150
		3151	...
		3152	atexit (program_exits);
		3153
		3154
2463	=head2 C<ev_async> - how to wake up another event loop	3155	=head2 C<ev_async> - how to wake up an event loop
2464		3156
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3157	In general, you cannot use an C<ev_run> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3158	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3159	loops - those are of course safe to use in different threads).
2468		3160
2469	Sometimes, however, you need to wake up another event loop you do not	3161	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3162	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3163	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3164	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3165
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3166	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3167	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3168	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3169	C<ev_async_sent> calls).
…		…
2483	=head3 Queueing	3174	=head3 Queueing
2484		3175
2485	C<ev_async> does not support queueing of data in any way. The reason	3176	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3177	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3178	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3179	need elaborate support such as pthreads or unportable memory access
		3180	semantics.
2489		3181
2490	That means that if you want to queue data, you have to provide your own	3182	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3183	queue. But at least I can tell you how to implement locking around your
2492	queue:	3184	queue:
2493		3185
…		…
2571	=over 4	3263	=over 4
2572		3264
2573	=item ev_async_init (ev_async *, callback)	3265	=item ev_async_init (ev_async *, callback)
2574		3266
2575	Initialises and configures the async watcher - it has no parameters of any	3267	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3268	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3269	trust me.
2578		3270
2579	=item ev_async_send (loop, ev_async *)	3271	=item ev_async_send (loop, ev_async *)
2580		3272
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3273	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3274	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3275	C<ev_feed_event>, this call is safe to do from other threads, signal or
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3276	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2585	section below on what exactly this means).	3277	section below on what exactly this means).
2586		3278
		3279	Note that, as with other watchers in libev, multiple events might get
		3280	compressed into a single callback invocation (another way to look at this
		3281	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3282	reset when the event loop detects that).
		3283
2587	This call incurs the overhead of a system call only once per loop iteration,	3284	This call incurs the overhead of a system call only once per event loop
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3285	iteration, so while the overhead might be noticeable, it doesn't apply to
2589	calls to C<ev_async_send>.	3286	repeated calls to C<ev_async_send> for the same event loop.
2590		3287
2591	=item bool = ev_async_pending (ev_async *)	3288	=item bool = ev_async_pending (ev_async *)
2592		3289
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3290	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3291	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3294	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3295	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3296	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3297	quickly check whether invoking the loop might be a good idea.
2601		3298
2602	Not that this does I<not> check whether the watcher itself is pending, only	3299	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3300	only whether it has been requested to make this watcher pending: there
		3301	is a time window between the event loop checking and resetting the async
		3302	notification, and the callback being invoked.
2604		3303
2605	=back	3304	=back
2606		3305
2607		3306
2608	=head1 OTHER FUNCTIONS	3307	=head1 OTHER FUNCTIONS
…		…
2625		3324
2626	If C<timeout> is less than 0, then no timeout watcher will be	3325	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3326	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3327	repeat = 0) will be started. C<0> is a valid timeout.
2629		3328
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3329	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3330	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3332	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3333	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3334	events precedence.
2636		3335
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3336	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3337
2639	static void stdin_ready (int revents, void *arg)	3338	static void stdin_ready (int revents, void *arg)
2640	{	3339	{
2641	if (revents & EV_READ)	3340	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3341	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3342	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3343	/* doh, nothing entered */;
2645	}	3344	}
2646		3345
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3347
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3348	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3349
2657	Feed an event on the given fd, as if a file descriptor backend detected	3350	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3351	the given events it.
2659		3352
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3353	=item ev_feed_signal_event (loop, int signum)
2661		3354
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3355	Feed an event as if the given signal occurred (C<loop> must be the default
2663	loop!).	3356	loop!).
2664		3357
2665	=back	3358	=back
…		…
2745		3438
2746	=over 4	3439	=over 4
2747		3440
2748	=item ev::TYPE::TYPE ()	3441	=item ev::TYPE::TYPE ()
2749		3442
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3443	=item ev::TYPE::TYPE (loop)
2751		3444
2752	=item ev::TYPE::~TYPE	3445	=item ev::TYPE::~TYPE
2753		3446
2754	The constructor (optionally) takes an event loop to associate the watcher	3447	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3448	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3480
2788	myclass obj;	3481	myclass obj;
2789	ev::io iow;	3482	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3483	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3484
		3485	=item w->set (object *)
		3486
		3487	This is a variation of a method callback - leaving out the method to call
		3488	will default the method to C<operator ()>, which makes it possible to use
		3489	functor objects without having to manually specify the C<operator ()> all
		3490	the time. Incidentally, you can then also leave out the template argument
		3491	list.
		3492
		3493	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3494	int revents)>.
		3495
		3496	See the method-C<set> above for more details.
		3497
		3498	Example: use a functor object as callback.
		3499
		3500	struct myfunctor
		3501	{
		3502	void operator() (ev::io &w, int revents)
		3503	{
		3504	...
		3505	}
		3506	}
		3507
		3508	myfunctor f;
		3509
		3510	ev::io w;
		3511	w.set (&f);
		3512
2792	=item w->set<function> (void *data = 0)	3513	=item w->set<function> (void *data = 0)
2793		3514
2794	Also sets a callback, but uses a static method or plain function as	3515	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	3516	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	3517	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	3523	Example: Use a plain function as callback.
2803		3524
2804	static void io_cb (ev::io &w, int revents) { }	3525	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	3526	iow.set <io_cb> ();
2806		3527
2807	=item w->set (struct ev_loop *)	3528	=item w->set (loop)
2808		3529
2809	Associates a different C<struct ev_loop> with this watcher. You can only	3530	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	3531	do this when the watcher is inactive (and not pending either).
2811		3532
2812	=item w->set ([arguments])	3533	=item w->set ([arguments])
2813		3534
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3535	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	3536	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	3537	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	3538	when reconfiguring it with this method.
2818		3539
2819	=item w->start ()	3540	=item w->start ()
2820		3541
2821	Starts the watcher. Note that there is no C<loop> argument, as the	3542	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	3543	constructor already stores the event loop.
2823		3544
		3545	=item w->start ([arguments])
		3546
		3547	Instead of calling C<set> and C<start> methods separately, it is often
		3548	convenient to wrap them in one call. Uses the same type of arguments as
		3549	the configure C<set> method of the watcher.
		3550
2824	=item w->stop ()	3551	=item w->stop ()
2825		3552
2826	Stops the watcher if it is active. Again, no C<loop> argument.	3553	Stops the watcher if it is active. Again, no C<loop> argument.
2827		3554
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3555	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		3567
2841	=back	3568	=back
2842		3569
2843	=back	3570	=back
2844		3571
2845	Example: Define a class with an IO and idle watcher, start one of them in	3572	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	3573	watchers in the constructor.
2847		3574
2848	class myclass	3575	class myclass
2849	{	3576	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	3577	ev::io io ; void io_cb (ev::io &w, int revents);
		3578	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3579	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		3580
2853	myclass (int fd)	3581	myclass (int fd)
2854	{	3582	{
2855	io .set <myclass, &myclass::io_cb > (this);	3583	io .set <myclass, &myclass::io_cb > (this);
		3584	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	3585	idle.set <myclass, &myclass::idle_cb> (this);
2857		3586
2858	io.start (fd, ev::READ);	3587	io.set (fd, ev::WRITE); // configure the watcher
		3588	io.start (); // start it whenever convenient
		3589
		3590	io2.start (fd, ev::READ); // set + start in one call
2859	}	3591	}
2860	};	3592	};
2861		3593
2862		3594
2863	=head1 OTHER LANGUAGE BINDINGS	3595	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	3614	L<http://software.schmorp.de/pkg/EV>.
2883		3615
2884	=item Python	3616	=item Python
2885		3617
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3618	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	3619	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		3620
2893	=item Ruby	3621	=item Ruby
2894		3622
2895	Tony Arcieri has written a ruby extension that offers access to a subset	3623	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	3624	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	3625	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	3626	L<http://rev.rubyforge.org/>.
2899		3627
		3628	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3629	makes rev work even on mingw.
		3630
		3631	=item Haskell
		3632
		3633	A haskell binding to libev is available at
		3634	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3635
2900	=item D	3636	=item D
2901		3637
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3638	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3639	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3640
		3641	=item Ocaml
		3642
		3643	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3644	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3645
		3646	=item Lua
		3647
		3648	Brian Maher has written a partial interface to libev for lua (at the
		3649	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3650	L<http://github.com/brimworks/lua-ev>.
2904		3651
2905	=back	3652	=back
2906		3653
2907		3654
2908	=head1 MACRO MAGIC	3655	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	3669	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	3670	C<EV_A_> is used when other arguments are following. Example:
2924		3671
2925	ev_unref (EV_A);	3672	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	3673	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	3674	ev_run (EV_A_ 0);
2928		3675
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3676	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	3677	which is often provided by the following macro.
2931		3678
2932	=item C<EV_P>, C<EV_P_>	3679	=item C<EV_P>, C<EV_P_>
…		…
2972	}	3719	}
2973		3720
2974	ev_check check;	3721	ev_check check;
2975	ev_check_init (&check, check_cb);	3722	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	3723	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	3724	ev_run (EV_DEFAULT_ 0);
2978		3725
2979	=head1 EMBEDDING	3726	=head1 EMBEDDING
2980		3727
2981	Libev can (and often is) directly embedded into host	3728	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	3729	applications. Examples of applications that embed it include the Deliantra
…		…
3009		3756
3010	#define EV_STANDALONE 1	3757	#define EV_STANDALONE 1
3011	#include "ev.h"	3758	#include "ev.h"
3012		3759
3013	Both header files and implementation files can be compiled with a C++	3760	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	3761	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	3762	as a bug).
3016		3763
3017	You need the following files in your source tree, or in a directory	3764	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	3765	in your include path (e.g. in libev/ when using -Ilibev):
3019		3766
…		…
3062	libev.m4	3809	libev.m4
3063		3810
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	3811	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		3812
3066	Libev can be configured via a variety of preprocessor symbols you have to	3813	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	3814	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	3815	the absence of autoconf is documented for every option.
		3816
		3817	Symbols marked with "(h)" do not change the ABI, and can have different
		3818	values when compiling libev vs. including F<ev.h>, so it is permissible
		3819	to redefine them before including F<ev.h> without breaking compatibility
		3820	to a compiled library. All other symbols change the ABI, which means all
		3821	users of libev and the libev code itself must be compiled with compatible
		3822	settings.
3069		3823
3070	=over 4	3824	=over 4
3071		3825
		3826	=item EV_COMPAT3 (h)
		3827
		3828	Backwards compatibility is a major concern for libev. This is why this
		3829	release of libev comes with wrappers for the functions and symbols that
		3830	have been renamed between libev version 3 and 4.
		3831
		3832	You can disable these wrappers (to test compatibility with future
		3833	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3834	sources. This has the additional advantage that you can drop the C<struct>
		3835	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3836	typedef in that case.
		3837
		3838	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3839	and in some even more future version the compatibility code will be
		3840	removed completely.
		3841
3072	=item EV_STANDALONE	3842	=item EV_STANDALONE (h)
3073		3843
3074	Must always be C<1> if you do not use autoconf configuration, which	3844	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	3845	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	3846	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	3847	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	3848	F<event.h> that are not directly supported by the libev core alone.
3079		3849
		3850	In standalone mode, libev will still try to automatically deduce the
		3851	configuration, but has to be more conservative.
		3852
3080	=item EV_USE_MONOTONIC	3853	=item EV_USE_MONOTONIC
3081		3854
3082	If defined to be C<1>, libev will try to detect the availability of the	3855	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	3856	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	3857	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	3858	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	3859	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	3860	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	3861	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		3862
3090	=item EV_USE_REALTIME	3863	=item EV_USE_REALTIME
3091		3864
3092	If defined to be C<1>, libev will try to detect the availability of the	3865	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	3866	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	3867	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3868	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3869	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3870	correctness. See the note about libraries in the description of
		3871	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3872	C<EV_USE_CLOCK_SYSCALL>.
		3873
		3874	=item EV_USE_CLOCK_SYSCALL
		3875
		3876	If defined to be C<1>, libev will try to use a direct syscall instead
		3877	of calling the system-provided C<clock_gettime> function. This option
		3878	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3879	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3880	programs needlessly. Using a direct syscall is slightly slower (in
		3881	theory), because no optimised vdso implementation can be used, but avoids
		3882	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3883	higher, as it simplifies linking (no need for C<-lrt>).
3098		3884
3099	=item EV_USE_NANOSLEEP	3885	=item EV_USE_NANOSLEEP
3100		3886
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3887	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	3888	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		3904
3119	=item EV_SELECT_USE_FD_SET	3905	=item EV_SELECT_USE_FD_SET
3120		3906
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	3907	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	3908	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3909	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	3910	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	3911	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3912	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	3913	configures the maximum size of the C<fd_set>.
3128		3914
3129	=item EV_SELECT_IS_WINSOCKET	3915	=item EV_SELECT_IS_WINSOCKET
3130		3916
3131	When defined to C<1>, the select backend will assume that	3917	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	3918	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	3920	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3921	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	3922	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	3923	on win32. Should not be defined on non-win32 platforms.
3138		3924
3139	=item EV_FD_TO_WIN32_HANDLE	3925	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		3926
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3927	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	3928	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	3929	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	3930	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	3931	in which case they can provide this function to map fds to socket handles.
		3932
		3933	=item EV_WIN32_HANDLE_TO_FD(handle)
		3934
		3935	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3936	using the standard C<_open_osfhandle> function. For programs implementing
		3937	their own fd to handle mapping, overwriting this function makes it easier
		3938	to do so. This can be done by defining this macro to an appropriate value.
		3939
		3940	=item EV_WIN32_CLOSE_FD(fd)
		3941
		3942	If programs implement their own fd to handle mapping on win32, then this
		3943	macro can be used to override the C<close> function, useful to unregister
		3944	file descriptors again. Note that the replacement function has to close
		3945	the underlying OS handle.
3146		3946
3147	=item EV_USE_POLL	3947	=item EV_USE_POLL
3148		3948
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3949	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	3950	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3197	as well as for signal and thread safety in C<ev_async> watchers.	3997	as well as for signal and thread safety in C<ev_async> watchers.
3198		3998
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	3999	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4000	(from F<signal.h>), which is usually good enough on most platforms.
3201		4001
3202	=item EV_H	4002	=item EV_H (h)
3203		4003
3204	The name of the F<ev.h> header file used to include it. The default if	4004	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4005	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4006	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4007
3208	=item EV_CONFIG_H	4008	=item EV_CONFIG_H (h)
3209		4009
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4010	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4011	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4012	C<EV_H>, above.
3213		4013
3214	=item EV_EVENT_H	4014	=item EV_EVENT_H (h)
3215		4015
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4016	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4017	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4018
3219	=item EV_PROTOTYPES	4019	=item EV_PROTOTYPES (h)
3220		4020
3221	If defined to be C<0>, then F<ev.h> will not define any function	4021	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4022	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4023	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4024	around libev functions.
…		…
3246	fine.	4046	fine.
3247		4047
3248	If your embedding application does not need any priorities, defining these	4048	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4049	both to C<0> will save some memory and CPU.
3250		4050
3251	=item EV_PERIODIC_ENABLE	4051	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4052	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4053	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4054
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4055	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4056	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4057	is not. Disabling watcher types mainly saves code size.
3256		4058
3257	=item EV_IDLE_ENABLE	4059	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4060
3286	If you need to shave off some kilobytes of code at the expense of some	4061	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4062	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4063	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4064	that can be enabled on the platform.
		4065
		4066	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4067	with some broad features you want) and then selectively re-enable
		4068	additional parts you want, for example if you want everything minimal,
		4069	but multiple event loop support, async and child watchers and the poll
		4070	backend, use this:
		4071
		4072	#define EV_FEATURES 0
		4073	#define EV_MULTIPLICITY 1
		4074	#define EV_USE_POLL 1
		4075	#define EV_CHILD_ENABLE 1
		4076	#define EV_ASYNC_ENABLE 1
		4077
		4078	The actual value is a bitset, it can be a combination of the following
		4079	values:
		4080
		4081	=over 4
		4082
		4083	=item C<1> - faster/larger code
		4084
		4085	Use larger code to speed up some operations.
		4086
		4087	Currently this is used to override some inlining decisions (enlarging the
		4088	code size by roughly 30% on amd64).
		4089
		4090	When optimising for size, use of compiler flags such as C<-Os> with
		4091	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4092	assertions.
		4093
		4094	=item C<2> - faster/larger data structures
		4095
		4096	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4097	hash table sizes and so on. This will usually further increase code size
		4098	and can additionally have an effect on the size of data structures at
		4099	runtime.
		4100
		4101	=item C<4> - full API configuration
		4102
		4103	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4104	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4105
		4106	=item C<8> - full API
		4107
		4108	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4109	details on which parts of the API are still available without this
		4110	feature, and do not complain if this subset changes over time.
		4111
		4112	=item C<16> - enable all optional watcher types
		4113
		4114	Enables all optional watcher types. If you want to selectively enable
		4115	only some watcher types other than I/O and timers (e.g. prepare,
		4116	embed, async, child...) you can enable them manually by defining
		4117	C<EV_watchertype_ENABLE> to C<1> instead.
		4118
		4119	=item C<32> - enable all backends
		4120
		4121	This enables all backends - without this feature, you need to enable at
		4122	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4123
		4124	=item C<64> - enable OS-specific "helper" APIs
		4125
		4126	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4127	default.
		4128
		4129	=back
		4130
		4131	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4132	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4133	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4134	watchers, timers and monotonic clock support.
		4135
		4136	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4137	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4138	your program might be left out as well - a binary starting a timer and an
		4139	I/O watcher then might come out at only 5Kb.
		4140
		4141	=item EV_AVOID_STDIO
		4142
		4143	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4144	functions (printf, scanf, perror etc.). This will increase the code size
		4145	somewhat, but if your program doesn't otherwise depend on stdio and your
		4146	libc allows it, this avoids linking in the stdio library which is quite
		4147	big.
		4148
		4149	Note that error messages might become less precise when this option is
		4150	enabled.
		4151
		4152	=item EV_NSIG
		4153
		4154	The highest supported signal number, +1 (or, the number of
		4155	signals): Normally, libev tries to deduce the maximum number of signals
		4156	automatically, but sometimes this fails, in which case it can be
		4157	specified. Also, using a lower number than detected (C<32> should be
		4158	good for about any system in existence) can save some memory, as libev
		4159	statically allocates some 12-24 bytes per signal number.
3290		4160
3291	=item EV_PID_HASHSIZE	4161	=item EV_PID_HASHSIZE
3292		4162
3293	C<ev_child> watchers use a small hash table to distribute workload by	4163	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4164	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4165	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4166	might want to increase this value (I<must> be a power of two).
3297		4167
3298	=item EV_INOTIFY_HASHSIZE	4168	=item EV_INOTIFY_HASHSIZE
3299		4169
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4170	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4171	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4172	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4173	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4174	power of two).
3305		4175
3306	=item EV_USE_4HEAP	4176	=item EV_USE_4HEAP
3307		4177
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4178	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4179	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4180	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4181	faster performance with many (thousands) of watchers.
3312		4182
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4183	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4184	will be C<0>.
3315		4185
3316	=item EV_HEAP_CACHE_AT	4186	=item EV_HEAP_CACHE_AT
3317		4187
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4188	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4189	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4190	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4191	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4192	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4193	noticeably with many (hundreds) of watchers.
3324		4194
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4195	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4196	will be C<0>.
3327		4197
3328	=item EV_VERIFY	4198	=item EV_VERIFY
3329		4199
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4200	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4201	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4202	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4203	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4204	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4205	verification code will be called very frequently, which will slow down
3336	libev considerably.	4206	libev considerably.
3337		4207
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4208	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4209	will be C<0>.
3340		4210
3341	=item EV_COMMON	4211	=item EV_COMMON
3342		4212
3343	By default, all watchers have a C<void *data> member. By redefining	4213	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4214	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4215	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4216	though, and it must be identical each time.
3347		4217
3348	For example, the perl EV module uses something like this:	4218	For example, the perl EV module uses something like this:
3349		4219
…		…
3402	file.	4272	file.
3403		4273
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4274	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4275	that everybody includes and which overrides some configure choices:
3406		4276
3407	#define EV_MINIMAL 1	4277	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4278	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4279	#define EV_PREPARE_ENABLE 1
		4280	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4281	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4282	#define EV_CHILD_ENABLE 1
		4283	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4284	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4285
3417	#include "ev++.h"	4286	#include "ev++.h"
3418		4287
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4288	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4289
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4349	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4350	watcher callback into the event loop interested in the signal.
3482		4351
3483	=back	4352	=back
3484		4353
		4354	=head4 THREAD LOCKING EXAMPLE
		4355
		4356	Here is a fictitious example of how to run an event loop in a different
		4357	thread than where callbacks are being invoked and watchers are
		4358	created/added/removed.
		4359
		4360	For a real-world example, see the C<EV::Loop::Async> perl module,
		4361	which uses exactly this technique (which is suited for many high-level
		4362	languages).
		4363
		4364	The example uses a pthread mutex to protect the loop data, a condition
		4365	variable to wait for callback invocations, an async watcher to notify the
		4366	event loop thread and an unspecified mechanism to wake up the main thread.
		4367
		4368	First, you need to associate some data with the event loop:
		4369
		4370	typedef struct {
		4371	mutex_t lock; /* global loop lock */
		4372	ev_async async_w;
		4373	thread_t tid;
		4374	cond_t invoke_cv;
		4375	} userdata;
		4376
		4377	void prepare_loop (EV_P)
		4378	{
		4379	// for simplicity, we use a static userdata struct.
		4380	static userdata u;
		4381
		4382	ev_async_init (&u->async_w, async_cb);
		4383	ev_async_start (EV_A_ &u->async_w);
		4384
		4385	pthread_mutex_init (&u->lock, 0);
		4386	pthread_cond_init (&u->invoke_cv, 0);
		4387
		4388	// now associate this with the loop
		4389	ev_set_userdata (EV_A_ u);
		4390	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4391	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4392
		4393	// then create the thread running ev_loop
		4394	pthread_create (&u->tid, 0, l_run, EV_A);
		4395	}
		4396
		4397	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4398	solely to wake up the event loop so it takes notice of any new watchers
		4399	that might have been added:
		4400
		4401	static void
		4402	async_cb (EV_P_ ev_async *w, int revents)
		4403	{
		4404	// just used for the side effects
		4405	}
		4406
		4407	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4408	protecting the loop data, respectively.
		4409
		4410	static void
		4411	l_release (EV_P)
		4412	{
		4413	userdata *u = ev_userdata (EV_A);
		4414	pthread_mutex_unlock (&u->lock);
		4415	}
		4416
		4417	static void
		4418	l_acquire (EV_P)
		4419	{
		4420	userdata *u = ev_userdata (EV_A);
		4421	pthread_mutex_lock (&u->lock);
		4422	}
		4423
		4424	The event loop thread first acquires the mutex, and then jumps straight
		4425	into C<ev_run>:
		4426
		4427	void *
		4428	l_run (void *thr_arg)
		4429	{
		4430	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4431
		4432	l_acquire (EV_A);
		4433	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4434	ev_run (EV_A_ 0);
		4435	l_release (EV_A);
		4436
		4437	return 0;
		4438	}
		4439
		4440	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4441	signal the main thread via some unspecified mechanism (signals? pipe
		4442	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4443	have been called (in a while loop because a) spurious wakeups are possible
		4444	and b) skipping inter-thread-communication when there are no pending
		4445	watchers is very beneficial):
		4446
		4447	static void
		4448	l_invoke (EV_P)
		4449	{
		4450	userdata *u = ev_userdata (EV_A);
		4451
		4452	while (ev_pending_count (EV_A))
		4453	{
		4454	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4455	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4456	}
		4457	}
		4458
		4459	Now, whenever the main thread gets told to invoke pending watchers, it
		4460	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4461	thread to continue:
		4462
		4463	static void
		4464	real_invoke_pending (EV_P)
		4465	{
		4466	userdata *u = ev_userdata (EV_A);
		4467
		4468	pthread_mutex_lock (&u->lock);
		4469	ev_invoke_pending (EV_A);
		4470	pthread_cond_signal (&u->invoke_cv);
		4471	pthread_mutex_unlock (&u->lock);
		4472	}
		4473
		4474	Whenever you want to start/stop a watcher or do other modifications to an
		4475	event loop, you will now have to lock:
		4476
		4477	ev_timer timeout_watcher;
		4478	userdata *u = ev_userdata (EV_A);
		4479
		4480	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4481
		4482	pthread_mutex_lock (&u->lock);
		4483	ev_timer_start (EV_A_ &timeout_watcher);
		4484	ev_async_send (EV_A_ &u->async_w);
		4485	pthread_mutex_unlock (&u->lock);
		4486
		4487	Note that sending the C<ev_async> watcher is required because otherwise
		4488	an event loop currently blocking in the kernel will have no knowledge
		4489	about the newly added timer. By waking up the loop it will pick up any new
		4490	watchers in the next event loop iteration.
		4491
3485	=head3 COROUTINES	4492	=head3 COROUTINES
3486		4493
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4494	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4495	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4496	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4497	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4498	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4499	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4500
3494	Care has been taken to ensure that libev does not keep local state inside	4501	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4502	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4503	they do not call any callbacks.
3497		4504
3498	=head2 COMPILER WARNINGS	4505	=head2 COMPILER WARNINGS
3499		4506
3500	Depending on your compiler and compiler settings, you might get no or a	4507	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4508	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4518	maintainable.
3512		4519
3513	And of course, some compiler warnings are just plain stupid, or simply	4520	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4521	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4522	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4523	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	4524	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4525	such buggy versions.
3519		4526
3520	While libev is written to generate as few warnings as possible,	4527	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	4528	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4542	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4543	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4544	==2274== still reachable: 256 bytes in 1 blocks.
3538		4545
3539	Then there is no memory leak, just as memory accounted to global variables	4546	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	4547	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4548
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4549	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4550	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	4551	although an acceptable workaround has been found here), or it might be
3545	confused.	4552	confused.
…		…
3557	I suggest using suppression lists.	4564	I suggest using suppression lists.
3558		4565
3559		4566
3560	=head1 PORTABILITY NOTES	4567	=head1 PORTABILITY NOTES
3561		4568
		4569	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4570
		4571	GNU/Linux is the only common platform that supports 64 bit file/large file
		4572	interfaces but I<disables> them by default.
		4573
		4574	That means that libev compiled in the default environment doesn't support
		4575	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4576
		4577	Unfortunately, many programs try to work around this GNU/Linux issue
		4578	by enabling the large file API, which makes them incompatible with the
		4579	standard libev compiled for their system.
		4580
		4581	Likewise, libev cannot enable the large file API itself as this would
		4582	suddenly make it incompatible to the default compile time environment,
		4583	i.e. all programs not using special compile switches.
		4584
		4585	=head2 OS/X AND DARWIN BUGS
		4586
		4587	The whole thing is a bug if you ask me - basically any system interface
		4588	you touch is broken, whether it is locales, poll, kqueue or even the
		4589	OpenGL drivers.
		4590
		4591	=head3 C<kqueue> is buggy
		4592
		4593	The kqueue syscall is broken in all known versions - most versions support
		4594	only sockets, many support pipes.
		4595
		4596	Libev tries to work around this by not using C<kqueue> by default on this
		4597	rotten platform, but of course you can still ask for it when creating a
		4598	loop - embedding a socket-only kqueue loop into a select-based one is
		4599	probably going to work well.
		4600
		4601	=head3 C<poll> is buggy
		4602
		4603	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4604	implementation by something calling C<kqueue> internally around the 10.5.6
		4605	release, so now C<kqueue> I<and> C<poll> are broken.
		4606
		4607	Libev tries to work around this by not using C<poll> by default on
		4608	this rotten platform, but of course you can still ask for it when creating
		4609	a loop.
		4610
		4611	=head3 C<select> is buggy
		4612
		4613	All that's left is C<select>, and of course Apple found a way to fuck this
		4614	one up as well: On OS/X, C<select> actively limits the number of file
		4615	descriptors you can pass in to 1024 - your program suddenly crashes when
		4616	you use more.
		4617
		4618	There is an undocumented "workaround" for this - defining
		4619	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4620	work on OS/X.
		4621
		4622	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4623
		4624	=head3 C<errno> reentrancy
		4625
		4626	The default compile environment on Solaris is unfortunately so
		4627	thread-unsafe that you can't even use components/libraries compiled
		4628	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4629	defined by default. A valid, if stupid, implementation choice.
		4630
		4631	If you want to use libev in threaded environments you have to make sure
		4632	it's compiled with C<_REENTRANT> defined.
		4633
		4634	=head3 Event port backend
		4635
		4636	The scalable event interface for Solaris is called "event
		4637	ports". Unfortunately, this mechanism is very buggy in all major
		4638	releases. If you run into high CPU usage, your program freezes or you get
		4639	a large number of spurious wakeups, make sure you have all the relevant
		4640	and latest kernel patches applied. No, I don't know which ones, but there
		4641	are multiple ones to apply, and afterwards, event ports actually work
		4642	great.
		4643
		4644	If you can't get it to work, you can try running the program by setting
		4645	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4646	C<select> backends.
		4647
		4648	=head2 AIX POLL BUG
		4649
		4650	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4651	this by trying to avoid the poll backend altogether (i.e. it's not even
		4652	compiled in), which normally isn't a big problem as C<select> works fine
		4653	with large bitsets on AIX, and AIX is dead anyway.
		4654
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4655	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4656
		4657	=head3 General issues
3563		4658
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4659	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	4660	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	4661	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4662	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	4663	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	4664	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4665	as every compielr comes with a slightly differently broken/incompatible
		4666	environment.
3570		4667
3571	Lifting these limitations would basically require the full	4668	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	4669	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	4670	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	4671	also that glib is the slowest event library known to man).
3575		4672
3576	There is no supported compilation method available on windows except	4673	There is no supported compilation method available on windows except
3577	embedding it into other applications.	4674	embedding it into other applications.
		4675
		4676	Sensible signal handling is officially unsupported by Microsoft - libev
		4677	tries its best, but under most conditions, signals will simply not work.
3578		4678
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	4679	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	4680	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	4681	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	4682	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	4687	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	4688	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	4689	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	4690	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	4691	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	4692	(due to Microsoft monopoly games).
3593		4693
3594	A typical way to use libev under windows is to embed it (see the embedding	4694	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	4695	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	4696	of F<ev.h>:
3597		4697
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	4704	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		4705
3606	#include "evwrap.h"	4706	#include "evwrap.h"
3607	#include "ev.c"	4707	#include "ev.c"
3608		4708
3609	=over 4
3610
3611	=item The winsocket select function	4709	=head3 The winsocket C<select> function
3612		4710
3613	The winsocket C<select> function doesn't follow POSIX in that it	4711	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	4712	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	4713	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	4714	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4723	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		4724
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	4725	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	4726	complexity in the O(n²) range when using win32.
3629		4727
3630	=item Limited number of file descriptors	4728	=head3 Limited number of file descriptors
3631		4729
3632	Windows has numerous arbitrary (and low) limits on things.	4730	Windows has numerous arbitrary (and low) limits on things.
3633		4731
3634	Early versions of winsocket's select only supported waiting for a maximum	4732	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	4733	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	4734	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	4735	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	4736	previous thread in each. Sounds great!).
3639		4737
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4738	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	4739	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	4740	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	4741	other interpreters do their own select emulation on windows).
3644		4742
3645	Another limit is the number of file descriptors in the Microsoft runtime	4743	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4744	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	4745	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4746	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	4747	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	4748	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	4749	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	4750	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	4751	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		4752
3659	=head2 PORTABILITY REQUIREMENTS	4753	=head2 PORTABILITY REQUIREMENTS
3660		4754
3661	In addition to a working ISO-C implementation and of course the	4755	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	4756	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	4763	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	4764	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	4765	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	4766	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	4767	calls them using an C<ev_watcher *> internally.
		4768
		4769	=item pointer accesses must be thread-atomic
		4770
		4771	Accessing a pointer value must be atomic, it must both be readable and
		4772	writable in one piece - this is the case on all current architectures.
3674		4773
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	4774	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		4775
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	4776	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4777	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3701	watchers.	4800	watchers.
3702		4801
3703	=item C<double> must hold a time value in seconds with enough accuracy	4802	=item C<double> must hold a time value in seconds with enough accuracy
3704		4803
3705	The type C<double> is used to represent timestamps. It is required to	4804	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4805	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	4806	good enough for at least into the year 4000 with millisecond accuracy
		4807	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	4808	implementations using IEEE 754, which is basically all existing ones. With
		4809	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3709		4810
3710	=back	4811	=back
3711		4812
3712	If you know of other additional requirements drop me a note.	4813	If you know of other additional requirements drop me a note.
3713		4814
…		…
3781	involves iterating over all running async watchers or all signal numbers.	4882	involves iterating over all running async watchers or all signal numbers.
3782		4883
3783	=back	4884	=back
3784		4885
3785		4886
		4887	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4888
		4889	The major version 4 introduced some incompatible changes to the API.
		4890
		4891	At the moment, the C<ev.h> header file provides compatibility definitions
		4892	for all changes, so most programs should still compile. The compatibility
		4893	layer might be removed in later versions of libev, so better update to the
		4894	new API early than late.
		4895
		4896	=over 4
		4897
		4898	=item C<EV_COMPAT3> backwards compatibility mechanism
		4899
		4900	The backward compatibility mechanism can be controlled by
		4901	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4902	section.
		4903
		4904	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4905
		4906	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4907
		4908	ev_loop_destroy (EV_DEFAULT_UC);
		4909	ev_loop_fork (EV_DEFAULT);
		4910
		4911	=item function/symbol renames
		4912
		4913	A number of functions and symbols have been renamed:
		4914
		4915	ev_loop => ev_run
		4916	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4917	EVLOOP_ONESHOT => EVRUN_ONCE
		4918
		4919	ev_unloop => ev_break
		4920	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4921	EVUNLOOP_ONE => EVBREAK_ONE
		4922	EVUNLOOP_ALL => EVBREAK_ALL
		4923
		4924	EV_TIMEOUT => EV_TIMER
		4925
		4926	ev_loop_count => ev_iteration
		4927	ev_loop_depth => ev_depth
		4928	ev_loop_verify => ev_verify
		4929
		4930	Most functions working on C<struct ev_loop> objects don't have an
		4931	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4932	associated constants have been renamed to not collide with the C<struct
		4933	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4934	as all other watcher types. Note that C<ev_loop_fork> is still called
		4935	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4936	typedef.
		4937
		4938	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4939
		4940	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4941	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4942	and work, but the library code will of course be larger.
		4943
		4944	=back
		4945
		4946
		4947	=head1 GLOSSARY
		4948
		4949	=over 4
		4950
		4951	=item active
		4952
		4953	A watcher is active as long as it has been started and not yet stopped.
		4954	See L<WATCHER STATES> for details.
		4955
		4956	=item application
		4957
		4958	In this document, an application is whatever is using libev.
		4959
		4960	=item backend
		4961
		4962	The part of the code dealing with the operating system interfaces.
		4963
		4964	=item callback
		4965
		4966	The address of a function that is called when some event has been
		4967	detected. Callbacks are being passed the event loop, the watcher that
		4968	received the event, and the actual event bitset.
		4969
		4970	=item callback/watcher invocation
		4971
		4972	The act of calling the callback associated with a watcher.
		4973
		4974	=item event
		4975
		4976	A change of state of some external event, such as data now being available
		4977	for reading on a file descriptor, time having passed or simply not having
		4978	any other events happening anymore.
		4979
		4980	In libev, events are represented as single bits (such as C<EV_READ> or
		4981	C<EV_TIMER>).
		4982
		4983	=item event library
		4984
		4985	A software package implementing an event model and loop.
		4986
		4987	=item event loop
		4988
		4989	An entity that handles and processes external events and converts them
		4990	into callback invocations.
		4991
		4992	=item event model
		4993
		4994	The model used to describe how an event loop handles and processes
		4995	watchers and events.
		4996
		4997	=item pending
		4998
		4999	A watcher is pending as soon as the corresponding event has been
		5000	detected. See L<WATCHER STATES> for details.
		5001
		5002	=item real time
		5003
		5004	The physical time that is observed. It is apparently strictly monotonic :)
		5005
		5006	=item wall-clock time
		5007
		5008	The time and date as shown on clocks. Unlike real time, it can actually
		5009	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5010	clock.
		5011
		5012	=item watcher
		5013
		5014	A data structure that describes interest in certain events. Watchers need
		5015	to be started (attached to an event loop) before they can receive events.
		5016
		5017	=back
		5018
3786	=head1 AUTHOR	5019	=head1 AUTHOR
3787		5020
3788	Marc Lehmann <libev@schmorp.de>.	5021	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5022	Magnusson and Emanuele Giaquinta.
3789		5023

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