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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 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
…		…
108	name C<loop> (which is always of type C<struct 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<struct 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 "unloop 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. ##TODO##
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	struct 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);
718	evf_unref (loop);	861	evf_unref (loop);
719		862
720	Example: For some weird reason, unregister the above signal handler again.	863	Example: For some weird reason, unregister the above signal handler again.
…		…
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, struct 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	struct 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
898	ran out of memory, a file descriptor was found to be closed or any other	1142	ran out of memory, a file descriptor was found to be closed or any other
		1143	problem. Libev considers these application bugs.
		1144
899	problem. You best act on it by reporting the problem and somehow coping	1145	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1146	watcher being stopped. Note that well-written programs should not receive
		1147	an error ever, so when your watcher receives it, this usually indicates a
		1148	bug in your program.
901		1149
902	Libev will usually signal a few "dummy" events together with an error, for	1150	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1151	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1152	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1153	the error from read() or write(). This will not work in multi-threaded
906	programs, though, as the fd could already be closed and reused for another	1154	programs, though, as the fd could already be closed and reused for another
907	thing, so beware.	1155	thing, so beware.
908		1156
909	=back	1157	=back
910		1158
		1159	=head2 WATCHER STATES
		1160
		1161	There are various watcher states mentioned throughout this manual -
		1162	active, pending and so on. In this section these states and the rules to
		1163	transition between them will be described in more detail - and while these
		1164	rules might look complicated, they usually do "the right thing".
		1165
		1166	=over 4
		1167
		1168	=item initialiased
		1169
		1170	Before a watcher can be registered with the event looop it has to be
		1171	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1172	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1173
		1174	In this state it is simply some block of memory that is suitable for use
		1175	in an event loop. It can be moved around, freed, reused etc. at will.
		1176
		1177	=item started/running/active
		1178
		1179	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1180	property of the event loop, and is actively waiting for events. While in
		1181	this state it cannot be accessed (except in a few documented ways), moved,
		1182	freed or anything else - the only legal thing is to keep a pointer to it,
		1183	and call libev functions on it that are documented to work on active watchers.
		1184
		1185	=item pending
		1186
		1187	If a watcher is active and libev determines that an event it is interested
		1188	in has occurred (such as a timer expiring), it will become pending. It will
		1189	stay in this pending state until either it is stopped or its callback is
		1190	about to be invoked, so it is not normally pending inside the watcher
		1191	callback.
		1192
		1193	The watcher might or might not be active while it is pending (for example,
		1194	an expired non-repeating timer can be pending but no longer active). If it
		1195	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1196	but it is still property of the event loop at this time, so cannot be
		1197	moved, freed or reused. And if it is active the rules described in the
		1198	previous item still apply.
		1199
		1200	It is also possible to feed an event on a watcher that is not active (e.g.
		1201	via C<ev_feed_event>), in which case it becomes pending without being
		1202	active.
		1203
		1204	=item stopped
		1205
		1206	A watcher can be stopped implicitly by libev (in which case it might still
		1207	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1208	latter will clear any pending state the watcher might be in, regardless
		1209	of whether it was active or not, so stopping a watcher explicitly before
		1210	freeing it is often a good idea.
		1211
		1212	While stopped (and not pending) the watcher is essentially in the
		1213	initialised state, that is it can be reused, moved, modified in any way
		1214	you wish.
		1215
		1216	=back
		1217
911	=head2 GENERIC WATCHER FUNCTIONS	1218	=head2 GENERIC WATCHER FUNCTIONS
912
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915		1219
916	=over 4	1220	=over 4
917		1221
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1222	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1223
…		…
925	which rolls both calls into one.	1229	which rolls both calls into one.
926		1230
927	You can reinitialise a watcher at any time as long as it has been stopped	1231	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1232	(or never started) and there are no pending events outstanding.
929		1233
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1234	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1235	int revents)>.
932		1236
933	Example: Initialise an C<ev_io> watcher in two steps.	1237	Example: Initialise an C<ev_io> watcher in two steps.
934		1238
935	ev_io w;	1239	ev_io w;
936	ev_init (&w, my_cb);	1240	ev_init (&w, my_cb);
937	ev_io_set (&w, STDIN_FILENO, EV_READ);	1241	ev_io_set (&w, STDIN_FILENO, EV_READ);
938		1242
939	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1243	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
940		1244
941	This macro initialises the type-specific parts of a watcher. You need to	1245	This macro initialises the type-specific parts of a watcher. You need to
942	call C<ev_init> at least once before you call this macro, but you can	1246	call C<ev_init> at least once before you call this macro, but you can
943	call C<ev_TYPE_set> any number of times. You must not, however, call this	1247	call C<ev_TYPE_set> any number of times. You must not, however, call this
944	macro on a watcher that is active (it can be pending, however, which is a	1248	macro on a watcher that is active (it can be pending, however, which is a
…		…
957		1261
958	Example: Initialise and set an C<ev_io> watcher in one step.	1262	Example: Initialise and set an C<ev_io> watcher in one step.
959		1263
960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1264	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
961		1265
962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1266	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
963		1267
964	Starts (activates) the given watcher. Only active watchers will receive	1268	Starts (activates) the given watcher. Only active watchers will receive
965	events. If the watcher is already active nothing will happen.	1269	events. If the watcher is already active nothing will happen.
966		1270
967	Example: Start the C<ev_io> watcher that is being abused as example in this	1271	Example: Start the C<ev_io> watcher that is being abused as example in this
968	whole section.	1272	whole section.
969		1273
970	ev_io_start (EV_DEFAULT_UC, &w);	1274	ev_io_start (EV_DEFAULT_UC, &w);
971		1275
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1276	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
973		1277
974	Stops the given watcher if active, and clears the pending status (whether	1278	Stops the given watcher if active, and clears the pending status (whether
975	the watcher was active or not).	1279	the watcher was active or not).
976		1280
977	It is possible that stopped watchers are pending - for example,	1281	It is possible that stopped watchers are pending - for example,
…		…
1002	=item ev_cb_set (ev_TYPE *watcher, callback)	1306	=item ev_cb_set (ev_TYPE *watcher, callback)
1003		1307
1004	Change the callback. You can change the callback at virtually any time	1308	Change the callback. You can change the callback at virtually any time
1005	(modulo threads).	1309	(modulo threads).
1006		1310
1007	=item ev_set_priority (ev_TYPE *watcher, priority)	1311	=item ev_set_priority (ev_TYPE *watcher, int priority)
1008		1312
1009	=item int ev_priority (ev_TYPE *watcher)	1313	=item int ev_priority (ev_TYPE *watcher)
1010		1314
1011	Set and query the priority of the watcher. The priority is a small	1315	Set and query the priority of the watcher. The priority is a small
1012	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1316	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1013	(default: C<-2>). Pending watchers with higher priority will be invoked	1317	(default: C<-2>). Pending watchers with higher priority will be invoked
1014	before watchers with lower priority, but priority will not keep watchers	1318	before watchers with lower priority, but priority will not keep watchers
1015	from being executed (except for C<ev_idle> watchers).	1319	from being executed (except for C<ev_idle> watchers).
1016		1320
1017	This means that priorities are I<only> used for ordering callback
1018	invocation after new events have been received. This is useful, for
1019	example, to reduce latency after idling, or more often, to bind two
1020	watchers on the same event and make sure one is called first.
1021
1022	If you need to suppress invocation when higher priority events are pending	1321	If you need to suppress invocation when higher priority events are pending
1023	you need to look at C<ev_idle> watchers, which provide this functionality.	1322	you need to look at C<ev_idle> watchers, which provide this functionality.
1024		1323
1025	You I<must not> change the priority of a watcher as long as it is active or	1324	You I<must not> change the priority of a watcher as long as it is active or
1026	pending.	1325	pending.
1027		1326
		1327	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1328	fine, as long as you do not mind that the priority value you query might
		1329	or might not have been clamped to the valid range.
		1330
1028	The default priority used by watchers when no priority has been set is	1331	The default priority used by watchers when no priority has been set is
1029	always C<0>, which is supposed to not be too high and not be too low :).	1332	always C<0>, which is supposed to not be too high and not be too low :).
1030		1333
1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1334	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1032	fine, as long as you do not mind that the priority value you query might	1335	priorities.
1033	or might not have been adjusted to be within valid range.
1034		1336
1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1337	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1036		1338
1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1339	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1038	C<loop> nor C<revents> need to be valid as long as the watcher callback	1340	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1045	returns its C<revents> bitset (as if its callback was invoked). If the	1347	returns its C<revents> bitset (as if its callback was invoked). If the
1046	watcher isn't pending it does nothing and returns C<0>.	1348	watcher isn't pending it does nothing and returns C<0>.
1047		1349
1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1350	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1049	callback to be invoked, which can be accomplished with this function.	1351	callback to be invoked, which can be accomplished with this function.
		1352
		1353	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1354
		1355	Feeds the given event set into the event loop, as if the specified event
		1356	had happened for the specified watcher (which must be a pointer to an
		1357	initialised but not necessarily started event watcher). Obviously you must
		1358	not free the watcher as long as it has pending events.
		1359
		1360	Stopping the watcher, letting libev invoke it, or calling
		1361	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1362	not started in the first place.
		1363
		1364	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1365	functions that do not need a watcher.
1050		1366
1051	=back	1367	=back
1052		1368
1053		1369
1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1060	member, you can also "subclass" the watcher type and provide your own	1376	member, you can also "subclass" the watcher type and provide your own
1061	data:	1377	data:
1062		1378
1063	struct my_io	1379	struct my_io
1064	{	1380	{
1065	struct ev_io io;	1381	ev_io io;
1066	int otherfd;	1382	int otherfd;
1067	void *somedata;	1383	void *somedata;
1068	struct whatever *mostinteresting;	1384	struct whatever *mostinteresting;
1069	};	1385	};
1070		1386
…		…
1073	ev_io_init (&w.io, my_cb, fd, EV_READ);	1389	ev_io_init (&w.io, my_cb, fd, EV_READ);
1074		1390
1075	And since your callback will be called with a pointer to the watcher, you	1391	And since your callback will be called with a pointer to the watcher, you
1076	can cast it back to your own type:	1392	can cast it back to your own type:
1077		1393
1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1394	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1079	{	1395	{
1080	struct my_io *w = (struct my_io *)w_;	1396	struct my_io *w = (struct my_io *)w_;
1081	...	1397	...
1082	}	1398	}
1083		1399
…		…
1101	programmers):	1417	programmers):
1102		1418
1103	#include <stddef.h>	1419	#include <stddef.h>
1104		1420
1105	static void	1421	static void
1106	t1_cb (EV_P_ struct ev_timer *w, int revents)	1422	t1_cb (EV_P_ ev_timer *w, int revents)
1107	{	1423	{
1108	struct my_biggy big = (struct my_biggy *	1424	struct my_biggy big = (struct my_biggy *)
1109	(((char *)w) - offsetof (struct my_biggy, t1));	1425	(((char *)w) - offsetof (struct my_biggy, t1));
1110	}	1426	}
1111		1427
1112	static void	1428	static void
1113	t2_cb (EV_P_ struct ev_timer *w, int revents)	1429	t2_cb (EV_P_ ev_timer *w, int revents)
1114	{	1430	{
1115	struct my_biggy big = (struct my_biggy *	1431	struct my_biggy big = (struct my_biggy *)
1116	(((char *)w) - offsetof (struct my_biggy, t2));	1432	(((char *)w) - offsetof (struct my_biggy, t2));
1117	}	1433	}
		1434
		1435	=head2 WATCHER PRIORITY MODELS
		1436
		1437	Many event loops support I<watcher priorities>, which are usually small
		1438	integers that influence the ordering of event callback invocation
		1439	between watchers in some way, all else being equal.
		1440
		1441	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1442	description for the more technical details such as the actual priority
		1443	range.
		1444
		1445	There are two common ways how these these priorities are being interpreted
		1446	by event loops:
		1447
		1448	In the more common lock-out model, higher priorities "lock out" invocation
		1449	of lower priority watchers, which means as long as higher priority
		1450	watchers receive events, lower priority watchers are not being invoked.
		1451
		1452	The less common only-for-ordering model uses priorities solely to order
		1453	callback invocation within a single event loop iteration: Higher priority
		1454	watchers are invoked before lower priority ones, but they all get invoked
		1455	before polling for new events.
		1456
		1457	Libev uses the second (only-for-ordering) model for all its watchers
		1458	except for idle watchers (which use the lock-out model).
		1459
		1460	The rationale behind this is that implementing the lock-out model for
		1461	watchers is not well supported by most kernel interfaces, and most event
		1462	libraries will just poll for the same events again and again as long as
		1463	their callbacks have not been executed, which is very inefficient in the
		1464	common case of one high-priority watcher locking out a mass of lower
		1465	priority ones.
		1466
		1467	Static (ordering) priorities are most useful when you have two or more
		1468	watchers handling the same resource: a typical usage example is having an
		1469	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1470	timeouts. Under load, data might be received while the program handles
		1471	other jobs, but since timers normally get invoked first, the timeout
		1472	handler will be executed before checking for data. In that case, giving
		1473	the timer a lower priority than the I/O watcher ensures that I/O will be
		1474	handled first even under adverse conditions (which is usually, but not
		1475	always, what you want).
		1476
		1477	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1478	will only be executed when no same or higher priority watchers have
		1479	received events, they can be used to implement the "lock-out" model when
		1480	required.
		1481
		1482	For example, to emulate how many other event libraries handle priorities,
		1483	you can associate an C<ev_idle> watcher to each such watcher, and in
		1484	the normal watcher callback, you just start the idle watcher. The real
		1485	processing is done in the idle watcher callback. This causes libev to
		1486	continuously poll and process kernel event data for the watcher, but when
		1487	the lock-out case is known to be rare (which in turn is rare :), this is
		1488	workable.
		1489
		1490	Usually, however, the lock-out model implemented that way will perform
		1491	miserably under the type of load it was designed to handle. In that case,
		1492	it might be preferable to stop the real watcher before starting the
		1493	idle watcher, so the kernel will not have to process the event in case
		1494	the actual processing will be delayed for considerable time.
		1495
		1496	Here is an example of an I/O watcher that should run at a strictly lower
		1497	priority than the default, and which should only process data when no
		1498	other events are pending:
		1499
		1500	ev_idle idle; // actual processing watcher
		1501	ev_io io; // actual event watcher
		1502
		1503	static void
		1504	io_cb (EV_P_ ev_io *w, int revents)
		1505	{
		1506	// stop the I/O watcher, we received the event, but
		1507	// are not yet ready to handle it.
		1508	ev_io_stop (EV_A_ w);
		1509
		1510	// start the idle watcher to handle the actual event.
		1511	// it will not be executed as long as other watchers
		1512	// with the default priority are receiving events.
		1513	ev_idle_start (EV_A_ &idle);
		1514	}
		1515
		1516	static void
		1517	idle_cb (EV_P_ ev_idle *w, int revents)
		1518	{
		1519	// actual processing
		1520	read (STDIN_FILENO, ...);
		1521
		1522	// have to start the I/O watcher again, as
		1523	// we have handled the event
		1524	ev_io_start (EV_P_ &io);
		1525	}
		1526
		1527	// initialisation
		1528	ev_idle_init (&idle, idle_cb);
		1529	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1530	ev_io_start (EV_DEFAULT_ &io);
		1531
		1532	In the "real" world, it might also be beneficial to start a timer, so that
		1533	low-priority connections can not be locked out forever under load. This
		1534	enables your program to keep a lower latency for important connections
		1535	during short periods of high load, while not completely locking out less
		1536	important ones.
1118		1537
1119		1538
1120	=head1 WATCHER TYPES	1539	=head1 WATCHER TYPES
1121		1540
1122	This section describes each watcher in detail, but will not repeat	1541	This section describes each watcher in detail, but will not repeat
…		…
1148	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1149	required if you know what you are doing).	1568	required if you know what you are doing).
1150		1569
1151	If you cannot use non-blocking mode, then force the use of a	1570	If you cannot use non-blocking mode, then force the use of a
1152	known-to-be-good backend (at the time of this writing, this includes only	1571	known-to-be-good backend (at the time of this writing, this includes only
1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1573	descriptors for which non-blocking operation makes no sense (such as
		1574	files) - libev doesn't guarantee any specific behaviour in that case.
1154		1575
1155	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1156	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is your callback might
1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1158	because there is no data. Not only are some backends known to create a	1579	because there is no data. Not only are some backends known to create a
…		…
1223		1644
1224	So when you encounter spurious, unexplained daemon exits, make sure you	1645	So when you encounter spurious, unexplained daemon exits, make sure you
1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1646	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1226	somewhere, as that would have given you a big clue).	1647	somewhere, as that would have given you a big clue).
1227		1648
		1649	=head3 The special problem of accept()ing when you can't
		1650
		1651	Many implementations of the POSIX C<accept> function (for example,
		1652	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1653	connection from the pending queue in all error cases.
		1654
		1655	For example, larger servers often run out of file descriptors (because
		1656	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1657	rejecting the connection, leading to libev signalling readiness on
		1658	the next iteration again (the connection still exists after all), and
		1659	typically causing the program to loop at 100% CPU usage.
		1660
		1661	Unfortunately, the set of errors that cause this issue differs between
		1662	operating systems, there is usually little the app can do to remedy the
		1663	situation, and no known thread-safe method of removing the connection to
		1664	cope with overload is known (to me).
		1665
		1666	One of the easiest ways to handle this situation is to just ignore it
		1667	- when the program encounters an overload, it will just loop until the
		1668	situation is over. While this is a form of busy waiting, no OS offers an
		1669	event-based way to handle this situation, so it's the best one can do.
		1670
		1671	A better way to handle the situation is to log any errors other than
		1672	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1673	messages, and continue as usual, which at least gives the user an idea of
		1674	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1675	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1676	usage.
		1677
		1678	If your program is single-threaded, then you could also keep a dummy file
		1679	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1680	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1681	close that fd, and create a new dummy fd. This will gracefully refuse
		1682	clients under typical overload conditions.
		1683
		1684	The last way to handle it is to simply log the error and C<exit>, as
		1685	is often done with C<malloc> failures, but this results in an easy
		1686	opportunity for a DoS attack.
1228		1687
1229	=head3 Watcher-Specific Functions	1688	=head3 Watcher-Specific Functions
1230		1689
1231	=over 4	1690	=over 4
1232		1691
…		…
1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1712	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1254	readable, but only once. Since it is likely line-buffered, you could	1713	readable, but only once. Since it is likely line-buffered, you could
1255	attempt to read a whole line in the callback.	1714	attempt to read a whole line in the callback.
1256		1715
1257	static void	1716	static void
1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1717	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1259	{	1718	{
1260	ev_io_stop (loop, w);	1719	ev_io_stop (loop, w);
1261	.. read from stdin here (or from w->fd) and handle any I/O errors	1720	.. read from stdin here (or from w->fd) and handle any I/O errors
1262	}	1721	}
1263		1722
1264	...	1723	...
1265	struct ev_loop *loop = ev_default_init (0);	1724	struct ev_loop *loop = ev_default_init (0);
1266	struct ev_io stdin_readable;	1725	ev_io stdin_readable;
1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1726	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1268	ev_io_start (loop, &stdin_readable);	1727	ev_io_start (loop, &stdin_readable);
1269	ev_loop (loop, 0);	1728	ev_run (loop, 0);
1270		1729
1271		1730
1272	=head2 C<ev_timer> - relative and optionally repeating timeouts	1731	=head2 C<ev_timer> - relative and optionally repeating timeouts
1273		1732
1274	Timer watchers are simple relative timers that generate an event after a	1733	Timer watchers are simple relative timers that generate an event after a
…		…
1279	year, it will still time out after (roughly) one hour. "Roughly" because	1738	year, it will still time out after (roughly) one hour. "Roughly" because
1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1281	monotonic clock option helps a lot here).	1740	monotonic clock option helps a lot here).
1282		1741
1283	The callback is guaranteed to be invoked only I<after> its timeout has	1742	The callback is guaranteed to be invoked only I<after> its timeout has
1284	passed, but if multiple timers become ready during the same loop iteration	1743	passed (not I<at>, so on systems with very low-resolution clocks this
1285	then order of execution is undefined.	1744	might introduce a small delay). If multiple timers become ready during the
		1745	same loop iteration then the ones with earlier time-out values are invoked
		1746	before ones of the same priority with later time-out values (but this is
		1747	no longer true when a callback calls C<ev_run> recursively).
		1748
		1749	=head3 Be smart about timeouts
		1750
		1751	Many real-world problems involve some kind of timeout, usually for error
		1752	recovery. A typical example is an HTTP request - if the other side hangs,
		1753	you want to raise some error after a while.
		1754
		1755	What follows are some ways to handle this problem, from obvious and
		1756	inefficient to smart and efficient.
		1757
		1758	In the following, a 60 second activity timeout is assumed - a timeout that
		1759	gets reset to 60 seconds each time there is activity (e.g. each time some
		1760	data or other life sign was received).
		1761
		1762	=over 4
		1763
		1764	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1765
		1766	This is the most obvious, but not the most simple way: In the beginning,
		1767	start the watcher:
		1768
		1769	ev_timer_init (timer, callback, 60., 0.);
		1770	ev_timer_start (loop, timer);
		1771
		1772	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1773	and start it again:
		1774
		1775	ev_timer_stop (loop, timer);
		1776	ev_timer_set (timer, 60., 0.);
		1777	ev_timer_start (loop, timer);
		1778
		1779	This is relatively simple to implement, but means that each time there is
		1780	some activity, libev will first have to remove the timer from its internal
		1781	data structure and then add it again. Libev tries to be fast, but it's
		1782	still not a constant-time operation.
		1783
		1784	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1785
		1786	This is the easiest way, and involves using C<ev_timer_again> instead of
		1787	C<ev_timer_start>.
		1788
		1789	To implement this, configure an C<ev_timer> with a C<repeat> value
		1790	of C<60> and then call C<ev_timer_again> at start and each time you
		1791	successfully read or write some data. If you go into an idle state where
		1792	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1793	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1794
		1795	That means you can ignore both the C<ev_timer_start> function and the
		1796	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1797	member and C<ev_timer_again>.
		1798
		1799	At start:
		1800
		1801	ev_init (timer, callback);
		1802	timer->repeat = 60.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	Each time there is some activity:
		1806
		1807	ev_timer_again (loop, timer);
		1808
		1809	It is even possible to change the time-out on the fly, regardless of
		1810	whether the watcher is active or not:
		1811
		1812	timer->repeat = 30.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	This is slightly more efficient then stopping/starting the timer each time
		1816	you want to modify its timeout value, as libev does not have to completely
		1817	remove and re-insert the timer from/into its internal data structure.
		1818
		1819	It is, however, even simpler than the "obvious" way to do it.
		1820
		1821	=item 3. Let the timer time out, but then re-arm it as required.
		1822
		1823	This method is more tricky, but usually most efficient: Most timeouts are
		1824	relatively long compared to the intervals between other activity - in
		1825	our example, within 60 seconds, there are usually many I/O events with
		1826	associated activity resets.
		1827
		1828	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1829	but remember the time of last activity, and check for a real timeout only
		1830	within the callback:
		1831
		1832	ev_tstamp last_activity; // time of last activity
		1833
		1834	static void
		1835	callback (EV_P_ ev_timer *w, int revents)
		1836	{
		1837	ev_tstamp now = ev_now (EV_A);
		1838	ev_tstamp timeout = last_activity + 60.;
		1839
		1840	// if last_activity + 60. is older than now, we did time out
		1841	if (timeout < now)
		1842	{
		1843	// timeout occurred, take action
		1844	}
		1845	else
		1846	{
		1847	// callback was invoked, but there was some activity, re-arm
		1848	// the watcher to fire in last_activity + 60, which is
		1849	// guaranteed to be in the future, so "again" is positive:
		1850	w->repeat = timeout - now;
		1851	ev_timer_again (EV_A_ w);
		1852	}
		1853	}
		1854
		1855	To summarise the callback: first calculate the real timeout (defined
		1856	as "60 seconds after the last activity"), then check if that time has
		1857	been reached, which means something I<did>, in fact, time out. Otherwise
		1858	the callback was invoked too early (C<timeout> is in the future), so
		1859	re-schedule the timer to fire at that future time, to see if maybe we have
		1860	a timeout then.
		1861
		1862	Note how C<ev_timer_again> is used, taking advantage of the
		1863	C<ev_timer_again> optimisation when the timer is already running.
		1864
		1865	This scheme causes more callback invocations (about one every 60 seconds
		1866	minus half the average time between activity), but virtually no calls to
		1867	libev to change the timeout.
		1868
		1869	To start the timer, simply initialise the watcher and set C<last_activity>
		1870	to the current time (meaning we just have some activity :), then call the
		1871	callback, which will "do the right thing" and start the timer:
		1872
		1873	ev_init (timer, callback);
		1874	last_activity = ev_now (loop);
		1875	callback (loop, timer, EV_TIMER);
		1876
		1877	And when there is some activity, simply store the current time in
		1878	C<last_activity>, no libev calls at all:
		1879
		1880	last_activity = ev_now (loop);
		1881
		1882	This technique is slightly more complex, but in most cases where the
		1883	time-out is unlikely to be triggered, much more efficient.
		1884
		1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1886	callback :) - just change the timeout and invoke the callback, which will
		1887	fix things for you.
		1888
		1889	=item 4. Wee, just use a double-linked list for your timeouts.
		1890
		1891	If there is not one request, but many thousands (millions...), all
		1892	employing some kind of timeout with the same timeout value, then one can
		1893	do even better:
		1894
		1895	When starting the timeout, calculate the timeout value and put the timeout
		1896	at the I<end> of the list.
		1897
		1898	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1899	the list is expected to fire (for example, using the technique #3).
		1900
		1901	When there is some activity, remove the timer from the list, recalculate
		1902	the timeout, append it to the end of the list again, and make sure to
		1903	update the C<ev_timer> if it was taken from the beginning of the list.
		1904
		1905	This way, one can manage an unlimited number of timeouts in O(1) time for
		1906	starting, stopping and updating the timers, at the expense of a major
		1907	complication, and having to use a constant timeout. The constant timeout
		1908	ensures that the list stays sorted.
		1909
		1910	=back
		1911
		1912	So which method the best?
		1913
		1914	Method #2 is a simple no-brain-required solution that is adequate in most
		1915	situations. Method #3 requires a bit more thinking, but handles many cases
		1916	better, and isn't very complicated either. In most case, choosing either
		1917	one is fine, with #3 being better in typical situations.
		1918
		1919	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1920	rather complicated, but extremely efficient, something that really pays
		1921	off after the first million or so of active timers, i.e. it's usually
		1922	overkill :)
1286		1923
1287	=head3 The special problem of time updates	1924	=head3 The special problem of time updates
1288		1925
1289	Establishing the current time is a costly operation (it usually takes at	1926	Establishing the current time is a costly operation (it usually takes at
1290	least two system calls): EV therefore updates its idea of the current	1927	least two system calls): EV therefore updates its idea of the current
1291	time only before and after C<ev_loop> collects new events, which causes a	1928	time only before and after C<ev_run> collects new events, which causes a
1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1293	lots of events in one iteration.	1930	lots of events in one iteration.
1294		1931
1295	The relative timeouts are calculated relative to the C<ev_now ()>	1932	The relative timeouts are calculated relative to the C<ev_now ()>
1296	time. This is usually the right thing as this timestamp refers to the time	1933	time. This is usually the right thing as this timestamp refers to the time
…		…
1302		1939
1303	If the event loop is suspended for a long time, you can also force an	1940	If the event loop is suspended for a long time, you can also force an
1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1305	()>.	1942	()>.
1306		1943
		1944	=head3 The special problems of suspended animation
		1945
		1946	When you leave the server world it is quite customary to hit machines that
		1947	can suspend/hibernate - what happens to the clocks during such a suspend?
		1948
		1949	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1950	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1951	to run until the system is suspended, but they will not advance while the
		1952	system is suspended. That means, on resume, it will be as if the program
		1953	was frozen for a few seconds, but the suspend time will not be counted
		1954	towards C<ev_timer> when a monotonic clock source is used. The real time
		1955	clock advanced as expected, but if it is used as sole clocksource, then a
		1956	long suspend would be detected as a time jump by libev, and timers would
		1957	be adjusted accordingly.
		1958
		1959	I would not be surprised to see different behaviour in different between
		1960	operating systems, OS versions or even different hardware.
		1961
		1962	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1963	time jump in the monotonic clocks and the realtime clock. If the program
		1964	is suspended for a very long time, and monotonic clock sources are in use,
		1965	then you can expect C<ev_timer>s to expire as the full suspension time
		1966	will be counted towards the timers. When no monotonic clock source is in
		1967	use, then libev will again assume a timejump and adjust accordingly.
		1968
		1969	It might be beneficial for this latter case to call C<ev_suspend>
		1970	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1971	deterministic behaviour in this case (you can do nothing against
		1972	C<SIGSTOP>).
		1973
1307	=head3 Watcher-Specific Functions and Data Members	1974	=head3 Watcher-Specific Functions and Data Members
1308		1975
1309	=over 4	1976	=over 4
1310		1977
1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1978	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1334	If the timer is started but non-repeating, stop it (as if it timed out).	2001	If the timer is started but non-repeating, stop it (as if it timed out).
1335		2002
1336	If the timer is repeating, either start it if necessary (with the	2003	If the timer is repeating, either start it if necessary (with the
1337	C<repeat> value), or reset the running timer to the C<repeat> value.	2004	C<repeat> value), or reset the running timer to the C<repeat> value.
1338		2005
1339	This sounds a bit complicated, but here is a useful and typical	2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1340	example: Imagine you have a TCP connection and you want a so-called idle	2007	usage example.
1341	timeout, that is, you want to be called when there have been, say, 60
1342	seconds of inactivity on the socket. The easiest way to do this is to
1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1344	C<ev_timer_again> each time you successfully read or write some data. If
1345	you go into an idle state where you do not expect data to travel on the
1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1347	automatically restart it if need be.
1348		2008
1349	That means you can ignore the C<after> value and C<ev_timer_start>	2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1351		2010
1352	ev_timer_init (timer, callback, 0., 5.);	2011	Returns the remaining time until a timer fires. If the timer is active,
1353	ev_timer_again (loop, timer);	2012	then this time is relative to the current event loop time, otherwise it's
1354	...	2013	the timeout value currently configured.
1355	timer->again = 17.;
1356	ev_timer_again (loop, timer);
1357	...
1358	timer->again = 10.;
1359	ev_timer_again (loop, timer);
1360		2014
1361	This is more slightly efficient then stopping/starting the timer each time	2015	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1362	you want to modify its timeout value.	2016	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1363		2017	will return C<4>. When the timer expires and is restarted, it will return
1364	Note, however, that it is often even more efficient to remember the	2018	roughly C<7> (likely slightly less as callback invocation takes some time,
1365	time of the last activity and let the timer time-out naturally. In the	2019	too), and so on.
1366	callback, you then check whether the time-out is real, or, if there was
1367	some activity, you reschedule the watcher to time-out in "last_activity +
1368	timeout - ev_now ()" seconds.
1369		2020
1370	=item ev_tstamp repeat [read-write]	2021	=item ev_tstamp repeat [read-write]
1371		2022
1372	The current C<repeat> value. Will be used each time the watcher times out	2023	The current C<repeat> value. Will be used each time the watcher times out
1373	or C<ev_timer_again> is called, and determines the next timeout (if any),	2024	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1378	=head3 Examples	2029	=head3 Examples
1379		2030
1380	Example: Create a timer that fires after 60 seconds.	2031	Example: Create a timer that fires after 60 seconds.
1381		2032
1382	static void	2033	static void
1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2034	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1384	{	2035	{
1385	.. one minute over, w is actually stopped right here	2036	.. one minute over, w is actually stopped right here
1386	}	2037	}
1387		2038
1388	struct ev_timer mytimer;	2039	ev_timer mytimer;
1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2040	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1390	ev_timer_start (loop, &mytimer);	2041	ev_timer_start (loop, &mytimer);
1391		2042
1392	Example: Create a timeout timer that times out after 10 seconds of	2043	Example: Create a timeout timer that times out after 10 seconds of
1393	inactivity.	2044	inactivity.
1394		2045
1395	static void	2046	static void
1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2047	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1397	{	2048	{
1398	.. ten seconds without any activity	2049	.. ten seconds without any activity
1399	}	2050	}
1400		2051
1401	struct ev_timer mytimer;	2052	ev_timer mytimer;
1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2053	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1403	ev_timer_again (&mytimer); /* start timer */	2054	ev_timer_again (&mytimer); /* start timer */
1404	ev_loop (loop, 0);	2055	ev_run (loop, 0);
1405		2056
1406	// and in some piece of code that gets executed on any "activity":	2057	// and in some piece of code that gets executed on any "activity":
1407	// reset the timeout to start ticking again at 10 seconds	2058	// reset the timeout to start ticking again at 10 seconds
1408	ev_timer_again (&mytimer);	2059	ev_timer_again (&mytimer);
1409		2060
…		…
1411	=head2 C<ev_periodic> - to cron or not to cron?	2062	=head2 C<ev_periodic> - to cron or not to cron?
1412		2063
1413	Periodic watchers are also timers of a kind, but they are very versatile	2064	Periodic watchers are also timers of a kind, but they are very versatile
1414	(and unfortunately a bit complex).	2065	(and unfortunately a bit complex).
1415		2066
1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2067	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1417	but on wall clock time (absolute time). You can tell a periodic watcher	2068	relative time, the physical time that passes) but on wall clock time
1418	to trigger after some specific point in time. For example, if you tell a	2069	(absolute time, the thing you can read on your calender or clock). The
1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2070	difference is that wall clock time can run faster or slower than real
1420	+ 10.>, that is, an absolute time not a delay) and then reset your system	2071	time, and time jumps are not uncommon (e.g. when you adjust your
1421	clock to January of the previous year, then it will take more than year	2072	wrist-watch).
1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1423	roughly 10 seconds later as it uses a relative timeout).
1424		2073
		2074	You can tell a periodic watcher to trigger after some specific point
		2075	in time: for example, if you tell a periodic watcher to trigger "in 10
		2076	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2077	not a delay) and then reset your system clock to January of the previous
		2078	year, then it will take a year or more to trigger the event (unlike an
		2079	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2080	it, as it uses a relative timeout).
		2081
1425	C<ev_periodic>s can also be used to implement vastly more complex timers,	2082	C<ev_periodic> watchers can also be used to implement vastly more complex
1426	such as triggering an event on each "midnight, local time", or other	2083	timers, such as triggering an event on each "midnight, local time", or
1427	complicated rules.	2084	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2085	those cannot react to time jumps.
1428		2086
1429	As with timers, the callback is guaranteed to be invoked only when the	2087	As with timers, the callback is guaranteed to be invoked only when the
1430	time (C<at>) has passed, but if multiple periodic timers become ready	2088	point in time where it is supposed to trigger has passed. If multiple
1431	during the same loop iteration, then order of execution is undefined.	2089	timers become ready during the same loop iteration then the ones with
		2090	earlier time-out values are invoked before ones with later time-out values
		2091	(but this is no longer true when a callback calls C<ev_run> recursively).
1432		2092
1433	=head3 Watcher-Specific Functions and Data Members	2093	=head3 Watcher-Specific Functions and Data Members
1434		2094
1435	=over 4	2095	=over 4
1436		2096
1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2097	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		2098
1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2099	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1440		2100
1441	Lots of arguments, lets sort it out... There are basically three modes of	2101	Lots of arguments, let's sort it out... There are basically three modes of
1442	operation, and we will explain them from simplest to most complex:	2102	operation, and we will explain them from simplest to most complex:
1443		2103
1444	=over 4	2104	=over 4
1445		2105
1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2106	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1447		2107
1448	In this configuration the watcher triggers an event after the wall clock	2108	In this configuration the watcher triggers an event after the wall clock
1449	time C<at> has passed. It will not repeat and will not adjust when a time	2109	time C<offset> has passed. It will not repeat and will not adjust when a
1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2110	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1451	only run when the system clock reaches or surpasses this time.	2111	will be stopped and invoked when the system clock reaches or surpasses
		2112	this point in time.
1452		2113
1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2114	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1454		2115
1455	In this mode the watcher will always be scheduled to time out at the next	2116	In this mode the watcher will always be scheduled to time out at the next
1456	C<at + N * interval> time (for some integer N, which can also be negative)	2117	C<offset + N * interval> time (for some integer N, which can also be
1457	and then repeat, regardless of any time jumps.	2118	negative) and then repeat, regardless of any time jumps. The C<offset>
		2119	argument is merely an offset into the C<interval> periods.
1458		2120
1459	This can be used to create timers that do not drift with respect to the	2121	This can be used to create timers that do not drift with respect to the
1460	system clock, for example, here is a C<ev_periodic> that triggers each	2122	system clock, for example, here is an C<ev_periodic> that triggers each
1461	hour, on the hour:	2123	hour, on the hour (with respect to UTC):
1462		2124
1463	ev_periodic_set (&periodic, 0., 3600., 0);	2125	ev_periodic_set (&periodic, 0., 3600., 0);
1464		2126
1465	This doesn't mean there will always be 3600 seconds in between triggers,	2127	This doesn't mean there will always be 3600 seconds in between triggers,
1466	but only that the callback will be called when the system time shows a	2128	but only that the callback will be called when the system time shows a
1467	full hour (UTC), or more correctly, when the system time is evenly divisible	2129	full hour (UTC), or more correctly, when the system time is evenly divisible
1468	by 3600.	2130	by 3600.
1469		2131
1470	Another way to think about it (for the mathematically inclined) is that	2132	Another way to think about it (for the mathematically inclined) is that
1471	C<ev_periodic> will try to run the callback in this mode at the next possible	2133	C<ev_periodic> will try to run the callback in this mode at the next possible
1472	time where C<time = at (mod interval)>, regardless of any time jumps.	2134	time where C<time = offset (mod interval)>, regardless of any time jumps.
1473		2135
1474	For numerical stability it is preferable that the C<at> value is near	2136	For numerical stability it is preferable that the C<offset> value is near
1475	C<ev_now ()> (the current time), but there is no range requirement for	2137	C<ev_now ()> (the current time), but there is no range requirement for
1476	this value, and in fact is often specified as zero.	2138	this value, and in fact is often specified as zero.
1477		2139
1478	Note also that there is an upper limit to how often a timer can fire (CPU	2140	Note also that there is an upper limit to how often a timer can fire (CPU
1479	speed for example), so if C<interval> is very small then timing stability	2141	speed for example), so if C<interval> is very small then timing stability
1480	will of course deteriorate. Libev itself tries to be exact to be about one	2142	will of course deteriorate. Libev itself tries to be exact to be about one
1481	millisecond (if the OS supports it and the machine is fast enough).	2143	millisecond (if the OS supports it and the machine is fast enough).
1482		2144
1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2145	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1484		2146
1485	In this mode the values for C<interval> and C<at> are both being	2147	In this mode the values for C<interval> and C<offset> are both being
1486	ignored. Instead, each time the periodic watcher gets scheduled, the	2148	ignored. Instead, each time the periodic watcher gets scheduled, the
1487	reschedule callback will be called with the watcher as first, and the	2149	reschedule callback will be called with the watcher as first, and the
1488	current time as second argument.	2150	current time as second argument.
1489		2151
1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2152	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1491	ever, or make ANY event loop modifications whatsoever>.	2153	or make ANY other event loop modifications whatsoever, unless explicitly
		2154	allowed by documentation here>.
1492		2155
1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2156	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2157	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1495	only event loop modification you are allowed to do).	2158	only event loop modification you are allowed to do).
1496		2159
1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2160	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1498	*w, ev_tstamp now)>, e.g.:	2161	*w, ev_tstamp now)>, e.g.:
1499		2162
		2163	static ev_tstamp
1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2164	my_rescheduler (ev_periodic *w, ev_tstamp now)
1501	{	2165	{
1502	return now + 60.;	2166	return now + 60.;
1503	}	2167	}
1504		2168
1505	It must return the next time to trigger, based on the passed time value	2169	It must return the next time to trigger, based on the passed time value
…		…
1525	a different time than the last time it was called (e.g. in a crond like	2189	a different time than the last time it was called (e.g. in a crond like
1526	program when the crontabs have changed).	2190	program when the crontabs have changed).
1527		2191
1528	=item ev_tstamp ev_periodic_at (ev_periodic *)	2192	=item ev_tstamp ev_periodic_at (ev_periodic *)
1529		2193
1530	When active, returns the absolute time that the watcher is supposed to	2194	When active, returns the absolute time that the watcher is supposed
1531	trigger next.	2195	to trigger next. This is not the same as the C<offset> argument to
		2196	C<ev_periodic_set>, but indeed works even in interval and manual
		2197	rescheduling modes.
1532		2198
1533	=item ev_tstamp offset [read-write]	2199	=item ev_tstamp offset [read-write]
1534		2200
1535	When repeating, this contains the offset value, otherwise this is the	2201	When repeating, this contains the offset value, otherwise this is the
1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2202	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2203	although libev might modify this value for better numerical stability).
1537		2204
1538	Can be modified any time, but changes only take effect when the periodic	2205	Can be modified any time, but changes only take effect when the periodic
1539	timer fires or C<ev_periodic_again> is being called.	2206	timer fires or C<ev_periodic_again> is being called.
1540		2207
1541	=item ev_tstamp interval [read-write]	2208	=item ev_tstamp interval [read-write]
1542		2209
1543	The current interval value. Can be modified any time, but changes only	2210	The current interval value. Can be modified any time, but changes only
1544	take effect when the periodic timer fires or C<ev_periodic_again> is being	2211	take effect when the periodic timer fires or C<ev_periodic_again> is being
1545	called.	2212	called.
1546		2213
1547	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2214	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1548		2215
1549	The current reschedule callback, or C<0>, if this functionality is	2216	The current reschedule callback, or C<0>, if this functionality is
1550	switched off. Can be changed any time, but changes only take effect when	2217	switched off. Can be changed any time, but changes only take effect when
1551	the periodic timer fires or C<ev_periodic_again> is being called.	2218	the periodic timer fires or C<ev_periodic_again> is being called.
1552		2219
…		…
1557	Example: Call a callback every hour, or, more precisely, whenever the	2224	Example: Call a callback every hour, or, more precisely, whenever the
1558	system time is divisible by 3600. The callback invocation times have	2225	system time is divisible by 3600. The callback invocation times have
1559	potentially a lot of jitter, but good long-term stability.	2226	potentially a lot of jitter, but good long-term stability.
1560		2227
1561	static void	2228	static void
1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2229	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1563	{	2230	{
1564	... its now a full hour (UTC, or TAI or whatever your clock follows)	2231	... its now a full hour (UTC, or TAI or whatever your clock follows)
1565	}	2232	}
1566		2233
1567	struct ev_periodic hourly_tick;	2234	ev_periodic hourly_tick;
1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2235	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1569	ev_periodic_start (loop, &hourly_tick);	2236	ev_periodic_start (loop, &hourly_tick);
1570		2237
1571	Example: The same as above, but use a reschedule callback to do it:	2238	Example: The same as above, but use a reschedule callback to do it:
1572		2239
1573	#include <math.h>	2240	#include <math.h>
1574		2241
1575	static ev_tstamp	2242	static ev_tstamp
1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2243	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1577	{	2244	{
1578	return now + (3600. - fmod (now, 3600.));	2245	return now + (3600. - fmod (now, 3600.));
1579	}	2246	}
1580		2247
1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2248	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1582		2249
1583	Example: Call a callback every hour, starting now:	2250	Example: Call a callback every hour, starting now:
1584		2251
1585	struct ev_periodic hourly_tick;	2252	ev_periodic hourly_tick;
1586	ev_periodic_init (&hourly_tick, clock_cb,	2253	ev_periodic_init (&hourly_tick, clock_cb,
1587	fmod (ev_now (loop), 3600.), 3600., 0);	2254	fmod (ev_now (loop), 3600.), 3600., 0);
1588	ev_periodic_start (loop, &hourly_tick);	2255	ev_periodic_start (loop, &hourly_tick);
1589		2256
1590		2257
…		…
1593	Signal watchers will trigger an event when the process receives a specific	2260	Signal watchers will trigger an event when the process receives a specific
1594	signal one or more times. Even though signals are very asynchronous, libev	2261	signal one or more times. Even though signals are very asynchronous, libev
1595	will try it's best to deliver signals synchronously, i.e. as part of the	2262	will try it's best to deliver signals synchronously, i.e. as part of the
1596	normal event processing, like any other event.	2263	normal event processing, like any other event.
1597		2264
1598	If you want signals asynchronously, just use C<sigaction> as you would	2265	If you want signals to be delivered truly asynchronously, just use
1599	do without libev and forget about sharing the signal. You can even use	2266	C<sigaction> as you would do without libev and forget about sharing
1600	C<ev_async> from a signal handler to synchronously wake up an event loop.	2267	the signal. You can even use C<ev_async> from a signal handler to
		2268	synchronously wake up an event loop.
1601		2269
1602	You can configure as many watchers as you like per signal. Only when the	2270	You can configure as many watchers as you like for the same signal, but
		2271	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2272	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2273	C<SIGINT> in both the default loop and another loop at the same time. At
		2274	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2275
1603	first watcher gets started will libev actually register a signal handler	2276	When the first watcher gets started will libev actually register something
1604	with the kernel (thus it coexists with your own signal handlers as long as	2277	with the kernel (thus it coexists with your own signal handlers as long as
1605	you don't register any with libev for the same signal). Similarly, when	2278	you don't register any with libev for the same signal).
1606	the last signal watcher for a signal is stopped, libev will reset the
1607	signal handler to SIG_DFL (regardless of what it was set to before).
1608		2279
1609	If possible and supported, libev will install its handlers with	2280	If possible and supported, libev will install its handlers with
1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1611	interrupted. If you have a problem with system calls getting interrupted by	2282	not be unduly interrupted. If you have a problem with system calls getting
1612	signals you can block all signals in an C<ev_check> watcher and unblock	2283	interrupted by signals you can block all signals in an C<ev_check> watcher
1613	them in an C<ev_prepare> watcher.	2284	and unblock them in an C<ev_prepare> watcher.
		2285
		2286	=head3 The special problem of inheritance over fork/execve/pthread_create
		2287
		2288	Both the signal mask (C<sigprocmask>) and the signal disposition
		2289	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2290	stopping it again), that is, libev might or might not block the signal,
		2291	and might or might not set or restore the installed signal handler.
		2292
		2293	While this does not matter for the signal disposition (libev never
		2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2295	C<execve>), this matters for the signal mask: many programs do not expect
		2296	certain signals to be blocked.
		2297
		2298	This means that before calling C<exec> (from the child) you should reset
		2299	the signal mask to whatever "default" you expect (all clear is a good
		2300	choice usually).
		2301
		2302	The simplest way to ensure that the signal mask is reset in the child is
		2303	to install a fork handler with C<pthread_atfork> that resets it. That will
		2304	catch fork calls done by libraries (such as the libc) as well.
		2305
		2306	In current versions of libev, the signal will not be blocked indefinitely
		2307	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2308	the window of opportunity for problems, it will not go away, as libev
		2309	I<has> to modify the signal mask, at least temporarily.
		2310
		2311	So I can't stress this enough: I<If you do not reset your signal mask when
		2312	you expect it to be empty, you have a race condition in your code>. This
		2313	is not a libev-specific thing, this is true for most event libraries.
1614		2314
1615	=head3 Watcher-Specific Functions and Data Members	2315	=head3 Watcher-Specific Functions and Data Members
1616		2316
1617	=over 4	2317	=over 4
1618		2318
…		…
1632	=head3 Examples	2332	=head3 Examples
1633		2333
1634	Example: Try to exit cleanly on SIGINT.	2334	Example: Try to exit cleanly on SIGINT.
1635		2335
1636	static void	2336	static void
1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2337	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1638	{	2338	{
1639	ev_unloop (loop, EVUNLOOP_ALL);	2339	ev_break (loop, EVBREAK_ALL);
1640	}	2340	}
1641		2341
1642	struct ev_signal signal_watcher;	2342	ev_signal signal_watcher;
1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2343	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1644	ev_signal_start (loop, &signal_watcher);	2344	ev_signal_start (loop, &signal_watcher);
1645		2345
1646		2346
1647	=head2 C<ev_child> - watch out for process status changes	2347	=head2 C<ev_child> - watch out for process status changes
…		…
1650	some child status changes (most typically when a child of yours dies or	2350	some child status changes (most typically when a child of yours dies or
1651	exits). It is permissible to install a child watcher I<after> the child	2351	exits). It is permissible to install a child watcher I<after> the child
1652	has been forked (which implies it might have already exited), as long	2352	has been forked (which implies it might have already exited), as long
1653	as the event loop isn't entered (or is continued from a watcher), i.e.,	2353	as the event loop isn't entered (or is continued from a watcher), i.e.,
1654	forking and then immediately registering a watcher for the child is fine,	2354	forking and then immediately registering a watcher for the child is fine,
1655	but forking and registering a watcher a few event loop iterations later is	2355	but forking and registering a watcher a few event loop iterations later or
1656	not.	2356	in the next callback invocation is not.
1657		2357
1658	Only the default event loop is capable of handling signals, and therefore	2358	Only the default event loop is capable of handling signals, and therefore
1659	you can only register child watchers in the default event loop.	2359	you can only register child watchers in the default event loop.
1660		2360
		2361	Due to some design glitches inside libev, child watchers will always be
		2362	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2363	libev)
		2364
1661	=head3 Process Interaction	2365	=head3 Process Interaction
1662		2366
1663	Libev grabs C<SIGCHLD> as soon as the default event loop is	2367	Libev grabs C<SIGCHLD> as soon as the default event loop is
1664	initialised. This is necessary to guarantee proper behaviour even if	2368	initialised. This is necessary to guarantee proper behaviour even if the
1665	the first child watcher is started after the child exits. The occurrence	2369	first child watcher is started after the child exits. The occurrence
1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2370	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1667	synchronously as part of the event loop processing. Libev always reaps all	2371	synchronously as part of the event loop processing. Libev always reaps all
1668	children, even ones not watched.	2372	children, even ones not watched.
1669		2373
1670	=head3 Overriding the Built-In Processing	2374	=head3 Overriding the Built-In Processing
…		…
1680	=head3 Stopping the Child Watcher	2384	=head3 Stopping the Child Watcher
1681		2385
1682	Currently, the child watcher never gets stopped, even when the	2386	Currently, the child watcher never gets stopped, even when the
1683	child terminates, so normally one needs to stop the watcher in the	2387	child terminates, so normally one needs to stop the watcher in the
1684	callback. Future versions of libev might stop the watcher automatically	2388	callback. Future versions of libev might stop the watcher automatically
1685	when a child exit is detected.	2389	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2390	problem).
1686		2391
1687	=head3 Watcher-Specific Functions and Data Members	2392	=head3 Watcher-Specific Functions and Data Members
1688		2393
1689	=over 4	2394	=over 4
1690		2395
…		…
1722	its completion.	2427	its completion.
1723		2428
1724	ev_child cw;	2429	ev_child cw;
1725		2430
1726	static void	2431	static void
1727	child_cb (EV_P_ struct ev_child *w, int revents)	2432	child_cb (EV_P_ ev_child *w, int revents)
1728	{	2433	{
1729	ev_child_stop (EV_A_ w);	2434	ev_child_stop (EV_A_ w);
1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2435	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1731	}	2436	}
1732		2437
…		…
1747		2452
1748		2453
1749	=head2 C<ev_stat> - did the file attributes just change?	2454	=head2 C<ev_stat> - did the file attributes just change?
1750		2455
1751	This watches a file system path for attribute changes. That is, it calls	2456	This watches a file system path for attribute changes. That is, it calls
1752	C<stat> regularly (or when the OS says it changed) and sees if it changed	2457	C<stat> on that path in regular intervals (or when the OS says it changed)
1753	compared to the last time, invoking the callback if it did.	2458	and sees if it changed compared to the last time, invoking the callback if
		2459	it did.
1754		2460
1755	The path does not need to exist: changing from "path exists" to "path does	2461	The path does not need to exist: changing from "path exists" to "path does
1756	not exist" is a status change like any other. The condition "path does	2462	not exist" is a status change like any other. The condition "path does not
1757	not exist" is signified by the C<st_nlink> field being zero (which is	2463	exist" (or more correctly "path cannot be stat'ed") is signified by the
1758	otherwise always forced to be at least one) and all the other fields of	2464	C<st_nlink> field being zero (which is otherwise always forced to be at
1759	the stat buffer having unspecified contents.	2465	least one) and all the other fields of the stat buffer having unspecified
		2466	contents.
1760		2467
1761	The path I<should> be absolute and I<must not> end in a slash. If it is	2468	The path I<must not> end in a slash or contain special components such as
		2469	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1762	relative and your working directory changes, the behaviour is undefined.	2470	your working directory changes, then the behaviour is undefined.
1763		2471
1764	Since there is no standard kernel interface to do this, the portable	2472	Since there is no portable change notification interface available, the
1765	implementation simply calls C<stat (2)> regularly on the path to see if	2473	portable implementation simply calls C<stat(2)> regularly on the path
1766	it changed somehow. You can specify a recommended polling interval for	2474	to see if it changed somehow. You can specify a recommended polling
1767	this case. If you specify a polling interval of C<0> (highly recommended!)	2475	interval for this case. If you specify a polling interval of C<0> (highly
1768	then a I<suitable, unspecified default> value will be used (which	2476	recommended!) then a I<suitable, unspecified default> value will be used
1769	you can expect to be around five seconds, although this might change	2477	(which you can expect to be around five seconds, although this might
1770	dynamically). Libev will also impose a minimum interval which is currently	2478	change dynamically). Libev will also impose a minimum interval which is
1771	around C<0.1>, but thats usually overkill.	2479	currently around C<0.1>, but that's usually overkill.
1772		2480
1773	This watcher type is not meant for massive numbers of stat watchers,	2481	This watcher type is not meant for massive numbers of stat watchers,
1774	as even with OS-supported change notifications, this can be	2482	as even with OS-supported change notifications, this can be
1775	resource-intensive.	2483	resource-intensive.
1776		2484
1777	At the time of this writing, the only OS-specific interface implemented	2485	At the time of this writing, the only OS-specific interface implemented
1778	is the Linux inotify interface (implementing kqueue support is left as	2486	is the Linux inotify interface (implementing kqueue support is left as an
1779	an exercise for the reader. Note, however, that the author sees no way	2487	exercise for the reader. Note, however, that the author sees no way of
1780	of implementing C<ev_stat> semantics with kqueue).	2488	implementing C<ev_stat> semantics with kqueue, except as a hint).
1781		2489
1782	=head3 ABI Issues (Largefile Support)	2490	=head3 ABI Issues (Largefile Support)
1783		2491
1784	Libev by default (unless the user overrides this) uses the default	2492	Libev by default (unless the user overrides this) uses the default
1785	compilation environment, which means that on systems with large file	2493	compilation environment, which means that on systems with large file
1786	support disabled by default, you get the 32 bit version of the stat	2494	support disabled by default, you get the 32 bit version of the stat
1787	structure. When using the library from programs that change the ABI to	2495	structure. When using the library from programs that change the ABI to
1788	use 64 bit file offsets the programs will fail. In that case you have to	2496	use 64 bit file offsets the programs will fail. In that case you have to
1789	compile libev with the same flags to get binary compatibility. This is	2497	compile libev with the same flags to get binary compatibility. This is
1790	obviously the case with any flags that change the ABI, but the problem is	2498	obviously the case with any flags that change the ABI, but the problem is
1791	most noticeably disabled with ev_stat and large file support.	2499	most noticeably displayed with ev_stat and large file support.
1792		2500
1793	The solution for this is to lobby your distribution maker to make large	2501	The solution for this is to lobby your distribution maker to make large
1794	file interfaces available by default (as e.g. FreeBSD does) and not	2502	file interfaces available by default (as e.g. FreeBSD does) and not
1795	optional. Libev cannot simply switch on large file support because it has	2503	optional. Libev cannot simply switch on large file support because it has
1796	to exchange stat structures with application programs compiled using the	2504	to exchange stat structures with application programs compiled using the
1797	default compilation environment.	2505	default compilation environment.
1798		2506
1799	=head3 Inotify and Kqueue	2507	=head3 Inotify and Kqueue
1800		2508
1801	When C<inotify (7)> support has been compiled into libev (generally only	2509	When C<inotify (7)> support has been compiled into libev and present at
1802	available with Linux) and present at runtime, it will be used to speed up	2510	runtime, it will be used to speed up change detection where possible. The
1803	change detection where possible. The inotify descriptor will be created lazily	2511	inotify descriptor will be created lazily when the first C<ev_stat>
1804	when the first C<ev_stat> watcher is being started.	2512	watcher is being started.
1805		2513
1806	Inotify presence does not change the semantics of C<ev_stat> watchers	2514	Inotify presence does not change the semantics of C<ev_stat> watchers
1807	except that changes might be detected earlier, and in some cases, to avoid	2515	except that changes might be detected earlier, and in some cases, to avoid
1808	making regular C<stat> calls. Even in the presence of inotify support	2516	making regular C<stat> calls. Even in the presence of inotify support
1809	there are many cases where libev has to resort to regular C<stat> polling,	2517	there are many cases where libev has to resort to regular C<stat> polling,
1810	but as long as the path exists, libev usually gets away without polling.	2518	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2519	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2520	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2521	xfs are fully working) libev usually gets away without polling.
1811		2522
1812	There is no support for kqueue, as apparently it cannot be used to	2523	There is no support for kqueue, as apparently it cannot be used to
1813	implement this functionality, due to the requirement of having a file	2524	implement this functionality, due to the requirement of having a file
1814	descriptor open on the object at all times, and detecting renames, unlinks	2525	descriptor open on the object at all times, and detecting renames, unlinks
1815	etc. is difficult.	2526	etc. is difficult.
1816		2527
		2528	=head3 C<stat ()> is a synchronous operation
		2529
		2530	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2531	the process. The exception are C<ev_stat> watchers - those call C<stat
		2532	()>, which is a synchronous operation.
		2533
		2534	For local paths, this usually doesn't matter: unless the system is very
		2535	busy or the intervals between stat's are large, a stat call will be fast,
		2536	as the path data is usually in memory already (except when starting the
		2537	watcher).
		2538
		2539	For networked file systems, calling C<stat ()> can block an indefinite
		2540	time due to network issues, and even under good conditions, a stat call
		2541	often takes multiple milliseconds.
		2542
		2543	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2544	paths, although this is fully supported by libev.
		2545
1817	=head3 The special problem of stat time resolution	2546	=head3 The special problem of stat time resolution
1818		2547
1819	The C<stat ()> system call only supports full-second resolution portably, and	2548	The C<stat ()> system call only supports full-second resolution portably,
1820	even on systems where the resolution is higher, most file systems still	2549	and even on systems where the resolution is higher, most file systems
1821	only support whole seconds.	2550	still only support whole seconds.
1822		2551
1823	That means that, if the time is the only thing that changes, you can	2552	That means that, if the time is the only thing that changes, you can
1824	easily miss updates: on the first update, C<ev_stat> detects a change and	2553	easily miss updates: on the first update, C<ev_stat> detects a change and
1825	calls your callback, which does something. When there is another update	2554	calls your callback, which does something. When there is another update
1826	within the same second, C<ev_stat> will be unable to detect unless the	2555	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1969		2698
1970	=head3 Watcher-Specific Functions and Data Members	2699	=head3 Watcher-Specific Functions and Data Members
1971		2700
1972	=over 4	2701	=over 4
1973		2702
1974	=item ev_idle_init (ev_signal *, callback)	2703	=item ev_idle_init (ev_idle *, callback)
1975		2704
1976	Initialises and configures the idle watcher - it has no parameters of any	2705	Initialises and configures the idle watcher - it has no parameters of any
1977	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2706	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1978	believe me.	2707	believe me.
1979		2708
…		…
1983		2712
1984	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2713	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1985	callback, free it. Also, use no error checking, as usual.	2714	callback, free it. Also, use no error checking, as usual.
1986		2715
1987	static void	2716	static void
1988	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1989	{	2718	{
1990	free (w);	2719	free (w);
1991	// now do something you wanted to do when the program has	2720	// now do something you wanted to do when the program has
1992	// no longer anything immediate to do.	2721	// no longer anything immediate to do.
1993	}	2722	}
1994		2723
1995	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1996	ev_idle_init (idle_watcher, idle_cb);	2725	ev_idle_init (idle_watcher, idle_cb);
1997	ev_idle_start (loop, idle_cb);	2726	ev_idle_start (loop, idle_watcher);
1998		2727
1999		2728
2000	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2001		2730
2002	Prepare and check watchers are usually (but not always) used in pairs:	2731	Prepare and check watchers are usually (but not always) used in pairs:
2003	prepare watchers get invoked before the process blocks and check watchers	2732	prepare watchers get invoked before the process blocks and check watchers
2004	afterwards.	2733	afterwards.
2005		2734
2006	You I<must not> call C<ev_loop> or similar functions that enter	2735	You I<must not> call C<ev_run> or similar functions that enter
2007	the current event loop from either C<ev_prepare> or C<ev_check>	2736	the current event loop from either C<ev_prepare> or C<ev_check>
2008	watchers. Other loops than the current one are fine, however. The	2737	watchers. Other loops than the current one are fine, however. The
2009	rationale behind this is that you do not need to check for recursion in	2738	rationale behind this is that you do not need to check for recursion in
2010	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2739	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2011	C<ev_check> so if you have one watcher of each kind they will always be	2740	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2081		2810
2082	static ev_io iow [nfd];	2811	static ev_io iow [nfd];
2083	static ev_timer tw;	2812	static ev_timer tw;
2084		2813
2085	static void	2814	static void
2086	io_cb (ev_loop *loop, ev_io *w, int revents)	2815	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2087	{	2816	{
2088	}	2817	}
2089		2818
2090	// create io watchers for each fd and a timer before blocking	2819	// create io watchers for each fd and a timer before blocking
2091	static void	2820	static void
2092	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2821	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2093	{	2822	{
2094	int timeout = 3600000;	2823	int timeout = 3600000;
2095	struct pollfd fds [nfd];	2824	struct pollfd fds [nfd];
2096	// actual code will need to loop here and realloc etc.	2825	// actual code will need to loop here and realloc etc.
2097	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2826	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2098		2827
2099	/* the callback is illegal, but won't be called as we stop during check */	2828	/* the callback is illegal, but won't be called as we stop during check */
2100	ev_timer_init (&tw, 0, timeout * 1e-3);	2829	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2101	ev_timer_start (loop, &tw);	2830	ev_timer_start (loop, &tw);
2102		2831
2103	// create one ev_io per pollfd	2832	// create one ev_io per pollfd
2104	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
2105	{	2834	{
…		…
2112	}	2841	}
2113	}	2842	}
2114		2843
2115	// stop all watchers after blocking	2844	// stop all watchers after blocking
2116	static void	2845	static void
2117	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2846	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2118	{	2847	{
2119	ev_timer_stop (loop, &tw);	2848	ev_timer_stop (loop, &tw);
2120		2849
2121	for (int i = 0; i < nfd; ++i)	2850	for (int i = 0; i < nfd; ++i)
2122	{	2851	{
…		…
2179		2908
2180	if (timeout >= 0)	2909	if (timeout >= 0)
2181	// create/start timer	2910	// create/start timer
2182		2911
2183	// poll	2912	// poll
2184	ev_loop (EV_A_ 0);	2913	ev_run (EV_A_ 0);
2185		2914
2186	// stop timer again	2915	// stop timer again
2187	if (timeout >= 0)	2916	if (timeout >= 0)
2188	ev_timer_stop (EV_A_ &to);	2917	ev_timer_stop (EV_A_ &to);
2189		2918
…		…
2218	some fds have to be watched and handled very quickly (with low latency),	2947	some fds have to be watched and handled very quickly (with low latency),
2219	and even priorities and idle watchers might have too much overhead. In	2948	and even priorities and idle watchers might have too much overhead. In
2220	this case you would put all the high priority stuff in one loop and all	2949	this case you would put all the high priority stuff in one loop and all
2221	the rest in a second one, and embed the second one in the first.	2950	the rest in a second one, and embed the second one in the first.
2222		2951
2223	As long as the watcher is active, the callback will be invoked every time	2952	As long as the watcher is active, the callback will be invoked every
2224	there might be events pending in the embedded loop. The callback must then	2953	time there might be events pending in the embedded loop. The callback
2225	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2954	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2226	their callbacks (you could also start an idle watcher to give the embedded	2955	sweep and invoke their callbacks (the callback doesn't need to invoke the
2227	loop strictly lower priority for example). You can also set the callback	2956	C<ev_embed_sweep> function directly, it could also start an idle watcher
2228	to C<0>, in which case the embed watcher will automatically execute the	2957	to give the embedded loop strictly lower priority for example).
2229	embedded loop sweep.
2230		2958
2231	As long as the watcher is started it will automatically handle events. The	2959	You can also set the callback to C<0>, in which case the embed watcher
2232	callback will be invoked whenever some events have been handled. You can	2960	will automatically execute the embedded loop sweep whenever necessary.
2233	set the callback to C<0> to avoid having to specify one if you are not
2234	interested in that.
2235		2961
2236	Also, there have not currently been made special provisions for forking:	2962	Fork detection will be handled transparently while the C<ev_embed> watcher
2237	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2963	is active, i.e., the embedded loop will automatically be forked when the
2238	but you will also have to stop and restart any C<ev_embed> watchers	2964	embedding loop forks. In other cases, the user is responsible for calling
2239	yourself - but you can use a fork watcher to handle this automatically,	2965	C<ev_loop_fork> on the embedded loop.
2240	and future versions of libev might do just that.
2241		2966
2242	Unfortunately, not all backends are embeddable: only the ones returned by	2967	Unfortunately, not all backends are embeddable: only the ones returned by
2243	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2968	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2244	portable one.	2969	portable one.
2245		2970
…		…
2271	if you do not want that, you need to temporarily stop the embed watcher).	2996	if you do not want that, you need to temporarily stop the embed watcher).
2272		2997
2273	=item ev_embed_sweep (loop, ev_embed *)	2998	=item ev_embed_sweep (loop, ev_embed *)
2274		2999
2275	Make a single, non-blocking sweep over the embedded loop. This works	3000	Make a single, non-blocking sweep over the embedded loop. This works
2276	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3001	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2277	appropriate way for embedded loops.	3002	appropriate way for embedded loops.
2278		3003
2279	=item struct ev_loop *other [read-only]	3004	=item struct ev_loop *other [read-only]
2280		3005
2281	The embedded event loop.	3006	The embedded event loop.
…		…
2290	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3015	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2291	used).	3016	used).
2292		3017
2293	struct ev_loop *loop_hi = ev_default_init (0);	3018	struct ev_loop *loop_hi = ev_default_init (0);
2294	struct ev_loop *loop_lo = 0;	3019	struct ev_loop *loop_lo = 0;
2295	struct ev_embed embed;	3020	ev_embed embed;
2296		3021
2297	// see if there is a chance of getting one that works	3022	// see if there is a chance of getting one that works
2298	// (remember that a flags value of 0 means autodetection)	3023	// (remember that a flags value of 0 means autodetection)
2299	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3024	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2300	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3025	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2314	kqueue implementation). Store the kqueue/socket-only event loop in	3039	kqueue implementation). Store the kqueue/socket-only event loop in
2315	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3040	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2316		3041
2317	struct ev_loop *loop = ev_default_init (0);	3042	struct ev_loop *loop = ev_default_init (0);
2318	struct ev_loop *loop_socket = 0;	3043	struct ev_loop *loop_socket = 0;
2319	struct ev_embed embed;	3044	ev_embed embed;
2320		3045
2321	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3046	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2322	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3047	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2323	{	3048	{
2324	ev_embed_init (&embed, 0, loop_socket);	3049	ev_embed_init (&embed, 0, loop_socket);
…		…
2339	event loop blocks next and before C<ev_check> watchers are being called,	3064	event loop blocks next and before C<ev_check> watchers are being called,
2340	and only in the child after the fork. If whoever good citizen calling	3065	and only in the child after the fork. If whoever good citizen calling
2341	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2342	handlers will be invoked, too, of course.	3067	handlers will be invoked, too, of course.
2343		3068
		3069	=head3 The special problem of life after fork - how is it possible?
		3070
		3071	Most uses of C<fork()> consist of forking, then some simple calls to set
		3072	up/change the process environment, followed by a call to C<exec()>. This
		3073	sequence should be handled by libev without any problems.
		3074
		3075	This changes when the application actually wants to do event handling
		3076	in the child, or both parent in child, in effect "continuing" after the
		3077	fork.
		3078
		3079	The default mode of operation (for libev, with application help to detect
		3080	forks) is to duplicate all the state in the child, as would be expected
		3081	when I<either> the parent I<or> the child process continues.
		3082
		3083	When both processes want to continue using libev, then this is usually the
		3084	wrong result. In that case, usually one process (typically the parent) is
		3085	supposed to continue with all watchers in place as before, while the other
		3086	process typically wants to start fresh, i.e. without any active watchers.
		3087
		3088	The cleanest and most efficient way to achieve that with libev is to
		3089	simply create a new event loop, which of course will be "empty", and
		3090	use that for new watchers. This has the advantage of not touching more
		3091	memory than necessary, and thus avoiding the copy-on-write, and the
		3092	disadvantage of having to use multiple event loops (which do not support
		3093	signal watchers).
		3094
		3095	When this is not possible, or you want to use the default loop for
		3096	other reasons, then in the process that wants to start "fresh", call
		3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3098	Destroying the default loop will "orphan" (not stop) all registered
		3099	watchers, so you have to be careful not to execute code that modifies
		3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
		3102
2344	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
2345		3104
2346	=over 4	3105	=over 4
2347		3106
2348	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
2349		3108
2350	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
2351	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2352	believe me.	3111	really.
2353		3112
2354	=back	3113	=back
2355		3114
2356		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
		3154
		3155
2357	=head2 C<ev_async> - how to wake up another event loop	3156	=head2 C<ev_async> - how to wake up an event loop
2358		3157
2359	In general, you cannot use an C<ev_loop> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
2360	asynchronous sources such as signal handlers (as opposed to multiple event	3159	asynchronous sources such as signal handlers (as opposed to multiple event
2361	loops - those are of course safe to use in different threads).	3160	loops - those are of course safe to use in different threads).
2362		3161
2363	Sometimes, however, you need to wake up another event loop you do not	3162	Sometimes, however, you need to wake up an event loop you do not control,
2364	control, for example because it belongs to another thread. This is what	3163	for example because it belongs to another thread. This is what C<ev_async>
2365	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3164	watchers do: as long as the C<ev_async> watcher is active, you can signal
2366	can signal it by calling C<ev_async_send>, which is thread- and signal	3165	it by calling C<ev_async_send>, which is thread- and signal safe.
2367	safe.
2368		3166
2369	This functionality is very similar to C<ev_signal> watchers, as signals,	3167	This functionality is very similar to C<ev_signal> watchers, as signals,
2370	too, are asynchronous in nature, and signals, too, will be compressed	3168	too, are asynchronous in nature, and signals, too, will be compressed
2371	(i.e. the number of callback invocations may be less than the number of	3169	(i.e. the number of callback invocations may be less than the number of
2372	C<ev_async_sent> calls).	3170	C<ev_async_sent> calls).
…		…
2377	=head3 Queueing	3175	=head3 Queueing
2378		3176
2379	C<ev_async> does not support queueing of data in any way. The reason	3177	C<ev_async> does not support queueing of data in any way. The reason
2380	is that the author does not know of a simple (or any) algorithm for a	3178	is that the author does not know of a simple (or any) algorithm for a
2381	multiple-writer-single-reader queue that works in all cases and doesn't	3179	multiple-writer-single-reader queue that works in all cases and doesn't
2382	need elaborate support such as pthreads.	3180	need elaborate support such as pthreads or unportable memory access
		3181	semantics.
2383		3182
2384	That means that if you want to queue data, you have to provide your own	3183	That means that if you want to queue data, you have to provide your own
2385	queue. But at least I can tell you how to implement locking around your	3184	queue. But at least I can tell you how to implement locking around your
2386	queue:	3185	queue:
2387		3186
…		…
2465	=over 4	3264	=over 4
2466		3265
2467	=item ev_async_init (ev_async *, callback)	3266	=item ev_async_init (ev_async *, callback)
2468		3267
2469	Initialises and configures the async watcher - it has no parameters of any	3268	Initialises and configures the async watcher - it has no parameters of any
2470	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3269	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2471	trust me.	3270	trust me.
2472		3271
2473	=item ev_async_send (loop, ev_async *)	3272	=item ev_async_send (loop, ev_async *)
2474		3273
2475	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2476	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2477	C<ev_feed_event>, this call is safe to do from other threads, signal or	3276	C<ev_feed_event>, this call is safe to do from other threads, signal or
2478	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2479	section below on what exactly this means).	3278	section below on what exactly this means).
2480		3279
		3280	Note that, as with other watchers in libev, multiple events might get
		3281	compressed into a single callback invocation (another way to look at this
		3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3283	reset when the event loop detects that).
		3284
2481	This call incurs the overhead of a system call only once per loop iteration,	3285	This call incurs the overhead of a system call only once per event loop
2482	so while the overhead might be noticeable, it doesn't apply to repeated	3286	iteration, so while the overhead might be noticeable, it doesn't apply to
2483	calls to C<ev_async_send>.	3287	repeated calls to C<ev_async_send> for the same event loop.
2484		3288
2485	=item bool = ev_async_pending (ev_async *)	3289	=item bool = ev_async_pending (ev_async *)
2486		3290
2487	Returns a non-zero value when C<ev_async_send> has been called on the	3291	Returns a non-zero value when C<ev_async_send> has been called on the
2488	watcher but the event has not yet been processed (or even noted) by the	3292	watcher but the event has not yet been processed (or even noted) by the
…		…
2491	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2492	the loop iterates next and checks for the watcher to have become active,	3296	the loop iterates next and checks for the watcher to have become active,
2493	it will reset the flag again. C<ev_async_pending> can be used to very	3297	it will reset the flag again. C<ev_async_pending> can be used to very
2494	quickly check whether invoking the loop might be a good idea.	3298	quickly check whether invoking the loop might be a good idea.
2495		3299
2496	Not that this does I<not> check whether the watcher itself is pending, only	3300	Not that this does I<not> check whether the watcher itself is pending,
2497	whether it has been requested to make this watcher pending.	3301	only whether it has been requested to make this watcher pending: there
		3302	is a time window between the event loop checking and resetting the async
		3303	notification, and the callback being invoked.
2498		3304
2499	=back	3305	=back
2500		3306
2501		3307
2502	=head1 OTHER FUNCTIONS	3308	=head1 OTHER FUNCTIONS
…		…
2519		3325
2520	If C<timeout> is less than 0, then no timeout watcher will be	3326	If C<timeout> is less than 0, then no timeout watcher will be
2521	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3327	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2522	repeat = 0) will be started. C<0> is a valid timeout.	3328	repeat = 0) will be started. C<0> is a valid timeout.
2523		3329
2524	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3330	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2525	passed an C<revents> set like normal event callbacks (a combination of	3331	passed an C<revents> set like normal event callbacks (a combination of
2526	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3332	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2527	value passed to C<ev_once>. Note that it is possible to receive I<both>	3333	value passed to C<ev_once>. Note that it is possible to receive I<both>
2528	a timeout and an io event at the same time - you probably should give io	3334	a timeout and an io event at the same time - you probably should give io
2529	events precedence.	3335	events precedence.
2530		3336
2531	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3337	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2532		3338
2533	static void stdin_ready (int revents, void *arg)	3339	static void stdin_ready (int revents, void *arg)
2534	{	3340	{
2535	if (revents & EV_READ)	3341	if (revents & EV_READ)
2536	/* stdin might have data for us, joy! */;	3342	/* stdin might have data for us, joy! */;
2537	else if (revents & EV_TIMEOUT)	3343	else if (revents & EV_TIMER)
2538	/* doh, nothing entered */;	3344	/* doh, nothing entered */;
2539	}	3345	}
2540		3346
2541	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2542		3348
2543	=item ev_feed_event (ev_loop *, watcher *, int revents)
2544
2545	Feeds the given event set into the event loop, as if the specified event
2546	had happened for the specified watcher (which must be a pointer to an
2547	initialised but not necessarily started event watcher).
2548
2549	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3349	=item ev_feed_fd_event (loop, int fd, int revents)
2550		3350
2551	Feed an event on the given fd, as if a file descriptor backend detected	3351	Feed an event on the given fd, as if a file descriptor backend detected
2552	the given events it.	3352	the given events it.
2553		3353
2554	=item ev_feed_signal_event (ev_loop *loop, int signum)	3354	=item ev_feed_signal_event (loop, int signum)
2555		3355
2556	Feed an event as if the given signal occurred (C<loop> must be the default	3356	Feed an event as if the given signal occurred (C<loop> must be the default
2557	loop!).	3357	loop!).
2558		3358
2559	=back	3359	=back
…		…
2639		3439
2640	=over 4	3440	=over 4
2641		3441
2642	=item ev::TYPE::TYPE ()	3442	=item ev::TYPE::TYPE ()
2643		3443
2644	=item ev::TYPE::TYPE (struct ev_loop *)	3444	=item ev::TYPE::TYPE (loop)
2645		3445
2646	=item ev::TYPE::~TYPE	3446	=item ev::TYPE::~TYPE
2647		3447
2648	The constructor (optionally) takes an event loop to associate the watcher	3448	The constructor (optionally) takes an event loop to associate the watcher
2649	with. If it is omitted, it will use C<EV_DEFAULT>.	3449	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2681		3481
2682	myclass obj;	3482	myclass obj;
2683	ev::io iow;	3483	ev::io iow;
2684	iow.set <myclass, &myclass::io_cb> (&obj);	3484	iow.set <myclass, &myclass::io_cb> (&obj);
2685		3485
		3486	=item w->set (object *)
		3487
		3488	This is a variation of a method callback - leaving out the method to call
		3489	will default the method to C<operator ()>, which makes it possible to use
		3490	functor objects without having to manually specify the C<operator ()> all
		3491	the time. Incidentally, you can then also leave out the template argument
		3492	list.
		3493
		3494	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3495	int revents)>.
		3496
		3497	See the method-C<set> above for more details.
		3498
		3499	Example: use a functor object as callback.
		3500
		3501	struct myfunctor
		3502	{
		3503	void operator() (ev::io &w, int revents)
		3504	{
		3505	...
		3506	}
		3507	}
		3508
		3509	myfunctor f;
		3510
		3511	ev::io w;
		3512	w.set (&f);
		3513
2686	=item w->set<function> (void *data = 0)	3514	=item w->set<function> (void *data = 0)
2687		3515
2688	Also sets a callback, but uses a static method or plain function as	3516	Also sets a callback, but uses a static method or plain function as
2689	callback. The optional C<data> argument will be stored in the watcher's	3517	callback. The optional C<data> argument will be stored in the watcher's
2690	C<data> member and is free for you to use.	3518	C<data> member and is free for you to use.
…		…
2696	Example: Use a plain function as callback.	3524	Example: Use a plain function as callback.
2697		3525
2698	static void io_cb (ev::io &w, int revents) { }	3526	static void io_cb (ev::io &w, int revents) { }
2699	iow.set <io_cb> ();	3527	iow.set <io_cb> ();
2700		3528
2701	=item w->set (struct ev_loop *)	3529	=item w->set (loop)
2702		3530
2703	Associates a different C<struct ev_loop> with this watcher. You can only	3531	Associates a different C<struct ev_loop> with this watcher. You can only
2704	do this when the watcher is inactive (and not pending either).	3532	do this when the watcher is inactive (and not pending either).
2705		3533
2706	=item w->set ([arguments])	3534	=item w->set ([arguments])
2707		3535
2708	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2709	called at least once. Unlike the C counterpart, an active watcher gets	3537	method or a suitable start method must be called at least once. Unlike the
2710	automatically stopped and restarted when reconfiguring it with this	3538	C counterpart, an active watcher gets automatically stopped and restarted
2711	method.	3539	when reconfiguring it with this method.
2712		3540
2713	=item w->start ()	3541	=item w->start ()
2714		3542
2715	Starts the watcher. Note that there is no C<loop> argument, as the	3543	Starts the watcher. Note that there is no C<loop> argument, as the
2716	constructor already stores the event loop.	3544	constructor already stores the event loop.
2717		3545
		3546	=item w->start ([arguments])
		3547
		3548	Instead of calling C<set> and C<start> methods separately, it is often
		3549	convenient to wrap them in one call. Uses the same type of arguments as
		3550	the configure C<set> method of the watcher.
		3551
2718	=item w->stop ()	3552	=item w->stop ()
2719		3553
2720	Stops the watcher if it is active. Again, no C<loop> argument.	3554	Stops the watcher if it is active. Again, no C<loop> argument.
2721		3555
2722	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3556	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2734		3568
2735	=back	3569	=back
2736		3570
2737	=back	3571	=back
2738		3572
2739	Example: Define a class with an IO and idle watcher, start one of them in	3573	Example: Define a class with two I/O and idle watchers, start the I/O
2740	the constructor.	3574	watchers in the constructor.
2741		3575
2742	class myclass	3576	class myclass
2743	{	3577	{
2744	ev::io io ; void io_cb (ev::io &w, int revents);	3578	ev::io io ; void io_cb (ev::io &w, int revents);
		3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2745	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2746		3581
2747	myclass (int fd)	3582	myclass (int fd)
2748	{	3583	{
2749	io .set <myclass, &myclass::io_cb > (this);	3584	io .set <myclass, &myclass::io_cb > (this);
		3585	io2 .set <myclass, &myclass::io2_cb > (this);
2750	idle.set <myclass, &myclass::idle_cb> (this);	3586	idle.set <myclass, &myclass::idle_cb> (this);
2751		3587
2752	io.start (fd, ev::READ);	3588	io.set (fd, ev::WRITE); // configure the watcher
		3589	io.start (); // start it whenever convenient
		3590
		3591	io2.start (fd, ev::READ); // set + start in one call
2753	}	3592	}
2754	};	3593	};
2755		3594
2756		3595
2757	=head1 OTHER LANGUAGE BINDINGS	3596	=head1 OTHER LANGUAGE BINDINGS
…		…
2776	L<http://software.schmorp.de/pkg/EV>.	3615	L<http://software.schmorp.de/pkg/EV>.
2777		3616
2778	=item Python	3617	=item Python
2779		3618
2780	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3619	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2781	seems to be quite complete and well-documented. Note, however, that the	3620	seems to be quite complete and well-documented.
2782	patch they require for libev is outright dangerous as it breaks the ABI
2783	for everybody else, and therefore, should never be applied in an installed
2784	libev (if python requires an incompatible ABI then it needs to embed
2785	libev).
2786		3621
2787	=item Ruby	3622	=item Ruby
2788		3623
2789	Tony Arcieri has written a ruby extension that offers access to a subset	3624	Tony Arcieri has written a ruby extension that offers access to a subset
2790	of the libev API and adds file handle abstractions, asynchronous DNS and	3625	of the libev API and adds file handle abstractions, asynchronous DNS and
2791	more on top of it. It can be found via gem servers. Its homepage is at	3626	more on top of it. It can be found via gem servers. Its homepage is at
2792	L<http://rev.rubyforge.org/>.	3627	L<http://rev.rubyforge.org/>.
2793		3628
		3629	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3630	makes rev work even on mingw.
		3631
		3632	=item Haskell
		3633
		3634	A haskell binding to libev is available at
		3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3636
2794	=item D	3637	=item D
2795		3638
2796	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2797	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3641
		3642	=item Ocaml
		3643
		3644	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3646
		3647	=item Lua
		3648
		3649	Brian Maher has written a partial interface to libev for lua (at the
		3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3651	L<http://github.com/brimworks/lua-ev>.
2798		3652
2799	=back	3653	=back
2800		3654
2801		3655
2802	=head1 MACRO MAGIC	3656	=head1 MACRO MAGIC
…		…
2816	loop argument"). The C<EV_A> form is used when this is the sole argument,	3670	loop argument"). The C<EV_A> form is used when this is the sole argument,
2817	C<EV_A_> is used when other arguments are following. Example:	3671	C<EV_A_> is used when other arguments are following. Example:
2818		3672
2819	ev_unref (EV_A);	3673	ev_unref (EV_A);
2820	ev_timer_add (EV_A_ watcher);	3674	ev_timer_add (EV_A_ watcher);
2821	ev_loop (EV_A_ 0);	3675	ev_run (EV_A_ 0);
2822		3676
2823	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3677	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2824	which is often provided by the following macro.	3678	which is often provided by the following macro.
2825		3679
2826	=item C<EV_P>, C<EV_P_>	3680	=item C<EV_P>, C<EV_P_>
…		…
2866	}	3720	}
2867		3721
2868	ev_check check;	3722	ev_check check;
2869	ev_check_init (&check, check_cb);	3723	ev_check_init (&check, check_cb);
2870	ev_check_start (EV_DEFAULT_ &check);	3724	ev_check_start (EV_DEFAULT_ &check);
2871	ev_loop (EV_DEFAULT_ 0);	3725	ev_run (EV_DEFAULT_ 0);
2872		3726
2873	=head1 EMBEDDING	3727	=head1 EMBEDDING
2874		3728
2875	Libev can (and often is) directly embedded into host	3729	Libev can (and often is) directly embedded into host
2876	applications. Examples of applications that embed it include the Deliantra	3730	applications. Examples of applications that embed it include the Deliantra
…		…
2903		3757
2904	#define EV_STANDALONE 1	3758	#define EV_STANDALONE 1
2905	#include "ev.h"	3759	#include "ev.h"
2906		3760
2907	Both header files and implementation files can be compiled with a C++	3761	Both header files and implementation files can be compiled with a C++
2908	compiler (at least, thats a stated goal, and breakage will be treated	3762	compiler (at least, that's a stated goal, and breakage will be treated
2909	as a bug).	3763	as a bug).
2910		3764
2911	You need the following files in your source tree, or in a directory	3765	You need the following files in your source tree, or in a directory
2912	in your include path (e.g. in libev/ when using -Ilibev):	3766	in your include path (e.g. in libev/ when using -Ilibev):
2913		3767
…		…
2956	libev.m4	3810	libev.m4
2957		3811
2958	=head2 PREPROCESSOR SYMBOLS/MACROS	3812	=head2 PREPROCESSOR SYMBOLS/MACROS
2959		3813
2960	Libev can be configured via a variety of preprocessor symbols you have to	3814	Libev can be configured via a variety of preprocessor symbols you have to
2961	define before including any of its files. The default in the absence of	3815	define before including (or compiling) any of its files. The default in
2962	autoconf is documented for every option.	3816	the absence of autoconf is documented for every option.
		3817
		3818	Symbols marked with "(h)" do not change the ABI, and can have different
		3819	values when compiling libev vs. including F<ev.h>, so it is permissible
		3820	to redefine them before including F<ev.h> without breaking compatibility
		3821	to a compiled library. All other symbols change the ABI, which means all
		3822	users of libev and the libev code itself must be compiled with compatible
		3823	settings.
2963		3824
2964	=over 4	3825	=over 4
2965		3826
		3827	=item EV_COMPAT3 (h)
		3828
		3829	Backwards compatibility is a major concern for libev. This is why this
		3830	release of libev comes with wrappers for the functions and symbols that
		3831	have been renamed between libev version 3 and 4.
		3832
		3833	You can disable these wrappers (to test compatibility with future
		3834	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3835	sources. This has the additional advantage that you can drop the C<struct>
		3836	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3837	typedef in that case.
		3838
		3839	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3840	and in some even more future version the compatibility code will be
		3841	removed completely.
		3842
2966	=item EV_STANDALONE	3843	=item EV_STANDALONE (h)
2967		3844
2968	Must always be C<1> if you do not use autoconf configuration, which	3845	Must always be C<1> if you do not use autoconf configuration, which
2969	keeps libev from including F<config.h>, and it also defines dummy	3846	keeps libev from including F<config.h>, and it also defines dummy
2970	implementations for some libevent functions (such as logging, which is not	3847	implementations for some libevent functions (such as logging, which is not
2971	supported). It will also not define any of the structs usually found in	3848	supported). It will also not define any of the structs usually found in
2972	F<event.h> that are not directly supported by the libev core alone.	3849	F<event.h> that are not directly supported by the libev core alone.
2973		3850
		3851	In standalone mode, libev will still try to automatically deduce the
		3852	configuration, but has to be more conservative.
		3853
2974	=item EV_USE_MONOTONIC	3854	=item EV_USE_MONOTONIC
2975		3855
2976	If defined to be C<1>, libev will try to detect the availability of the	3856	If defined to be C<1>, libev will try to detect the availability of the
2977	monotonic clock option at both compile time and runtime. Otherwise no use	3857	monotonic clock option at both compile time and runtime. Otherwise no
2978	of the monotonic clock option will be attempted. If you enable this, you	3858	use of the monotonic clock option will be attempted. If you enable this,
2979	usually have to link against librt or something similar. Enabling it when	3859	you usually have to link against librt or something similar. Enabling it
2980	the functionality isn't available is safe, though, although you have	3860	when the functionality isn't available is safe, though, although you have
2981	to make sure you link against any libraries where the C<clock_gettime>	3861	to make sure you link against any libraries where the C<clock_gettime>
2982	function is hiding in (often F<-lrt>).	3862	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2983		3863
2984	=item EV_USE_REALTIME	3864	=item EV_USE_REALTIME
2985		3865
2986	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
2987	real-time clock option at compile time (and assume its availability at	3867	real-time clock option at compile time (and assume its availability
2988	runtime if successful). Otherwise no use of the real-time clock option will	3868	at runtime if successful). Otherwise no use of the real-time clock
2989	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3869	option will be attempted. This effectively replaces C<gettimeofday>
2990	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3870	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2991	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3871	correctness. See the note about libraries in the description of
		3872	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3873	C<EV_USE_CLOCK_SYSCALL>.
		3874
		3875	=item EV_USE_CLOCK_SYSCALL
		3876
		3877	If defined to be C<1>, libev will try to use a direct syscall instead
		3878	of calling the system-provided C<clock_gettime> function. This option
		3879	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3880	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3881	programs needlessly. Using a direct syscall is slightly slower (in
		3882	theory), because no optimised vdso implementation can be used, but avoids
		3883	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3884	higher, as it simplifies linking (no need for C<-lrt>).
2992		3885
2993	=item EV_USE_NANOSLEEP	3886	=item EV_USE_NANOSLEEP
2994		3887
2995	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3888	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2996	and will use it for delays. Otherwise it will use C<select ()>.	3889	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3012		3905
3013	=item EV_SELECT_USE_FD_SET	3906	=item EV_SELECT_USE_FD_SET
3014		3907
3015	If defined to C<1>, then the select backend will use the system C<fd_set>	3908	If defined to C<1>, then the select backend will use the system C<fd_set>
3016	structure. This is useful if libev doesn't compile due to a missing	3909	structure. This is useful if libev doesn't compile due to a missing
3017	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3910	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3018	exotic systems. This usually limits the range of file descriptors to some	3911	on exotic systems. This usually limits the range of file descriptors to
3019	low limit such as 1024 or might have other limitations (winsocket only	3912	some low limit such as 1024 or might have other limitations (winsocket
3020	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3913	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3021	influence the size of the C<fd_set> used.	3914	configures the maximum size of the C<fd_set>.
3022		3915
3023	=item EV_SELECT_IS_WINSOCKET	3916	=item EV_SELECT_IS_WINSOCKET
3024		3917
3025	When defined to C<1>, the select backend will assume that	3918	When defined to C<1>, the select backend will assume that
3026	select/socket/connect etc. don't understand file descriptors but	3919	select/socket/connect etc. don't understand file descriptors but
…		…
3028	be used is the winsock select). This means that it will call	3921	be used is the winsock select). This means that it will call
3029	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3922	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3030	it is assumed that all these functions actually work on fds, even	3923	it is assumed that all these functions actually work on fds, even
3031	on win32. Should not be defined on non-win32 platforms.	3924	on win32. Should not be defined on non-win32 platforms.
3032		3925
3033	=item EV_FD_TO_WIN32_HANDLE	3926	=item EV_FD_TO_WIN32_HANDLE(fd)
3034		3927
3035	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3928	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3036	file descriptors to socket handles. When not defining this symbol (the	3929	file descriptors to socket handles. When not defining this symbol (the
3037	default), then libev will call C<_get_osfhandle>, which is usually	3930	default), then libev will call C<_get_osfhandle>, which is usually
3038	correct. In some cases, programs use their own file descriptor management,	3931	correct. In some cases, programs use their own file descriptor management,
3039	in which case they can provide this function to map fds to socket handles.	3932	in which case they can provide this function to map fds to socket handles.
		3933
		3934	=item EV_WIN32_HANDLE_TO_FD(handle)
		3935
		3936	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3937	using the standard C<_open_osfhandle> function. For programs implementing
		3938	their own fd to handle mapping, overwriting this function makes it easier
		3939	to do so. This can be done by defining this macro to an appropriate value.
		3940
		3941	=item EV_WIN32_CLOSE_FD(fd)
		3942
		3943	If programs implement their own fd to handle mapping on win32, then this
		3944	macro can be used to override the C<close> function, useful to unregister
		3945	file descriptors again. Note that the replacement function has to close
		3946	the underlying OS handle.
3040		3947
3041	=item EV_USE_POLL	3948	=item EV_USE_POLL
3042		3949
3043	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3044	backend. Otherwise it will be enabled on non-win32 platforms. It	3951	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3091	as well as for signal and thread safety in C<ev_async> watchers.	3998	as well as for signal and thread safety in C<ev_async> watchers.
3092		3999
3093	In the absence of this define, libev will use C<sig_atomic_t volatile>	4000	In the absence of this define, libev will use C<sig_atomic_t volatile>
3094	(from F<signal.h>), which is usually good enough on most platforms.	4001	(from F<signal.h>), which is usually good enough on most platforms.
3095		4002
3096	=item EV_H	4003	=item EV_H (h)
3097		4004
3098	The name of the F<ev.h> header file used to include it. The default if	4005	The name of the F<ev.h> header file used to include it. The default if
3099	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4006	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3100	used to virtually rename the F<ev.h> header file in case of conflicts.	4007	used to virtually rename the F<ev.h> header file in case of conflicts.
3101		4008
3102	=item EV_CONFIG_H	4009	=item EV_CONFIG_H (h)
3103		4010
3104	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4011	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3105	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4012	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3106	C<EV_H>, above.	4013	C<EV_H>, above.
3107		4014
3108	=item EV_EVENT_H	4015	=item EV_EVENT_H (h)
3109		4016
3110	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4017	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3111	of how the F<event.h> header can be found, the default is C<"event.h">.	4018	of how the F<event.h> header can be found, the default is C<"event.h">.
3112		4019
3113	=item EV_PROTOTYPES	4020	=item EV_PROTOTYPES (h)
3114		4021
3115	If defined to be C<0>, then F<ev.h> will not define any function	4022	If defined to be C<0>, then F<ev.h> will not define any function
3116	prototypes, but still define all the structs and other symbols. This is	4023	prototypes, but still define all the structs and other symbols. This is
3117	occasionally useful if you want to provide your own wrapper functions	4024	occasionally useful if you want to provide your own wrapper functions
3118	around libev functions.	4025	around libev functions.
…		…
3140	fine.	4047	fine.
3141		4048
3142	If your embedding application does not need any priorities, defining these	4049	If your embedding application does not need any priorities, defining these
3143	both to C<0> will save some memory and CPU.	4050	both to C<0> will save some memory and CPU.
3144		4051
3145	=item EV_PERIODIC_ENABLE	4052	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4053	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4054	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3146		4055
3147	If undefined or defined to be C<1>, then periodic timers are supported. If	4056	If undefined or defined to be C<1> (and the platform supports it), then
3148	defined to be C<0>, then they are not. Disabling them saves a few kB of	4057	the respective watcher type is supported. If defined to be C<0>, then it
3149	code.	4058	is not. Disabling watcher types mainly saves code size.
3150		4059
3151	=item EV_IDLE_ENABLE	4060	=item EV_FEATURES
3152
3153	If undefined or defined to be C<1>, then idle watchers are supported. If
3154	defined to be C<0>, then they are not. Disabling them saves a few kB of
3155	code.
3156
3157	=item EV_EMBED_ENABLE
3158
3159	If undefined or defined to be C<1>, then embed watchers are supported. If
3160	defined to be C<0>, then they are not. Embed watchers rely on most other
3161	watcher types, which therefore must not be disabled.
3162
3163	=item EV_STAT_ENABLE
3164
3165	If undefined or defined to be C<1>, then stat watchers are supported. If
3166	defined to be C<0>, then they are not.
3167
3168	=item EV_FORK_ENABLE
3169
3170	If undefined or defined to be C<1>, then fork watchers are supported. If
3171	defined to be C<0>, then they are not.
3172
3173	=item EV_ASYNC_ENABLE
3174
3175	If undefined or defined to be C<1>, then async watchers are supported. If
3176	defined to be C<0>, then they are not.
3177
3178	=item EV_MINIMAL
3179		4061
3180	If you need to shave off some kilobytes of code at the expense of some	4062	If you need to shave off some kilobytes of code at the expense of some
3181	speed, define this symbol to C<1>. Currently this is used to override some	4063	speed (but with the full API), you can define this symbol to request
3182	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4064	certain subsets of functionality. The default is to enable all features
3183	much smaller 2-heap for timer management over the default 4-heap.	4065	that can be enabled on the platform.
		4066
		4067	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4068	with some broad features you want) and then selectively re-enable
		4069	additional parts you want, for example if you want everything minimal,
		4070	but multiple event loop support, async and child watchers and the poll
		4071	backend, use this:
		4072
		4073	#define EV_FEATURES 0
		4074	#define EV_MULTIPLICITY 1
		4075	#define EV_USE_POLL 1
		4076	#define EV_CHILD_ENABLE 1
		4077	#define EV_ASYNC_ENABLE 1
		4078
		4079	The actual value is a bitset, it can be a combination of the following
		4080	values:
		4081
		4082	=over 4
		4083
		4084	=item C<1> - faster/larger code
		4085
		4086	Use larger code to speed up some operations.
		4087
		4088	Currently this is used to override some inlining decisions (enlarging the
		4089	code size by roughly 30% on amd64).
		4090
		4091	When optimising for size, use of compiler flags such as C<-Os> with
		4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4093	assertions.
		4094
		4095	=item C<2> - faster/larger data structures
		4096
		4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4098	hash table sizes and so on. This will usually further increase code size
		4099	and can additionally have an effect on the size of data structures at
		4100	runtime.
		4101
		4102	=item C<4> - full API configuration
		4103
		4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4105	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4106
		4107	=item C<8> - full API
		4108
		4109	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4110	details on which parts of the API are still available without this
		4111	feature, and do not complain if this subset changes over time.
		4112
		4113	=item C<16> - enable all optional watcher types
		4114
		4115	Enables all optional watcher types. If you want to selectively enable
		4116	only some watcher types other than I/O and timers (e.g. prepare,
		4117	embed, async, child...) you can enable them manually by defining
		4118	C<EV_watchertype_ENABLE> to C<1> instead.
		4119
		4120	=item C<32> - enable all backends
		4121
		4122	This enables all backends - without this feature, you need to enable at
		4123	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4124
		4125	=item C<64> - enable OS-specific "helper" APIs
		4126
		4127	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4128	default.
		4129
		4130	=back
		4131
		4132	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4133	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4134	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4135	watchers, timers and monotonic clock support.
		4136
		4137	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4139	your program might be left out as well - a binary starting a timer and an
		4140	I/O watcher then might come out at only 5Kb.
		4141
		4142	=item EV_AVOID_STDIO
		4143
		4144	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4145	functions (printf, scanf, perror etc.). This will increase the code size
		4146	somewhat, but if your program doesn't otherwise depend on stdio and your
		4147	libc allows it, this avoids linking in the stdio library which is quite
		4148	big.
		4149
		4150	Note that error messages might become less precise when this option is
		4151	enabled.
		4152
		4153	=item EV_NSIG
		4154
		4155	The highest supported signal number, +1 (or, the number of
		4156	signals): Normally, libev tries to deduce the maximum number of signals
		4157	automatically, but sometimes this fails, in which case it can be
		4158	specified. Also, using a lower number than detected (C<32> should be
		4159	good for about any system in existence) can save some memory, as libev
		4160	statically allocates some 12-24 bytes per signal number.
3184		4161
3185	=item EV_PID_HASHSIZE	4162	=item EV_PID_HASHSIZE
3186		4163
3187	C<ev_child> watchers use a small hash table to distribute workload by	4164	C<ev_child> watchers use a small hash table to distribute workload by
3188	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4165	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3189	than enough. If you need to manage thousands of children you might want to	4166	usually more than enough. If you need to manage thousands of children you
3190	increase this value (I<must> be a power of two).	4167	might want to increase this value (I<must> be a power of two).
3191		4168
3192	=item EV_INOTIFY_HASHSIZE	4169	=item EV_INOTIFY_HASHSIZE
3193		4170
3194	C<ev_stat> watchers use a small hash table to distribute workload by	4171	C<ev_stat> watchers use a small hash table to distribute workload by
3195	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4172	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3196	usually more than enough. If you need to manage thousands of C<ev_stat>	4173	disabled), usually more than enough. If you need to manage thousands of
3197	watchers you might want to increase this value (I<must> be a power of	4174	C<ev_stat> watchers you might want to increase this value (I<must> be a
3198	two).	4175	power of two).
3199		4176
3200	=item EV_USE_4HEAP	4177	=item EV_USE_4HEAP
3201		4178
3202	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4179	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3203	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4180	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3204	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4181	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3205	faster performance with many (thousands) of watchers.	4182	faster performance with many (thousands) of watchers.
3206		4183
3207	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4184	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3208	(disabled).	4185	will be C<0>.
3209		4186
3210	=item EV_HEAP_CACHE_AT	4187	=item EV_HEAP_CACHE_AT
3211		4188
3212	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3213	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4190	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3214	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4191	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3215	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4192	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3216	but avoids random read accesses on heap changes. This improves performance	4193	but avoids random read accesses on heap changes. This improves performance
3217	noticeably with many (hundreds) of watchers.	4194	noticeably with many (hundreds) of watchers.
3218		4195
3219	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3220	(disabled).	4197	will be C<0>.
3221		4198
3222	=item EV_VERIFY	4199	=item EV_VERIFY
3223		4200
3224	Controls how much internal verification (see C<ev_loop_verify ()>) will	4201	Controls how much internal verification (see C<ev_verify ()>) will
3225	be done: If set to C<0>, no internal verification code will be compiled	4202	be done: If set to C<0>, no internal verification code will be compiled
3226	in. If set to C<1>, then verification code will be compiled in, but not	4203	in. If set to C<1>, then verification code will be compiled in, but not
3227	called. If set to C<2>, then the internal verification code will be	4204	called. If set to C<2>, then the internal verification code will be
3228	called once per loop, which can slow down libev. If set to C<3>, then the	4205	called once per loop, which can slow down libev. If set to C<3>, then the
3229	verification code will be called very frequently, which will slow down	4206	verification code will be called very frequently, which will slow down
3230	libev considerably.	4207	libev considerably.
3231		4208
3232	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4209	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3233	C<0>.	4210	will be C<0>.
3234		4211
3235	=item EV_COMMON	4212	=item EV_COMMON
3236		4213
3237	By default, all watchers have a C<void *data> member. By redefining	4214	By default, all watchers have a C<void *data> member. By redefining
3238	this macro to a something else you can include more and other types of	4215	this macro to something else you can include more and other types of
3239	members. You have to define it each time you include one of the files,	4216	members. You have to define it each time you include one of the files,
3240	though, and it must be identical each time.	4217	though, and it must be identical each time.
3241		4218
3242	For example, the perl EV module uses something like this:	4219	For example, the perl EV module uses something like this:
3243		4220
…		…
3296	file.	4273	file.
3297		4274
3298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4275	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3299	that everybody includes and which overrides some configure choices:	4276	that everybody includes and which overrides some configure choices:
3300		4277
3301	#define EV_MINIMAL 1	4278	#define EV_FEATURES 8
3302	#define EV_USE_POLL 0	4279	#define EV_USE_SELECT 1
3303	#define EV_MULTIPLICITY 0
3304	#define EV_PERIODIC_ENABLE 0	4280	#define EV_PREPARE_ENABLE 1
		4281	#define EV_IDLE_ENABLE 1
3305	#define EV_STAT_ENABLE 0	4282	#define EV_SIGNAL_ENABLE 1
3306	#define EV_FORK_ENABLE 0	4283	#define EV_CHILD_ENABLE 1
		4284	#define EV_USE_STDEXCEPT 0
3307	#define EV_CONFIG_H <config.h>	4285	#define EV_CONFIG_H <config.h>
3308	#define EV_MINPRI 0
3309	#define EV_MAXPRI 0
3310		4286
3311	#include "ev++.h"	4287	#include "ev++.h"
3312		4288
3313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3314		4290
…		…
3374	default loop and triggering an C<ev_async> watcher from the default loop	4350	default loop and triggering an C<ev_async> watcher from the default loop
3375	watcher callback into the event loop interested in the signal.	4351	watcher callback into the event loop interested in the signal.
3376		4352
3377	=back	4353	=back
3378		4354
		4355	=head4 THREAD LOCKING EXAMPLE
		4356
		4357	Here is a fictitious example of how to run an event loop in a different
		4358	thread than where callbacks are being invoked and watchers are
		4359	created/added/removed.
		4360
		4361	For a real-world example, see the C<EV::Loop::Async> perl module,
		4362	which uses exactly this technique (which is suited for many high-level
		4363	languages).
		4364
		4365	The example uses a pthread mutex to protect the loop data, a condition
		4366	variable to wait for callback invocations, an async watcher to notify the
		4367	event loop thread and an unspecified mechanism to wake up the main thread.
		4368
		4369	First, you need to associate some data with the event loop:
		4370
		4371	typedef struct {
		4372	mutex_t lock; /* global loop lock */
		4373	ev_async async_w;
		4374	thread_t tid;
		4375	cond_t invoke_cv;
		4376	} userdata;
		4377
		4378	void prepare_loop (EV_P)
		4379	{
		4380	// for simplicity, we use a static userdata struct.
		4381	static userdata u;
		4382
		4383	ev_async_init (&u->async_w, async_cb);
		4384	ev_async_start (EV_A_ &u->async_w);
		4385
		4386	pthread_mutex_init (&u->lock, 0);
		4387	pthread_cond_init (&u->invoke_cv, 0);
		4388
		4389	// now associate this with the loop
		4390	ev_set_userdata (EV_A_ u);
		4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4393
		4394	// then create the thread running ev_loop
		4395	pthread_create (&u->tid, 0, l_run, EV_A);
		4396	}
		4397
		4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4399	solely to wake up the event loop so it takes notice of any new watchers
		4400	that might have been added:
		4401
		4402	static void
		4403	async_cb (EV_P_ ev_async *w, int revents)
		4404	{
		4405	// just used for the side effects
		4406	}
		4407
		4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4409	protecting the loop data, respectively.
		4410
		4411	static void
		4412	l_release (EV_P)
		4413	{
		4414	userdata *u = ev_userdata (EV_A);
		4415	pthread_mutex_unlock (&u->lock);
		4416	}
		4417
		4418	static void
		4419	l_acquire (EV_P)
		4420	{
		4421	userdata *u = ev_userdata (EV_A);
		4422	pthread_mutex_lock (&u->lock);
		4423	}
		4424
		4425	The event loop thread first acquires the mutex, and then jumps straight
		4426	into C<ev_run>:
		4427
		4428	void *
		4429	l_run (void *thr_arg)
		4430	{
		4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4432
		4433	l_acquire (EV_A);
		4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4435	ev_run (EV_A_ 0);
		4436	l_release (EV_A);
		4437
		4438	return 0;
		4439	}
		4440
		4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4442	signal the main thread via some unspecified mechanism (signals? pipe
		4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4444	have been called (in a while loop because a) spurious wakeups are possible
		4445	and b) skipping inter-thread-communication when there are no pending
		4446	watchers is very beneficial):
		4447
		4448	static void
		4449	l_invoke (EV_P)
		4450	{
		4451	userdata *u = ev_userdata (EV_A);
		4452
		4453	while (ev_pending_count (EV_A))
		4454	{
		4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4457	}
		4458	}
		4459
		4460	Now, whenever the main thread gets told to invoke pending watchers, it
		4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4462	thread to continue:
		4463
		4464	static void
		4465	real_invoke_pending (EV_P)
		4466	{
		4467	userdata *u = ev_userdata (EV_A);
		4468
		4469	pthread_mutex_lock (&u->lock);
		4470	ev_invoke_pending (EV_A);
		4471	pthread_cond_signal (&u->invoke_cv);
		4472	pthread_mutex_unlock (&u->lock);
		4473	}
		4474
		4475	Whenever you want to start/stop a watcher or do other modifications to an
		4476	event loop, you will now have to lock:
		4477
		4478	ev_timer timeout_watcher;
		4479	userdata *u = ev_userdata (EV_A);
		4480
		4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4482
		4483	pthread_mutex_lock (&u->lock);
		4484	ev_timer_start (EV_A_ &timeout_watcher);
		4485	ev_async_send (EV_A_ &u->async_w);
		4486	pthread_mutex_unlock (&u->lock);
		4487
		4488	Note that sending the C<ev_async> watcher is required because otherwise
		4489	an event loop currently blocking in the kernel will have no knowledge
		4490	about the newly added timer. By waking up the loop it will pick up any new
		4491	watchers in the next event loop iteration.
		4492
3379	=head3 COROUTINES	4493	=head3 COROUTINES
3380		4494
3381	Libev is very accommodating to coroutines ("cooperative threads"):	4495	Libev is very accommodating to coroutines ("cooperative threads"):
3382	libev fully supports nesting calls to its functions from different	4496	libev fully supports nesting calls to its functions from different
3383	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4497	coroutines (e.g. you can call C<ev_run> on the same loop from two
3384	different coroutines, and switch freely between both coroutines running the	4498	different coroutines, and switch freely between both coroutines running
3385	loop, as long as you don't confuse yourself). The only exception is that	4499	the loop, as long as you don't confuse yourself). The only exception is
3386	you must not do this from C<ev_periodic> reschedule callbacks.	4500	that you must not do this from C<ev_periodic> reschedule callbacks.
3387		4501
3388	Care has been taken to ensure that libev does not keep local state inside	4502	Care has been taken to ensure that libev does not keep local state inside
3389	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4503	C<ev_run>, and other calls do not usually allow for coroutine switches as
3390	they do not clal any callbacks.	4504	they do not call any callbacks.
3391		4505
3392	=head2 COMPILER WARNINGS	4506	=head2 COMPILER WARNINGS
3393		4507
3394	Depending on your compiler and compiler settings, you might get no or a	4508	Depending on your compiler and compiler settings, you might get no or a
3395	lot of warnings when compiling libev code. Some people are apparently	4509	lot of warnings when compiling libev code. Some people are apparently
…		…
3405	maintainable.	4519	maintainable.
3406		4520
3407	And of course, some compiler warnings are just plain stupid, or simply	4521	And of course, some compiler warnings are just plain stupid, or simply
3408	wrong (because they don't actually warn about the condition their message	4522	wrong (because they don't actually warn about the condition their message
3409	seems to warn about). For example, certain older gcc versions had some	4523	seems to warn about). For example, certain older gcc versions had some
3410	warnings that resulted an extreme number of false positives. These have	4524	warnings that resulted in an extreme number of false positives. These have
3411	been fixed, but some people still insist on making code warn-free with	4525	been fixed, but some people still insist on making code warn-free with
3412	such buggy versions.	4526	such buggy versions.
3413		4527
3414	While libev is written to generate as few warnings as possible,	4528	While libev is written to generate as few warnings as possible,
3415	"warn-free" code is not a goal, and it is recommended not to build libev	4529	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3429	==2274== definitely lost: 0 bytes in 0 blocks.	4543	==2274== definitely lost: 0 bytes in 0 blocks.
3430	==2274== possibly lost: 0 bytes in 0 blocks.	4544	==2274== possibly lost: 0 bytes in 0 blocks.
3431	==2274== still reachable: 256 bytes in 1 blocks.	4545	==2274== still reachable: 256 bytes in 1 blocks.
3432		4546
3433	Then there is no memory leak, just as memory accounted to global variables	4547	Then there is no memory leak, just as memory accounted to global variables
3434	is not a memleak - the memory is still being refernced, and didn't leak.	4548	is not a memleak - the memory is still being referenced, and didn't leak.
3435		4549
3436	Similarly, under some circumstances, valgrind might report kernel bugs	4550	Similarly, under some circumstances, valgrind might report kernel bugs
3437	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4551	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3438	although an acceptable workaround has been found here), or it might be	4552	although an acceptable workaround has been found here), or it might be
3439	confused.	4553	confused.
…		…
3451	I suggest using suppression lists.	4565	I suggest using suppression lists.
3452		4566
3453		4567
3454	=head1 PORTABILITY NOTES	4568	=head1 PORTABILITY NOTES
3455		4569
		4570	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4571
		4572	GNU/Linux is the only common platform that supports 64 bit file/large file
		4573	interfaces but I<disables> them by default.
		4574
		4575	That means that libev compiled in the default environment doesn't support
		4576	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4577
		4578	Unfortunately, many programs try to work around this GNU/Linux issue
		4579	by enabling the large file API, which makes them incompatible with the
		4580	standard libev compiled for their system.
		4581
		4582	Likewise, libev cannot enable the large file API itself as this would
		4583	suddenly make it incompatible to the default compile time environment,
		4584	i.e. all programs not using special compile switches.
		4585
		4586	=head2 OS/X AND DARWIN BUGS
		4587
		4588	The whole thing is a bug if you ask me - basically any system interface
		4589	you touch is broken, whether it is locales, poll, kqueue or even the
		4590	OpenGL drivers.
		4591
		4592	=head3 C<kqueue> is buggy
		4593
		4594	The kqueue syscall is broken in all known versions - most versions support
		4595	only sockets, many support pipes.
		4596
		4597	Libev tries to work around this by not using C<kqueue> by default on this
		4598	rotten platform, but of course you can still ask for it when creating a
		4599	loop - embedding a socket-only kqueue loop into a select-based one is
		4600	probably going to work well.
		4601
		4602	=head3 C<poll> is buggy
		4603
		4604	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4605	implementation by something calling C<kqueue> internally around the 10.5.6
		4606	release, so now C<kqueue> I<and> C<poll> are broken.
		4607
		4608	Libev tries to work around this by not using C<poll> by default on
		4609	this rotten platform, but of course you can still ask for it when creating
		4610	a loop.
		4611
		4612	=head3 C<select> is buggy
		4613
		4614	All that's left is C<select>, and of course Apple found a way to fuck this
		4615	one up as well: On OS/X, C<select> actively limits the number of file
		4616	descriptors you can pass in to 1024 - your program suddenly crashes when
		4617	you use more.
		4618
		4619	There is an undocumented "workaround" for this - defining
		4620	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4621	work on OS/X.
		4622
		4623	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4624
		4625	=head3 C<errno> reentrancy
		4626
		4627	The default compile environment on Solaris is unfortunately so
		4628	thread-unsafe that you can't even use components/libraries compiled
		4629	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4630	defined by default. A valid, if stupid, implementation choice.
		4631
		4632	If you want to use libev in threaded environments you have to make sure
		4633	it's compiled with C<_REENTRANT> defined.
		4634
		4635	=head3 Event port backend
		4636
		4637	The scalable event interface for Solaris is called "event
		4638	ports". Unfortunately, this mechanism is very buggy in all major
		4639	releases. If you run into high CPU usage, your program freezes or you get
		4640	a large number of spurious wakeups, make sure you have all the relevant
		4641	and latest kernel patches applied. No, I don't know which ones, but there
		4642	are multiple ones to apply, and afterwards, event ports actually work
		4643	great.
		4644
		4645	If you can't get it to work, you can try running the program by setting
		4646	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4647	C<select> backends.
		4648
		4649	=head2 AIX POLL BUG
		4650
		4651	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4652	this by trying to avoid the poll backend altogether (i.e. it's not even
		4653	compiled in), which normally isn't a big problem as C<select> works fine
		4654	with large bitsets on AIX, and AIX is dead anyway.
		4655
3456	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4656	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4657
		4658	=head3 General issues
3457		4659
3458	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4660	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3459	requires, and its I/O model is fundamentally incompatible with the POSIX	4661	requires, and its I/O model is fundamentally incompatible with the POSIX
3460	model. Libev still offers limited functionality on this platform in	4662	model. Libev still offers limited functionality on this platform in
3461	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3462	descriptors. This only applies when using Win32 natively, not when using	4664	descriptors. This only applies when using Win32 natively, not when using
3463	e.g. cygwin.	4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4666	as every compielr comes with a slightly differently broken/incompatible
		4667	environment.
3464		4668
3465	Lifting these limitations would basically require the full	4669	Lifting these limitations would basically require the full
3466	re-implementation of the I/O system. If you are into these kinds of	4670	re-implementation of the I/O system. If you are into this kind of thing,
3467	things, then note that glib does exactly that for you in a very portable	4671	then note that glib does exactly that for you in a very portable way (note
3468	way (note also that glib is the slowest event library known to man).	4672	also that glib is the slowest event library known to man).
3469		4673
3470	There is no supported compilation method available on windows except	4674	There is no supported compilation method available on windows except
3471	embedding it into other applications.	4675	embedding it into other applications.
		4676
		4677	Sensible signal handling is officially unsupported by Microsoft - libev
		4678	tries its best, but under most conditions, signals will simply not work.
3472		4679
3473	Not a libev limitation but worth mentioning: windows apparently doesn't	4680	Not a libev limitation but worth mentioning: windows apparently doesn't
3474	accept large writes: instead of resulting in a partial write, windows will	4681	accept large writes: instead of resulting in a partial write, windows will
3475	either accept everything or return C<ENOBUFS> if the buffer is too large,	4682	either accept everything or return C<ENOBUFS> if the buffer is too large,
3476	so make sure you only write small amounts into your sockets (less than a	4683	so make sure you only write small amounts into your sockets (less than a
…		…
3481	the abysmal performance of winsockets, using a large number of sockets	4688	the abysmal performance of winsockets, using a large number of sockets
3482	is not recommended (and not reasonable). If your program needs to use	4689	is not recommended (and not reasonable). If your program needs to use
3483	more than a hundred or so sockets, then likely it needs to use a totally	4690	more than a hundred or so sockets, then likely it needs to use a totally
3484	different implementation for windows, as libev offers the POSIX readiness	4691	different implementation for windows, as libev offers the POSIX readiness
3485	notification model, which cannot be implemented efficiently on windows	4692	notification model, which cannot be implemented efficiently on windows
3486	(Microsoft monopoly games).	4693	(due to Microsoft monopoly games).
3487		4694
3488	A typical way to use libev under windows is to embed it (see the embedding	4695	A typical way to use libev under windows is to embed it (see the embedding
3489	section for details) and use the following F<evwrap.h> header file instead	4696	section for details) and use the following F<evwrap.h> header file instead
3490	of F<ev.h>:	4697	of F<ev.h>:
3491		4698
…		…
3498	you do I<not> compile the F<ev.c> or any other embedded source files!):	4705	you do I<not> compile the F<ev.c> or any other embedded source files!):
3499		4706
3500	#include "evwrap.h"	4707	#include "evwrap.h"
3501	#include "ev.c"	4708	#include "ev.c"
3502		4709
3503	=over 4
3504
3505	=item The winsocket select function	4710	=head3 The winsocket C<select> function
3506		4711
3507	The winsocket C<select> function doesn't follow POSIX in that it	4712	The winsocket C<select> function doesn't follow POSIX in that it
3508	requires socket I<handles> and not socket I<file descriptors> (it is	4713	requires socket I<handles> and not socket I<file descriptors> (it is
3509	also extremely buggy). This makes select very inefficient, and also	4714	also extremely buggy). This makes select very inefficient, and also
3510	requires a mapping from file descriptors to socket handles (the Microsoft	4715	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3519	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4724	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3520		4725
3521	Note that winsockets handling of fd sets is O(n), so you can easily get a	4726	Note that winsockets handling of fd sets is O(n), so you can easily get a
3522	complexity in the O(n²) range when using win32.	4727	complexity in the O(n²) range when using win32.
3523		4728
3524	=item Limited number of file descriptors	4729	=head3 Limited number of file descriptors
3525		4730
3526	Windows has numerous arbitrary (and low) limits on things.	4731	Windows has numerous arbitrary (and low) limits on things.
3527		4732
3528	Early versions of winsocket's select only supported waiting for a maximum	4733	Early versions of winsocket's select only supported waiting for a maximum
3529	of C<64> handles (probably owning to the fact that all windows kernels	4734	of C<64> handles (probably owning to the fact that all windows kernels
3530	can only wait for C<64> things at the same time internally; Microsoft	4735	can only wait for C<64> things at the same time internally; Microsoft
3531	recommends spawning a chain of threads and wait for 63 handles and the	4736	recommends spawning a chain of threads and wait for 63 handles and the
3532	previous thread in each. Great).	4737	previous thread in each. Sounds great!).
3533		4738
3534	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4739	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3535	to some high number (e.g. C<2048>) before compiling the winsocket select	4740	to some high number (e.g. C<2048>) before compiling the winsocket select
3536	call (which might be in libev or elsewhere, for example, perl does its own	4741	call (which might be in libev or elsewhere, for example, perl and many
3537	select emulation on windows).	4742	other interpreters do their own select emulation on windows).
3538		4743
3539	Another limit is the number of file descriptors in the Microsoft runtime	4744	Another limit is the number of file descriptors in the Microsoft runtime
3540	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4745	libraries, which by default is C<64> (there must be a hidden I<64>
3541	or something like this inside Microsoft). You can increase this by calling	4746	fetish or something like this inside Microsoft). You can increase this
3542	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4747	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3543	arbitrary limit), but is broken in many versions of the Microsoft runtime	4748	(another arbitrary limit), but is broken in many versions of the Microsoft
3544	libraries.
3545
3546	This might get you to about C<512> or C<2048> sockets (depending on	4749	runtime libraries. This might get you to about C<512> or C<2048> sockets
3547	windows version and/or the phase of the moon). To get more, you need to	4750	(depending on windows version and/or the phase of the moon). To get more,
3548	wrap all I/O functions and provide your own fd management, but the cost of	4751	you need to wrap all I/O functions and provide your own fd management, but
3549	calling select (O(n²)) will likely make this unworkable.	4752	the cost of calling select (O(n²)) will likely make this unworkable.
3550
3551	=back
3552		4753
3553	=head2 PORTABILITY REQUIREMENTS	4754	=head2 PORTABILITY REQUIREMENTS
3554		4755
3555	In addition to a working ISO-C implementation and of course the	4756	In addition to a working ISO-C implementation and of course the
3556	backend-specific APIs, libev relies on a few additional extensions:	4757	backend-specific APIs, libev relies on a few additional extensions:
…		…
3563	Libev assumes not only that all watcher pointers have the same internal	4764	Libev assumes not only that all watcher pointers have the same internal
3564	structure (guaranteed by POSIX but not by ISO C for example), but it also	4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
3565	assumes that the same (machine) code can be used to call any watcher	4766	assumes that the same (machine) code can be used to call any watcher
3566	callback: The watcher callbacks have different type signatures, but libev	4767	callback: The watcher callbacks have different type signatures, but libev
3567	calls them using an C<ev_watcher *> internally.	4768	calls them using an C<ev_watcher *> internally.
		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
3568		4774
3569	=item C<sig_atomic_t volatile> must be thread-atomic as well	4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
3570		4776
3571	The type C<sig_atomic_t volatile> (or whatever is defined as	4777	The type C<sig_atomic_t volatile> (or whatever is defined as
3572	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3595	watchers.	4801	watchers.
3596		4802
3597	=item C<double> must hold a time value in seconds with enough accuracy	4803	=item C<double> must hold a time value in seconds with enough accuracy
3598		4804
3599	The type C<double> is used to represent timestamps. It is required to	4805	The type C<double> is used to represent timestamps. It is required to
3600	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3601	enough for at least into the year 4000. This requirement is fulfilled by	4807	good enough for at least into the year 4000 with millisecond accuracy
		4808	(the design goal for libev). This requirement is overfulfilled by
3602	implementations implementing IEEE 754 (basically all existing ones).	4809	implementations using IEEE 754, which is basically all existing ones. With
		4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3603		4811
3604	=back	4812	=back
3605		4813
3606	If you know of other additional requirements drop me a note.	4814	If you know of other additional requirements drop me a note.
3607		4815
…		…
3675	involves iterating over all running async watchers or all signal numbers.	4883	involves iterating over all running async watchers or all signal numbers.
3676		4884
3677	=back	4885	=back
3678		4886
3679		4887
		4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4889
		4890	The major version 4 introduced some incompatible changes to the API.
		4891
		4892	At the moment, the C<ev.h> header file provides compatibility definitions
		4893	for all changes, so most programs should still compile. The compatibility
		4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
		4896
		4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
		4911
		4912	=item function/symbol renames
		4913
		4914	A number of functions and symbols have been renamed:
		4915
		4916	ev_loop => ev_run
		4917	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4918	EVLOOP_ONESHOT => EVRUN_ONCE
		4919
		4920	ev_unloop => ev_break
		4921	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4922	EVUNLOOP_ONE => EVBREAK_ONE
		4923	EVUNLOOP_ALL => EVBREAK_ALL
		4924
		4925	EV_TIMEOUT => EV_TIMER
		4926
		4927	ev_loop_count => ev_iteration
		4928	ev_loop_depth => ev_depth
		4929	ev_loop_verify => ev_verify
		4930
		4931	Most functions working on C<struct ev_loop> objects don't have an
		4932	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4933	associated constants have been renamed to not collide with the C<struct
		4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4935	as all other watcher types. Note that C<ev_loop_fork> is still called
		4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4937	typedef.
		4938
		4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4940
		4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4943	and work, but the library code will of course be larger.
		4944
		4945	=back
		4946
		4947
		4948	=head1 GLOSSARY
		4949
		4950	=over 4
		4951
		4952	=item active
		4953
		4954	A watcher is active as long as it has been started and not yet stopped.
		4955	See L<WATCHER STATES> for details.
		4956
		4957	=item application
		4958
		4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
		4964
		4965	=item callback
		4966
		4967	The address of a function that is called when some event has been
		4968	detected. Callbacks are being passed the event loop, the watcher that
		4969	received the event, and the actual event bitset.
		4970
		4971	=item callback/watcher invocation
		4972
		4973	The act of calling the callback associated with a watcher.
		4974
		4975	=item event
		4976
		4977	A change of state of some external event, such as data now being available
		4978	for reading on a file descriptor, time having passed or simply not having
		4979	any other events happening anymore.
		4980
		4981	In libev, events are represented as single bits (such as C<EV_READ> or
		4982	C<EV_TIMER>).
		4983
		4984	=item event library
		4985
		4986	A software package implementing an event model and loop.
		4987
		4988	=item event loop
		4989
		4990	An entity that handles and processes external events and converts them
		4991	into callback invocations.
		4992
		4993	=item event model
		4994
		4995	The model used to describe how an event loop handles and processes
		4996	watchers and events.
		4997
		4998	=item pending
		4999
		5000	A watcher is pending as soon as the corresponding event has been
		5001	detected. See L<WATCHER STATES> for details.
		5002
		5003	=item real time
		5004
		5005	The physical time that is observed. It is apparently strictly monotonic :)
		5006
		5007	=item wall-clock time
		5008
		5009	The time and date as shown on clocks. Unlike real time, it can actually
		5010	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5011	clock.
		5012
		5013	=item watcher
		5014
		5015	A data structure that describes interest in certain events. Watchers need
		5016	to be started (attached to an event loop) before they can receive events.
		5017
		5018	=back
		5019
3680	=head1 AUTHOR	5020	=head1 AUTHOR
3681		5021
3682	Marc Lehmann <libev@schmorp.de>.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
3683		5024

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