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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	// break was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
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_now_update> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
160	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
161		192
162	=item int ev_version_major ()	193	=item int ev_version_major ()
163		194
164	=item int ev_version_minor ()	195	=item int ev_version_minor ()
165		196
…		…
176	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	209	not a problem.
179		210
180	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
182		214
183	assert (("libev version mismatch",	215	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
186		218
…		…
197	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
199		231
200	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
201		233
202	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
208		241
209	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
210		243
211	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
216		249
217	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
218		251
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		253
221	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	283	}
251		284
252	...	285	...
253	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
254		287
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		289
257	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	305	}
273		306
274	...	307	...
275	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
276		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
277	=back	323	=back
278		324
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		326
281	An event loop is described by a C<struct ev_loop *>. The library knows two	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	329	libev 3 had an C<ev_loop> function colliding with the struct name).
		330
		331	The library knows two types of such loops, the I<default> loop, which
		332	supports child process events, and dynamically created event loops which
		333	do not.
284		334
285	=over 4	335	=over 4
286		336
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		338
289	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
293		349
294	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
295	function.	351	function (or via the C<EV_DEFAULT> macro).
296		352
297	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
300		357
301	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
307		382
308	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		385
311	The following flags are supported:	386	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
327	around bugs.	402	around bugs.
328		403
329	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
330		405
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		408
335	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	418	flag.
345		419
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	421	environment variable.
348		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		459
351	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		488
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
382	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
383	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
384	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	497	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	498
387	cases and requiring a system call per fd change, no fork support and bad	499	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	500	of the more advanced event mechanisms: mere annoyances include silently
		501	dropping file descriptors, requiring a system call per change per file
		502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
		505	0.1ms) and so on. The biggest issue is fork races, however - if a program
		506	forks then I<both> parent and child process have to recreate the epoll
		507	set, which can take considerable time (one syscall per file descriptor)
		508	and is of course hard to detect.
		509
		510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		511	but of course I<doesn't>, and epoll just loves to report events for
		512	totally I<different> file descriptors (even already closed ones, so
		513	one cannot even remove them from the set) than registered in the set
		514	(especially on SMP systems). Libev tries to counter these spurious
		515	notifications by employing an additional generation counter and comparing
		516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
389		526
390	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	528	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	529	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	531	file descriptors might not work very well if you register events for both
395		532	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		533
400	Best performance from this backend is achieved by not unregistering all	534	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	535	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	536	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	537	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	538	extra overhead. A fork can both result in spurious notifications as well
		539	as in libev having to destroy and recreate the epoll object, which can
		540	take considerable time and thus should be avoided.
		541
		542	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		543	faster than epoll for maybe up to a hundred file descriptors, depending on
		544	the usage. So sad.
405		545
406	While nominally embeddable in other event loops, this feature is broken in	546	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	547	all kernel versions tested so far.
408		548
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	549	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	550	C<EVBACKEND_POLL>.
411		551
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	552	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		553
414	Kqueue deserves special mention, as at the time of this writing, it was	554	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	555	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	556	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	557	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	558	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	559	without API changes to existing programs. For this reason it's not being
		560	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		561	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		562	system like NetBSD.
420		563
421	You still can embed kqueue into a normal poll or select backend and use it	564	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	565	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	566	the target platform). See C<ev_embed> watchers for more info.
424		567
425	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	572	two event changes per incident. Support for C<fork ()> is very bad (you
		573	might have to leak fd's on fork, but it's more sane than epoll) and it
430	drops fds silently in similarly hard-to-detect cases.	574	drops fds silently in similarly hard-to-detect cases
431		575
432	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
433		577
434	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	580	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	581	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	582	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	583	also broken on OS X)) and, did I mention it, using it only for sockets.
440		584
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	585	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	586	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	587	C<NOTE_EOF>.
444		588
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		597
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
455	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
456		600
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	604	might perform better.
465		605
466	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
470		620
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
473		623
474	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
475		625
476	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		629
480	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		639
482	=back	640	=back
483		641
484	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
487		645	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		646
516	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
517		648
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	650	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
521		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
522	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
523		659
524	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	666	for example).
531		667
532	Note that certain global state, such as signal state, will not be freed by	668	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	669	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
535		671
536	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
540		680
541	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
542		682
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
554		693
555	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
558		700
559	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
563	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		715
572	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
573		717
574	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	719	otherwise.
576		720
577	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
578		722
579	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
582		726
583	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
586		745
587	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
588		747
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	749	use.
…		…
599		758
600	=item ev_now_update (loop)	759	=item ev_now_update (loop)
601		760
602	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
605		764
606	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	767	the current time is a good idea.
609		768
610	See also "The special problem of time updates" in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
611		770
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
612	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
613		798
614	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
616	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
617		804
618	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
620		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
621	Please note that an explicit C<ev_unloop> is usually better than	813	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	814	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	816	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	817	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	818	beauty.
627		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	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	826	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	827	block your process in case there are no events and will return after one
631	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
632		830
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	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	832	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	833	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	834	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	835	user-registered callback will be called), and will return after one
638	iteration of the loop.	836	iteration of the loop.
639		837
640	This is useful if you are waiting for some external event in conjunction	838	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	839	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	840	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.	841	usually a better approach for this kind of thing.
644		842
645	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
646		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	856	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	867	- Queue all expired timers.
663	- Queue all expired periodics.	868	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	870	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- 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	872	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
672		881
673	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	883	anymore.
675		884
676	... queue jobs here, make sure they register event watchers as long	885	... 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..)	886	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
680		889
681	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
682		891
683	Can be used to make a call to C<ev_loop> return early (but only after it	892	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	893	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	894	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.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		896
688	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
689		898
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
691		901
692	=item ev_ref (loop)	902	=item ev_ref (loop)
693		903
694	=item ev_unref (loop)	904	=item ev_unref (loop)
695		905
696	Ref/unref can be used to add or remove a reference count on the event	906	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	907	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.	908	count is nonzero, C<ev_run> will not return on its own.
699		909
700	If you have a watcher you never unregister that should not keep C<ev_loop>	910	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	911	unregister, but that nevertheless should not keep C<ev_run> from
		912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	913	before stopping it.
703		914
704	As an example, libev itself uses this for its internal signal pipe: It is	915	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	916	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	917	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	918	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>	919	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,	920	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	921	before, respectively. Note also that libev might stop watchers itself
		922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		923	in the callback).
711		924
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	926	running when nothing else is active.
714		927
715	struct ev_signal exitsig;	928	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	931	ev_unref (loop);
719		932
720	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
721		934
722	ev_ref (loop);	935	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
744		957
745	By setting a higher I<io collect interval> you allow libev to spend more	958	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,	959	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	960	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	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		963	sleep time ensures that libev will not poll for I/O events more often then
		964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
750		966
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	969	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	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		972
757	Many (busy) programs can usually benefit by setting the I/O collect	973	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	974	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	975	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>,	976	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.	977	as this approaches the timing granularity of most systems. Note that if
		978	you do transactions with the outside world and you can't increase the
		979	parallelity, then this setting will limit your transaction rate (if you
		980	need to poll once per transaction and the I/O collect interval is 0.01,
		981	then you can't do more than 100 transactions per second).
762		982
763	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	984	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	985	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	986	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	987	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	988	they fire on, say, one-second boundaries only.
769		989
		990	Example: we only need 0.1s timeout granularity, and we wish not to poll
		991	more often than 100 times per second:
		992
		993	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		995
		996	=item ev_invoke_pending (loop)
		997
		998	This call will simply invoke all pending watchers while resetting their
		999	pending state. Normally, C<ev_run> does this automatically when required,
		1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1005
		1006	=item int ev_pending_count (loop)
		1007
		1008	Returns the number of pending watchers - zero indicates that no watchers
		1009	are pending.
		1010
		1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1012
		1013	This overrides the invoke pending functionality of the loop: Instead of
		1014	invoking all pending watchers when there are any, C<ev_run> will call
		1015	this callback instead. This is useful, for example, when you want to
		1016	invoke the actual watchers inside another context (another thread etc.).
		1017
		1018	If you want to reset the callback, use C<ev_invoke_pending> as new
		1019	callback.
		1020
		1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1022
		1023	Sometimes you want to share the same loop between multiple threads. This
		1024	can be done relatively simply by putting mutex_lock/unlock calls around
		1025	each call to a libev function.
		1026
		1027	However, C<ev_run> can run an indefinite time, so it is not feasible
		1028	to wait for it to return. One way around this is to wake up the event
		1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1030	I<release> and I<acquire> callbacks on the loop.
		1031
		1032	When set, then C<release> will be called just before the thread is
		1033	suspended waiting for new events, and C<acquire> is called just
		1034	afterwards.
		1035
		1036	Ideally, C<release> will just call your mutex_unlock function, and
		1037	C<acquire> will just call the mutex_lock function again.
		1038
		1039	While event loop modifications are allowed between invocations of
		1040	C<release> and C<acquire> (that's their only purpose after all), no
		1041	modifications done will affect the event loop, i.e. adding watchers will
		1042	have no effect on the set of file descriptors being watched, or the time
		1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1044	to take note of any changes you made.
		1045
		1046	In theory, threads executing C<ev_run> will be async-cancel safe between
		1047	invocations of C<release> and C<acquire>.
		1048
		1049	See also the locking example in the C<THREADS> section later in this
		1050	document.
		1051
		1052	=item ev_set_userdata (loop, void *data)
		1053
		1054	=item void *ev_userdata (loop)
		1055
		1056	Set and retrieve a single C<void *> associated with a loop. When
		1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1058	C<0>.
		1059
		1060	These two functions can be used to associate arbitrary data with a loop,
		1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1062	C<acquire> callbacks described above, but of course can be (ab-)used for
		1063	any other purpose as well.
		1064
770	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
771		1066
772	This function only does something when C<EV_VERIFY> support has been	1067	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	1068	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	1069	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	1070	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1071	error and call C<abort ()>.
777		1072
778	This can be used to catch bugs inside libev itself: under normal	1073	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1077	=back
783		1078
784		1079
785	=head1 ANATOMY OF A WATCHER	1080	=head1 ANATOMY OF A WATCHER
786		1081
		1082	In the following description, uppercase C<TYPE> in names stands for the
		1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1084	watchers and C<ev_io_start> for I/O watchers.
		1085
787	A watcher is a structure that you create and register to record your	1086	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	1087	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:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
790		1090
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1092	{
793	ev_io_stop (w);	1093	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
795	}	1095	}
796		1096
797	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
		1098
798	struct ev_io stdin_watcher;	1099	ev_io stdin_watcher;
		1100
799	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
		1104
802	ev_loop (loop, 0);	1105	ev_run (loop, 0);
803		1106
804	As you can see, you are responsible for allocating the memory for your	1107	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,	1108	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1109	stack).
807		1110
		1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1113
808	Each watcher structure must be initialised by a call to C<ev_init	1114	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	1115	*, 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	1116	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	1117	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1118	and/or writable).
813		1119
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1120	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	1121	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	1122	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
818		1124
819	To make the watcher actually watch out for events, you have to start it	1125	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	1126	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	1127	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1128	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1129
824	As long as your watcher is active (has been started but not stopped) you	1130	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	1131	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1132	reinitialise it or call its C<ev_TYPE_set> macro.
827		1133
828	Each and every callback receives the event loop pointer as first, the	1134	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	1135	registered watcher structure as second, and a bitset of received events as
830	third argument.	1136	third argument.
831		1137
…		…
840	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
841		1147
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1149	writable.
844		1150
845	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
846		1152
847	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
848		1154
849	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
850		1156
…		…
868		1174
869	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
870		1176
871	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
872		1178
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
874	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
876	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
877	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
879	C<ev_loop> from blocking).	1190	blocking).
880		1191
881	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
882		1193
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1195
885	=item C<EV_FORK>	1196	=item C<EV_FORK>
886		1197
887	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1199	C<ev_fork>).
889		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
		1204
890	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
891		1206
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
		1208
		1209	=item C<EV_CUSTOM>
		1210
		1211	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1212	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1213
894	=item C<EV_ERROR>	1214	=item C<EV_ERROR>
895		1215
896	An unspecified error has occurred, the watcher has been stopped. This might	1216	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1217	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	1218	ran out of memory, a file descriptor was found to be closed or any other
		1219	problem. Libev considers these application bugs.
		1220
899	problem. You best act on it by reporting the problem and somehow coping	1221	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1222	watcher being stopped. Note that well-written programs should not receive
		1223	an error ever, so when your watcher receives it, this usually indicates a
		1224	bug in your program.
901		1225
902	Libev will usually signal a few "dummy" events together with an error, for	1226	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	1227	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	1228	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	1229	the error from read() or write(). This will not work in multi-threaded
…		…
908		1232
909	=back	1233	=back
910		1234
911	=head2 GENERIC WATCHER FUNCTIONS	1235	=head2 GENERIC WATCHER FUNCTIONS
912		1236
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
916	=over 4	1237	=over 4
917		1238
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1239	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1240
920	This macro initialises the generic portion of a watcher. The contents	1241	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1246	which rolls both calls into one.
926		1247
927	You can reinitialise a watcher at any time as long as it has been stopped	1248	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.	1249	(or never started) and there are no pending events outstanding.
929		1250
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1251	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1252	int revents)>.
932		1253
933	Example: Initialise an C<ev_io> watcher in two steps.	1254	Example: Initialise an C<ev_io> watcher in two steps.
934		1255
935	ev_io w;	1256	ev_io w;
936	ev_init (&w, my_cb);	1257	ev_init (&w, my_cb);
937	ev_io_set (&w, STDIN_FILENO, EV_READ);	1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
938		1259
939	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
940		1261
941	This macro initialises the type-specific parts of a watcher. You need to	1262	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	1263	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	1264	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	1265	macro on a watcher that is active (it can be pending, however, which is a
…		…
957		1278
958	Example: Initialise and set an C<ev_io> watcher in one step.	1279	Example: Initialise and set an C<ev_io> watcher in one step.
959		1280
960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
961		1282
962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
963		1284
964	Starts (activates) the given watcher. Only active watchers will receive	1285	Starts (activates) the given watcher. Only active watchers will receive
965	events. If the watcher is already active nothing will happen.	1286	events. If the watcher is already active nothing will happen.
966		1287
967	Example: Start the C<ev_io> watcher that is being abused as example in this	1288	Example: Start the C<ev_io> watcher that is being abused as example in this
968	whole section.	1289	whole section.
969		1290
970	ev_io_start (EV_DEFAULT_UC, &w);	1291	ev_io_start (EV_DEFAULT_UC, &w);
971		1292
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
973		1294
974	Stops the given watcher again (if active) and clears the pending	1295	Stops the given watcher if active, and clears the pending status (whether
		1296	the watcher was active or not).
		1297
975	status. It is possible that stopped watchers are pending (for example,	1298	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1299	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1300	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1301	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1302	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1303
981	=item bool ev_is_active (ev_TYPE *watcher)	1304	=item bool ev_is_active (ev_TYPE *watcher)
982		1305
983	Returns a true value iff the watcher is active (i.e. it has been started	1306	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1307	and not yet been stopped). As long as a watcher is active you must not modify
…		…
995		1318
996	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
997		1320
998	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
999		1322
1000	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1001		1324
1002	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1003	(modulo threads).	1326	(modulo threads).
1004		1327
1005	=item ev_set_priority (ev_TYPE *watcher, priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
1006		1329
1007	=item int ev_priority (ev_TYPE *watcher)	1330	=item int ev_priority (ev_TYPE *watcher)
1008		1331
1009	Set and query the priority of the watcher. The priority is a small	1332	Set and query the priority of the watcher. The priority is a small
1010	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1011	(default: C<-2>). Pending watchers with higher priority will be invoked	1334	(default: C<-2>). Pending watchers with higher priority will be invoked
1012	before watchers with lower priority, but priority will not keep watchers	1335	before watchers with lower priority, but priority will not keep watchers
1013	from being executed (except for C<ev_idle> watchers).	1336	from being executed (except for C<ev_idle> watchers).
1014		1337
1015	This means that priorities are I<only> used for ordering callback
1016	invocation after new events have been received. This is useful, for
1017	example, to reduce latency after idling, or more often, to bind two
1018	watchers on the same event and make sure one is called first.
1019
1020	If you need to suppress invocation when higher priority events are pending	1338	If you need to suppress invocation when higher priority events are pending
1021	you need to look at C<ev_idle> watchers, which provide this functionality.	1339	you need to look at C<ev_idle> watchers, which provide this functionality.
1022		1340
1023	You I<must not> change the priority of a watcher as long as it is active or	1341	You I<must not> change the priority of a watcher as long as it is active or
1024	pending.	1342	pending.
1025		1343
		1344	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1345	fine, as long as you do not mind that the priority value you query might
		1346	or might not have been clamped to the valid range.
		1347
1026	The default priority used by watchers when no priority has been set is	1348	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1349	always C<0>, which is supposed to not be too high and not be too low :).
1028		1350
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1030	fine, as long as you do not mind that the priority value you query might	1352	priorities.
1031	or might not have been adjusted to be within valid range.
1032		1353
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1355
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1357	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1044	watcher isn't pending it does nothing and returns C<0>.	1365	watcher isn't pending it does nothing and returns C<0>.
1045		1366
1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1367	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1047	callback to be invoked, which can be accomplished with this function.	1368	callback to be invoked, which can be accomplished with this function.
1048		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
1049	=back	1384	=back
1050		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1051		1388
1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1053		1390
1054	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1055	and read at any time: libev will completely ignore it. This can be used	1392	active, pending and so on. In this section these states and the rules to
1056	to associate arbitrary data with your watcher. If you need more data and	1393	transition between them will be described in more detail - and while these
1057	don't want to allocate memory and store a pointer to it in that data	1394	rules might look complicated, they usually do "the right thing".
1058	member, you can also "subclass" the watcher type and provide your own
1059	data:
1060		1395
1061	struct my_io	1396	=over 4
		1397
		1398	=item initialiased
		1399
		1400	Before a watcher can be registered with the event loop it has to be
		1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1403
		1404	In this state it is simply some block of memory that is suitable for
		1405	use in an event loop. It can be moved around, freed, reused etc. at
		1406	will - as long as you either keep the memory contents intact, or call
		1407	C<ev_TYPE_init> again.
		1408
		1409	=item started/running/active
		1410
		1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
		1416
		1417	=item pending
		1418
		1419	If a watcher is active and libev determines that an event it is interested
		1420	in has occurred (such as a timer expiring), it will become pending. It will
		1421	stay in this pending state until either it is stopped or its callback is
		1422	about to be invoked, so it is not normally pending inside the watcher
		1423	callback.
		1424
		1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
		1431
		1432	It is also possible to feed an event on a watcher that is not active (e.g.
		1433	via C<ev_feed_event>), in which case it becomes pending without being
		1434	active.
		1435
		1436	=item stopped
		1437
		1438	A watcher can be stopped implicitly by libev (in which case it might still
		1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1440	latter will clear any pending state the watcher might be in, regardless
		1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
		1450
		1451	=head2 WATCHER PRIORITY MODELS
		1452
		1453	Many event loops support I<watcher priorities>, which are usually small
		1454	integers that influence the ordering of event callback invocation
		1455	between watchers in some way, all else being equal.
		1456
		1457	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1458	description for the more technical details such as the actual priority
		1459	range.
		1460
		1461	There are two common ways how these these priorities are being interpreted
		1462	by event loops:
		1463
		1464	In the more common lock-out model, higher priorities "lock out" invocation
		1465	of lower priority watchers, which means as long as higher priority
		1466	watchers receive events, lower priority watchers are not being invoked.
		1467
		1468	The less common only-for-ordering model uses priorities solely to order
		1469	callback invocation within a single event loop iteration: Higher priority
		1470	watchers are invoked before lower priority ones, but they all get invoked
		1471	before polling for new events.
		1472
		1473	Libev uses the second (only-for-ordering) model for all its watchers
		1474	except for idle watchers (which use the lock-out model).
		1475
		1476	The rationale behind this is that implementing the lock-out model for
		1477	watchers is not well supported by most kernel interfaces, and most event
		1478	libraries will just poll for the same events again and again as long as
		1479	their callbacks have not been executed, which is very inefficient in the
		1480	common case of one high-priority watcher locking out a mass of lower
		1481	priority ones.
		1482
		1483	Static (ordering) priorities are most useful when you have two or more
		1484	watchers handling the same resource: a typical usage example is having an
		1485	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1486	timeouts. Under load, data might be received while the program handles
		1487	other jobs, but since timers normally get invoked first, the timeout
		1488	handler will be executed before checking for data. In that case, giving
		1489	the timer a lower priority than the I/O watcher ensures that I/O will be
		1490	handled first even under adverse conditions (which is usually, but not
		1491	always, what you want).
		1492
		1493	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1494	will only be executed when no same or higher priority watchers have
		1495	received events, they can be used to implement the "lock-out" model when
		1496	required.
		1497
		1498	For example, to emulate how many other event libraries handle priorities,
		1499	you can associate an C<ev_idle> watcher to each such watcher, and in
		1500	the normal watcher callback, you just start the idle watcher. The real
		1501	processing is done in the idle watcher callback. This causes libev to
		1502	continuously poll and process kernel event data for the watcher, but when
		1503	the lock-out case is known to be rare (which in turn is rare :), this is
		1504	workable.
		1505
		1506	Usually, however, the lock-out model implemented that way will perform
		1507	miserably under the type of load it was designed to handle. In that case,
		1508	it might be preferable to stop the real watcher before starting the
		1509	idle watcher, so the kernel will not have to process the event in case
		1510	the actual processing will be delayed for considerable time.
		1511
		1512	Here is an example of an I/O watcher that should run at a strictly lower
		1513	priority than the default, and which should only process data when no
		1514	other events are pending:
		1515
		1516	ev_idle idle; // actual processing watcher
		1517	ev_io io; // actual event watcher
		1518
		1519	static void
		1520	io_cb (EV_P_ ev_io *w, int revents)
1062	{	1521	{
1063	struct ev_io io;	1522	// stop the I/O watcher, we received the event, but
1064	int otherfd;	1523	// are not yet ready to handle it.
1065	void *somedata;	1524	ev_io_stop (EV_A_ w);
1066	struct whatever *mostinteresting;	1525
		1526	// start the idle watcher to handle the actual event.
		1527	// it will not be executed as long as other watchers
		1528	// with the default priority are receiving events.
		1529	ev_idle_start (EV_A_ &idle);
1067	};	1530	}
1068		1531
1069	...	1532	static void
1070	struct my_io w;	1533	idle_cb (EV_P_ ev_idle *w, int revents)
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072
1073	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:
1075
1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
1077	{	1534	{
1078	struct my_io *w = (struct my_io *)w_;	1535	// actual processing
1079	...	1536	read (STDIN_FILENO, ...);
		1537
		1538	// have to start the I/O watcher again, as
		1539	// we have handled the event
		1540	ev_io_start (EV_P_ &io);
1080	}	1541	}
1081		1542
1082	More interesting and less C-conformant ways of casting your callback type	1543	// initialisation
1083	instead have been omitted.	1544	ev_idle_init (&idle, idle_cb);
		1545	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1546	ev_io_start (EV_DEFAULT_ &io);
1084		1547
1085	Another common scenario is to use some data structure with multiple	1548	In the "real" world, it might also be beneficial to start a timer, so that
1086	embedded watchers:	1549	low-priority connections can not be locked out forever under load. This
1087		1550	enables your program to keep a lower latency for important connections
1088	struct my_biggy	1551	during short periods of high load, while not completely locking out less
1089	{	1552	important ones.
1090	int some_data;
1091	ev_timer t1;
1092	ev_timer t2;
1093	}
1094
1095	In this case getting the pointer to C<my_biggy> is a bit more
1096	complicated: Either you store the address of your C<my_biggy> struct
1097	in the C<data> member of the watcher (for woozies), or you need to use
1098	some pointer arithmetic using C<offsetof> inside your watchers (for real
1099	programmers):
1100
1101	#include <stddef.h>
1102
1103	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
1105	{
1106	struct my_biggy big = (struct my_biggy *
1107	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}
1109
1110	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)
1112	{
1113	struct my_biggy big = (struct my_biggy *
1114	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}
1116		1553
1117		1554
1118	=head1 WATCHER TYPES	1555	=head1 WATCHER TYPES
1119		1556
1120	This section describes each watcher in detail, but will not repeat	1557	This section describes each watcher in detail, but will not repeat
…		…
1144	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1145	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1146	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1147	required if you know what you are doing).	1584	required if you know what you are doing).
1148		1585
1149	If you cannot use non-blocking mode, then force the use of a
1150	known-to-be-good backend (at the time of this writing, this includes only
1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1152
1153	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1154	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1156	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1157	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1158	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1159	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1160	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1161		1593
1162	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1163	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1164	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1165	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1166	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1167	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1168	indefinitely.	1600	indefinitely.
1169		1601
1170	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1171		1603
…		…
1199		1631
1200	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1201	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1202	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1203		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1204	=head3 The special problem of fork	1669	=head3 The special problem of fork
1205		1670
1206	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1207	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1208	it in the child.	1673	it in the child if you want to continue to use it in the child.
1209		1674
1210	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1211	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1213	C<EVBACKEND_POLL>.
1214		1678
1215	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1216		1680
1217	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1218	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1221		1685
1222	So when you encounter spurious, unexplained daemon exits, make sure you	1686	So when you encounter spurious, unexplained daemon exits, make sure you
1223	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1687	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1224	somewhere, as that would have given you a big clue).	1688	somewhere, as that would have given you a big clue).
1225		1689
		1690	=head3 The special problem of accept()ing when you can't
		1691
		1692	Many implementations of the POSIX C<accept> function (for example,
		1693	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1694	connection from the pending queue in all error cases.
		1695
		1696	For example, larger servers often run out of file descriptors (because
		1697	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1698	rejecting the connection, leading to libev signalling readiness on
		1699	the next iteration again (the connection still exists after all), and
		1700	typically causing the program to loop at 100% CPU usage.
		1701
		1702	Unfortunately, the set of errors that cause this issue differs between
		1703	operating systems, there is usually little the app can do to remedy the
		1704	situation, and no known thread-safe method of removing the connection to
		1705	cope with overload is known (to me).
		1706
		1707	One of the easiest ways to handle this situation is to just ignore it
		1708	- when the program encounters an overload, it will just loop until the
		1709	situation is over. While this is a form of busy waiting, no OS offers an
		1710	event-based way to handle this situation, so it's the best one can do.
		1711
		1712	A better way to handle the situation is to log any errors other than
		1713	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1714	messages, and continue as usual, which at least gives the user an idea of
		1715	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1716	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1717	usage.
		1718
		1719	If your program is single-threaded, then you could also keep a dummy file
		1720	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1721	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1722	close that fd, and create a new dummy fd. This will gracefully refuse
		1723	clients under typical overload conditions.
		1724
		1725	The last way to handle it is to simply log the error and C<exit>, as
		1726	is often done with C<malloc> failures, but this results in an easy
		1727	opportunity for a DoS attack.
1226		1728
1227	=head3 Watcher-Specific Functions	1729	=head3 Watcher-Specific Functions
1228		1730
1229	=over 4	1731	=over 4
1230		1732
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1753	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1754	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1755	attempt to read a whole line in the callback.
1254		1756
1255	static void	1757	static void
1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1758	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1257	{	1759	{
1258	ev_io_stop (loop, w);	1760	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1761	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1762	}
1261		1763
1262	...	1764	...
1263	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1766	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1767	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1268		1770
1269		1771
1270	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1271		1773
1272	Timer watchers are simple relative timers that generate an event after a	1774	Timer watchers are simple relative timers that generate an event after a
…		…
1277	year, it will still time out after (roughly) one hour. "Roughly" because	1779	year, it will still time out after (roughly) one hour. "Roughly" because
1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1279	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1280		1782
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1283	then order of execution is undefined.	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
		1787	iteration then the ones with earlier time-out values are invoked before
		1788	ones of the same priority with later time-out values (but this is no
		1789	longer true when a callback calls C<ev_run> recursively).
		1790
		1791	=head3 Be smart about timeouts
		1792
		1793	Many real-world problems involve some kind of timeout, usually for error
		1794	recovery. A typical example is an HTTP request - if the other side hangs,
		1795	you want to raise some error after a while.
		1796
		1797	What follows are some ways to handle this problem, from obvious and
		1798	inefficient to smart and efficient.
		1799
		1800	In the following, a 60 second activity timeout is assumed - a timeout that
		1801	gets reset to 60 seconds each time there is activity (e.g. each time some
		1802	data or other life sign was received).
		1803
		1804	=over 4
		1805
		1806	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1807
		1808	This is the most obvious, but not the most simple way: In the beginning,
		1809	start the watcher:
		1810
		1811	ev_timer_init (timer, callback, 60., 0.);
		1812	ev_timer_start (loop, timer);
		1813
		1814	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1815	and start it again:
		1816
		1817	ev_timer_stop (loop, timer);
		1818	ev_timer_set (timer, 60., 0.);
		1819	ev_timer_start (loop, timer);
		1820
		1821	This is relatively simple to implement, but means that each time there is
		1822	some activity, libev will first have to remove the timer from its internal
		1823	data structure and then add it again. Libev tries to be fast, but it's
		1824	still not a constant-time operation.
		1825
		1826	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1827
		1828	This is the easiest way, and involves using C<ev_timer_again> instead of
		1829	C<ev_timer_start>.
		1830
		1831	To implement this, configure an C<ev_timer> with a C<repeat> value
		1832	of C<60> and then call C<ev_timer_again> at start and each time you
		1833	successfully read or write some data. If you go into an idle state where
		1834	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1835	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1836
		1837	That means you can ignore both the C<ev_timer_start> function and the
		1838	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1839	member and C<ev_timer_again>.
		1840
		1841	At start:
		1842
		1843	ev_init (timer, callback);
		1844	timer->repeat = 60.;
		1845	ev_timer_again (loop, timer);
		1846
		1847	Each time there is some activity:
		1848
		1849	ev_timer_again (loop, timer);
		1850
		1851	It is even possible to change the time-out on the fly, regardless of
		1852	whether the watcher is active or not:
		1853
		1854	timer->repeat = 30.;
		1855	ev_timer_again (loop, timer);
		1856
		1857	This is slightly more efficient then stopping/starting the timer each time
		1858	you want to modify its timeout value, as libev does not have to completely
		1859	remove and re-insert the timer from/into its internal data structure.
		1860
		1861	It is, however, even simpler than the "obvious" way to do it.
		1862
		1863	=item 3. Let the timer time out, but then re-arm it as required.
		1864
		1865	This method is more tricky, but usually most efficient: Most timeouts are
		1866	relatively long compared to the intervals between other activity - in
		1867	our example, within 60 seconds, there are usually many I/O events with
		1868	associated activity resets.
		1869
		1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1871	but remember the time of last activity, and check for a real timeout only
		1872	within the callback:
		1873
		1874	ev_tstamp timeout = 60.;
		1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
		1877
		1878	static void
		1879	callback (EV_P_ ev_timer *w, int revents)
		1880	{
		1881	// calculate when the timeout would happen
		1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
		1883
		1884	// if negative, it means we the timeout already occurred
		1885	if (after < 0.)
		1886	{
		1887	// timeout occurred, take action
		1888	}
		1889	else
		1890	{
		1891	// callback was invoked, but there was some recent
		1892	// activity. simply restart the timer to time out
		1893	// after "after" seconds, which is the earliest time
		1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
		1896	ev_timer_start (EV_A_ w);
		1897	}
		1898	}
		1899
		1900	To summarise the callback: first calculate in how many seconds the
		1901	timeout will occur (by calculating the absolute time when it would occur,
		1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
		1903	(EV_A)> from that).
		1904
		1905	If this value is negative, then we are already past the timeout, i.e. we
		1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
		1914
		1915	This scheme causes more callback invocations (about one every 60 seconds
		1916	minus half the average time between activity), but virtually no calls to
		1917	libev to change the timeout.
		1918
		1919	To start the machinery, simply initialise the watcher and set
		1920	C<last_activity> to the current time (meaning there was some activity just
		1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
		1923
		1924	last_activity = ev_now (EV_A);
		1925	ev_init (&timer, callback);
		1926	callback (EV_A_ &timer, 0);
		1927
		1928	When there is some activity, simply store the current time in
		1929	C<last_activity>, no libev calls at all:
		1930
		1931	if (activity detected)
		1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
		1941
		1942	This technique is slightly more complex, but in most cases where the
		1943	time-out is unlikely to be triggered, much more efficient.
		1944
		1945	=item 4. Wee, just use a double-linked list for your timeouts.
		1946
		1947	If there is not one request, but many thousands (millions...), all
		1948	employing some kind of timeout with the same timeout value, then one can
		1949	do even better:
		1950
		1951	When starting the timeout, calculate the timeout value and put the timeout
		1952	at the I<end> of the list.
		1953
		1954	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1955	the list is expected to fire (for example, using the technique #3).
		1956
		1957	When there is some activity, remove the timer from the list, recalculate
		1958	the timeout, append it to the end of the list again, and make sure to
		1959	update the C<ev_timer> if it was taken from the beginning of the list.
		1960
		1961	This way, one can manage an unlimited number of timeouts in O(1) time for
		1962	starting, stopping and updating the timers, at the expense of a major
		1963	complication, and having to use a constant timeout. The constant timeout
		1964	ensures that the list stays sorted.
		1965
		1966	=back
		1967
		1968	So which method the best?
		1969
		1970	Method #2 is a simple no-brain-required solution that is adequate in most
		1971	situations. Method #3 requires a bit more thinking, but handles many cases
		1972	better, and isn't very complicated either. In most case, choosing either
		1973	one is fine, with #3 being better in typical situations.
		1974
		1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1976	rather complicated, but extremely efficient, something that really pays
		1977	off after the first million or so of active timers, i.e. it's usually
		1978	overkill :)
		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
1284		2016
1285	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1286		2018
1287	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1288	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1289	time only before and after C<ev_loop> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1291	lots of events in one iteration.	2023	lots of events in one iteration.
1292		2024
1293	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
1294	time. This is usually the right thing as this timestamp refers to the time	2026	time. This is usually the right thing as this timestamp refers to the time
…		…
1300		2032
1301	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1303	()>.	2035	()>.
1304		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
		2069
		2070	=head3 The special problems of suspended animation
		2071
		2072	When you leave the server world it is quite customary to hit machines that
		2073	can suspend/hibernate - what happens to the clocks during such a suspend?
		2074
		2075	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2076	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2077	to run until the system is suspended, but they will not advance while the
		2078	system is suspended. That means, on resume, it will be as if the program
		2079	was frozen for a few seconds, but the suspend time will not be counted
		2080	towards C<ev_timer> when a monotonic clock source is used. The real time
		2081	clock advanced as expected, but if it is used as sole clocksource, then a
		2082	long suspend would be detected as a time jump by libev, and timers would
		2083	be adjusted accordingly.
		2084
		2085	I would not be surprised to see different behaviour in different between
		2086	operating systems, OS versions or even different hardware.
		2087
		2088	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2089	time jump in the monotonic clocks and the realtime clock. If the program
		2090	is suspended for a very long time, and monotonic clock sources are in use,
		2091	then you can expect C<ev_timer>s to expire as the full suspension time
		2092	will be counted towards the timers. When no monotonic clock source is in
		2093	use, then libev will again assume a timejump and adjust accordingly.
		2094
		2095	It might be beneficial for this latter case to call C<ev_suspend>
		2096	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2097	deterministic behaviour in this case (you can do nothing against
		2098	C<SIGSTOP>).
		2099
1305	=head3 Watcher-Specific Functions and Data Members	2100	=head3 Watcher-Specific Functions and Data Members
1306		2101
1307	=over 4	2102	=over 4
1308		2103
1309	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2104	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1322	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1323	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1324		2119
1325	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1326		2121
1327	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1328	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1329		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1330	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1331		2132
1332	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1333		2135
1334	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1336		2138
1337	This sounds a bit complicated, but here is a useful and typical	2139	=back
1338	example: Imagine you have a TCP connection and you want a so-called idle
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346		2140
1347	That means you can ignore the C<after> value and C<ev_timer_start>	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:	2142	usage example.
1349		2143
1350	ev_timer_init (timer, callback, 0., 5.);	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1351	ev_timer_again (loop, timer);
1352	...
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358		2145
1359	This is more slightly efficient then stopping/starting the timer each time	2146	Returns the remaining time until a timer fires. If the timer is active,
1360	you want to modify its timeout value.	2147	then this time is relative to the current event loop time, otherwise it's
		2148	the timeout value currently configured.
1361		2149
1362	Note, however, that it is often even more efficient to remember the	2150	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1363	time of the last activity and let the timer time-out naturally. In the	2151	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1364	callback, you then check whether the time-out is real, or, if there was	2152	will return C<4>. When the timer expires and is restarted, it will return
1365	some activity, you reschedule the watcher to time-out in "last_activity +	2153	roughly C<7> (likely slightly less as callback invocation takes some time,
1366	timeout - ev_now ()" seconds.	2154	too), and so on.
1367		2155
1368	=item ev_tstamp repeat [read-write]	2156	=item ev_tstamp repeat [read-write]
1369		2157
1370	The current C<repeat> value. Will be used each time the watcher times out	2158	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	2159	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	2164	=head3 Examples
1377		2165
1378	Example: Create a timer that fires after 60 seconds.	2166	Example: Create a timer that fires after 60 seconds.
1379		2167
1380	static void	2168	static void
1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2169	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1382	{	2170	{
1383	.. one minute over, w is actually stopped right here	2171	.. one minute over, w is actually stopped right here
1384	}	2172	}
1385		2173
1386	struct ev_timer mytimer;	2174	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2175	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	2176	ev_timer_start (loop, &mytimer);
1389		2177
1390	Example: Create a timeout timer that times out after 10 seconds of	2178	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	2179	inactivity.
1392		2180
1393	static void	2181	static void
1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2182	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1395	{	2183	{
1396	.. ten seconds without any activity	2184	.. ten seconds without any activity
1397	}	2185	}
1398		2186
1399	struct ev_timer mytimer;	2187	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2188	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1403		2191
1404	// and in some piece of code that gets executed on any "activity":	2192	// and in some piece of code that gets executed on any "activity":
1405	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1406	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1407		2195
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	2197	=head2 C<ev_periodic> - to cron or not to cron?
1410		2198
1411	Periodic watchers are also timers of a kind, but they are very versatile	2199	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	2200	(and unfortunately a bit complex).
1413		2201
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2202	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	2203	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	2204	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2205	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	2206	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	2207	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		2208
		2209	You can tell a periodic watcher to trigger after some specific point
		2210	in time: for example, if you tell a periodic watcher to trigger "in 10
		2211	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2212	not a delay) and then reset your system clock to January of the previous
		2213	year, then it will take a year or more to trigger the event (unlike an
		2214	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2215	it, as it uses a relative timeout).
		2216
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	2217	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	2218	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	2219	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2220	those cannot react to time jumps.
1426		2221
1427	As with timers, the callback is guaranteed to be invoked only when the	2222	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	2223	point in time where it is supposed to trigger has passed. If multiple
1429	during the same loop iteration, then order of execution is undefined.	2224	timers become ready during the same loop iteration then the ones with
		2225	earlier time-out values are invoked before ones with later time-out values
		2226	(but this is no longer true when a callback calls C<ev_run> recursively).
1430		2227
1431	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1432		2229
1433	=over 4	2230	=over 4
1434		2231
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2232	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		2233
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2234	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		2235
1439	Lots of arguments, lets sort it out... There are basically three modes of	2236	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	2237	operation, and we will explain them from simplest to most complex:
1441		2238
1442	=over 4	2239	=over 4
1443		2240
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2241	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		2242
1446	In this configuration the watcher triggers an event after the wall clock	2243	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	2244	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2245	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	2246	will be stopped and invoked when the system clock reaches or surpasses
		2247	this point in time.
1450		2248
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2249	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		2250
1453	In this mode the watcher will always be scheduled to time out at the next	2251	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	2252	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	2253	negative) and then repeat, regardless of any time jumps. The C<offset>
		2254	argument is merely an offset into the C<interval> periods.
1456		2255
1457	This can be used to create timers that do not drift with respect to the	2256	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	2257	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	2258	hour, on the hour (with respect to UTC):
1460		2259
1461	ev_periodic_set (&periodic, 0., 3600., 0);	2260	ev_periodic_set (&periodic, 0., 3600., 0);
1462		2261
1463	This doesn't mean there will always be 3600 seconds in between triggers,	2262	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	2263	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	2264	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	2265	by 3600.
1467		2266
1468	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		2270
1472	For numerical stability it is preferable that the C<at> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
1473	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
1474	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
1475		2277
1476	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
1480		2282
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2283	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		2284
1483	In this mode the values for C<interval> and C<at> are both being	2285	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	2286	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	2287	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	2288	current time as second argument.
1487		2289
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2290	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	2291	or make ANY other event loop modifications whatsoever, unless explicitly
		2292	allowed by documentation here>.
1490		2293
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2294	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2295	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	2296	only event loop modification you are allowed to do).
1494		2297
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2298	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	2299	*w, ev_tstamp now)>, e.g.:
1497		2300
		2301	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2302	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	2303	{
1500	return now + 60.;	2304	return now + 60.;
1501	}	2305	}
1502		2306
1503	It must return the next time to trigger, based on the passed time value	2307	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	2327	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	2328	program when the crontabs have changed).
1525		2329
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	2330	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		2331
1528	When active, returns the absolute time that the watcher is supposed to	2332	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	2333	to trigger next. This is not the same as the C<offset> argument to
		2334	C<ev_periodic_set>, but indeed works even in interval and manual
		2335	rescheduling modes.
1530		2336
1531	=item ev_tstamp offset [read-write]	2337	=item ev_tstamp offset [read-write]
1532		2338
1533	When repeating, this contains the offset value, otherwise this is the	2339	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2340	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2341	although libev might modify this value for better numerical stability).
1535		2342
1536	Can be modified any time, but changes only take effect when the periodic	2343	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	2344	timer fires or C<ev_periodic_again> is being called.
1538		2345
1539	=item ev_tstamp interval [read-write]	2346	=item ev_tstamp interval [read-write]
1540		2347
1541	The current interval value. Can be modified any time, but changes only	2348	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	2349	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	2350	called.
1544		2351
1545	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2352	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1546		2353
1547	The current reschedule callback, or C<0>, if this functionality is	2354	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	2355	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	2356	the periodic timer fires or C<ev_periodic_again> is being called.
1550		2357
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
1558		2365
1559	static void	2366	static void
1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1561	{	2368	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	2369	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	2370	}
1564		2371
1565	struct ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2373	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	2374	ev_periodic_start (loop, &hourly_tick);
1568		2375
1569	Example: The same as above, but use a reschedule callback to do it:	2376	Example: The same as above, but use a reschedule callback to do it:
1570		2377
1571	#include <math.h>	2378	#include <math.h>
1572		2379
1573	static ev_tstamp	2380	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2381	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	2382	{
1576	return now + (3600. - fmod (now, 3600.));	2383	return now + (3600. - fmod (now, 3600.));
1577	}	2384	}
1578		2385
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2386	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		2387
1581	Example: Call a callback every hour, starting now:	2388	Example: Call a callback every hour, starting now:
1582		2389
1583	struct ev_periodic hourly_tick;	2390	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	2391	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	2392	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	2393	ev_periodic_start (loop, &hourly_tick);
1587		2394
1588		2395
1589	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
1590		2397
1591	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
1592	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
1593	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
1594	normal event processing, like any other event.	2401	normal event processing, like any other event.
1595		2402
1596	If you want signals asynchronously, just use C<sigaction> as you would	2403	If you want signals to be delivered truly asynchronously, just use
1597	do without libev and forget about sharing the signal. You can even use	2404	C<sigaction> as you would do without libev and forget about sharing
1598	C<ev_async> from a signal handler to synchronously wake up an event loop.	2405	the signal. You can even use C<ev_async> from a signal handler to
		2406	synchronously wake up an event loop.
1599		2407
1600	You can configure as many watchers as you like per signal. Only when the	2408	You can configure as many watchers as you like for the same signal, but
		2409	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2410	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2411	C<SIGINT> in both the default loop and another loop at the same time. At
		2412	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2413
1601	first watcher gets started will libev actually register a signal handler	2414	When the first watcher gets started will libev actually register something
1602	with the kernel (thus it coexists with your own signal handlers as long as	2415	with the kernel (thus it coexists with your own signal handlers as long as
1603	you don't register any with libev for the same signal). Similarly, when	2416	you don't register any with libev for the same signal).
1604	the last signal watcher for a signal is stopped, libev will reset the
1605	signal handler to SIG_DFL (regardless of what it was set to before).
1606		2417
1607	If possible and supported, libev will install its handlers with	2418	If possible and supported, libev will install its handlers with
1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2419	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1609	interrupted. If you have a problem with system calls getting interrupted by	2420	not be unduly interrupted. If you have a problem with system calls getting
1610	signals you can block all signals in an C<ev_check> watcher and unblock	2421	interrupted by signals you can block all signals in an C<ev_check> watcher
1611	them in an C<ev_prepare> watcher.	2422	and unblock them in an C<ev_prepare> watcher.
		2423
		2424	=head3 The special problem of inheritance over fork/execve/pthread_create
		2425
		2426	Both the signal mask (C<sigprocmask>) and the signal disposition
		2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2428	stopping it again), that is, libev might or might not block the signal,
		2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
		2431
		2432	While this does not matter for the signal disposition (libev never
		2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2434	C<execve>), this matters for the signal mask: many programs do not expect
		2435	certain signals to be blocked.
		2436
		2437	This means that before calling C<exec> (from the child) you should reset
		2438	the signal mask to whatever "default" you expect (all clear is a good
		2439	choice usually).
		2440
		2441	The simplest way to ensure that the signal mask is reset in the child is
		2442	to install a fork handler with C<pthread_atfork> that resets it. That will
		2443	catch fork calls done by libraries (such as the libc) as well.
		2444
		2445	In current versions of libev, the signal will not be blocked indefinitely
		2446	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2447	the window of opportunity for problems, it will not go away, as libev
		2448	I<has> to modify the signal mask, at least temporarily.
		2449
		2450	So I can't stress this enough: I<If you do not reset your signal mask when
		2451	you expect it to be empty, you have a race condition in your code>. This
		2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
1612		2467
1613	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
1614		2469
1615	=over 4	2470	=over 4
1616		2471
…		…
1630	=head3 Examples	2485	=head3 Examples
1631		2486
1632	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
1633		2488
1634	static void	2489	static void
1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1636	{	2491	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
1638	}	2493	}
1639		2494
1640	struct ev_signal signal_watcher;	2495	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
1643		2498
1644		2499
1645	=head2 C<ev_child> - watch out for process status changes	2500	=head2 C<ev_child> - watch out for process status changes
…		…
1648	some child status changes (most typically when a child of yours dies or	2503	some child status changes (most typically when a child of yours dies or
1649	exits). It is permissible to install a child watcher I<after> the child	2504	exits). It is permissible to install a child watcher I<after> the child
1650	has been forked (which implies it might have already exited), as long	2505	has been forked (which implies it might have already exited), as long
1651	as the event loop isn't entered (or is continued from a watcher), i.e.,	2506	as the event loop isn't entered (or is continued from a watcher), i.e.,
1652	forking and then immediately registering a watcher for the child is fine,	2507	forking and then immediately registering a watcher for the child is fine,
1653	but forking and registering a watcher a few event loop iterations later is	2508	but forking and registering a watcher a few event loop iterations later or
1654	not.	2509	in the next callback invocation is not.
1655		2510
1656	Only the default event loop is capable of handling signals, and therefore	2511	Only the default event loop is capable of handling signals, and therefore
1657	you can only register child watchers in the default event loop.	2512	you can only register child watchers in the default event loop.
1658		2513
		2514	Due to some design glitches inside libev, child watchers will always be
		2515	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2516	libev)
		2517
1659	=head3 Process Interaction	2518	=head3 Process Interaction
1660		2519
1661	Libev grabs C<SIGCHLD> as soon as the default event loop is	2520	Libev grabs C<SIGCHLD> as soon as the default event loop is
1662	initialised. This is necessary to guarantee proper behaviour even if	2521	initialised. This is necessary to guarantee proper behaviour even if the
1663	the first child watcher is started after the child exits. The occurrence	2522	first child watcher is started after the child exits. The occurrence
1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2523	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1665	synchronously as part of the event loop processing. Libev always reaps all	2524	synchronously as part of the event loop processing. Libev always reaps all
1666	children, even ones not watched.	2525	children, even ones not watched.
1667		2526
1668	=head3 Overriding the Built-In Processing	2527	=head3 Overriding the Built-In Processing
…		…
1678	=head3 Stopping the Child Watcher	2537	=head3 Stopping the Child Watcher
1679		2538
1680	Currently, the child watcher never gets stopped, even when the	2539	Currently, the child watcher never gets stopped, even when the
1681	child terminates, so normally one needs to stop the watcher in the	2540	child terminates, so normally one needs to stop the watcher in the
1682	callback. Future versions of libev might stop the watcher automatically	2541	callback. Future versions of libev might stop the watcher automatically
1683	when a child exit is detected.	2542	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2543	problem).
1684		2544
1685	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1686		2546
1687	=over 4	2547	=over 4
1688		2548
…		…
1720	its completion.	2580	its completion.
1721		2581
1722	ev_child cw;	2582	ev_child cw;
1723		2583
1724	static void	2584	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	2585	child_cb (EV_P_ ev_child *w, int revents)
1726	{	2586	{
1727	ev_child_stop (EV_A_ w);	2587	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2588	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	2589	}
1730		2590
…		…
1745		2605
1746		2606
1747	=head2 C<ev_stat> - did the file attributes just change?	2607	=head2 C<ev_stat> - did the file attributes just change?
1748		2608
1749	This watches a file system path for attribute changes. That is, it calls	2609	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	2610	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	2611	and sees if it changed compared to the last time, invoking the callback if
		2612	it did.
1752		2613
1753	The path does not need to exist: changing from "path exists" to "path does	2614	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	2615	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	2616	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	2617	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	2618	least one) and all the other fields of the stat buffer having unspecified
		2619	contents.
1758		2620
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	2621	The path I<must not> end in a slash or contain special components such as
		2622	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	2623	your working directory changes, then the behaviour is undefined.
1761		2624
1762	Since there is no standard kernel interface to do this, the portable	2625	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	2626	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	2627	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	2628	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	2629	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	2630	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	2631	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	2632	currently around C<0.1>, but that's usually overkill.
1770		2633
1771	This watcher type is not meant for massive numbers of stat watchers,	2634	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	2635	as even with OS-supported change notifications, this can be
1773	resource-intensive.	2636	resource-intensive.
1774		2637
1775	At the time of this writing, the only OS-specific interface implemented	2638	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	2639	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	2640	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	2641	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		2642
1780	=head3 ABI Issues (Largefile Support)	2643	=head3 ABI Issues (Largefile Support)
1781		2644
1782	Libev by default (unless the user overrides this) uses the default	2645	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	2646	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	2647	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	2648	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	2649	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	2650	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	2651	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	2652	most noticeably displayed with ev_stat and large file support.
1790		2653
1791	The solution for this is to lobby your distribution maker to make large	2654	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	2655	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	2656	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	2657	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2658	default compilation environment.
1796		2659
1797	=head3 Inotify and Kqueue	2660	=head3 Inotify and Kqueue
1798		2661
1799	When C<inotify (7)> support has been compiled into libev (generally only	2662	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2663	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2664	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2665	watcher is being started.
1803		2666
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2667	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2668	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2669	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2670	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2671	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2672	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2673	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2674	xfs are fully working) libev usually gets away without polling.
1809		2675
1810	There is no support for kqueue, as apparently it cannot be used to	2676	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2677	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2678	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2679	etc. is difficult.
1814		2680
		2681	=head3 C<stat ()> is a synchronous operation
		2682
		2683	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2684	the process. The exception are C<ev_stat> watchers - those call C<stat
		2685	()>, which is a synchronous operation.
		2686
		2687	For local paths, this usually doesn't matter: unless the system is very
		2688	busy or the intervals between stat's are large, a stat call will be fast,
		2689	as the path data is usually in memory already (except when starting the
		2690	watcher).
		2691
		2692	For networked file systems, calling C<stat ()> can block an indefinite
		2693	time due to network issues, and even under good conditions, a stat call
		2694	often takes multiple milliseconds.
		2695
		2696	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2697	paths, although this is fully supported by libev.
		2698
1815	=head3 The special problem of stat time resolution	2699	=head3 The special problem of stat time resolution
1816		2700
1817	The C<stat ()> system call only supports full-second resolution portably, and	2701	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2702	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2703	still only support whole seconds.
1820		2704
1821	That means that, if the time is the only thing that changes, you can	2705	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2706	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2707	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2708	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1963	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
1964	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
1965	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
1966	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
1967		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2864	example.
		2865
1968	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
1969		2867
1970	=over 4	2868	=over 4
1971		2869
1972	=item ev_idle_init (ev_signal *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
1973		2871
1974	Initialises and configures the idle watcher - it has no parameters of any	2872	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2874	believe me.
1977		2875
…		…
1981		2879
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2880	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
1984		2882
1985	static void	2883	static void
1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1987	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
1988	free (w);	2890	free (w);
		2891
1989	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
1991	}	2894	}
1992		2895
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2897	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2898	ev_idle_start (loop, idle_watcher);
1996		2899
1997		2900
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1999		2902
2000	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2001	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2002	afterwards.	2905	afterwards.
2003		2906
2004	You I<must not> call C<ev_loop> or similar functions that enter	2907	You I<must not> call C<ev_run> or similar functions that enter
2005	the current event loop from either C<ev_prepare> or C<ev_check>	2908	the current event loop from either C<ev_prepare> or C<ev_check>
2006	watchers. Other loops than the current one are fine, however. The	2909	watchers. Other loops than the current one are fine, however. The
2007	rationale behind this is that you do not need to check for recursion in	2910	rationale behind this is that you do not need to check for recursion in
2008	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2911	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2009	C<ev_check> so if you have one watcher of each kind they will always be	2912	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2033	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2034	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2035	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2036	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2037		2940
2038	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2039	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2040	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2041		2945
2042	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2043	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2044	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2045	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2046	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2047	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2048	others).	2952	others).
2049		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
		2973
2050	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2051		2975
2052	=over 4	2976	=over 4
2053		2977
2054	=item ev_prepare_init (ev_prepare *, callback)	2978	=item ev_prepare_init (ev_prepare *, callback)
…		…
2079		3003
2080	static ev_io iow [nfd];	3004	static ev_io iow [nfd];
2081	static ev_timer tw;	3005	static ev_timer tw;
2082		3006
2083	static void	3007	static void
2084	io_cb (ev_loop *loop, ev_io *w, int revents)	3008	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2085	{	3009	{
2086	}	3010	}
2087		3011
2088	// create io watchers for each fd and a timer before blocking	3012	// create io watchers for each fd and a timer before blocking
2089	static void	3013	static void
2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	3014	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2091	{	3015	{
2092	int timeout = 3600000;	3016	int timeout = 3600000;
2093	struct pollfd fds [nfd];	3017	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	3018	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3019	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2096		3020
2097	/* the callback is illegal, but won't be called as we stop during check */	3021	/* the callback is illegal, but won't be called as we stop during check */
2098	ev_timer_init (&tw, 0, timeout * 1e-3);	3022	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2099	ev_timer_start (loop, &tw);	3023	ev_timer_start (loop, &tw);
2100		3024
2101	// create one ev_io per pollfd	3025	// create one ev_io per pollfd
2102	for (int i = 0; i < nfd; ++i)	3026	for (int i = 0; i < nfd; ++i)
2103	{	3027	{
…		…
2110	}	3034	}
2111	}	3035	}
2112		3036
2113	// stop all watchers after blocking	3037	// stop all watchers after blocking
2114	static void	3038	static void
2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	3039	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2116	{	3040	{
2117	ev_timer_stop (loop, &tw);	3041	ev_timer_stop (loop, &tw);
2118		3042
2119	for (int i = 0; i < nfd; ++i)	3043	for (int i = 0; i < nfd; ++i)
2120	{	3044	{
…		…
2177		3101
2178	if (timeout >= 0)	3102	if (timeout >= 0)
2179	// create/start timer	3103	// create/start timer
2180		3104
2181	// poll	3105	// poll
2182	ev_loop (EV_A_ 0);	3106	ev_run (EV_A_ 0);
2183		3107
2184	// stop timer again	3108	// stop timer again
2185	if (timeout >= 0)	3109	if (timeout >= 0)
2186	ev_timer_stop (EV_A_ &to);	3110	ev_timer_stop (EV_A_ &to);
2187		3111
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	3140	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	3141	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	3142	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	3143	the rest in a second one, and embed the second one in the first.
2220		3144
2221	As long as the watcher is active, the callback will be invoked every time	3145	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	3146	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3147	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	3148	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	3149	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	3150	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		3151
2229	As long as the watcher is started it will automatically handle events. The	3152	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	3153	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		3154
2234	Also, there have not currently been made special provisions for forking:	3155	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3156	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	3157	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	3158	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		3159
2240	Unfortunately, not all backends are embeddable: only the ones returned by	3160	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3161	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	3162	portable one.
2243		3163
…		…
2269	if you do not want that, you need to temporarily stop the embed watcher).	3189	if you do not want that, you need to temporarily stop the embed watcher).
2270		3190
2271	=item ev_embed_sweep (loop, ev_embed *)	3191	=item ev_embed_sweep (loop, ev_embed *)
2272		3192
2273	Make a single, non-blocking sweep over the embedded loop. This works	3193	Make a single, non-blocking sweep over the embedded loop. This works
2274	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3194	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2275	appropriate way for embedded loops.	3195	appropriate way for embedded loops.
2276		3196
2277	=item struct ev_loop *other [read-only]	3197	=item struct ev_loop *other [read-only]
2278		3198
2279	The embedded event loop.	3199	The embedded event loop.
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3208	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	3209	used).
2290		3210
2291	struct ev_loop *loop_hi = ev_default_init (0);	3211	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	3212	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	3213	ev_embed embed;
2294		3214
2295	// see if there is a chance of getting one that works	3215	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	3216	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3217	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3218	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	3232	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3233	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		3234
2315	struct ev_loop *loop = ev_default_init (0);	3235	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	3236	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	3237	ev_embed embed;
2318		3238
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3239	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3240	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	3241	{
2322	ev_embed_init (&embed, 0, loop_socket);	3242	ev_embed_init (&embed, 0, loop_socket);
…		…
2337	event loop blocks next and before C<ev_check> watchers are being called,	3257	event loop blocks next and before C<ev_check> watchers are being called,
2338	and only in the child after the fork. If whoever good citizen calling	3258	and only in the child after the fork. If whoever good citizen calling
2339	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2340	handlers will be invoked, too, of course.	3260	handlers will be invoked, too, of course.
2341		3261
		3262	=head3 The special problem of life after fork - how is it possible?
		3263
		3264	Most uses of C<fork()> consist of forking, then some simple calls to set
		3265	up/change the process environment, followed by a call to C<exec()>. This
		3266	sequence should be handled by libev without any problems.
		3267
		3268	This changes when the application actually wants to do event handling
		3269	in the child, or both parent in child, in effect "continuing" after the
		3270	fork.
		3271
		3272	The default mode of operation (for libev, with application help to detect
		3273	forks) is to duplicate all the state in the child, as would be expected
		3274	when I<either> the parent I<or> the child process continues.
		3275
		3276	When both processes want to continue using libev, then this is usually the
		3277	wrong result. In that case, usually one process (typically the parent) is
		3278	supposed to continue with all watchers in place as before, while the other
		3279	process typically wants to start fresh, i.e. without any active watchers.
		3280
		3281	The cleanest and most efficient way to achieve that with libev is to
		3282	simply create a new event loop, which of course will be "empty", and
		3283	use that for new watchers. This has the advantage of not touching more
		3284	memory than necessary, and thus avoiding the copy-on-write, and the
		3285	disadvantage of having to use multiple event loops (which do not support
		3286	signal watchers).
		3287
		3288	When this is not possible, or you want to use the default loop for
		3289	other reasons, then in the process that wants to start "fresh", call
		3290	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3291	Destroying the default loop will "orphan" (not stop) all registered
		3292	watchers, so you have to be careful not to execute code that modifies
		3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
		3295
2342	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
2343		3297
2344	=over 4	3298	=over 4
2345		3299
2346	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
2347		3301
2348	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
2349	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2350	believe me.	3304	really.
2351		3305
2352	=back	3306	=back
2353		3307
2354		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
2355	=head2 C<ev_async> - how to wake up another event loop	3349	=head2 C<ev_async> - how to wake up an event loop
2356		3350
2357	In general, you cannot use an C<ev_loop> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
2358	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
2359	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
2360		3354
2361	Sometimes, however, you need to wake up another event loop you do not	3355	Sometimes, however, you need to wake up an event loop you do not control,
2362	control, for example because it belongs to another thread. This is what	3356	for example because it belongs to another thread. This is what C<ev_async>
2363	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3357	watchers do: as long as the C<ev_async> watcher is active, you can signal
2364	can signal it by calling C<ev_async_send>, which is thread- and signal	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
2365	safe.
2366		3359
2367	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
2368	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
2369	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
2370	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2371		3364	of "global async watchers" by using a watcher on an otherwise unused
2372	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2373	just the default loop.	3366	even without knowing which loop owns the signal.
2374		3367
2375	=head3 Queueing	3368	=head3 Queueing
2376		3369
2377	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
2378	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
2379	multiple-writer-single-reader queue that works in all cases and doesn't	3372	multiple-writer-single-reader queue that works in all cases and doesn't
2380	need elaborate support such as pthreads.	3373	need elaborate support such as pthreads or unportable memory access
		3374	semantics.
2381		3375
2382	That means that if you want to queue data, you have to provide your own	3376	That means that if you want to queue data, you have to provide your own
2383	queue. But at least I can tell you how to implement locking around your	3377	queue. But at least I can tell you how to implement locking around your
2384	queue:	3378	queue:
2385		3379
…		…
2463	=over 4	3457	=over 4
2464		3458
2465	=item ev_async_init (ev_async *, callback)	3459	=item ev_async_init (ev_async *, callback)
2466		3460
2467	Initialises and configures the async watcher - it has no parameters of any	3461	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3462	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	3463	trust me.
2470		3464
2471	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
2472		3466
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2477	section below on what exactly this means).	3473	embedding section below on what exactly this means).
2478		3474
2479	This call incurs the overhead of a system call only once per loop iteration,	3475	Note that, as with other watchers in libev, multiple events might get
2480	so while the overhead might be noticeable, it doesn't apply to repeated	3476	compressed into a single callback invocation (another way to look at
2481	calls to C<ev_async_send>.	3477	this is that C<ev_async> watchers are level-triggered: they are set on
		3478	C<ev_async_send>, reset when the event loop detects that).
		3479
		3480	This call incurs the overhead of at most one extra system call per event
		3481	loop iteration, if the event loop is blocked, and no syscall at all if
		3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
2482		3486
2483	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
2484		3488
2485	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3493	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	3494	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	3495	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	3496	quickly check whether invoking the loop might be a good idea.
2493		3497
2494	Not that this does I<not> check whether the watcher itself is pending, only	3498	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	3499	only whether it has been requested to make this watcher pending: there
		3500	is a time window between the event loop checking and resetting the async
		3501	notification, and the callback being invoked.
2496		3502
2497	=back	3503	=back
2498		3504
2499		3505
2500	=head1 OTHER FUNCTIONS	3506	=head1 OTHER FUNCTIONS
…		…
2517		3523
2518	If C<timeout> is less than 0, then no timeout watcher will be	3524	If C<timeout> is less than 0, then no timeout watcher will be
2519	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3525	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2520	repeat = 0) will be started. C<0> is a valid timeout.	3526	repeat = 0) will be started. C<0> is a valid timeout.
2521		3527
2522	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3528	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2523	passed an C<revents> set like normal event callbacks (a combination of	3529	passed an C<revents> set like normal event callbacks (a combination of
2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3530	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2525	value passed to C<ev_once>. Note that it is possible to receive I<both>	3531	value passed to C<ev_once>. Note that it is possible to receive I<both>
2526	a timeout and an io event at the same time - you probably should give io	3532	a timeout and an io event at the same time - you probably should give io
2527	events precedence.	3533	events precedence.
2528		3534
2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3535	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2530		3536
2531	static void stdin_ready (int revents, void *arg)	3537	static void stdin_ready (int revents, void *arg)
2532	{	3538	{
2533	if (revents & EV_READ)	3539	if (revents & EV_READ)
2534	/* stdin might have data for us, joy! */;	3540	/* stdin might have data for us, joy! */;
2535	else if (revents & EV_TIMEOUT)	3541	else if (revents & EV_TIMER)
2536	/* doh, nothing entered */;	3542	/* doh, nothing entered */;
2537	}	3543	}
2538		3544
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		3546
2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
2542
2543	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).
2546
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
2548		3548
2549	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	3550	the given events.
2551		3551
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
2553		3553
2554	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2555	loop!).	3555	which is async-safe.
2556		3556
2557	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, C<ev_break> will not work alone.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
2558		3908
2559		3909
2560	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
2561		3911
2562	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
2563	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
2564		3914
2565	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
2566		3921
2567	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
2568		3923
2569	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
2570	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
2576	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
2577	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
2578	is an ev_pri field.	3933	is an ev_pri field.
2579		3934
2580	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
2581	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
2582		3937
2583	=item * Other members are not supported.	3938	=item * Other members are not supported.
2584		3939
2585	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2586	to use the libev header file and library.	3941	to use the libev header file and library.
2587		3942
2588	=back	3943	=back
2589		3944
2590	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
2591		3979
2592	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2593	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
2594	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
2595		3983
…		…
2605	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
2606	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
2607	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
2608	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
2609		3997
2610	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
2611	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
2612	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
2613	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
2614	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
2615		4007
2616	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
2617		4009
2618	=over 4	4010	=over 4
2619		4011
…		…
2629	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2630		4022
2631	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2632	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2633	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2634	defines by many implementations.	4026	defined by many implementations.
2635		4027
2636	All of those classes have these methods:	4028	All of those classes have these methods:
2637		4029
2638	=over 4	4030	=over 4
2639		4031
2640	=item ev::TYPE::TYPE ()	4032	=item ev::TYPE::TYPE ()
2641		4033
2642	=item ev::TYPE::TYPE (struct ev_loop *)	4034	=item ev::TYPE::TYPE (loop)
2643		4035
2644	=item ev::TYPE::~TYPE	4036	=item ev::TYPE::~TYPE
2645		4037
2646	The constructor (optionally) takes an event loop to associate the watcher	4038	The constructor (optionally) takes an event loop to associate the watcher
2647	with. If it is omitted, it will use C<EV_DEFAULT>.	4039	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2679		4071
2680	myclass obj;	4072	myclass obj;
2681	ev::io iow;	4073	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	4074	iow.set <myclass, &myclass::io_cb> (&obj);
2683		4075
		4076	=item w->set (object *)
		4077
		4078	This is a variation of a method callback - leaving out the method to call
		4079	will default the method to C<operator ()>, which makes it possible to use
		4080	functor objects without having to manually specify the C<operator ()> all
		4081	the time. Incidentally, you can then also leave out the template argument
		4082	list.
		4083
		4084	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4085	int revents)>.
		4086
		4087	See the method-C<set> above for more details.
		4088
		4089	Example: use a functor object as callback.
		4090
		4091	struct myfunctor
		4092	{
		4093	void operator() (ev::io &w, int revents)
		4094	{
		4095	...
		4096	}
		4097	}
		4098
		4099	myfunctor f;
		4100
		4101	ev::io w;
		4102	w.set (&f);
		4103
2684	=item w->set<function> (void *data = 0)	4104	=item w->set<function> (void *data = 0)
2685		4105
2686	Also sets a callback, but uses a static method or plain function as	4106	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	4107	callback. The optional C<data> argument will be stored in the watcher's
2688	C<data> member and is free for you to use.	4108	C<data> member and is free for you to use.
…		…
2694	Example: Use a plain function as callback.	4114	Example: Use a plain function as callback.
2695		4115
2696	static void io_cb (ev::io &w, int revents) { }	4116	static void io_cb (ev::io &w, int revents) { }
2697	iow.set <io_cb> ();	4117	iow.set <io_cb> ();
2698		4118
2699	=item w->set (struct ev_loop *)	4119	=item w->set (loop)
2700		4120
2701	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
2702	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
2703		4123
2704	=item w->set ([arguments])	4124	=item w->set ([arguments])
2705		4125
2706	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4126	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2707	called at least once. Unlike the C counterpart, an active watcher gets	4127	method or a suitable start method must be called at least once. Unlike the
2708	automatically stopped and restarted when reconfiguring it with this	4128	C counterpart, an active watcher gets automatically stopped and restarted
2709	method.	4129	when reconfiguring it with this method.
2710		4130
2711	=item w->start ()	4131	=item w->start ()
2712		4132
2713	Starts the watcher. Note that there is no C<loop> argument, as the	4133	Starts the watcher. Note that there is no C<loop> argument, as the
2714	constructor already stores the event loop.	4134	constructor already stores the event loop.
2715		4135
		4136	=item w->start ([arguments])
		4137
		4138	Instead of calling C<set> and C<start> methods separately, it is often
		4139	convenient to wrap them in one call. Uses the same type of arguments as
		4140	the configure C<set> method of the watcher.
		4141
2716	=item w->stop ()	4142	=item w->stop ()
2717		4143
2718	Stops the watcher if it is active. Again, no C<loop> argument.	4144	Stops the watcher if it is active. Again, no C<loop> argument.
2719		4145
2720	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4146	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2732		4158
2733	=back	4159	=back
2734		4160
2735	=back	4161	=back
2736		4162
2737	Example: Define a class with an IO and idle watcher, start one of them in	4163	Example: Define a class with two I/O and idle watchers, start the I/O
2738	the constructor.	4164	watchers in the constructor.
2739		4165
2740	class myclass	4166	class myclass
2741	{	4167	{
2742	ev::io io ; void io_cb (ev::io &w, int revents);	4168	ev::io io ; void io_cb (ev::io &w, int revents);
		4169	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4170	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2744		4171
2745	myclass (int fd)	4172	myclass (int fd)
2746	{	4173	{
2747	io .set <myclass, &myclass::io_cb > (this);	4174	io .set <myclass, &myclass::io_cb > (this);
		4175	io2 .set <myclass, &myclass::io2_cb > (this);
2748	idle.set <myclass, &myclass::idle_cb> (this);	4176	idle.set <myclass, &myclass::idle_cb> (this);
2749		4177
2750	io.start (fd, ev::READ);	4178	io.set (fd, ev::WRITE); // configure the watcher
		4179	io.start (); // start it whenever convenient
		4180
		4181	io2.start (fd, ev::READ); // set + start in one call
2751	}	4182	}
2752	};	4183	};
2753		4184
2754		4185
2755	=head1 OTHER LANGUAGE BINDINGS	4186	=head1 OTHER LANGUAGE BINDINGS
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	4205	L<http://software.schmorp.de/pkg/EV>.
2775		4206
2776	=item Python	4207	=item Python
2777		4208
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4209	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	4210	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		4211
2785	=item Ruby	4212	=item Ruby
2786		4213
2787	Tony Arcieri has written a ruby extension that offers access to a subset	4214	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	4215	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	4216	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	4217	L<http://rev.rubyforge.org/>.
2791		4218
		4219	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4220	makes rev work even on mingw.
		4221
		4222	=item Haskell
		4223
		4224	A haskell binding to libev is available at
		4225	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4226
2792	=item D	4227	=item D
2793		4228
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4229	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4230	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4231
		4232	=item Ocaml
		4233
		4234	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4235	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4236
		4237	=item Lua
		4238
		4239	Brian Maher has written a partial interface to libev for lua (at the
		4240	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4241	L<http://github.com/brimworks/lua-ev>.
		4242
		4243	=item Javascript
		4244
		4245	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4246
		4247	=item Others
		4248
		4249	There are others, and I stopped counting.
2796		4250
2797	=back	4251	=back
2798		4252
2799		4253
2800	=head1 MACRO MAGIC	4254	=head1 MACRO MAGIC
…		…
2814	loop argument"). The C<EV_A> form is used when this is the sole argument,	4268	loop argument"). The C<EV_A> form is used when this is the sole argument,
2815	C<EV_A_> is used when other arguments are following. Example:	4269	C<EV_A_> is used when other arguments are following. Example:
2816		4270
2817	ev_unref (EV_A);	4271	ev_unref (EV_A);
2818	ev_timer_add (EV_A_ watcher);	4272	ev_timer_add (EV_A_ watcher);
2819	ev_loop (EV_A_ 0);	4273	ev_run (EV_A_ 0);
2820		4274
2821	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4275	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2822	which is often provided by the following macro.	4276	which is often provided by the following macro.
2823		4277
2824	=item C<EV_P>, C<EV_P_>	4278	=item C<EV_P>, C<EV_P_>
…		…
2837	suitable for use with C<EV_A>.	4291	suitable for use with C<EV_A>.
2838		4292
2839	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4293	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2840		4294
2841	Similar to the other two macros, this gives you the value of the default	4295	Similar to the other two macros, this gives you the value of the default
2842	loop, if multiple loops are supported ("ev loop default").	4296	loop, if multiple loops are supported ("ev loop default"). The default loop
		4297	will be initialised if it isn't already initialised.
		4298
		4299	For non-multiplicity builds, these macros do nothing, so you always have
		4300	to initialise the loop somewhere.
2843		4301
2844	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4302	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2845		4303
2846	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4304	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2847	default loop has been initialised (C<UC> == unchecked). Their behaviour	4305	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2864	}	4322	}
2865		4323
2866	ev_check check;	4324	ev_check check;
2867	ev_check_init (&check, check_cb);	4325	ev_check_init (&check, check_cb);
2868	ev_check_start (EV_DEFAULT_ &check);	4326	ev_check_start (EV_DEFAULT_ &check);
2869	ev_loop (EV_DEFAULT_ 0);	4327	ev_run (EV_DEFAULT_ 0);
2870		4328
2871	=head1 EMBEDDING	4329	=head1 EMBEDDING
2872		4330
2873	Libev can (and often is) directly embedded into host	4331	Libev can (and often is) directly embedded into host
2874	applications. Examples of applications that embed it include the Deliantra	4332	applications. Examples of applications that embed it include the Deliantra
…		…
2901		4359
2902	#define EV_STANDALONE 1	4360	#define EV_STANDALONE 1
2903	#include "ev.h"	4361	#include "ev.h"
2904		4362
2905	Both header files and implementation files can be compiled with a C++	4363	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	4364	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	4365	as a bug).
2908		4366
2909	You need the following files in your source tree, or in a directory	4367	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	4368	in your include path (e.g. in libev/ when using -Ilibev):
2911		4369
…		…
2954	libev.m4	4412	libev.m4
2955		4413
2956	=head2 PREPROCESSOR SYMBOLS/MACROS	4414	=head2 PREPROCESSOR SYMBOLS/MACROS
2957		4415
2958	Libev can be configured via a variety of preprocessor symbols you have to	4416	Libev can be configured via a variety of preprocessor symbols you have to
2959	define before including any of its files. The default in the absence of	4417	define before including (or compiling) any of its files. The default in
2960	autoconf is documented for every option.	4418	the absence of autoconf is documented for every option.
		4419
		4420	Symbols marked with "(h)" do not change the ABI, and can have different
		4421	values when compiling libev vs. including F<ev.h>, so it is permissible
		4422	to redefine them before including F<ev.h> without breaking compatibility
		4423	to a compiled library. All other symbols change the ABI, which means all
		4424	users of libev and the libev code itself must be compiled with compatible
		4425	settings.
2961		4426
2962	=over 4	4427	=over 4
2963		4428
		4429	=item EV_COMPAT3 (h)
		4430
		4431	Backwards compatibility is a major concern for libev. This is why this
		4432	release of libev comes with wrappers for the functions and symbols that
		4433	have been renamed between libev version 3 and 4.
		4434
		4435	You can disable these wrappers (to test compatibility with future
		4436	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4437	sources. This has the additional advantage that you can drop the C<struct>
		4438	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4439	typedef in that case.
		4440
		4441	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4442	and in some even more future version the compatibility code will be
		4443	removed completely.
		4444
2964	=item EV_STANDALONE	4445	=item EV_STANDALONE (h)
2965		4446
2966	Must always be C<1> if you do not use autoconf configuration, which	4447	Must always be C<1> if you do not use autoconf configuration, which
2967	keeps libev from including F<config.h>, and it also defines dummy	4448	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	4449	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	4450	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	4451	F<event.h> that are not directly supported by the libev core alone.
2971		4452
		4453	In standalone mode, libev will still try to automatically deduce the
		4454	configuration, but has to be more conservative.
		4455
		4456	=item EV_USE_FLOOR
		4457
		4458	If defined to be C<1>, libev will use the C<floor ()> function for its
		4459	periodic reschedule calculations, otherwise libev will fall back on a
		4460	portable (slower) implementation. If you enable this, you usually have to
		4461	link against libm or something equivalent. Enabling this when the C<floor>
		4462	function is not available will fail, so the safe default is to not enable
		4463	this.
		4464
2972	=item EV_USE_MONOTONIC	4465	=item EV_USE_MONOTONIC
2973		4466
2974	If defined to be C<1>, libev will try to detect the availability of the	4467	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	4468	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	4469	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	4470	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	4471	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	4472	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	4473	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		4474
2982	=item EV_USE_REALTIME	4475	=item EV_USE_REALTIME
2983		4476
2984	If defined to be C<1>, libev will try to detect the availability of the	4477	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	4478	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	4479	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4480	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4481	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4482	correctness. See the note about libraries in the description of
		4483	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4484	C<EV_USE_CLOCK_SYSCALL>.
		4485
		4486	=item EV_USE_CLOCK_SYSCALL
		4487
		4488	If defined to be C<1>, libev will try to use a direct syscall instead
		4489	of calling the system-provided C<clock_gettime> function. This option
		4490	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4491	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4492	programs needlessly. Using a direct syscall is slightly slower (in
		4493	theory), because no optimised vdso implementation can be used, but avoids
		4494	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4495	higher, as it simplifies linking (no need for C<-lrt>).
2990		4496
2991	=item EV_USE_NANOSLEEP	4497	=item EV_USE_NANOSLEEP
2992		4498
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4499	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	4500	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		4516
3011	=item EV_SELECT_USE_FD_SET	4517	=item EV_SELECT_USE_FD_SET
3012		4518
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	4519	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	4520	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4521	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	4522	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	4523	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4524	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	4525	configures the maximum size of the C<fd_set>.
3020		4526
3021	=item EV_SELECT_IS_WINSOCKET	4527	=item EV_SELECT_IS_WINSOCKET
3022		4528
3023	When defined to C<1>, the select backend will assume that	4529	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	4530	select/socket/connect etc. don't understand file descriptors but
…		…
3026	be used is the winsock select). This means that it will call	4532	be used is the winsock select). This means that it will call
3027	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4533	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3028	it is assumed that all these functions actually work on fds, even	4534	it is assumed that all these functions actually work on fds, even
3029	on win32. Should not be defined on non-win32 platforms.	4535	on win32. Should not be defined on non-win32 platforms.
3030		4536
3031	=item EV_FD_TO_WIN32_HANDLE	4537	=item EV_FD_TO_WIN32_HANDLE(fd)
3032		4538
3033	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4539	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3034	file descriptors to socket handles. When not defining this symbol (the	4540	file descriptors to socket handles. When not defining this symbol (the
3035	default), then libev will call C<_get_osfhandle>, which is usually	4541	default), then libev will call C<_get_osfhandle>, which is usually
3036	correct. In some cases, programs use their own file descriptor management,	4542	correct. In some cases, programs use their own file descriptor management,
3037	in which case they can provide this function to map fds to socket handles.	4543	in which case they can provide this function to map fds to socket handles.
		4544
		4545	=item EV_WIN32_HANDLE_TO_FD(handle)
		4546
		4547	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4548	using the standard C<_open_osfhandle> function. For programs implementing
		4549	their own fd to handle mapping, overwriting this function makes it easier
		4550	to do so. This can be done by defining this macro to an appropriate value.
		4551
		4552	=item EV_WIN32_CLOSE_FD(fd)
		4553
		4554	If programs implement their own fd to handle mapping on win32, then this
		4555	macro can be used to override the C<close> function, useful to unregister
		4556	file descriptors again. Note that the replacement function has to close
		4557	the underlying OS handle.
3038		4558
3039	=item EV_USE_POLL	4559	=item EV_USE_POLL
3040		4560
3041	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4561	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3042	backend. Otherwise it will be enabled on non-win32 platforms. It	4562	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3078	If defined to be C<1>, libev will compile in support for the Linux inotify	4598	If defined to be C<1>, libev will compile in support for the Linux inotify
3079	interface to speed up C<ev_stat> watchers. Its actual availability will	4599	interface to speed up C<ev_stat> watchers. Its actual availability will
3080	be detected at runtime. If undefined, it will be enabled if the headers	4600	be detected at runtime. If undefined, it will be enabled if the headers
3081	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4601	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3082		4602
		4603	=item EV_NO_SMP
		4604
		4605	If defined to be C<1>, libev will assume that memory is always coherent
		4606	between threads, that is, threads can be used, but threads never run on
		4607	different cpus (or different cpu cores). This reduces dependencies
		4608	and makes libev faster.
		4609
		4610	=item EV_NO_THREADS
		4611
		4612	If defined to be C<1>, libev will assume that it will never be called
		4613	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4614	above. This reduces dependencies and makes libev faster.
		4615
3083	=item EV_ATOMIC_T	4616	=item EV_ATOMIC_T
3084		4617
3085	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4618	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3086	access is atomic with respect to other threads or signal contexts. No such	4619	access is atomic and serialised with respect to other threads or signal
3087	type is easily found in the C language, so you can provide your own type	4620	contexts. No such type is easily found in the C language, so you can
3088	that you know is safe for your purposes. It is used both for signal handler "locking"	4621	provide your own type that you know is safe for your purposes. It is used
3089	as well as for signal and thread safety in C<ev_async> watchers.	4622	both for signal handler "locking" as well as for signal and thread safety
		4623	in C<ev_async> watchers.
3090		4624
3091	In the absence of this define, libev will use C<sig_atomic_t volatile>	4625	In the absence of this define, libev will use C<sig_atomic_t volatile>
3092	(from F<signal.h>), which is usually good enough on most platforms.	4626	(from F<signal.h>), which is usually good enough on most platforms,
		4627	although strictly speaking using a type that also implies a memory fence
		4628	is required.
3093		4629
3094	=item EV_H	4630	=item EV_H (h)
3095		4631
3096	The name of the F<ev.h> header file used to include it. The default if	4632	The name of the F<ev.h> header file used to include it. The default if
3097	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4633	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3098	used to virtually rename the F<ev.h> header file in case of conflicts.	4634	used to virtually rename the F<ev.h> header file in case of conflicts.
3099		4635
3100	=item EV_CONFIG_H	4636	=item EV_CONFIG_H (h)
3101		4637
3102	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4638	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3103	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4639	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3104	C<EV_H>, above.	4640	C<EV_H>, above.
3105		4641
3106	=item EV_EVENT_H	4642	=item EV_EVENT_H (h)
3107		4643
3108	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4644	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3109	of how the F<event.h> header can be found, the default is C<"event.h">.	4645	of how the F<event.h> header can be found, the default is C<"event.h">.
3110		4646
3111	=item EV_PROTOTYPES	4647	=item EV_PROTOTYPES (h)
3112		4648
3113	If defined to be C<0>, then F<ev.h> will not define any function	4649	If defined to be C<0>, then F<ev.h> will not define any function
3114	prototypes, but still define all the structs and other symbols. This is	4650	prototypes, but still define all the structs and other symbols. This is
3115	occasionally useful if you want to provide your own wrapper functions	4651	occasionally useful if you want to provide your own wrapper functions
3116	around libev functions.	4652	around libev functions.
…		…
3121	will have the C<struct ev_loop *> as first argument, and you can create	4657	will have the C<struct ev_loop *> as first argument, and you can create
3122	additional independent event loops. Otherwise there will be no support	4658	additional independent event loops. Otherwise there will be no support
3123	for multiple event loops and there is no first event loop pointer	4659	for multiple event loops and there is no first event loop pointer
3124	argument. Instead, all functions act on the single default loop.	4660	argument. Instead, all functions act on the single default loop.
3125		4661
		4662	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4663	default loop when multiplicity is switched off - you always have to
		4664	initialise the loop manually in this case.
		4665
3126	=item EV_MINPRI	4666	=item EV_MINPRI
3127		4667
3128	=item EV_MAXPRI	4668	=item EV_MAXPRI
3129		4669
3130	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4670	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3138	fine.	4678	fine.
3139		4679
3140	If your embedding application does not need any priorities, defining these	4680	If your embedding application does not need any priorities, defining these
3141	both to C<0> will save some memory and CPU.	4681	both to C<0> will save some memory and CPU.
3142		4682
3143	=item EV_PERIODIC_ENABLE	4683	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4684	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4685	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3144		4686
3145	If undefined or defined to be C<1>, then periodic timers are supported. If	4687	If undefined or defined to be C<1> (and the platform supports it), then
3146	defined to be C<0>, then they are not. Disabling them saves a few kB of	4688	the respective watcher type is supported. If defined to be C<0>, then it
3147	code.	4689	is not. Disabling watcher types mainly saves code size.
3148		4690
3149	=item EV_IDLE_ENABLE	4691	=item EV_FEATURES
3150
3151	If undefined or defined to be C<1>, then idle watchers are supported. If
3152	defined to be C<0>, then they are not. Disabling them saves a few kB of
3153	code.
3154
3155	=item EV_EMBED_ENABLE
3156
3157	If undefined or defined to be C<1>, then embed watchers are supported. If
3158	defined to be C<0>, then they are not. Embed watchers rely on most other
3159	watcher types, which therefore must not be disabled.
3160
3161	=item EV_STAT_ENABLE
3162
3163	If undefined or defined to be C<1>, then stat watchers are supported. If
3164	defined to be C<0>, then they are not.
3165
3166	=item EV_FORK_ENABLE
3167
3168	If undefined or defined to be C<1>, then fork watchers are supported. If
3169	defined to be C<0>, then they are not.
3170
3171	=item EV_ASYNC_ENABLE
3172
3173	If undefined or defined to be C<1>, then async watchers are supported. If
3174	defined to be C<0>, then they are not.
3175
3176	=item EV_MINIMAL
3177		4692
3178	If you need to shave off some kilobytes of code at the expense of some	4693	If you need to shave off some kilobytes of code at the expense of some
3179	speed, define this symbol to C<1>. Currently this is used to override some	4694	speed (but with the full API), you can define this symbol to request
3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4695	certain subsets of functionality. The default is to enable all features
3181	much smaller 2-heap for timer management over the default 4-heap.	4696	that can be enabled on the platform.
		4697
		4698	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4699	with some broad features you want) and then selectively re-enable
		4700	additional parts you want, for example if you want everything minimal,
		4701	but multiple event loop support, async and child watchers and the poll
		4702	backend, use this:
		4703
		4704	#define EV_FEATURES 0
		4705	#define EV_MULTIPLICITY 1
		4706	#define EV_USE_POLL 1
		4707	#define EV_CHILD_ENABLE 1
		4708	#define EV_ASYNC_ENABLE 1
		4709
		4710	The actual value is a bitset, it can be a combination of the following
		4711	values (by default, all of these are enabled):
		4712
		4713	=over 4
		4714
		4715	=item C<1> - faster/larger code
		4716
		4717	Use larger code to speed up some operations.
		4718
		4719	Currently this is used to override some inlining decisions (enlarging the
		4720	code size by roughly 30% on amd64).
		4721
		4722	When optimising for size, use of compiler flags such as C<-Os> with
		4723	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4724	assertions.
		4725
		4726	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4727	(e.g. gcc with C<-Os>).
		4728
		4729	=item C<2> - faster/larger data structures
		4730
		4731	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4732	hash table sizes and so on. This will usually further increase code size
		4733	and can additionally have an effect on the size of data structures at
		4734	runtime.
		4735
		4736	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4737	(e.g. gcc with C<-Os>).
		4738
		4739	=item C<4> - full API configuration
		4740
		4741	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4742	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4743
		4744	=item C<8> - full API
		4745
		4746	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4747	details on which parts of the API are still available without this
		4748	feature, and do not complain if this subset changes over time.
		4749
		4750	=item C<16> - enable all optional watcher types
		4751
		4752	Enables all optional watcher types. If you want to selectively enable
		4753	only some watcher types other than I/O and timers (e.g. prepare,
		4754	embed, async, child...) you can enable them manually by defining
		4755	C<EV_watchertype_ENABLE> to C<1> instead.
		4756
		4757	=item C<32> - enable all backends
		4758
		4759	This enables all backends - without this feature, you need to enable at
		4760	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4761
		4762	=item C<64> - enable OS-specific "helper" APIs
		4763
		4764	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4765	default.
		4766
		4767	=back
		4768
		4769	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4770	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4771	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4772	watchers, timers and monotonic clock support.
		4773
		4774	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4775	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4776	your program might be left out as well - a binary starting a timer and an
		4777	I/O watcher then might come out at only 5Kb.
		4778
		4779	=item EV_API_STATIC
		4780
		4781	If this symbol is defined (by default it is not), then all identifiers
		4782	will have static linkage. This means that libev will not export any
		4783	identifiers, and you cannot link against libev anymore. This can be useful
		4784	when you embed libev, only want to use libev functions in a single file,
		4785	and do not want its identifiers to be visible.
		4786
		4787	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4788	wants to use libev.
		4789
		4790	This option only works when libev is compiled with a C compiler, as C++
		4791	doesn't support the required declaration syntax.
		4792
		4793	=item EV_AVOID_STDIO
		4794
		4795	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4796	functions (printf, scanf, perror etc.). This will increase the code size
		4797	somewhat, but if your program doesn't otherwise depend on stdio and your
		4798	libc allows it, this avoids linking in the stdio library which is quite
		4799	big.
		4800
		4801	Note that error messages might become less precise when this option is
		4802	enabled.
		4803
		4804	=item EV_NSIG
		4805
		4806	The highest supported signal number, +1 (or, the number of
		4807	signals): Normally, libev tries to deduce the maximum number of signals
		4808	automatically, but sometimes this fails, in which case it can be
		4809	specified. Also, using a lower number than detected (C<32> should be
		4810	good for about any system in existence) can save some memory, as libev
		4811	statically allocates some 12-24 bytes per signal number.
3182		4812
3183	=item EV_PID_HASHSIZE	4813	=item EV_PID_HASHSIZE
3184		4814
3185	C<ev_child> watchers use a small hash table to distribute workload by	4815	C<ev_child> watchers use a small hash table to distribute workload by
3186	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4816	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3187	than enough. If you need to manage thousands of children you might want to	4817	usually more than enough. If you need to manage thousands of children you
3188	increase this value (I<must> be a power of two).	4818	might want to increase this value (I<must> be a power of two).
3189		4819
3190	=item EV_INOTIFY_HASHSIZE	4820	=item EV_INOTIFY_HASHSIZE
3191		4821
3192	C<ev_stat> watchers use a small hash table to distribute workload by	4822	C<ev_stat> watchers use a small hash table to distribute workload by
3193	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4823	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3194	usually more than enough. If you need to manage thousands of C<ev_stat>	4824	disabled), usually more than enough. If you need to manage thousands of
3195	watchers you might want to increase this value (I<must> be a power of	4825	C<ev_stat> watchers you might want to increase this value (I<must> be a
3196	two).	4826	power of two).
3197		4827
3198	=item EV_USE_4HEAP	4828	=item EV_USE_4HEAP
3199		4829
3200	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4830	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3201	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4831	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4832	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3203	faster performance with many (thousands) of watchers.	4833	faster performance with many (thousands) of watchers.
3204		4834
3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4835	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3206	(disabled).	4836	will be C<0>.
3207		4837
3208	=item EV_HEAP_CACHE_AT	4838	=item EV_HEAP_CACHE_AT
3209		4839
3210	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4840	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3211	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4841	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3212	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4842	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3213	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4843	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3214	but avoids random read accesses on heap changes. This improves performance	4844	but avoids random read accesses on heap changes. This improves performance
3215	noticeably with many (hundreds) of watchers.	4845	noticeably with many (hundreds) of watchers.
3216		4846
3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4847	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3218	(disabled).	4848	will be C<0>.
3219		4849
3220	=item EV_VERIFY	4850	=item EV_VERIFY
3221		4851
3222	Controls how much internal verification (see C<ev_loop_verify ()>) will	4852	Controls how much internal verification (see C<ev_verify ()>) will
3223	be done: If set to C<0>, no internal verification code will be compiled	4853	be done: If set to C<0>, no internal verification code will be compiled
3224	in. If set to C<1>, then verification code will be compiled in, but not	4854	in. If set to C<1>, then verification code will be compiled in, but not
3225	called. If set to C<2>, then the internal verification code will be	4855	called. If set to C<2>, then the internal verification code will be
3226	called once per loop, which can slow down libev. If set to C<3>, then the	4856	called once per loop, which can slow down libev. If set to C<3>, then the
3227	verification code will be called very frequently, which will slow down	4857	verification code will be called very frequently, which will slow down
3228	libev considerably.	4858	libev considerably.
3229		4859
3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4860	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3231	C<0>.	4861	will be C<0>.
3232		4862
3233	=item EV_COMMON	4863	=item EV_COMMON
3234		4864
3235	By default, all watchers have a C<void *data> member. By redefining	4865	By default, all watchers have a C<void *data> member. By redefining
3236	this macro to a something else you can include more and other types of	4866	this macro to something else you can include more and other types of
3237	members. You have to define it each time you include one of the files,	4867	members. You have to define it each time you include one of the files,
3238	though, and it must be identical each time.	4868	though, and it must be identical each time.
3239		4869
3240	For example, the perl EV module uses something like this:	4870	For example, the perl EV module uses something like this:
3241		4871
…		…
3294	file.	4924	file.
3295		4925
3296	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4926	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3297	that everybody includes and which overrides some configure choices:	4927	that everybody includes and which overrides some configure choices:
3298		4928
3299	#define EV_MINIMAL 1	4929	#define EV_FEATURES 8
3300	#define EV_USE_POLL 0	4930	#define EV_USE_SELECT 1
3301	#define EV_MULTIPLICITY 0
3302	#define EV_PERIODIC_ENABLE 0	4931	#define EV_PREPARE_ENABLE 1
		4932	#define EV_IDLE_ENABLE 1
3303	#define EV_STAT_ENABLE 0	4933	#define EV_SIGNAL_ENABLE 1
3304	#define EV_FORK_ENABLE 0	4934	#define EV_CHILD_ENABLE 1
		4935	#define EV_USE_STDEXCEPT 0
3305	#define EV_CONFIG_H <config.h>	4936	#define EV_CONFIG_H <config.h>
3306	#define EV_MINPRI 0
3307	#define EV_MAXPRI 0
3308		4937
3309	#include "ev++.h"	4938	#include "ev++.h"
3310		4939
3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4940	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3312		4941
3313	#include "ev_cpp.h"	4942	#include "ev_cpp.h"
3314	#include "ev.c"	4943	#include "ev.c"
3315		4944
3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4945	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3317		4946
3318	=head2 THREADS AND COROUTINES	4947	=head2 THREADS AND COROUTINES
3319		4948
3320	=head3 THREADS	4949	=head3 THREADS
3321		4950
…		…
3372	default loop and triggering an C<ev_async> watcher from the default loop	5001	default loop and triggering an C<ev_async> watcher from the default loop
3373	watcher callback into the event loop interested in the signal.	5002	watcher callback into the event loop interested in the signal.
3374		5003
3375	=back	5004	=back
3376		5005
		5006	See also L</THREAD LOCKING EXAMPLE>.
		5007
3377	=head3 COROUTINES	5008	=head3 COROUTINES
3378		5009
3379	Libev is very accommodating to coroutines ("cooperative threads"):	5010	Libev is very accommodating to coroutines ("cooperative threads"):
3380	libev fully supports nesting calls to its functions from different	5011	libev fully supports nesting calls to its functions from different
3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5012	coroutines (e.g. you can call C<ev_run> on the same loop from two
3382	different coroutines, and switch freely between both coroutines running the	5013	different coroutines, and switch freely between both coroutines running
3383	loop, as long as you don't confuse yourself). The only exception is that	5014	the loop, as long as you don't confuse yourself). The only exception is
3384	you must not do this from C<ev_periodic> reschedule callbacks.	5015	that you must not do this from C<ev_periodic> reschedule callbacks.
3385		5016
3386	Care has been taken to ensure that libev does not keep local state inside	5017	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5018	C<ev_run>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	5019	they do not call any callbacks.
3389		5020
3390	=head2 COMPILER WARNINGS	5021	=head2 COMPILER WARNINGS
3391		5022
3392	Depending on your compiler and compiler settings, you might get no or a	5023	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	5024	lot of warnings when compiling libev code. Some people are apparently
…		…
3403	maintainable.	5034	maintainable.
3404		5035
3405	And of course, some compiler warnings are just plain stupid, or simply	5036	And of course, some compiler warnings are just plain stupid, or simply
3406	wrong (because they don't actually warn about the condition their message	5037	wrong (because they don't actually warn about the condition their message
3407	seems to warn about). For example, certain older gcc versions had some	5038	seems to warn about). For example, certain older gcc versions had some
3408	warnings that resulted an extreme number of false positives. These have	5039	warnings that resulted in an extreme number of false positives. These have
3409	been fixed, but some people still insist on making code warn-free with	5040	been fixed, but some people still insist on making code warn-free with
3410	such buggy versions.	5041	such buggy versions.
3411		5042
3412	While libev is written to generate as few warnings as possible,	5043	While libev is written to generate as few warnings as possible,
3413	"warn-free" code is not a goal, and it is recommended not to build libev	5044	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	5058	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	5059	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	5060	==2274== still reachable: 256 bytes in 1 blocks.
3430		5061
3431	Then there is no memory leak, just as memory accounted to global variables	5062	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	5063	is not a memleak - the memory is still being referenced, and didn't leak.
3433		5064
3434	Similarly, under some circumstances, valgrind might report kernel bugs	5065	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5066	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	5067	although an acceptable workaround has been found here), or it might be
3437	confused.	5068	confused.
…		…
3449	I suggest using suppression lists.	5080	I suggest using suppression lists.
3450		5081
3451		5082
3452	=head1 PORTABILITY NOTES	5083	=head1 PORTABILITY NOTES
3453		5084
		5085	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5086
		5087	GNU/Linux is the only common platform that supports 64 bit file/large file
		5088	interfaces but I<disables> them by default.
		5089
		5090	That means that libev compiled in the default environment doesn't support
		5091	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5092
		5093	Unfortunately, many programs try to work around this GNU/Linux issue
		5094	by enabling the large file API, which makes them incompatible with the
		5095	standard libev compiled for their system.
		5096
		5097	Likewise, libev cannot enable the large file API itself as this would
		5098	suddenly make it incompatible to the default compile time environment,
		5099	i.e. all programs not using special compile switches.
		5100
		5101	=head2 OS/X AND DARWIN BUGS
		5102
		5103	The whole thing is a bug if you ask me - basically any system interface
		5104	you touch is broken, whether it is locales, poll, kqueue or even the
		5105	OpenGL drivers.
		5106
		5107	=head3 C<kqueue> is buggy
		5108
		5109	The kqueue syscall is broken in all known versions - most versions support
		5110	only sockets, many support pipes.
		5111
		5112	Libev tries to work around this by not using C<kqueue> by default on this
		5113	rotten platform, but of course you can still ask for it when creating a
		5114	loop - embedding a socket-only kqueue loop into a select-based one is
		5115	probably going to work well.
		5116
		5117	=head3 C<poll> is buggy
		5118
		5119	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5120	implementation by something calling C<kqueue> internally around the 10.5.6
		5121	release, so now C<kqueue> I<and> C<poll> are broken.
		5122
		5123	Libev tries to work around this by not using C<poll> by default on
		5124	this rotten platform, but of course you can still ask for it when creating
		5125	a loop.
		5126
		5127	=head3 C<select> is buggy
		5128
		5129	All that's left is C<select>, and of course Apple found a way to fuck this
		5130	one up as well: On OS/X, C<select> actively limits the number of file
		5131	descriptors you can pass in to 1024 - your program suddenly crashes when
		5132	you use more.
		5133
		5134	There is an undocumented "workaround" for this - defining
		5135	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5136	work on OS/X.
		5137
		5138	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5139
		5140	=head3 C<errno> reentrancy
		5141
		5142	The default compile environment on Solaris is unfortunately so
		5143	thread-unsafe that you can't even use components/libraries compiled
		5144	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5145	defined by default. A valid, if stupid, implementation choice.
		5146
		5147	If you want to use libev in threaded environments you have to make sure
		5148	it's compiled with C<_REENTRANT> defined.
		5149
		5150	=head3 Event port backend
		5151
		5152	The scalable event interface for Solaris is called "event
		5153	ports". Unfortunately, this mechanism is very buggy in all major
		5154	releases. If you run into high CPU usage, your program freezes or you get
		5155	a large number of spurious wakeups, make sure you have all the relevant
		5156	and latest kernel patches applied. No, I don't know which ones, but there
		5157	are multiple ones to apply, and afterwards, event ports actually work
		5158	great.
		5159
		5160	If you can't get it to work, you can try running the program by setting
		5161	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5162	C<select> backends.
		5163
		5164	=head2 AIX POLL BUG
		5165
		5166	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5167	this by trying to avoid the poll backend altogether (i.e. it's not even
		5168	compiled in), which normally isn't a big problem as C<select> works fine
		5169	with large bitsets on AIX, and AIX is dead anyway.
		5170
3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5171	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5172
		5173	=head3 General issues
3455		5174
3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5175	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3457	requires, and its I/O model is fundamentally incompatible with the POSIX	5176	requires, and its I/O model is fundamentally incompatible with the POSIX
3458	model. Libev still offers limited functionality on this platform in	5177	model. Libev still offers limited functionality on this platform in
3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5178	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3460	descriptors. This only applies when using Win32 natively, not when using	5179	descriptors. This only applies when using Win32 natively, not when using
3461	e.g. cygwin.	5180	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5181	as every compiler comes with a slightly differently broken/incompatible
		5182	environment.
3462		5183
3463	Lifting these limitations would basically require the full	5184	Lifting these limitations would basically require the full
3464	re-implementation of the I/O system. If you are into these kinds of	5185	re-implementation of the I/O system. If you are into this kind of thing,
3465	things, then note that glib does exactly that for you in a very portable	5186	then note that glib does exactly that for you in a very portable way (note
3466	way (note also that glib is the slowest event library known to man).	5187	also that glib is the slowest event library known to man).
3467		5188
3468	There is no supported compilation method available on windows except	5189	There is no supported compilation method available on windows except
3469	embedding it into other applications.	5190	embedding it into other applications.
		5191
		5192	Sensible signal handling is officially unsupported by Microsoft - libev
		5193	tries its best, but under most conditions, signals will simply not work.
3470		5194
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	5195	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	5196	accept large writes: instead of resulting in a partial write, windows will
3473	either accept everything or return C<ENOBUFS> if the buffer is too large,	5197	either accept everything or return C<ENOBUFS> if the buffer is too large,
3474	so make sure you only write small amounts into your sockets (less than a	5198	so make sure you only write small amounts into your sockets (less than a
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	5203	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	5204	is not recommended (and not reasonable). If your program needs to use
3481	more than a hundred or so sockets, then likely it needs to use a totally	5205	more than a hundred or so sockets, then likely it needs to use a totally
3482	different implementation for windows, as libev offers the POSIX readiness	5206	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	5207	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	5208	(due to Microsoft monopoly games).
3485		5209
3486	A typical way to use libev under windows is to embed it (see the embedding	5210	A typical way to use libev under windows is to embed it (see the embedding
3487	section for details) and use the following F<evwrap.h> header file instead	5211	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	5212	of F<ev.h>:
3489		5213
…		…
3496	you do I<not> compile the F<ev.c> or any other embedded source files!):	5220	you do I<not> compile the F<ev.c> or any other embedded source files!):
3497		5221
3498	#include "evwrap.h"	5222	#include "evwrap.h"
3499	#include "ev.c"	5223	#include "ev.c"
3500		5224
3501	=over 4
3502
3503	=item The winsocket select function	5225	=head3 The winsocket C<select> function
3504		5226
3505	The winsocket C<select> function doesn't follow POSIX in that it	5227	The winsocket C<select> function doesn't follow POSIX in that it
3506	requires socket I<handles> and not socket I<file descriptors> (it is	5228	requires socket I<handles> and not socket I<file descriptors> (it is
3507	also extremely buggy). This makes select very inefficient, and also	5229	also extremely buggy). This makes select very inefficient, and also
3508	requires a mapping from file descriptors to socket handles (the Microsoft	5230	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3517	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5239	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3518		5240
3519	Note that winsockets handling of fd sets is O(n), so you can easily get a	5241	Note that winsockets handling of fd sets is O(n), so you can easily get a
3520	complexity in the O(n²) range when using win32.	5242	complexity in the O(n²) range when using win32.
3521		5243
3522	=item Limited number of file descriptors	5244	=head3 Limited number of file descriptors
3523		5245
3524	Windows has numerous arbitrary (and low) limits on things.	5246	Windows has numerous arbitrary (and low) limits on things.
3525		5247
3526	Early versions of winsocket's select only supported waiting for a maximum	5248	Early versions of winsocket's select only supported waiting for a maximum
3527	of C<64> handles (probably owning to the fact that all windows kernels	5249	of C<64> handles (probably owning to the fact that all windows kernels
3528	can only wait for C<64> things at the same time internally; Microsoft	5250	can only wait for C<64> things at the same time internally; Microsoft
3529	recommends spawning a chain of threads and wait for 63 handles and the	5251	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	5252	previous thread in each. Sounds great!).
3531		5253
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5254	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3533	to some high number (e.g. C<2048>) before compiling the winsocket select	5255	to some high number (e.g. C<2048>) before compiling the winsocket select
3534	call (which might be in libev or elsewhere, for example, perl does its own	5256	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	5257	other interpreters do their own select emulation on windows).
3536		5258
3537	Another limit is the number of file descriptors in the Microsoft runtime	5259	Another limit is the number of file descriptors in the Microsoft runtime
3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5260	libraries, which by default is C<64> (there must be a hidden I<64>
3539	or something like this inside Microsoft). You can increase this by calling	5261	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5262	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	arbitrary limit), but is broken in many versions of the Microsoft runtime	5263	(another arbitrary limit), but is broken in many versions of the Microsoft
3542	libraries.
3543
3544	This might get you to about C<512> or C<2048> sockets (depending on	5264	runtime libraries. This might get you to about C<512> or C<2048> sockets
3545	windows version and/or the phase of the moon). To get more, you need to	5265	(depending on windows version and/or the phase of the moon). To get more,
3546	wrap all I/O functions and provide your own fd management, but the cost of	5266	you need to wrap all I/O functions and provide your own fd management, but
3547	calling select (O(n²)) will likely make this unworkable.	5267	the cost of calling select (O(n²)) will likely make this unworkable.
3548
3549	=back
3550		5268
3551	=head2 PORTABILITY REQUIREMENTS	5269	=head2 PORTABILITY REQUIREMENTS
3552		5270
3553	In addition to a working ISO-C implementation and of course the	5271	In addition to a working ISO-C implementation and of course the
3554	backend-specific APIs, libev relies on a few additional extensions:	5272	backend-specific APIs, libev relies on a few additional extensions:
…		…
3561	Libev assumes not only that all watcher pointers have the same internal	5279	Libev assumes not only that all watcher pointers have the same internal
3562	structure (guaranteed by POSIX but not by ISO C for example), but it also	5280	structure (guaranteed by POSIX but not by ISO C for example), but it also
3563	assumes that the same (machine) code can be used to call any watcher	5281	assumes that the same (machine) code can be used to call any watcher
3564	callback: The watcher callbacks have different type signatures, but libev	5282	callback: The watcher callbacks have different type signatures, but libev
3565	calls them using an C<ev_watcher *> internally.	5283	calls them using an C<ev_watcher *> internally.
		5284
		5285	=item pointer accesses must be thread-atomic
		5286
		5287	Accessing a pointer value must be atomic, it must both be readable and
		5288	writable in one piece - this is the case on all current architectures.
3566		5289
3567	=item C<sig_atomic_t volatile> must be thread-atomic as well	5290	=item C<sig_atomic_t volatile> must be thread-atomic as well
3568		5291
3569	The type C<sig_atomic_t volatile> (or whatever is defined as	5292	The type C<sig_atomic_t volatile> (or whatever is defined as
3570	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5293	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3593	watchers.	5316	watchers.
3594		5317
3595	=item C<double> must hold a time value in seconds with enough accuracy	5318	=item C<double> must hold a time value in seconds with enough accuracy
3596		5319
3597	The type C<double> is used to represent timestamps. It is required to	5320	The type C<double> is used to represent timestamps. It is required to
3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5321	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3599	enough for at least into the year 4000. This requirement is fulfilled by	5322	good enough for at least into the year 4000 with millisecond accuracy
		5323	(the design goal for libev). This requirement is overfulfilled by
3600	implementations implementing IEEE 754 (basically all existing ones).	5324	implementations using IEEE 754, which is basically all existing ones.
		5325
		5326	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5327	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5328	is either obsolete or somebody patched it to use C<long double> or
		5329	something like that, just kidding).
3601		5330
3602	=back	5331	=back
3603		5332
3604	If you know of other additional requirements drop me a note.	5333	If you know of other additional requirements drop me a note.
3605		5334
…		…
3667	=item Processing ev_async_send: O(number_of_async_watchers)	5396	=item Processing ev_async_send: O(number_of_async_watchers)
3668		5397
3669	=item Processing signals: O(max_signal_number)	5398	=item Processing signals: O(max_signal_number)
3670		5399
3671	Sending involves a system call I<iff> there were no other C<ev_async_send>	5400	Sending involves a system call I<iff> there were no other C<ev_async_send>
3672	calls in the current loop iteration. Checking for async and signal events	5401	calls in the current loop iteration and the loop is currently
		5402	blocked. Checking for async and signal events involves iterating over all
3673	involves iterating over all running async watchers or all signal numbers.	5403	running async watchers or all signal numbers.
3674		5404
3675	=back	5405	=back
3676		5406
3677		5407
		5408	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5409
		5410	The major version 4 introduced some incompatible changes to the API.
		5411
		5412	At the moment, the C<ev.h> header file provides compatibility definitions
		5413	for all changes, so most programs should still compile. The compatibility
		5414	layer might be removed in later versions of libev, so better update to the
		5415	new API early than late.
		5416
		5417	=over 4
		5418
		5419	=item C<EV_COMPAT3> backwards compatibility mechanism
		5420
		5421	The backward compatibility mechanism can be controlled by
		5422	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5423	section.
		5424
		5425	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5426
		5427	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5428
		5429	ev_loop_destroy (EV_DEFAULT_UC);
		5430	ev_loop_fork (EV_DEFAULT);
		5431
		5432	=item function/symbol renames
		5433
		5434	A number of functions and symbols have been renamed:
		5435
		5436	ev_loop => ev_run
		5437	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5438	EVLOOP_ONESHOT => EVRUN_ONCE
		5439
		5440	ev_unloop => ev_break
		5441	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5442	EVUNLOOP_ONE => EVBREAK_ONE
		5443	EVUNLOOP_ALL => EVBREAK_ALL
		5444
		5445	EV_TIMEOUT => EV_TIMER
		5446
		5447	ev_loop_count => ev_iteration
		5448	ev_loop_depth => ev_depth
		5449	ev_loop_verify => ev_verify
		5450
		5451	Most functions working on C<struct ev_loop> objects don't have an
		5452	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5453	associated constants have been renamed to not collide with the C<struct
		5454	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5455	as all other watcher types. Note that C<ev_loop_fork> is still called
		5456	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5457	typedef.
		5458
		5459	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5460
		5461	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5462	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5463	and work, but the library code will of course be larger.
		5464
		5465	=back
		5466
		5467
		5468	=head1 GLOSSARY
		5469
		5470	=over 4
		5471
		5472	=item active
		5473
		5474	A watcher is active as long as it has been started and not yet stopped.
		5475	See L</WATCHER STATES> for details.
		5476
		5477	=item application
		5478
		5479	In this document, an application is whatever is using libev.
		5480
		5481	=item backend
		5482
		5483	The part of the code dealing with the operating system interfaces.
		5484
		5485	=item callback
		5486
		5487	The address of a function that is called when some event has been
		5488	detected. Callbacks are being passed the event loop, the watcher that
		5489	received the event, and the actual event bitset.
		5490
		5491	=item callback/watcher invocation
		5492
		5493	The act of calling the callback associated with a watcher.
		5494
		5495	=item event
		5496
		5497	A change of state of some external event, such as data now being available
		5498	for reading on a file descriptor, time having passed or simply not having
		5499	any other events happening anymore.
		5500
		5501	In libev, events are represented as single bits (such as C<EV_READ> or
		5502	C<EV_TIMER>).
		5503
		5504	=item event library
		5505
		5506	A software package implementing an event model and loop.
		5507
		5508	=item event loop
		5509
		5510	An entity that handles and processes external events and converts them
		5511	into callback invocations.
		5512
		5513	=item event model
		5514
		5515	The model used to describe how an event loop handles and processes
		5516	watchers and events.
		5517
		5518	=item pending
		5519
		5520	A watcher is pending as soon as the corresponding event has been
		5521	detected. See L</WATCHER STATES> for details.
		5522
		5523	=item real time
		5524
		5525	The physical time that is observed. It is apparently strictly monotonic :)
		5526
		5527	=item wall-clock time
		5528
		5529	The time and date as shown on clocks. Unlike real time, it can actually
		5530	be wrong and jump forwards and backwards, e.g. when you adjust your
		5531	clock.
		5532
		5533	=item watcher
		5534
		5535	A data structure that describes interest in certain events. Watchers need
		5536	to be started (attached to an event loop) before they can receive events.
		5537
		5538	=back
		5539
3678	=head1 AUTHOR	5540	=head1 AUTHOR
3679		5541
3680	Marc Lehmann <libev@schmorp.de>.	5542	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5543	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3681		5544

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