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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	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	249	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	250	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	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	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	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<ev_loop *>. The library knows two	321	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	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	323	libev 3 had an C<ev_loop> function colliding with the struct name).
		324
		325	The library knows two types of such loops, the I<default> loop, which
		326	supports child process events, and dynamically created event loops which
		327	do not.
284		328
285	=over 4	329	=over 4
286		330
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		332
289	This will initialise the default event loop if it hasn't been initialised	333	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	334	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	335	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).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
293		343
294	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
295	function.	345	function (or via the C<EV_DEFAULT> macro).
296		346
297	Note that this function is I<not> thread-safe, so if you want to use it	347	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,	348	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
300		351
301	The default loop is the only loop that can handle C<ev_signal> and	352	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	353	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	354	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	355	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	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
307		376
308	The flags argument can be used to specify special behaviour or specific	377	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>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		379
311	The following flags are supported:	380	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
327	around bugs.	396	around bugs.
328		397
329	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
330		399
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	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	401	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		402
335	This works by calling C<getpid ()> on every iteration of the loop,	403	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	404	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	405	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	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	412	flag.
345		413
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	415	environment variable.
348		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
		451
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		453
351	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	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	456	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	480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		482
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
382	For few fds, this backend is a bit little slower than poll and select,	488	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	489	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	490	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	491	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	492
387	cases and requiring a system call per fd change, no fork support and bad	493	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	494	of the more advanced event mechanisms: mere annoyances include silently
		495	dropping file descriptors, requiring a system call per change per file
		496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
		499	0.1ms) and so on. The biggest issue is fork races, however - if a program
		500	forks then I<both> parent and child process have to recreate the epoll
		501	set, which can take considerable time (one syscall per file descriptor)
		502	and is of course hard to detect.
		503
		504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		505	of course I<doesn't>, and epoll just loves to report events for totally
		506	I<different> file descriptors (even already closed ones, so one cannot
		507	even remove them from the set) than registered in the set (especially
		508	on SMP systems). Libev tries to counter these spurious notifications by
		509	employing an additional generation counter and comparing that against the
		510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
389		517
390	While stopping, setting and starting an I/O watcher in the same iteration	518	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	519	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	520	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	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	522	file descriptors might not work very well if you register events for both
395		523	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		524
400	Best performance from this backend is achieved by not unregistering all	525	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	526	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	527	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	528	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	529	extra overhead. A fork can both result in spurious notifications as well
		530	as in libev having to destroy and recreate the epoll object, which can
		531	take considerable time and thus should be avoided.
		532
		533	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		534	faster than epoll for maybe up to a hundred file descriptors, depending on
		535	the usage. So sad.
405		536
406	While nominally embeddable in other event loops, this feature is broken in	537	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	538	all kernel versions tested so far.
408		539
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	540	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	541	C<EVBACKEND_POLL>.
411		542
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	543	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		544
414	Kqueue deserves special mention, as at the time of this writing, it was	545	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	546	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	547	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	548	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	549	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.	550	without API changes to existing programs. For this reason it's not being
		551	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		552	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		553	system like NetBSD.
420		554
421	You still can embed kqueue into a normal poll or select backend and use it	555	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	556	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.	557	the target platform). See C<ev_embed> watchers for more info.
424		558
425	It scales in the same way as the epoll backend, but the interface to the	559	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	560	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	561	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	562	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	563	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	564	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		565	cases
431		566
432	This backend usually performs well under most conditions.	567	This backend usually performs well under most conditions.
433		568
434	While nominally embeddable in other event loops, this doesn't work	569	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	570	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	571	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	572	(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,	573	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	574	also broken on OS X)) and, did I mention it, using it only for sockets.
440		575
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	576	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	577	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	578	C<NOTE_EOF>.
444		579
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		588
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	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)).	590	it's really slow, but it still scales very well (O(active_fds)).
456		591
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	592	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	593	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	595	might perform better.
465		596
466	On the positive side, with the exception of the spurious readiness	597	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	598	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
470		611
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
473		614
474	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
475		616
476	Try all backends (even potentially broken ones that wouldn't be tried	617	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	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		620
480	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		630
482	=back	631	=back
483		632
484	If one or more of these are or'ed into the flags value, then only these	633	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	634	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.	635	here). If none are specified, all backends in C<ev_recommended_backends
487		636	()> 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		637
516	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
517		639
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	641	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
521		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
522	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
523		650
524	Destroys the default loop again (frees all memory and kernel state	651	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	652	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	653	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>	654	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	655	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	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	657	for example).
531		658
532	Note that certain global state, such as signal state, will not be freed by	659	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	660	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
535		662
536	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	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	669	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>).	670	and C<ev_loop_destroy>.
540		671
541	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
542		673
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	674	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	675	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	676	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	677	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	678	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
554		684
555	On the other hand, you only need to call this function in the child	685	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	686	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.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
558		691
559	The function itself is quite fast and it's usually not a problem to call	692	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	693	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
563	pthread_atfork (0, 0, ev_default_fork);	705	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		706
572	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
573		708
574	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	710	otherwise.
576		711
577	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
578		713
579	Returns the count of loop iterations for the loop, which is identical to	714	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	715	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
582		717
583	This value can sometimes be useful as a generation counter of sorts (it	718	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	719	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
		722
		723	=item unsigned int ev_depth (loop)
		724
		725	Returns the number of times C<ev_run> was entered minus the number of
		726	times C<ev_run> was exited normally, in other words, the recursion depth.
		727
		728	Outside C<ev_run>, this number is zero. In a callback, this number is
		729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		730	in which case it is higher.
		731
		732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
586		736
587	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
588		738
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	740	use.
…		…
599		749
600	=item ev_now_update (loop)	750	=item ev_now_update (loop)
601		751
602	Establishes the current time by querying the kernel, updating the time	752	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	753	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
605		755
606	This function is rarely useful, but when some event callback runs for a	756	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	757	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	758	the current time is a good idea.
609		759
610	See also "The special problem of time updates" in the C<ev_timer> section.	760	See also L<The special problem of time updates> in the C<ev_timer> section.
611		761
		762	=item ev_suspend (loop)
		763
		764	=item ev_resume (loop)
		765
		766	These two functions suspend and resume an event loop, for use when the
		767	loop is not used for a while and timeouts should not be processed.
		768
		769	A typical use case would be an interactive program such as a game: When
		770	the user presses C<^Z> to suspend the game and resumes it an hour later it
		771	would be best to handle timeouts as if no time had actually passed while
		772	the program was suspended. This can be achieved by calling C<ev_suspend>
		773	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		774	C<ev_resume> directly afterwards to resume timer processing.
		775
		776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		778	will be rescheduled (that is, they will lose any events that would have
		779	occurred while suspended).
		780
		781	After calling C<ev_suspend> you B<must not> call I<any> function on the
		782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		783	without a previous call to C<ev_suspend>.
		784
		785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		786	event loop time (see C<ev_now_update>).
		787
612	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
613		789
614	Finally, this is it, the event handler. This function usually is called	790	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	791	after you have initialised all your watchers and you want to start
616	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
617		795
618	If the flags argument is specified as C<0>, it will not return until	796	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.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
620		799
621	Please note that an explicit C<ev_unloop> is usually better than	800	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	801	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	803	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	804	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	805	beauty.
627		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	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	813	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	814	block your process in case there are no events and will return after one
631	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
632		817
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	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	819	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	820	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	821	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	822	user-registered callback will be called), and will return after one
638	iteration of the loop.	823	iteration of the loop.
639		824
640	This is useful if you are waiting for some external event in conjunction	825	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	826	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	827	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.	828	usually a better approach for this kind of thing.
644		829
645	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
646		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	841	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	852	- Queue all expired timers.
663	- Queue all expired periodics.	853	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	855	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- 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	857	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
672		866
673	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	868	anymore.
675		869
676	... queue jobs here, make sure they register event watchers as long	870	... 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..)	871	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called unloop. yeah!
680		874
681	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
682		876
683	Can be used to make a call to C<ev_loop> return early (but only after it	877	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	878	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	879	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.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		881
688	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
689		883
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
691		886
692	=item ev_ref (loop)	887	=item ev_ref (loop)
693		888
694	=item ev_unref (loop)	889	=item ev_unref (loop)
695		890
696	Ref/unref can be used to add or remove a reference count on the event	891	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	892	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.	893	count is nonzero, C<ev_run> will not return on its own.
699		894
700	If you have a watcher you never unregister that should not keep C<ev_loop>	895	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	896	unregister, but that nevertheless should not keep C<ev_run> from
		897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	898	before stopping it.
703		899
704	As an example, libev itself uses this for its internal signal pipe: It is	900	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	901	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	902	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	903	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>	904	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,	905	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	906	before, respectively. Note also that libev might stop watchers itself
		907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		908	in the callback).
711		909
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	911	running when nothing else is active.
714		912
715	ev_signal exitsig;	913	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	916	ev_unref (loop);
719		917
720	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
721		919
722	ev_ref (loop);	920	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
744		942
745	By setting a higher I<io collect interval> you allow libev to spend more	943	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,	944	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	945	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	946	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	947	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		948	sleep time ensures that libev will not poll for I/O events more often then
		949	once per this interval, on average.
750		950
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	951	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	952	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	953	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	954	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		956
757	Many (busy) programs can usually benefit by setting the I/O collect	957	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	958	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	959	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>,	960	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.	961	as this approaches the timing granularity of most systems. Note that if
		962	you do transactions with the outside world and you can't increase the
		963	parallelity, then this setting will limit your transaction rate (if you
		964	need to poll once per transaction and the I/O collect interval is 0.01,
		965	then you can't do more than 100 transactions per second).
762		966
763	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	968	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	969	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	970	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	971	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	972	they fire on, say, one-second boundaries only.
769		973
		974	Example: we only need 0.1s timeout granularity, and we wish not to poll
		975	more often than 100 times per second:
		976
		977	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		979
		980	=item ev_invoke_pending (loop)
		981
		982	This call will simply invoke all pending watchers while resetting their
		983	pending state. Normally, C<ev_run> does this automatically when required,
		984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		989
		990	=item int ev_pending_count (loop)
		991
		992	Returns the number of pending watchers - zero indicates that no watchers
		993	are pending.
		994
		995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		996
		997	This overrides the invoke pending functionality of the loop: Instead of
		998	invoking all pending watchers when there are any, C<ev_run> will call
		999	this callback instead. This is useful, for example, when you want to
		1000	invoke the actual watchers inside another context (another thread etc.).
		1001
		1002	If you want to reset the callback, use C<ev_invoke_pending> as new
		1003	callback.
		1004
		1005	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1006
		1007	Sometimes you want to share the same loop between multiple threads. This
		1008	can be done relatively simply by putting mutex_lock/unlock calls around
		1009	each call to a libev function.
		1010
		1011	However, C<ev_run> can run an indefinite time, so it is not feasible
		1012	to wait for it to return. One way around this is to wake up the event
		1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1014	I<release> and I<acquire> callbacks on the loop.
		1015
		1016	When set, then C<release> will be called just before the thread is
		1017	suspended waiting for new events, and C<acquire> is called just
		1018	afterwards.
		1019
		1020	Ideally, C<release> will just call your mutex_unlock function, and
		1021	C<acquire> will just call the mutex_lock function again.
		1022
		1023	While event loop modifications are allowed between invocations of
		1024	C<release> and C<acquire> (that's their only purpose after all), no
		1025	modifications done will affect the event loop, i.e. adding watchers will
		1026	have no effect on the set of file descriptors being watched, or the time
		1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1028	to take note of any changes you made.
		1029
		1030	In theory, threads executing C<ev_run> will be async-cancel safe between
		1031	invocations of C<release> and C<acquire>.
		1032
		1033	See also the locking example in the C<THREADS> section later in this
		1034	document.
		1035
		1036	=item ev_set_userdata (loop, void *data)
		1037
		1038	=item void *ev_userdata (loop)
		1039
		1040	Set and retrieve a single C<void *> associated with a loop. When
		1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1042	C<0>.
		1043
		1044	These two functions can be used to associate arbitrary data with a loop,
		1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1046	C<acquire> callbacks described above, but of course can be (ab-)used for
		1047	any other purpose as well.
		1048
770	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
771		1050
772	This function only does something when C<EV_VERIFY> support has been	1051	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	1052	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	1053	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	1054	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1055	error and call C<abort ()>.
777		1056
778	This can be used to catch bugs inside libev itself: under normal	1057	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1061	=back
783		1062
784		1063
785	=head1 ANATOMY OF A WATCHER	1064	=head1 ANATOMY OF A WATCHER
786		1065
		1066	In the following description, uppercase C<TYPE> in names stands for the
		1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1068	watchers and C<ev_io_start> for I/O watchers.
		1069
787	A watcher is a structure that you create and register to record your	1070	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	1071	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:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
790		1074
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1076	{
793	ev_io_stop (w);	1077	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
795	}	1079	}
796		1080
797	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
		1082
798	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
		1084
799	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
		1088
802	ev_loop (loop, 0);	1089	ev_run (loop, 0);
803		1090
804	As you can see, you are responsible for allocating the memory for your	1091	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,	1092	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1093	stack).
807		1094
		1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1097
808	Each watcher structure must be initialised by a call to C<ev_init	1098	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	1099	*, 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	1100	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	1101	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1102	and/or writable).
813		1103
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1104	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	1105	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	1106	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
818		1108
819	To make the watcher actually watch out for events, you have to start it	1109	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	1110	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	1111	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1112	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1113
824	As long as your watcher is active (has been started but not stopped) you	1114	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	1115	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1116	reinitialise it or call its C<ev_TYPE_set> macro.
827		1117
828	Each and every callback receives the event loop pointer as first, the	1118	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	1119	registered watcher structure as second, and a bitset of received events as
830	third argument.	1120	third argument.
831		1121
…		…
840	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
841		1131
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1133	writable.
844		1134
845	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
846		1136
847	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
848		1138
849	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
850		1140
…		…
868		1158
869	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
870		1160
871	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
872		1162
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
874	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
876	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
877	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
879	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
880		1170
881	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
882		1172
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1174
885	=item C<EV_FORK>	1175	=item C<EV_FORK>
886		1176
887	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1178	C<ev_fork>).
889		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
		1183
890	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
891		1185
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
		1187
		1188	=item C<EV_CUSTOM>
		1189
		1190	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1191	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1192
894	=item C<EV_ERROR>	1193	=item C<EV_ERROR>
895		1194
896	An unspecified error has occurred, the watcher has been stopped. This might	1195	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1196	happen because the watcher could not be properly started because libev
…		…
912		1211
913	=back	1212	=back
914		1213
915	=head2 GENERIC WATCHER FUNCTIONS	1214	=head2 GENERIC WATCHER FUNCTIONS
916		1215
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1216	=over 4
921		1217
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1218	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1219
924	This macro initialises the generic portion of a watcher. The contents	1220	This macro initialises the generic portion of a watcher. The contents
…		…
938		1234
939	ev_io w;	1235	ev_io w;
940	ev_init (&w, my_cb);	1236	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1237	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1238
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1239	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1240
945	This macro initialises the type-specific parts of a watcher. You need to	1241	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1242	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1243	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1244	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1257
962	Example: Initialise and set an C<ev_io> watcher in one step.	1258	Example: Initialise and set an C<ev_io> watcher in one step.
963		1259
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1260	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1261
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1262	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1263
968	Starts (activates) the given watcher. Only active watchers will receive	1264	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1265	events. If the watcher is already active nothing will happen.
970		1266
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1267	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1268	whole section.
973		1269
974	ev_io_start (EV_DEFAULT_UC, &w);	1270	ev_io_start (EV_DEFAULT_UC, &w);
975		1271
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1272	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1273
978	Stops the given watcher if active, and clears the pending status (whether	1274	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1275	the watcher was active or not).
980		1276
981	It is possible that stopped watchers are pending - for example,	1277	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1302	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1303
1008	Change the callback. You can change the callback at virtually any time	1304	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1305	(modulo threads).
1010		1306
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1307	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1308
1013	=item int ev_priority (ev_TYPE *watcher)	1309	=item int ev_priority (ev_TYPE *watcher)
1014		1310
1015	Set and query the priority of the watcher. The priority is a small	1311	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1312	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1313	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1314	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1315	from being executed (except for C<ev_idle> watchers).
1020		1316
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1317	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1318	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1319
1029	You I<must not> change the priority of a watcher as long as it is active or	1320	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1321	pending.
1031		1322
		1323	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1324	fine, as long as you do not mind that the priority value you query might
		1325	or might not have been clamped to the valid range.
		1326
1032	The default priority used by watchers when no priority has been set is	1327	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1328	always C<0>, which is supposed to not be too high and not be too low :).
1034		1329
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1330	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1331	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1332
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1333	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1334
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1335	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1336	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1344	watcher isn't pending it does nothing and returns C<0>.
1051		1345
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1346	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1347	callback to be invoked, which can be accomplished with this function.
1054		1348
		1349	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Feeds the given event set into the event loop, as if the specified event
		1352	had happened for the specified watcher (which must be a pointer to an
		1353	initialised but not necessarily started event watcher). Obviously you must
		1354	not free the watcher as long as it has pending events.
		1355
		1356	Stopping the watcher, letting libev invoke it, or calling
		1357	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1358	not started in the first place.
		1359
		1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1361	functions that do not need a watcher.
		1362
1055	=back	1363	=back
1056		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1057		1367
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1059		1369
1060	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1061	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1062	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1063	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1374
1067	struct my_io	1375	=over 4
		1376
		1377	=item initialiased
		1378
		1379	Before a watcher can be registered with the event looop it has to be
		1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1382
		1383	In this state it is simply some block of memory that is suitable for
		1384	use in an event loop. It can be moved around, freed, reused etc. at
		1385	will - as long as you either keep the memory contents intact, or call
		1386	C<ev_TYPE_init> again.
		1387
		1388	=item started/running/active
		1389
		1390	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1391	property of the event loop, and is actively waiting for events. While in
		1392	this state it cannot be accessed (except in a few documented ways), moved,
		1393	freed or anything else - the only legal thing is to keep a pointer to it,
		1394	and call libev functions on it that are documented to work on active watchers.
		1395
		1396	=item pending
		1397
		1398	If a watcher is active and libev determines that an event it is interested
		1399	in has occurred (such as a timer expiring), it will become pending. It will
		1400	stay in this pending state until either it is stopped or its callback is
		1401	about to be invoked, so it is not normally pending inside the watcher
		1402	callback.
		1403
		1404	The watcher might or might not be active while it is pending (for example,
		1405	an expired non-repeating timer can be pending but no longer active). If it
		1406	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1407	but it is still property of the event loop at this time, so cannot be
		1408	moved, freed or reused. And if it is active the rules described in the
		1409	previous item still apply.
		1410
		1411	It is also possible to feed an event on a watcher that is not active (e.g.
		1412	via C<ev_feed_event>), in which case it becomes pending without being
		1413	active.
		1414
		1415	=item stopped
		1416
		1417	A watcher can be stopped implicitly by libev (in which case it might still
		1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1419	latter will clear any pending state the watcher might be in, regardless
		1420	of whether it was active or not, so stopping a watcher explicitly before
		1421	freeing it is often a good idea.
		1422
		1423	While stopped (and not pending) the watcher is essentially in the
		1424	initialised state, that is, it can be reused, moved, modified in any way
		1425	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1426	it again).
		1427
		1428	=back
		1429
		1430	=head2 WATCHER PRIORITY MODELS
		1431
		1432	Many event loops support I<watcher priorities>, which are usually small
		1433	integers that influence the ordering of event callback invocation
		1434	between watchers in some way, all else being equal.
		1435
		1436	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1437	description for the more technical details such as the actual priority
		1438	range.
		1439
		1440	There are two common ways how these these priorities are being interpreted
		1441	by event loops:
		1442
		1443	In the more common lock-out model, higher priorities "lock out" invocation
		1444	of lower priority watchers, which means as long as higher priority
		1445	watchers receive events, lower priority watchers are not being invoked.
		1446
		1447	The less common only-for-ordering model uses priorities solely to order
		1448	callback invocation within a single event loop iteration: Higher priority
		1449	watchers are invoked before lower priority ones, but they all get invoked
		1450	before polling for new events.
		1451
		1452	Libev uses the second (only-for-ordering) model for all its watchers
		1453	except for idle watchers (which use the lock-out model).
		1454
		1455	The rationale behind this is that implementing the lock-out model for
		1456	watchers is not well supported by most kernel interfaces, and most event
		1457	libraries will just poll for the same events again and again as long as
		1458	their callbacks have not been executed, which is very inefficient in the
		1459	common case of one high-priority watcher locking out a mass of lower
		1460	priority ones.
		1461
		1462	Static (ordering) priorities are most useful when you have two or more
		1463	watchers handling the same resource: a typical usage example is having an
		1464	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1465	timeouts. Under load, data might be received while the program handles
		1466	other jobs, but since timers normally get invoked first, the timeout
		1467	handler will be executed before checking for data. In that case, giving
		1468	the timer a lower priority than the I/O watcher ensures that I/O will be
		1469	handled first even under adverse conditions (which is usually, but not
		1470	always, what you want).
		1471
		1472	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1473	will only be executed when no same or higher priority watchers have
		1474	received events, they can be used to implement the "lock-out" model when
		1475	required.
		1476
		1477	For example, to emulate how many other event libraries handle priorities,
		1478	you can associate an C<ev_idle> watcher to each such watcher, and in
		1479	the normal watcher callback, you just start the idle watcher. The real
		1480	processing is done in the idle watcher callback. This causes libev to
		1481	continuously poll and process kernel event data for the watcher, but when
		1482	the lock-out case is known to be rare (which in turn is rare :), this is
		1483	workable.
		1484
		1485	Usually, however, the lock-out model implemented that way will perform
		1486	miserably under the type of load it was designed to handle. In that case,
		1487	it might be preferable to stop the real watcher before starting the
		1488	idle watcher, so the kernel will not have to process the event in case
		1489	the actual processing will be delayed for considerable time.
		1490
		1491	Here is an example of an I/O watcher that should run at a strictly lower
		1492	priority than the default, and which should only process data when no
		1493	other events are pending:
		1494
		1495	ev_idle idle; // actual processing watcher
		1496	ev_io io; // actual event watcher
		1497
		1498	static void
		1499	io_cb (EV_P_ ev_io *w, int revents)
1068	{	1500	{
1069	ev_io io;	1501	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1502	// are not yet ready to handle it.
1071	void *somedata;	1503	ev_io_stop (EV_A_ w);
1072	struct whatever *mostinteresting;	1504
		1505	// start the idle watcher to handle the actual event.
		1506	// it will not be executed as long as other watchers
		1507	// with the default priority are receiving events.
		1508	ev_idle_start (EV_A_ &idle);
1073	};	1509	}
1074		1510
1075	...	1511	static void
1076	struct my_io w;	1512	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1513	{
1084	struct my_io *w = (struct my_io *)w_;	1514	// actual processing
1085	...	1515	read (STDIN_FILENO, ...);
		1516
		1517	// have to start the I/O watcher again, as
		1518	// we have handled the event
		1519	ev_io_start (EV_P_ &io);
1086	}	1520	}
1087		1521
1088	More interesting and less C-conformant ways of casting your callback type	1522	// initialisation
1089	instead have been omitted.	1523	ev_idle_init (&idle, idle_cb);
		1524	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1525	ev_io_start (EV_DEFAULT_ &io);
1090		1526
1091	Another common scenario is to use some data structure with multiple	1527	In the "real" world, it might also be beneficial to start a timer, so that
1092	embedded watchers:	1528	low-priority connections can not be locked out forever under load. This
1093		1529	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1530	during short periods of high load, while not completely locking out less
1095	{	1531	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1532
1123		1533
1124	=head1 WATCHER TYPES	1534	=head1 WATCHER TYPES
1125		1535
1126	This section describes each watcher in detail, but will not repeat	1536	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1560	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1561	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1562	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1563	required if you know what you are doing).
1154		1564
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1565	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1566	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1567	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1568	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1569	with a relatively standard program structure. Thus it is best to always
1164	this situation even with a relatively standard program structure. Thus	1570	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1571	preferable to a program hanging until some data arrives.
1167		1572
1168	If you cannot run the fd in non-blocking mode (for example you should	1573	If you cannot run the fd in non-blocking mode (for example you should
1169	not play around with an Xlib connection), then you have to separately	1574	not play around with an Xlib connection), then you have to separately
1170	re-test whether a file descriptor is really ready with a known-to-be good	1575	re-test whether a file descriptor is really ready with a known-to-be good
1171	interface such as poll (fortunately in our Xlib example, Xlib already	1576	interface such as poll (fortunately in the case of Xlib, it already does
1172	does this on its own, so its quite safe to use). Some people additionally	1577	this on its own, so its quite safe to use). Some people additionally
1173	use C<SIGALRM> and an interval timer, just to be sure you won't block	1578	use C<SIGALRM> and an interval timer, just to be sure you won't block
1174	indefinitely.	1579	indefinitely.
1175		1580
1176	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1177		1582
…		…
1205		1610
1206	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		1614
		1615	=head3 The special problem of files
		1616
		1617	Many people try to use C<select> (or libev) on file descriptors
		1618	representing files, and expect it to become ready when their program
		1619	doesn't block on disk accesses (which can take a long time on their own).
		1620
		1621	However, this cannot ever work in the "expected" way - you get a readiness
		1622	notification as soon as the kernel knows whether and how much data is
		1623	there, and in the case of open files, that's always the case, so you
		1624	always get a readiness notification instantly, and your read (or possibly
		1625	write) will still block on the disk I/O.
		1626
		1627	Another way to view it is that in the case of sockets, pipes, character
		1628	devices and so on, there is another party (the sender) that delivers data
		1629	on its own, but in the case of files, there is no such thing: the disk
		1630	will not send data on its own, simply because it doesn't know what you
		1631	wish to read - you would first have to request some data.
		1632
		1633	Since files are typically not-so-well supported by advanced notification
		1634	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1635	to files, even though you should not use it. The reason for this is
		1636	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1637	usually a tty, often a pipe, but also sometimes files or special devices
		1638	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1639	F</dev/urandom>), and even though the file might better be served with
		1640	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1641	it "just works" instead of freezing.
		1642
		1643	So avoid file descriptors pointing to files when you know it (e.g. use
		1644	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1645	when you rarely read from a file instead of from a socket, and want to
		1646	reuse the same code path.
		1647
1210	=head3 The special problem of fork	1648	=head3 The special problem of fork
1211		1649
1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1650	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1213	useless behaviour. Libev fully supports fork, but needs to be told about	1651	useless behaviour. Libev fully supports fork, but needs to be told about
1214	it in the child.	1652	it in the child if you want to continue to use it in the child.
1215		1653
1216	To support fork in your programs, you either have to call	1654	To support fork in your child processes, you have to call C<ev_loop_fork
1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1655	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1657
1221	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1222		1659
1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1660	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1224	when writing to a pipe whose other end has been closed, your program gets	1661	when writing to a pipe whose other end has been closed, your program gets
…		…
1227		1664
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1665	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1666	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1667	somewhere, as that would have given you a big clue).
1231		1668
		1669	=head3 The special problem of accept()ing when you can't
		1670
		1671	Many implementations of the POSIX C<accept> function (for example,
		1672	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1673	connection from the pending queue in all error cases.
		1674
		1675	For example, larger servers often run out of file descriptors (because
		1676	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1677	rejecting the connection, leading to libev signalling readiness on
		1678	the next iteration again (the connection still exists after all), and
		1679	typically causing the program to loop at 100% CPU usage.
		1680
		1681	Unfortunately, the set of errors that cause this issue differs between
		1682	operating systems, there is usually little the app can do to remedy the
		1683	situation, and no known thread-safe method of removing the connection to
		1684	cope with overload is known (to me).
		1685
		1686	One of the easiest ways to handle this situation is to just ignore it
		1687	- when the program encounters an overload, it will just loop until the
		1688	situation is over. While this is a form of busy waiting, no OS offers an
		1689	event-based way to handle this situation, so it's the best one can do.
		1690
		1691	A better way to handle the situation is to log any errors other than
		1692	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1693	messages, and continue as usual, which at least gives the user an idea of
		1694	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1695	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1696	usage.
		1697
		1698	If your program is single-threaded, then you could also keep a dummy file
		1699	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1700	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1701	close that fd, and create a new dummy fd. This will gracefully refuse
		1702	clients under typical overload conditions.
		1703
		1704	The last way to handle it is to simply log the error and C<exit>, as
		1705	is often done with C<malloc> failures, but this results in an easy
		1706	opportunity for a DoS attack.
1232		1707
1233	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1234		1709
1235	=over 4	1710	=over 4
1236		1711
…		…
1268	...	1743	...
1269	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1745	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1746	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1274		1749
1275		1750
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1752
1278	Timer watchers are simple relative timers that generate an event after a	1753	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1758	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1759	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1760	monotonic clock option helps a lot here).
1286		1761
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1762	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1763	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1764	might introduce a small delay). If multiple timers become ready during the
		1765	same loop iteration then the ones with earlier time-out values are invoked
		1766	before ones of the same priority with later time-out values (but this is
		1767	no longer true when a callback calls C<ev_run> recursively).
1290		1768
1291	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1292		1770
1293	Many real-world problems invole some kind of time-out, usually for error	1771	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1772	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1773	you want to raise some error after a while.
1296		1774
1297	Here are some ways on how to handle this problem, from simple and	1775	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1776	inefficient to smart and efficient.
1299		1777
1300	In the following examples a 60 second activity timeout is assumed - a	1778	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1779	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1780	data or other life sign was received).
1303		1781
1304	=over 4	1782	=over 4
1305		1783
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1784	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1785
1308	This is the most obvious, but not the most simple way: In the beginning,	1786	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1787	start the watcher:
1310		1788
1311	ev_timer_init (timer, callback, 60., 0.);	1789	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1790	ev_timer_start (loop, timer);
1313		1791
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1792	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1793	and start it again:
1316		1794
1317	ev_timer_stop (loop, timer);	1795	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1796	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1797	ev_timer_start (loop, timer);
1320		1798
1321	This is relatively simple to implement, but means that each time there	1799	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1800	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1801	data structure and then add it again. Libev tries to be fast, but it's
		1802	still not a constant-time operation.
1324		1803
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1804	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1805
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1806	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1807	C<ev_timer_start>.
1329		1808
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1809	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1810	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1811	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1812	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1813	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1814
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1815	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1816	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1817	member and C<ev_timer_again>.
1338		1818
1339	At start:	1819	At start:
1340		1820
1341	ev_timer_init (timer, callback, 0., 60.);	1821	ev_init (timer, callback);
		1822	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1823	ev_timer_again (loop, timer);
1343		1824
1344	Each time you receive some data:	1825	Each time there is some activity:
1345		1826
1346	ev_timer_again (loop, timer);	1827	ev_timer_again (loop, timer);
1347		1828
1348	It is even possible to change the time-out on the fly:	1829	It is even possible to change the time-out on the fly, regardless of
		1830	whether the watcher is active or not:
1349		1831
1350	timer->repeat = 30.;	1832	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1833	ev_timer_again (loop, timer);
1352		1834
1353	This is slightly more efficient then stopping/starting the timer each time	1835	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1836	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1837	remove and re-insert the timer from/into its internal data structure.
		1838
		1839	It is, however, even simpler than the "obvious" way to do it.
1356		1840
1357	=item 3. Let the timer time out, but then re-arm it as required.	1841	=item 3. Let the timer time out, but then re-arm it as required.
1358		1842
1359	This method is more tricky, but usually most efficient: Most timeouts are	1843	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1844	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1845	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1846	associated activity resets.
1363		1847
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1848	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1849	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1850	within the callback:
1367		1851
1368	ev_tstamp last_activity; // time of last activity	1852	ev_tstamp last_activity; // time of last activity
1369		1853
1370	static void	1854	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1855	callback (EV_P_ ev_timer *w, int revents)
1372	{	1856	{
1373	ev_tstamp now = ev_now (EV_A);	1857	ev_tstamp now = ev_now (EV_A);
1374	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1375		1859
1376	// if last_activity is older than now - timeout, we did time out	1860	// if last_activity + 60. is older than now, we did time out
1377	if (timeout < now)	1861	if (timeout < now)
1378	{	1862	{
1379	// timeout occured, take action	1863	// timeout occurred, take action
1380	}	1864	}
1381	else	1865	else
1382	{	1866	{
1383	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1384	// to fire in last_activity + 60.	1868	// the watcher to fire in last_activity + 60, which is
		1869	// guaranteed to be in the future, so "again" is positive:
1385	w->again = timeout - now;	1870	w->repeat = timeout - now;
1386	ev_timer_again (EV_A_ w);	1871	ev_timer_again (EV_A_ w);
1387	}	1872	}
1388	}	1873	}
1389		1874
1390	To summarise the callback: first calculate the real time-out (defined as	1875	To summarise the callback: first calculate the real timeout (defined
1391	"60 seconds after the last activity"), then check if that time has been	1876	as "60 seconds after the last activity"), then check if that time has
1392	reached, which means there was a real timeout. Otherwise the callback was	1877	been reached, which means something I<did>, in fact, time out. Otherwise
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1878	the callback was invoked too early (C<timeout> is in the future), so
1394	fire at that future time.	1879	re-schedule the timer to fire at that future time, to see if maybe we have
		1880	a timeout then.
1395		1881
1396	Note how C<ev_timer_again> is used, taking advantage of the	1882	Note how C<ev_timer_again> is used, taking advantage of the
1397	C<ev_timer_again> optimisation when the timer is already running.	1883	C<ev_timer_again> optimisation when the timer is already running.
1398		1884
1399	This scheme causes more callback invocations (about one every 60 seconds),	1885	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1886	minus half the average time between activity), but virtually no calls to
		1887	libev to change the timeout.
1401		1888
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1889	To start the timer, simply initialise the watcher and set C<last_activity>
1403	then call the callback:	1890	to the current time (meaning we just have some activity :), then call the
		1891	callback, which will "do the right thing" and start the timer:
1404		1892
1405	ev_timer_init (timer, callback);	1893	ev_init (timer, callback);
1406	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1407	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1408		1896
1409	And when there is some activity, simply remember the time in	1897	And when there is some activity, simply store the current time in
1410	C<last_activity>:	1898	C<last_activity>, no libev calls at all:
1411		1899
1412	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1413		1901
1414	This technique is slightly more complex, but in most cases where the	1902	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1416		1904
		1905	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1906	callback :) - just change the timeout and invoke the callback, which will
		1907	fix things for you.
		1908
		1909	=item 4. Wee, just use a double-linked list for your timeouts.
		1910
		1911	If there is not one request, but many thousands (millions...), all
		1912	employing some kind of timeout with the same timeout value, then one can
		1913	do even better:
		1914
		1915	When starting the timeout, calculate the timeout value and put the timeout
		1916	at the I<end> of the list.
		1917
		1918	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1919	the list is expected to fire (for example, using the technique #3).
		1920
		1921	When there is some activity, remove the timer from the list, recalculate
		1922	the timeout, append it to the end of the list again, and make sure to
		1923	update the C<ev_timer> if it was taken from the beginning of the list.
		1924
		1925	This way, one can manage an unlimited number of timeouts in O(1) time for
		1926	starting, stopping and updating the timers, at the expense of a major
		1927	complication, and having to use a constant timeout. The constant timeout
		1928	ensures that the list stays sorted.
		1929
1417	=back	1930	=back
		1931
		1932	So which method the best?
		1933
		1934	Method #2 is a simple no-brain-required solution that is adequate in most
		1935	situations. Method #3 requires a bit more thinking, but handles many cases
		1936	better, and isn't very complicated either. In most case, choosing either
		1937	one is fine, with #3 being better in typical situations.
		1938
		1939	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1940	rather complicated, but extremely efficient, something that really pays
		1941	off after the first million or so of active timers, i.e. it's usually
		1942	overkill :)
1418		1943
1419	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1420		1945
1421	Establishing the current time is a costly operation (it usually takes at	1946	Establishing the current time is a costly operation (it usually takes at
1422	least two system calls): EV therefore updates its idea of the current	1947	least two system calls): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	1948	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1949	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	1950	lots of events in one iteration.
1426		1951
1427	The relative timeouts are calculated relative to the C<ev_now ()>	1952	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	1953	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		1959
1435	If the event loop is suspended for a long time, you can also force an	1960	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1961	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	1962	()>.
1438		1963
		1964	=head3 The special problems of suspended animation
		1965
		1966	When you leave the server world it is quite customary to hit machines that
		1967	can suspend/hibernate - what happens to the clocks during such a suspend?
		1968
		1969	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1970	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1971	to run until the system is suspended, but they will not advance while the
		1972	system is suspended. That means, on resume, it will be as if the program
		1973	was frozen for a few seconds, but the suspend time will not be counted
		1974	towards C<ev_timer> when a monotonic clock source is used. The real time
		1975	clock advanced as expected, but if it is used as sole clocksource, then a
		1976	long suspend would be detected as a time jump by libev, and timers would
		1977	be adjusted accordingly.
		1978
		1979	I would not be surprised to see different behaviour in different between
		1980	operating systems, OS versions or even different hardware.
		1981
		1982	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1983	time jump in the monotonic clocks and the realtime clock. If the program
		1984	is suspended for a very long time, and monotonic clock sources are in use,
		1985	then you can expect C<ev_timer>s to expire as the full suspension time
		1986	will be counted towards the timers. When no monotonic clock source is in
		1987	use, then libev will again assume a timejump and adjust accordingly.
		1988
		1989	It might be beneficial for this latter case to call C<ev_suspend>
		1990	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1991	deterministic behaviour in this case (you can do nothing against
		1992	C<SIGSTOP>).
		1993
1439	=head3 Watcher-Specific Functions and Data Members	1994	=head3 Watcher-Specific Functions and Data Members
1440		1995
1441	=over 4	1996	=over 4
1442		1997
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1998	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2021	If the timer is started but non-repeating, stop it (as if it timed out).
1467		2022
1468	If the timer is repeating, either start it if necessary (with the	2023	If the timer is repeating, either start it if necessary (with the
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2024	C<repeat> value), or reset the running timer to the C<repeat> value.
1470		2025
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2026	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	2027	usage example.
		2028
		2029	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2030
		2031	Returns the remaining time until a timer fires. If the timer is active,
		2032	then this time is relative to the current event loop time, otherwise it's
		2033	the timeout value currently configured.
		2034
		2035	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2036	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2037	will return C<4>. When the timer expires and is restarted, it will return
		2038	roughly C<7> (likely slightly less as callback invocation takes some time,
		2039	too), and so on.
1473		2040
1474	=item ev_tstamp repeat [read-write]	2041	=item ev_tstamp repeat [read-write]
1475		2042
1476	The current C<repeat> value. Will be used each time the watcher times out	2043	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2044	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2070	}
1504		2071
1505	ev_timer mytimer;	2072	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2073	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1509		2076
1510	// and in some piece of code that gets executed on any "activity":	2077	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1513		2080
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2082	=head2 C<ev_periodic> - to cron or not to cron?
1516		2083
1517	Periodic watchers are also timers of a kind, but they are very versatile	2084	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2085	(and unfortunately a bit complex).
1519		2086
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2087	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2088	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2089	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2090	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2091	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2092	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2093
		2094	You can tell a periodic watcher to trigger after some specific point
		2095	in time: for example, if you tell a periodic watcher to trigger "in 10
		2096	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2097	not a delay) and then reset your system clock to January of the previous
		2098	year, then it will take a year or more to trigger the event (unlike an
		2099	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2100	it, as it uses a relative timeout).
		2101
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2102	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2103	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2104	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2105	those cannot react to time jumps.
1532		2106
1533	As with timers, the callback is guaranteed to be invoked only when the	2107	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2108	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2109	timers become ready during the same loop iteration then the ones with
		2110	earlier time-out values are invoked before ones with later time-out values
		2111	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2112
1537	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1538		2114
1539	=over 4	2115	=over 4
1540		2116
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2117	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2118
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2119	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2120
1545	Lots of arguments, lets sort it out... There are basically three modes of	2121	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2122	operation, and we will explain them from simplest to most complex:
1547		2123
1548	=over 4	2124	=over 4
1549		2125
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2126	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2127
1552	In this configuration the watcher triggers an event after the wall clock	2128	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2129	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2130	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2131	will be stopped and invoked when the system clock reaches or surpasses
		2132	this point in time.
1556		2133
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2134	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2135
1559	In this mode the watcher will always be scheduled to time out at the next	2136	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2137	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2138	negative) and then repeat, regardless of any time jumps. The C<offset>
		2139	argument is merely an offset into the C<interval> periods.
1562		2140
1563	This can be used to create timers that do not drift with respect to the	2141	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2142	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2143	hour, on the hour (with respect to UTC):
1566		2144
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2145	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2146
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2147	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2148	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2149	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2150	by 3600.
1573		2151
1574	Another way to think about it (for the mathematically inclined) is that	2152	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2153	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2154	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2155
1578	For numerical stability it is preferable that the C<at> value is near	2156	For numerical stability it is preferable that the C<offset> value is near
1579	C<ev_now ()> (the current time), but there is no range requirement for	2157	C<ev_now ()> (the current time), but there is no range requirement for
1580	this value, and in fact is often specified as zero.	2158	this value, and in fact is often specified as zero.
1581		2159
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2160	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2161	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2162	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2163	millisecond (if the OS supports it and the machine is fast enough).
1586		2164
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2165	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2166
1589	In this mode the values for C<interval> and C<at> are both being	2167	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2168	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2169	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2170	current time as second argument.
1593		2171
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2172	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2173	or make ANY other event loop modifications whatsoever, unless explicitly
		2174	allowed by documentation here>.
1596		2175
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2176	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2177	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2178	only event loop modification you are allowed to do).
1600		2179
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2209	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2210	program when the crontabs have changed).
1632		2211
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2212	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2213
1635	When active, returns the absolute time that the watcher is supposed to	2214	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2215	to trigger next. This is not the same as the C<offset> argument to
		2216	C<ev_periodic_set>, but indeed works even in interval and manual
		2217	rescheduling modes.
1637		2218
1638	=item ev_tstamp offset [read-write]	2219	=item ev_tstamp offset [read-write]
1639		2220
1640	When repeating, this contains the offset value, otherwise this is the	2221	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2222	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2223	although libev might modify this value for better numerical stability).
1642		2224
1643	Can be modified any time, but changes only take effect when the periodic	2225	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2226	timer fires or C<ev_periodic_again> is being called.
1645		2227
1646	=item ev_tstamp interval [read-write]	2228	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2244	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2245	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2246	potentially a lot of jitter, but good long-term stability.
1665		2247
1666	static void	2248	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2249	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2250	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2251	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2252	}
1671		2253
1672	ev_periodic hourly_tick;	2254	ev_periodic hourly_tick;
…		…
1695		2277
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2279
1698	Signal watchers will trigger an event when the process receives a specific	2280	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2281	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2282	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2283	normal event processing, like any other event.
1702		2284
1703	If you want signals asynchronously, just use C<sigaction> as you would	2285	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2286	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2287	the signal. You can even use C<ev_async> from a signal handler to
		2288	synchronously wake up an event loop.
1706		2289
1707	You can configure as many watchers as you like per signal. Only when the	2290	You can configure as many watchers as you like for the same signal, but
		2291	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2292	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2293	C<SIGINT> in both the default loop and another loop at the same time. At
		2294	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2295
1708	first watcher gets started will libev actually register a signal handler	2296	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2297	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2298	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2299
1714	If possible and supported, libev will install its handlers with	2300	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2301	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2302	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2303	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2304	and unblock them in an C<ev_prepare> watcher.
		2305
		2306	=head3 The special problem of inheritance over fork/execve/pthread_create
		2307
		2308	Both the signal mask (C<sigprocmask>) and the signal disposition
		2309	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2310	stopping it again), that is, libev might or might not block the signal,
		2311	and might or might not set or restore the installed signal handler (but
		2312	see C<EVFLAG_NOSIGMASK>).
		2313
		2314	While this does not matter for the signal disposition (libev never
		2315	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2316	C<execve>), this matters for the signal mask: many programs do not expect
		2317	certain signals to be blocked.
		2318
		2319	This means that before calling C<exec> (from the child) you should reset
		2320	the signal mask to whatever "default" you expect (all clear is a good
		2321	choice usually).
		2322
		2323	The simplest way to ensure that the signal mask is reset in the child is
		2324	to install a fork handler with C<pthread_atfork> that resets it. That will
		2325	catch fork calls done by libraries (such as the libc) as well.
		2326
		2327	In current versions of libev, the signal will not be blocked indefinitely
		2328	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2329	the window of opportunity for problems, it will not go away, as libev
		2330	I<has> to modify the signal mask, at least temporarily.
		2331
		2332	So I can't stress this enough: I<If you do not reset your signal mask when
		2333	you expect it to be empty, you have a race condition in your code>. This
		2334	is not a libev-specific thing, this is true for most event libraries.
		2335
		2336	=head3 The special problem of threads signal handling
		2337
		2338	POSIX threads has problematic signal handling semantics, specifically,
		2339	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2340	threads in a process block signals, which is hard to achieve.
		2341
		2342	When you want to use sigwait (or mix libev signal handling with your own
		2343	for the same signals), you can tackle this problem by globally blocking
		2344	all signals before creating any threads (or creating them with a fully set
		2345	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2346	loops. Then designate one thread as "signal receiver thread" which handles
		2347	these signals. You can pass on any signals that libev might be interested
		2348	in by calling C<ev_feed_signal>.
1719		2349
1720	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
1721		2351
1722	=over 4	2352	=over 4
1723		2353
…		…
1739	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
1740		2370
1741	static void	2371	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2373	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
1745	}	2375	}
1746		2376
1747	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2385	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2386	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2387	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2388	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2389	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2390	but forking and registering a watcher a few event loop iterations later or
1761	not.	2391	in the next callback invocation is not.
1762		2392
1763	Only the default event loop is capable of handling signals, and therefore	2393	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2394	you can only register child watchers in the default event loop.
1765		2395
		2396	Due to some design glitches inside libev, child watchers will always be
		2397	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2398	libev)
		2399
1766	=head3 Process Interaction	2400	=head3 Process Interaction
1767		2401
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2402	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2403	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2404	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2405	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2406	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2407	children, even ones not watched.
1774		2408
1775	=head3 Overriding the Built-In Processing	2409	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2419	=head3 Stopping the Child Watcher
1786		2420
1787	Currently, the child watcher never gets stopped, even when the	2421	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2422	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2423	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2424	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2425	problem).
1791		2426
1792	=head3 Watcher-Specific Functions and Data Members	2427	=head3 Watcher-Specific Functions and Data Members
1793		2428
1794	=over 4	2429	=over 4
1795		2430
…		…
1852		2487
1853		2488
1854	=head2 C<ev_stat> - did the file attributes just change?	2489	=head2 C<ev_stat> - did the file attributes just change?
1855		2490
1856	This watches a file system path for attribute changes. That is, it calls	2491	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2492	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2493	and sees if it changed compared to the last time, invoking the callback if
		2494	it did.
1859		2495
1860	The path does not need to exist: changing from "path exists" to "path does	2496	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2497	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2498	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2499	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2500	least one) and all the other fields of the stat buffer having unspecified
		2501	contents.
1865		2502
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2503	The path I<must not> end in a slash or contain special components such as
		2504	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2505	your working directory changes, then the behaviour is undefined.
1868		2506
1869	Since there is no standard kernel interface to do this, the portable	2507	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2508	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2509	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2510	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2511	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2512	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2513	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2514	currently around C<0.1>, but that's usually overkill.
1877		2515
1878	This watcher type is not meant for massive numbers of stat watchers,	2516	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2517	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2518	resource-intensive.
1881		2519
1882	At the time of this writing, the only OS-specific interface implemented	2520	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2521	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2522	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2523	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2524
1887	=head3 ABI Issues (Largefile Support)	2525	=head3 ABI Issues (Largefile Support)
1888		2526
1889	Libev by default (unless the user overrides this) uses the default	2527	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2528	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2529	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2530	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2531	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2532	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2533	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2534	most noticeably displayed with ev_stat and large file support.
1897		2535
1898	The solution for this is to lobby your distribution maker to make large	2536	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2537	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2538	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2539	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2540	default compilation environment.
1903		2541
1904	=head3 Inotify and Kqueue	2542	=head3 Inotify and Kqueue
1905		2543
1906	When C<inotify (7)> support has been compiled into libev (generally	2544	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2545	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2546	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2547	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2548
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2549	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2550	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2551	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2552	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2553	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2554	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2555	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2556	xfs are fully working) libev usually gets away without polling.
1917		2557
1918	There is no support for kqueue, as apparently it cannot be used to	2558	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2559	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2560	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2561	etc. is difficult.
1922		2562
		2563	=head3 C<stat ()> is a synchronous operation
		2564
		2565	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2566	the process. The exception are C<ev_stat> watchers - those call C<stat
		2567	()>, which is a synchronous operation.
		2568
		2569	For local paths, this usually doesn't matter: unless the system is very
		2570	busy or the intervals between stat's are large, a stat call will be fast,
		2571	as the path data is usually in memory already (except when starting the
		2572	watcher).
		2573
		2574	For networked file systems, calling C<stat ()> can block an indefinite
		2575	time due to network issues, and even under good conditions, a stat call
		2576	often takes multiple milliseconds.
		2577
		2578	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2579	paths, although this is fully supported by libev.
		2580
1923	=head3 The special problem of stat time resolution	2581	=head3 The special problem of stat time resolution
1924		2582
1925	The C<stat ()> system call only supports full-second resolution portably, and	2583	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2584	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2585	still only support whole seconds.
1928		2586
1929	That means that, if the time is the only thing that changes, you can	2587	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2588	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2589	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2590	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2733
2076	=head3 Watcher-Specific Functions and Data Members	2734	=head3 Watcher-Specific Functions and Data Members
2077		2735
2078	=over 4	2736	=over 4
2079		2737
2080	=item ev_idle_init (ev_signal *, callback)	2738	=item ev_idle_init (ev_idle *, callback)
2081		2739
2082	Initialises and configures the idle watcher - it has no parameters of any	2740	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2741	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2742	believe me.
2085		2743
…		…
2098	// no longer anything immediate to do.	2756	// no longer anything immediate to do.
2099	}	2757	}
2100		2758
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2759	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2760	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2761	ev_idle_start (loop, idle_watcher);
2104		2762
2105		2763
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2764	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2765
2108	Prepare and check watchers are usually (but not always) used in pairs:	2766	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2768	afterwards.
2111		2769
2112	You I<must not> call C<ev_loop> or similar functions that enter	2770	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2771	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2772	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2773	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2774	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2775	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2859	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2860	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2861	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2862
2205	/* the callback is illegal, but won't be called as we stop during check */	2863	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2864	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2865	ev_timer_start (loop, &tw);
2208		2866
2209	// create one ev_io per pollfd	2867	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2868	for (int i = 0; i < nfd; ++i)
2211	{	2869	{
…		…
2285		2943
2286	if (timeout >= 0)	2944	if (timeout >= 0)
2287	// create/start timer	2945	// create/start timer
2288		2946
2289	// poll	2947	// poll
2290	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2291		2949
2292	// stop timer again	2950	// stop timer again
2293	if (timeout >= 0)	2951	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2295		2953
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	2982	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	2983	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	2984	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	2985	the rest in a second one, and embed the second one in the first.
2328		2986
2329	As long as the watcher is active, the callback will be invoked every time	2987	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	2988	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2989	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	2990	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	2991	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	2992	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		2993
2337	As long as the watcher is started it will automatically handle events. The	2994	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	2995	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		2996
2342	Also, there have not currently been made special provisions for forking:	2997	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2998	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	2999	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3000	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3001
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3002	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3003	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3004	portable one.
2351		3005
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	3031	if you do not want that, you need to temporarily stop the embed watcher).
2378		3032
2379	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2380		3034
2381	Make a single, non-blocking sweep over the embedded loop. This works	3035	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3036	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2384		3038
2385	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2386		3040
2387	The embedded event loop.	3041	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3099	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3100	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3101	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3102	handlers will be invoked, too, of course.
2449		3103
		3104	=head3 The special problem of life after fork - how is it possible?
		3105
		3106	Most uses of C<fork()> consist of forking, then some simple calls to set
		3107	up/change the process environment, followed by a call to C<exec()>. This
		3108	sequence should be handled by libev without any problems.
		3109
		3110	This changes when the application actually wants to do event handling
		3111	in the child, or both parent in child, in effect "continuing" after the
		3112	fork.
		3113
		3114	The default mode of operation (for libev, with application help to detect
		3115	forks) is to duplicate all the state in the child, as would be expected
		3116	when I<either> the parent I<or> the child process continues.
		3117
		3118	When both processes want to continue using libev, then this is usually the
		3119	wrong result. In that case, usually one process (typically the parent) is
		3120	supposed to continue with all watchers in place as before, while the other
		3121	process typically wants to start fresh, i.e. without any active watchers.
		3122
		3123	The cleanest and most efficient way to achieve that with libev is to
		3124	simply create a new event loop, which of course will be "empty", and
		3125	use that for new watchers. This has the advantage of not touching more
		3126	memory than necessary, and thus avoiding the copy-on-write, and the
		3127	disadvantage of having to use multiple event loops (which do not support
		3128	signal watchers).
		3129
		3130	When this is not possible, or you want to use the default loop for
		3131	other reasons, then in the process that wants to start "fresh", call
		3132	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3133	Destroying the default loop will "orphan" (not stop) all registered
		3134	watchers, so you have to be careful not to execute code that modifies
		3135	those watchers. Note also that in that case, you have to re-register any
		3136	signal watchers.
		3137
2450	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
2451		3139
2452	=over 4	3140	=over 4
2453		3141
2454	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
2455		3143
2456	Initialises and configures the fork watcher - it has no parameters of any	3144	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3145	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3146	really.
2459		3147
2460	=back	3148	=back
2461		3149
2462		3150
		3151	=head2 C<ev_cleanup> - even the best things end
		3152
		3153	Cleanup watchers are called just before the event loop is being destroyed
		3154	by a call to C<ev_loop_destroy>.
		3155
		3156	While there is no guarantee that the event loop gets destroyed, cleanup
		3157	watchers provide a convenient method to install cleanup hooks for your
		3158	program, worker threads and so on - you just to make sure to destroy the
		3159	loop when you want them to be invoked.
		3160
		3161	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3162	all other watchers, they do not keep a reference to the event loop (which
		3163	makes a lot of sense if you think about it). Like all other watchers, you
		3164	can call libev functions in the callback, except C<ev_cleanup_start>.
		3165
		3166	=head3 Watcher-Specific Functions and Data Members
		3167
		3168	=over 4
		3169
		3170	=item ev_cleanup_init (ev_cleanup *, callback)
		3171
		3172	Initialises and configures the cleanup watcher - it has no parameters of
		3173	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3174	pointless, I assure you.
		3175
		3176	=back
		3177
		3178	Example: Register an atexit handler to destroy the default loop, so any
		3179	cleanup functions are called.
		3180
		3181	static void
		3182	program_exits (void)
		3183	{
		3184	ev_loop_destroy (EV_DEFAULT_UC);
		3185	}
		3186
		3187	...
		3188	atexit (program_exits);
		3189
		3190
2463	=head2 C<ev_async> - how to wake up another event loop	3191	=head2 C<ev_async> - how to wake up an event loop
2464		3192
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	In general, you cannot use an C<ev_run> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
2468		3196
2469	Sometimes, however, you need to wake up another event loop you do not	3197	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3198	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3199	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3200	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3201
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3202	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3203	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3204	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3205	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3206	of "global async watchers" by using a watcher on an otherwise unused
		3207	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3208	even without knowing which loop owns the signal.
2479		3209
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3210	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2481	just the default loop.	3211	just the default loop.
2482		3212
2483	=head3 Queueing	3213	=head3 Queueing
2484		3214
2485	C<ev_async> does not support queueing of data in any way. The reason	3215	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3216	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3217	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3218	need elaborate support such as pthreads or unportable memory access
		3219	semantics.
2489		3220
2490	That means that if you want to queue data, you have to provide your own	3221	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3222	queue. But at least I can tell you how to implement locking around your
2492	queue:	3223	queue:
2493		3224
…		…
2571	=over 4	3302	=over 4
2572		3303
2573	=item ev_async_init (ev_async *, callback)	3304	=item ev_async_init (ev_async *, callback)
2574		3305
2575	Initialises and configures the async watcher - it has no parameters of any	3306	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3307	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3308	trust me.
2578		3309
2579	=item ev_async_send (loop, ev_async *)	3310	=item ev_async_send (loop, ev_async *)
2580		3311
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3312	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3313	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3314	C<ev_feed_event>, this call is safe to do from other threads, signal or
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3315	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2585	section below on what exactly this means).	3316	section below on what exactly this means).
2586		3317
		3318	Note that, as with other watchers in libev, multiple events might get
		3319	compressed into a single callback invocation (another way to look at this
		3320	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3321	reset when the event loop detects that).
		3322
2587	This call incurs the overhead of a system call only once per loop iteration,	3323	This call incurs the overhead of a system call only once per event loop
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3324	iteration, so while the overhead might be noticeable, it doesn't apply to
2589	calls to C<ev_async_send>.	3325	repeated calls to C<ev_async_send> for the same event loop.
2590		3326
2591	=item bool = ev_async_pending (ev_async *)	3327	=item bool = ev_async_pending (ev_async *)
2592		3328
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3329	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3330	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3333	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3334	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3335	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3336	quickly check whether invoking the loop might be a good idea.
2601		3337
2602	Not that this does I<not> check whether the watcher itself is pending, only	3338	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3339	only whether it has been requested to make this watcher pending: there
		3340	is a time window between the event loop checking and resetting the async
		3341	notification, and the callback being invoked.
2604		3342
2605	=back	3343	=back
2606		3344
2607		3345
2608	=head1 OTHER FUNCTIONS	3346	=head1 OTHER FUNCTIONS
…		…
2625		3363
2626	If C<timeout> is less than 0, then no timeout watcher will be	3364	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3365	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3366	repeat = 0) will be started. C<0> is a valid timeout.
2629		3367
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3368	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3369	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3370	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3371	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3372	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3373	events precedence.
2636		3374
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3375	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3376
2639	static void stdin_ready (int revents, void *arg)	3377	static void stdin_ready (int revents, void *arg)
2640	{	3378	{
2641	if (revents & EV_READ)	3379	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3380	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3381	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3382	/* doh, nothing entered */;
2645	}	3383	}
2646		3384
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3385	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3386
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3387	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3388
2657	Feed an event on the given fd, as if a file descriptor backend detected	3389	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3390	the given events it.
2659		3391
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3392	=item ev_feed_signal_event (loop, int signum)
2661		3393
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3394	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3395	which is async-safe.
2664		3396
2665	=back	3397	=back
		3398
		3399
		3400	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3401
		3402	This section explains some common idioms that are not immediately
		3403	obvious. Note that examples are sprinkled over the whole manual, and this
		3404	section only contains stuff that wouldn't fit anywhere else.
		3405
		3406	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3407
		3408	Each watcher has, by default, a C<void *data> member that you can read
		3409	or modify at any time: libev will completely ignore it. This can be used
		3410	to associate arbitrary data with your watcher. If you need more data and
		3411	don't want to allocate memory separately and store a pointer to it in that
		3412	data member, you can also "subclass" the watcher type and provide your own
		3413	data:
		3414
		3415	struct my_io
		3416	{
		3417	ev_io io;
		3418	int otherfd;
		3419	void *somedata;
		3420	struct whatever *mostinteresting;
		3421	};
		3422
		3423	...
		3424	struct my_io w;
		3425	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3426
		3427	And since your callback will be called with a pointer to the watcher, you
		3428	can cast it back to your own type:
		3429
		3430	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3431	{
		3432	struct my_io *w = (struct my_io *)w_;
		3433	...
		3434	}
		3435
		3436	More interesting and less C-conformant ways of casting your callback
		3437	function type instead have been omitted.
		3438
		3439	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3440
		3441	Another common scenario is to use some data structure with multiple
		3442	embedded watchers, in effect creating your own watcher that combines
		3443	multiple libev event sources into one "super-watcher":
		3444
		3445	struct my_biggy
		3446	{
		3447	int some_data;
		3448	ev_timer t1;
		3449	ev_timer t2;
		3450	}
		3451
		3452	In this case getting the pointer to C<my_biggy> is a bit more
		3453	complicated: Either you store the address of your C<my_biggy> struct in
		3454	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3455	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3456	real programmers):
		3457
		3458	#include <stddef.h>
		3459
		3460	static void
		3461	t1_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t1));
		3465	}
		3466
		3467	static void
		3468	t2_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t2));
		3472	}
		3473
		3474	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3475
		3476	Often (especially in GUI toolkits) there are places where you have
		3477	I<modal> interaction, which is most easily implemented by recursively
		3478	invoking C<ev_run>.
		3479
		3480	This brings the problem of exiting - a callback might want to finish the
		3481	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3482	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3483	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3484	other combination: In these cases, C<ev_break> will not work alone.
		3485
		3486	The solution is to maintain "break this loop" variable for each C<ev_run>
		3487	invocation, and use a loop around C<ev_run> until the condition is
		3488	triggered, using C<EVRUN_ONCE>:
		3489
		3490	// main loop
		3491	int exit_main_loop = 0;
		3492
		3493	while (!exit_main_loop)
		3494	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3495
		3496	// in a model watcher
		3497	int exit_nested_loop = 0;
		3498
		3499	while (!exit_nested_loop)
		3500	ev_run (EV_A_ EVRUN_ONCE);
		3501
		3502	To exit from any of these loops, just set the corresponding exit variable:
		3503
		3504	// exit modal loop
		3505	exit_nested_loop = 1;
		3506
		3507	// exit main program, after modal loop is finished
		3508	exit_main_loop = 1;
		3509
		3510	// exit both
		3511	exit_main_loop = exit_nested_loop = 1;
		3512
		3513	=head2 THREAD LOCKING EXAMPLE
		3514
		3515	Here is a fictitious example of how to run an event loop in a different
		3516	thread from where callbacks are being invoked and watchers are
		3517	created/added/removed.
		3518
		3519	For a real-world example, see the C<EV::Loop::Async> perl module,
		3520	which uses exactly this technique (which is suited for many high-level
		3521	languages).
		3522
		3523	The example uses a pthread mutex to protect the loop data, a condition
		3524	variable to wait for callback invocations, an async watcher to notify the
		3525	event loop thread and an unspecified mechanism to wake up the main thread.
		3526
		3527	First, you need to associate some data with the event loop:
		3528
		3529	typedef struct {
		3530	mutex_t lock; /* global loop lock */
		3531	ev_async async_w;
		3532	thread_t tid;
		3533	cond_t invoke_cv;
		3534	} userdata;
		3535
		3536	void prepare_loop (EV_P)
		3537	{
		3538	// for simplicity, we use a static userdata struct.
		3539	static userdata u;
		3540
		3541	ev_async_init (&u->async_w, async_cb);
		3542	ev_async_start (EV_A_ &u->async_w);
		3543
		3544	pthread_mutex_init (&u->lock, 0);
		3545	pthread_cond_init (&u->invoke_cv, 0);
		3546
		3547	// now associate this with the loop
		3548	ev_set_userdata (EV_A_ u);
		3549	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3550	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3551
		3552	// then create the thread running ev_loop
		3553	pthread_create (&u->tid, 0, l_run, EV_A);
		3554	}
		3555
		3556	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3557	solely to wake up the event loop so it takes notice of any new watchers
		3558	that might have been added:
		3559
		3560	static void
		3561	async_cb (EV_P_ ev_async *w, int revents)
		3562	{
		3563	// just used for the side effects
		3564	}
		3565
		3566	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3567	protecting the loop data, respectively.
		3568
		3569	static void
		3570	l_release (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_unlock (&u->lock);
		3574	}
		3575
		3576	static void
		3577	l_acquire (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_lock (&u->lock);
		3581	}
		3582
		3583	The event loop thread first acquires the mutex, and then jumps straight
		3584	into C<ev_run>:
		3585
		3586	void *
		3587	l_run (void *thr_arg)
		3588	{
		3589	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3590
		3591	l_acquire (EV_A);
		3592	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3593	ev_run (EV_A_ 0);
		3594	l_release (EV_A);
		3595
		3596	return 0;
		3597	}
		3598
		3599	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3600	signal the main thread via some unspecified mechanism (signals? pipe
		3601	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3602	have been called (in a while loop because a) spurious wakeups are possible
		3603	and b) skipping inter-thread-communication when there are no pending
		3604	watchers is very beneficial):
		3605
		3606	static void
		3607	l_invoke (EV_P)
		3608	{
		3609	userdata *u = ev_userdata (EV_A);
		3610
		3611	while (ev_pending_count (EV_A))
		3612	{
		3613	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3614	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3615	}
		3616	}
		3617
		3618	Now, whenever the main thread gets told to invoke pending watchers, it
		3619	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3620	thread to continue:
		3621
		3622	static void
		3623	real_invoke_pending (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	pthread_mutex_lock (&u->lock);
		3628	ev_invoke_pending (EV_A);
		3629	pthread_cond_signal (&u->invoke_cv);
		3630	pthread_mutex_unlock (&u->lock);
		3631	}
		3632
		3633	Whenever you want to start/stop a watcher or do other modifications to an
		3634	event loop, you will now have to lock:
		3635
		3636	ev_timer timeout_watcher;
		3637	userdata *u = ev_userdata (EV_A);
		3638
		3639	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3640
		3641	pthread_mutex_lock (&u->lock);
		3642	ev_timer_start (EV_A_ &timeout_watcher);
		3643	ev_async_send (EV_A_ &u->async_w);
		3644	pthread_mutex_unlock (&u->lock);
		3645
		3646	Note that sending the C<ev_async> watcher is required because otherwise
		3647	an event loop currently blocking in the kernel will have no knowledge
		3648	about the newly added timer. By waking up the loop it will pick up any new
		3649	watchers in the next event loop iteration.
		3650
		3651	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3652
		3653	While the overhead of a callback that e.g. schedules a thread is small, it
		3654	is still an overhead. If you embed libev, and your main usage is with some
		3655	kind of threads or coroutines, you might want to customise libev so that
		3656	doesn't need callbacks anymore.
		3657
		3658	Imagine you have coroutines that you can switch to using a function
		3659	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3660	and that due to some magic, the currently active coroutine is stored in a
		3661	global called C<current_coro>. Then you can build your own "wait for libev
		3662	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3663	the differing C<;> conventions):
		3664
		3665	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3666	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3667
		3668	That means instead of having a C callback function, you store the
		3669	coroutine to switch to in each watcher, and instead of having libev call
		3670	your callback, you instead have it switch to that coroutine.
		3671
		3672	A coroutine might now wait for an event with a function called
		3673	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3674	matter when, or whether the watcher is active or not when this function is
		3675	called):
		3676
		3677	void
		3678	wait_for_event (ev_watcher *w)
		3679	{
		3680	ev_cb_set (w) = current_coro;
		3681	switch_to (libev_coro);
		3682	}
		3683
		3684	That basically suspends the coroutine inside C<wait_for_event> and
		3685	continues the libev coroutine, which, when appropriate, switches back to
		3686	this or any other coroutine. I am sure if you sue this your own :)
		3687
		3688	You can do similar tricks if you have, say, threads with an event queue -
		3689	instead of storing a coroutine, you store the queue object and instead of
		3690	switching to a coroutine, you push the watcher onto the queue and notify
		3691	any waiters.
		3692
		3693	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3694	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3695
		3696	// my_ev.h
		3697	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3698	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3699	#include "../libev/ev.h"
		3700
		3701	// my_ev.c
		3702	#define EV_H "my_ev.h"
		3703	#include "../libev/ev.c"
		3704
		3705	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3706	F<my_ev.c> into your project. When properly specifying include paths, you
		3707	can even use F<ev.h> as header file name directly.
2666		3708
2667		3709
2668	=head1 LIBEVENT EMULATION	3710	=head1 LIBEVENT EMULATION
2669		3711
2670	Libev offers a compatibility emulation layer for libevent. It cannot	3712	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	3713	emulate the internals of libevent, so here are some usage hints:
2672		3714
2673	=over 4	3715	=over 4
		3716
		3717	=item * Only the libevent-1.4.1-beta API is being emulated.
		3718
		3719	This was the newest libevent version available when libev was implemented,
		3720	and is still mostly unchanged in 2010.
2674		3721
2675	=item * Use it by including <event.h>, as usual.	3722	=item * Use it by including <event.h>, as usual.
2676		3723
2677	=item * The following members are fully supported: ev_base, ev_callback,	3724	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	3725	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3731	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3732	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3733	is an ev_pri field.
2687		3734
2688	=item * In libevent, the last base created gets the signals, in libev, the	3735	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3736	base that registered the signal gets the signals.
2690		3737
2691	=item * Other members are not supported.	3738	=item * Other members are not supported.
2692		3739
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3740	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3741	to use the libev header file and library.
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	3760	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	3761	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	3762	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	3763	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		3764
2718	Currently, functions, and static and non-static member functions can be	3765	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	3766	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	3767	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	3768	you need support for other types of functors please contact the author
2722	it).	3769	(preferably after implementing it).
2723		3770
2724	Here is a list of things available in the C<ev> namespace:	3771	Here is a list of things available in the C<ev> namespace:
2725		3772
2726	=over 4	3773	=over 4
2727		3774
…		…
2745		3792
2746	=over 4	3793	=over 4
2747		3794
2748	=item ev::TYPE::TYPE ()	3795	=item ev::TYPE::TYPE ()
2749		3796
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3797	=item ev::TYPE::TYPE (loop)
2751		3798
2752	=item ev::TYPE::~TYPE	3799	=item ev::TYPE::~TYPE
2753		3800
2754	The constructor (optionally) takes an event loop to associate the watcher	3801	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3802	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3834
2788	myclass obj;	3835	myclass obj;
2789	ev::io iow;	3836	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3837	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3838
		3839	=item w->set (object *)
		3840
		3841	This is a variation of a method callback - leaving out the method to call
		3842	will default the method to C<operator ()>, which makes it possible to use
		3843	functor objects without having to manually specify the C<operator ()> all
		3844	the time. Incidentally, you can then also leave out the template argument
		3845	list.
		3846
		3847	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3848	int revents)>.
		3849
		3850	See the method-C<set> above for more details.
		3851
		3852	Example: use a functor object as callback.
		3853
		3854	struct myfunctor
		3855	{
		3856	void operator() (ev::io &w, int revents)
		3857	{
		3858	...
		3859	}
		3860	}
		3861
		3862	myfunctor f;
		3863
		3864	ev::io w;
		3865	w.set (&f);
		3866
2792	=item w->set<function> (void *data = 0)	3867	=item w->set<function> (void *data = 0)
2793		3868
2794	Also sets a callback, but uses a static method or plain function as	3869	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	3870	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	3871	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	3877	Example: Use a plain function as callback.
2803		3878
2804	static void io_cb (ev::io &w, int revents) { }	3879	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	3880	iow.set <io_cb> ();
2806		3881
2807	=item w->set (struct ev_loop *)	3882	=item w->set (loop)
2808		3883
2809	Associates a different C<struct ev_loop> with this watcher. You can only	3884	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	3885	do this when the watcher is inactive (and not pending either).
2811		3886
2812	=item w->set ([arguments])	3887	=item w->set ([arguments])
2813		3888
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3889	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	3890	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	3891	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	3892	when reconfiguring it with this method.
2818		3893
2819	=item w->start ()	3894	=item w->start ()
2820		3895
2821	Starts the watcher. Note that there is no C<loop> argument, as the	3896	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	3897	constructor already stores the event loop.
2823		3898
		3899	=item w->start ([arguments])
		3900
		3901	Instead of calling C<set> and C<start> methods separately, it is often
		3902	convenient to wrap them in one call. Uses the same type of arguments as
		3903	the configure C<set> method of the watcher.
		3904
2824	=item w->stop ()	3905	=item w->stop ()
2825		3906
2826	Stops the watcher if it is active. Again, no C<loop> argument.	3907	Stops the watcher if it is active. Again, no C<loop> argument.
2827		3908
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3909	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		3921
2841	=back	3922	=back
2842		3923
2843	=back	3924	=back
2844		3925
2845	Example: Define a class with an IO and idle watcher, start one of them in	3926	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	3927	watchers in the constructor.
2847		3928
2848	class myclass	3929	class myclass
2849	{	3930	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	3931	ev::io io ; void io_cb (ev::io &w, int revents);
		3932	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3933	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		3934
2853	myclass (int fd)	3935	myclass (int fd)
2854	{	3936	{
2855	io .set <myclass, &myclass::io_cb > (this);	3937	io .set <myclass, &myclass::io_cb > (this);
		3938	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	3939	idle.set <myclass, &myclass::idle_cb> (this);
2857		3940
2858	io.start (fd, ev::READ);	3941	io.set (fd, ev::WRITE); // configure the watcher
		3942	io.start (); // start it whenever convenient
		3943
		3944	io2.start (fd, ev::READ); // set + start in one call
2859	}	3945	}
2860	};	3946	};
2861		3947
2862		3948
2863	=head1 OTHER LANGUAGE BINDINGS	3949	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	3968	L<http://software.schmorp.de/pkg/EV>.
2883		3969
2884	=item Python	3970	=item Python
2885		3971
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3972	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	3973	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		3974
2893	=item Ruby	3975	=item Ruby
2894		3976
2895	Tony Arcieri has written a ruby extension that offers access to a subset	3977	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	3978	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	3979	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	3980	L<http://rev.rubyforge.org/>.
2899		3981
		3982	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3983	makes rev work even on mingw.
		3984
		3985	=item Haskell
		3986
		3987	A haskell binding to libev is available at
		3988	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3989
2900	=item D	3990	=item D
2901		3991
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3992	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3993	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3994
		3995	=item Ocaml
		3996
		3997	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3998	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3999
		4000	=item Lua
		4001
		4002	Brian Maher has written a partial interface to libev for lua (at the
		4003	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4004	L<http://github.com/brimworks/lua-ev>.
2904		4005
2905	=back	4006	=back
2906		4007
2907		4008
2908	=head1 MACRO MAGIC	4009	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4023	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4024	C<EV_A_> is used when other arguments are following. Example:
2924		4025
2925	ev_unref (EV_A);	4026	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4027	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4028	ev_run (EV_A_ 0);
2928		4029
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4030	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4031	which is often provided by the following macro.
2931		4032
2932	=item C<EV_P>, C<EV_P_>	4033	=item C<EV_P>, C<EV_P_>
…		…
2972	}	4073	}
2973		4074
2974	ev_check check;	4075	ev_check check;
2975	ev_check_init (&check, check_cb);	4076	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4077	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4078	ev_run (EV_DEFAULT_ 0);
2978		4079
2979	=head1 EMBEDDING	4080	=head1 EMBEDDING
2980		4081
2981	Libev can (and often is) directly embedded into host	4082	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4083	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4110
3010	#define EV_STANDALONE 1	4111	#define EV_STANDALONE 1
3011	#include "ev.h"	4112	#include "ev.h"
3012		4113
3013	Both header files and implementation files can be compiled with a C++	4114	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4115	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4116	as a bug).
3016		4117
3017	You need the following files in your source tree, or in a directory	4118	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4119	in your include path (e.g. in libev/ when using -Ilibev):
3019		4120
…		…
3062	libev.m4	4163	libev.m4
3063		4164
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4165	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4166
3066	Libev can be configured via a variety of preprocessor symbols you have to	4167	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4168	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4169	the absence of autoconf is documented for every option.
		4170
		4171	Symbols marked with "(h)" do not change the ABI, and can have different
		4172	values when compiling libev vs. including F<ev.h>, so it is permissible
		4173	to redefine them before including F<ev.h> without breaking compatibility
		4174	to a compiled library. All other symbols change the ABI, which means all
		4175	users of libev and the libev code itself must be compiled with compatible
		4176	settings.
3069		4177
3070	=over 4	4178	=over 4
3071		4179
		4180	=item EV_COMPAT3 (h)
		4181
		4182	Backwards compatibility is a major concern for libev. This is why this
		4183	release of libev comes with wrappers for the functions and symbols that
		4184	have been renamed between libev version 3 and 4.
		4185
		4186	You can disable these wrappers (to test compatibility with future
		4187	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4188	sources. This has the additional advantage that you can drop the C<struct>
		4189	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4190	typedef in that case.
		4191
		4192	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4193	and in some even more future version the compatibility code will be
		4194	removed completely.
		4195
3072	=item EV_STANDALONE	4196	=item EV_STANDALONE (h)
3073		4197
3074	Must always be C<1> if you do not use autoconf configuration, which	4198	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4199	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4200	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4201	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4202	F<event.h> that are not directly supported by the libev core alone.
3079		4203
		4204	In standalone mode, libev will still try to automatically deduce the
		4205	configuration, but has to be more conservative.
		4206
3080	=item EV_USE_MONOTONIC	4207	=item EV_USE_MONOTONIC
3081		4208
3082	If defined to be C<1>, libev will try to detect the availability of the	4209	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4210	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4211	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4212	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4213	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4214	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4215	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4216
3090	=item EV_USE_REALTIME	4217	=item EV_USE_REALTIME
3091		4218
3092	If defined to be C<1>, libev will try to detect the availability of the	4219	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4220	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4221	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4222	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4223	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4224	correctness. See the note about libraries in the description of
		4225	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4226	C<EV_USE_CLOCK_SYSCALL>.
		4227
		4228	=item EV_USE_CLOCK_SYSCALL
		4229
		4230	If defined to be C<1>, libev will try to use a direct syscall instead
		4231	of calling the system-provided C<clock_gettime> function. This option
		4232	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4233	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4234	programs needlessly. Using a direct syscall is slightly slower (in
		4235	theory), because no optimised vdso implementation can be used, but avoids
		4236	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4237	higher, as it simplifies linking (no need for C<-lrt>).
3098		4238
3099	=item EV_USE_NANOSLEEP	4239	=item EV_USE_NANOSLEEP
3100		4240
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4241	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4242	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4258
3119	=item EV_SELECT_USE_FD_SET	4259	=item EV_SELECT_USE_FD_SET
3120		4260
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4261	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4262	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4263	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4264	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4265	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4266	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4267	configures the maximum size of the C<fd_set>.
3128		4268
3129	=item EV_SELECT_IS_WINSOCKET	4269	=item EV_SELECT_IS_WINSOCKET
3130		4270
3131	When defined to C<1>, the select backend will assume that	4271	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4272	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4274	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4275	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4276	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4277	on win32. Should not be defined on non-win32 platforms.
3138		4278
3139	=item EV_FD_TO_WIN32_HANDLE	4279	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4280
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4281	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4282	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4283	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4284	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4285	in which case they can provide this function to map fds to socket handles.
		4286
		4287	=item EV_WIN32_HANDLE_TO_FD(handle)
		4288
		4289	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4290	using the standard C<_open_osfhandle> function. For programs implementing
		4291	their own fd to handle mapping, overwriting this function makes it easier
		4292	to do so. This can be done by defining this macro to an appropriate value.
		4293
		4294	=item EV_WIN32_CLOSE_FD(fd)
		4295
		4296	If programs implement their own fd to handle mapping on win32, then this
		4297	macro can be used to override the C<close> function, useful to unregister
		4298	file descriptors again. Note that the replacement function has to close
		4299	the underlying OS handle.
3146		4300
3147	=item EV_USE_POLL	4301	=item EV_USE_POLL
3148		4302
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4303	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4304	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3197	as well as for signal and thread safety in C<ev_async> watchers.	4351	as well as for signal and thread safety in C<ev_async> watchers.
3198		4352
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4353	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4354	(from F<signal.h>), which is usually good enough on most platforms.
3201		4355
3202	=item EV_H	4356	=item EV_H (h)
3203		4357
3204	The name of the F<ev.h> header file used to include it. The default if	4358	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4360	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4361
3208	=item EV_CONFIG_H	4362	=item EV_CONFIG_H (h)
3209		4363
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4366	C<EV_H>, above.
3213		4367
3214	=item EV_EVENT_H	4368	=item EV_EVENT_H (h)
3215		4369
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4371	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4372
3219	=item EV_PROTOTYPES	4373	=item EV_PROTOTYPES (h)
3220		4374
3221	If defined to be C<0>, then F<ev.h> will not define any function	4375	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4376	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4377	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4378	around libev functions.
…		…
3246	fine.	4400	fine.
3247		4401
3248	If your embedding application does not need any priorities, defining these	4402	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4403	both to C<0> will save some memory and CPU.
3250		4404
3251	=item EV_PERIODIC_ENABLE	4405	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4406	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4407	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4408
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4409	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4410	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4411	is not. Disabling watcher types mainly saves code size.
3256		4412
3257	=item EV_IDLE_ENABLE	4413	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4414
3286	If you need to shave off some kilobytes of code at the expense of some	4415	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4416	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4417	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4418	that can be enabled on the platform.
		4419
		4420	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4421	with some broad features you want) and then selectively re-enable
		4422	additional parts you want, for example if you want everything minimal,
		4423	but multiple event loop support, async and child watchers and the poll
		4424	backend, use this:
		4425
		4426	#define EV_FEATURES 0
		4427	#define EV_MULTIPLICITY 1
		4428	#define EV_USE_POLL 1
		4429	#define EV_CHILD_ENABLE 1
		4430	#define EV_ASYNC_ENABLE 1
		4431
		4432	The actual value is a bitset, it can be a combination of the following
		4433	values:
		4434
		4435	=over 4
		4436
		4437	=item C<1> - faster/larger code
		4438
		4439	Use larger code to speed up some operations.
		4440
		4441	Currently this is used to override some inlining decisions (enlarging the
		4442	code size by roughly 30% on amd64).
		4443
		4444	When optimising for size, use of compiler flags such as C<-Os> with
		4445	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4446	assertions.
		4447
		4448	=item C<2> - faster/larger data structures
		4449
		4450	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4451	hash table sizes and so on. This will usually further increase code size
		4452	and can additionally have an effect on the size of data structures at
		4453	runtime.
		4454
		4455	=item C<4> - full API configuration
		4456
		4457	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4458	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4459
		4460	=item C<8> - full API
		4461
		4462	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4463	details on which parts of the API are still available without this
		4464	feature, and do not complain if this subset changes over time.
		4465
		4466	=item C<16> - enable all optional watcher types
		4467
		4468	Enables all optional watcher types. If you want to selectively enable
		4469	only some watcher types other than I/O and timers (e.g. prepare,
		4470	embed, async, child...) you can enable them manually by defining
		4471	C<EV_watchertype_ENABLE> to C<1> instead.
		4472
		4473	=item C<32> - enable all backends
		4474
		4475	This enables all backends - without this feature, you need to enable at
		4476	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4477
		4478	=item C<64> - enable OS-specific "helper" APIs
		4479
		4480	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4481	default.
		4482
		4483	=back
		4484
		4485	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4486	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4487	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4488	watchers, timers and monotonic clock support.
		4489
		4490	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4491	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4492	your program might be left out as well - a binary starting a timer and an
		4493	I/O watcher then might come out at only 5Kb.
		4494
		4495	=item EV_AVOID_STDIO
		4496
		4497	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4498	functions (printf, scanf, perror etc.). This will increase the code size
		4499	somewhat, but if your program doesn't otherwise depend on stdio and your
		4500	libc allows it, this avoids linking in the stdio library which is quite
		4501	big.
		4502
		4503	Note that error messages might become less precise when this option is
		4504	enabled.
		4505
		4506	=item EV_NSIG
		4507
		4508	The highest supported signal number, +1 (or, the number of
		4509	signals): Normally, libev tries to deduce the maximum number of signals
		4510	automatically, but sometimes this fails, in which case it can be
		4511	specified. Also, using a lower number than detected (C<32> should be
		4512	good for about any system in existence) can save some memory, as libev
		4513	statically allocates some 12-24 bytes per signal number.
3290		4514
3291	=item EV_PID_HASHSIZE	4515	=item EV_PID_HASHSIZE
3292		4516
3293	C<ev_child> watchers use a small hash table to distribute workload by	4517	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4518	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4519	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4520	might want to increase this value (I<must> be a power of two).
3297		4521
3298	=item EV_INOTIFY_HASHSIZE	4522	=item EV_INOTIFY_HASHSIZE
3299		4523
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4524	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4525	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4526	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4527	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4528	power of two).
3305		4529
3306	=item EV_USE_4HEAP	4530	=item EV_USE_4HEAP
3307		4531
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4532	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4533	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4534	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4535	faster performance with many (thousands) of watchers.
3312		4536
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4537	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4538	will be C<0>.
3315		4539
3316	=item EV_HEAP_CACHE_AT	4540	=item EV_HEAP_CACHE_AT
3317		4541
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4542	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4543	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4544	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4545	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4546	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4547	noticeably with many (hundreds) of watchers.
3324		4548
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4549	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4550	will be C<0>.
3327		4551
3328	=item EV_VERIFY	4552	=item EV_VERIFY
3329		4553
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4554	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4555	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4556	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4557	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4558	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4559	verification code will be called very frequently, which will slow down
3336	libev considerably.	4560	libev considerably.
3337		4561
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4563	will be C<0>.
3340		4564
3341	=item EV_COMMON	4565	=item EV_COMMON
3342		4566
3343	By default, all watchers have a C<void *data> member. By redefining	4567	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4568	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4569	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4570	though, and it must be identical each time.
3347		4571
3348	For example, the perl EV module uses something like this:	4572	For example, the perl EV module uses something like this:
3349		4573
…		…
3402	file.	4626	file.
3403		4627
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4628	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4629	that everybody includes and which overrides some configure choices:
3406		4630
3407	#define EV_MINIMAL 1	4631	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4632	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4633	#define EV_PREPARE_ENABLE 1
		4634	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4635	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4636	#define EV_CHILD_ENABLE 1
		4637	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4638	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4639
3417	#include "ev++.h"	4640	#include "ev++.h"
3418		4641
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4642	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4643
3421	#include "ev_cpp.h"	4644	#include "ev_cpp.h"
3422	#include "ev.c"	4645	#include "ev.c"
3423		4646
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4647	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		4648
3426	=head2 THREADS AND COROUTINES	4649	=head2 THREADS AND COROUTINES
3427		4650
3428	=head3 THREADS	4651	=head3 THREADS
3429		4652
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4703	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4704	watcher callback into the event loop interested in the signal.
3482		4705
3483	=back	4706	=back
3484		4707
		4708	See also L<THREAD LOCKING EXAMPLE>.
		4709
3485	=head3 COROUTINES	4710	=head3 COROUTINES
3486		4711
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4712	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4713	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4714	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4715	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4716	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4717	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4718
3494	Care has been taken to ensure that libev does not keep local state inside	4719	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4720	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4721	they do not call any callbacks.
3497		4722
3498	=head2 COMPILER WARNINGS	4723	=head2 COMPILER WARNINGS
3499		4724
3500	Depending on your compiler and compiler settings, you might get no or a	4725	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4726	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4736	maintainable.
3512		4737
3513	And of course, some compiler warnings are just plain stupid, or simply	4738	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4739	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4740	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4741	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	4742	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4743	such buggy versions.
3519		4744
3520	While libev is written to generate as few warnings as possible,	4745	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	4746	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4760	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4761	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4762	==2274== still reachable: 256 bytes in 1 blocks.
3538		4763
3539	Then there is no memory leak, just as memory accounted to global variables	4764	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	4765	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4766
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4767	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4768	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	4769	although an acceptable workaround has been found here), or it might be
3545	confused.	4770	confused.
…		…
3557	I suggest using suppression lists.	4782	I suggest using suppression lists.
3558		4783
3559		4784
3560	=head1 PORTABILITY NOTES	4785	=head1 PORTABILITY NOTES
3561		4786
		4787	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4788
		4789	GNU/Linux is the only common platform that supports 64 bit file/large file
		4790	interfaces but I<disables> them by default.
		4791
		4792	That means that libev compiled in the default environment doesn't support
		4793	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4794
		4795	Unfortunately, many programs try to work around this GNU/Linux issue
		4796	by enabling the large file API, which makes them incompatible with the
		4797	standard libev compiled for their system.
		4798
		4799	Likewise, libev cannot enable the large file API itself as this would
		4800	suddenly make it incompatible to the default compile time environment,
		4801	i.e. all programs not using special compile switches.
		4802
		4803	=head2 OS/X AND DARWIN BUGS
		4804
		4805	The whole thing is a bug if you ask me - basically any system interface
		4806	you touch is broken, whether it is locales, poll, kqueue or even the
		4807	OpenGL drivers.
		4808
		4809	=head3 C<kqueue> is buggy
		4810
		4811	The kqueue syscall is broken in all known versions - most versions support
		4812	only sockets, many support pipes.
		4813
		4814	Libev tries to work around this by not using C<kqueue> by default on this
		4815	rotten platform, but of course you can still ask for it when creating a
		4816	loop - embedding a socket-only kqueue loop into a select-based one is
		4817	probably going to work well.
		4818
		4819	=head3 C<poll> is buggy
		4820
		4821	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4822	implementation by something calling C<kqueue> internally around the 10.5.6
		4823	release, so now C<kqueue> I<and> C<poll> are broken.
		4824
		4825	Libev tries to work around this by not using C<poll> by default on
		4826	this rotten platform, but of course you can still ask for it when creating
		4827	a loop.
		4828
		4829	=head3 C<select> is buggy
		4830
		4831	All that's left is C<select>, and of course Apple found a way to fuck this
		4832	one up as well: On OS/X, C<select> actively limits the number of file
		4833	descriptors you can pass in to 1024 - your program suddenly crashes when
		4834	you use more.
		4835
		4836	There is an undocumented "workaround" for this - defining
		4837	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4838	work on OS/X.
		4839
		4840	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4841
		4842	=head3 C<errno> reentrancy
		4843
		4844	The default compile environment on Solaris is unfortunately so
		4845	thread-unsafe that you can't even use components/libraries compiled
		4846	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4847	defined by default. A valid, if stupid, implementation choice.
		4848
		4849	If you want to use libev in threaded environments you have to make sure
		4850	it's compiled with C<_REENTRANT> defined.
		4851
		4852	=head3 Event port backend
		4853
		4854	The scalable event interface for Solaris is called "event
		4855	ports". Unfortunately, this mechanism is very buggy in all major
		4856	releases. If you run into high CPU usage, your program freezes or you get
		4857	a large number of spurious wakeups, make sure you have all the relevant
		4858	and latest kernel patches applied. No, I don't know which ones, but there
		4859	are multiple ones to apply, and afterwards, event ports actually work
		4860	great.
		4861
		4862	If you can't get it to work, you can try running the program by setting
		4863	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4864	C<select> backends.
		4865
		4866	=head2 AIX POLL BUG
		4867
		4868	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4869	this by trying to avoid the poll backend altogether (i.e. it's not even
		4870	compiled in), which normally isn't a big problem as C<select> works fine
		4871	with large bitsets on AIX, and AIX is dead anyway.
		4872
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4873	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4874
		4875	=head3 General issues
3563		4876
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4877	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	4878	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	4879	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	4881	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	4882	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4883	as every compielr comes with a slightly differently broken/incompatible
		4884	environment.
3570		4885
3571	Lifting these limitations would basically require the full	4886	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	4887	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	4888	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	4889	also that glib is the slowest event library known to man).
3575		4890
3576	There is no supported compilation method available on windows except	4891	There is no supported compilation method available on windows except
3577	embedding it into other applications.	4892	embedding it into other applications.
		4893
		4894	Sensible signal handling is officially unsupported by Microsoft - libev
		4895	tries its best, but under most conditions, signals will simply not work.
3578		4896
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	4897	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	4898	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	4899	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	4900	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	4905	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	4906	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	4907	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	4908	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	4909	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	4910	(due to Microsoft monopoly games).
3593		4911
3594	A typical way to use libev under windows is to embed it (see the embedding	4912	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	4913	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	4914	of F<ev.h>:
3597		4915
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	4922	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		4923
3606	#include "evwrap.h"	4924	#include "evwrap.h"
3607	#include "ev.c"	4925	#include "ev.c"
3608		4926
3609	=over 4
3610
3611	=item The winsocket select function	4927	=head3 The winsocket C<select> function
3612		4928
3613	The winsocket C<select> function doesn't follow POSIX in that it	4929	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	4930	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	4931	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	4932	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4941	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		4942
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	4943	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	4944	complexity in the O(n²) range when using win32.
3629		4945
3630	=item Limited number of file descriptors	4946	=head3 Limited number of file descriptors
3631		4947
3632	Windows has numerous arbitrary (and low) limits on things.	4948	Windows has numerous arbitrary (and low) limits on things.
3633		4949
3634	Early versions of winsocket's select only supported waiting for a maximum	4950	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	4951	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	4952	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	4953	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	4954	previous thread in each. Sounds great!).
3639		4955
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4956	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	4957	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	4958	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	4959	other interpreters do their own select emulation on windows).
3644		4960
3645	Another limit is the number of file descriptors in the Microsoft runtime	4961	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4962	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	4963	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4964	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	4965	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	4966	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	4967	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	4968	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	4969	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		4970
3659	=head2 PORTABILITY REQUIREMENTS	4971	=head2 PORTABILITY REQUIREMENTS
3660		4972
3661	In addition to a working ISO-C implementation and of course the	4973	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	4974	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	4981	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	4982	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	4983	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	4984	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	4985	calls them using an C<ev_watcher *> internally.
		4986
		4987	=item pointer accesses must be thread-atomic
		4988
		4989	Accessing a pointer value must be atomic, it must both be readable and
		4990	writable in one piece - this is the case on all current architectures.
3674		4991
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	4992	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		4993
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	4994	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4995	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3701	watchers.	5018	watchers.
3702		5019
3703	=item C<double> must hold a time value in seconds with enough accuracy	5020	=item C<double> must hold a time value in seconds with enough accuracy
3704		5021
3705	The type C<double> is used to represent timestamps. It is required to	5022	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5023	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5024	good enough for at least into the year 4000 with millisecond accuracy
		5025	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5026	implementations using IEEE 754, which is basically all existing ones. With
		5027	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3709		5028
3710	=back	5029	=back
3711		5030
3712	If you know of other additional requirements drop me a note.	5031	If you know of other additional requirements drop me a note.
3713		5032
…		…
3781	involves iterating over all running async watchers or all signal numbers.	5100	involves iterating over all running async watchers or all signal numbers.
3782		5101
3783	=back	5102	=back
3784		5103
3785		5104
		5105	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5106
		5107	The major version 4 introduced some incompatible changes to the API.
		5108
		5109	At the moment, the C<ev.h> header file provides compatibility definitions
		5110	for all changes, so most programs should still compile. The compatibility
		5111	layer might be removed in later versions of libev, so better update to the
		5112	new API early than late.
		5113
		5114	=over 4
		5115
		5116	=item C<EV_COMPAT3> backwards compatibility mechanism
		5117
		5118	The backward compatibility mechanism can be controlled by
		5119	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5120	section.
		5121
		5122	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5123
		5124	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5125
		5126	ev_loop_destroy (EV_DEFAULT_UC);
		5127	ev_loop_fork (EV_DEFAULT);
		5128
		5129	=item function/symbol renames
		5130
		5131	A number of functions and symbols have been renamed:
		5132
		5133	ev_loop => ev_run
		5134	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5135	EVLOOP_ONESHOT => EVRUN_ONCE
		5136
		5137	ev_unloop => ev_break
		5138	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5139	EVUNLOOP_ONE => EVBREAK_ONE
		5140	EVUNLOOP_ALL => EVBREAK_ALL
		5141
		5142	EV_TIMEOUT => EV_TIMER
		5143
		5144	ev_loop_count => ev_iteration
		5145	ev_loop_depth => ev_depth
		5146	ev_loop_verify => ev_verify
		5147
		5148	Most functions working on C<struct ev_loop> objects don't have an
		5149	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5150	associated constants have been renamed to not collide with the C<struct
		5151	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5152	as all other watcher types. Note that C<ev_loop_fork> is still called
		5153	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5154	typedef.
		5155
		5156	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5157
		5158	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5159	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5160	and work, but the library code will of course be larger.
		5161
		5162	=back
		5163
		5164
		5165	=head1 GLOSSARY
		5166
		5167	=over 4
		5168
		5169	=item active
		5170
		5171	A watcher is active as long as it has been started and not yet stopped.
		5172	See L<WATCHER STATES> for details.
		5173
		5174	=item application
		5175
		5176	In this document, an application is whatever is using libev.
		5177
		5178	=item backend
		5179
		5180	The part of the code dealing with the operating system interfaces.
		5181
		5182	=item callback
		5183
		5184	The address of a function that is called when some event has been
		5185	detected. Callbacks are being passed the event loop, the watcher that
		5186	received the event, and the actual event bitset.
		5187
		5188	=item callback/watcher invocation
		5189
		5190	The act of calling the callback associated with a watcher.
		5191
		5192	=item event
		5193
		5194	A change of state of some external event, such as data now being available
		5195	for reading on a file descriptor, time having passed or simply not having
		5196	any other events happening anymore.
		5197
		5198	In libev, events are represented as single bits (such as C<EV_READ> or
		5199	C<EV_TIMER>).
		5200
		5201	=item event library
		5202
		5203	A software package implementing an event model and loop.
		5204
		5205	=item event loop
		5206
		5207	An entity that handles and processes external events and converts them
		5208	into callback invocations.
		5209
		5210	=item event model
		5211
		5212	The model used to describe how an event loop handles and processes
		5213	watchers and events.
		5214
		5215	=item pending
		5216
		5217	A watcher is pending as soon as the corresponding event has been
		5218	detected. See L<WATCHER STATES> for details.
		5219
		5220	=item real time
		5221
		5222	The physical time that is observed. It is apparently strictly monotonic :)
		5223
		5224	=item wall-clock time
		5225
		5226	The time and date as shown on clocks. Unlike real time, it can actually
		5227	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5228	clock.
		5229
		5230	=item watcher
		5231
		5232	A data structure that describes interest in certain events. Watchers need
		5233	to be started (attached to an event loop) before they can receive events.
		5234
		5235	=back
		5236
3786	=head1 AUTHOR	5237	=head1 AUTHOR
3787		5238
3788	Marc Lehmann <libev@schmorp.de>.	5239	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5240	Magnusson and Emanuele Giaquinta.
3789		5241

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