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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	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);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	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
70	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
71	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
72		92
73	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
74	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
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	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
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	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
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	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
96	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
97	(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>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	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
101	for example).	122	for example).
102		123
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	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
118	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
119	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
120	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
121	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
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	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
155	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
156	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>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	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
161	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
…		…
178	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
179	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
180	not a problem.	203	not a problem.
181		204
182	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
183	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
184		208
185	assert (("libev version mismatch",	209	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
188		212
…		…
199	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
201		225
202	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
203		227
204	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
205	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
206	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
207	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
208	(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
209	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
210		235
211	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
212		237
213	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
214	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
215	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
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
218		243
219	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
220		245
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
222		247
223	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
224	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
225	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
226	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
…		…
252	}	277	}
253		278
254	...	279	...
255	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
256		281
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
258		283
259	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
260	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
261	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
262	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
…		…
274	}	299	}
275		300
276	...	301	...
277	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
278		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
279	=back	317	=back
280		318
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		320
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
286		324
287	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
289	not.	327	do not.
290		328
291	=over 4	329	=over 4
292		330
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		332
295	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
296	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
297	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
298	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".
299		343
300	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
301	function.	345	function (or via the C<EV_DEFAULT> macro).
302		346
303	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
304	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
305	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
306		351
307	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,
308	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
309	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
310	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
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	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.
313		376
314	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
315	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>).
316		379
317	The following flags are supported:	380	The following flags are supported:
…		…
332	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
333	around bugs.	396	around bugs.
334		397
335	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
336		399
337	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
338	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.
339	enabling this flag.
340		402
341	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,
342	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
343	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
344	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
…		…
350	flag.	412	flag.
351		413
352	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>
353	environment variable.	415	environment variable.
354		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	This flag's behaviour will become the default in future versions of libev.
		448
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		450
357	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		479
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
388	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
392		489
393	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	499	and is of course hard to detect.
401		500
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
403	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
404	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
405	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
406	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
407	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
408	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
409		514
410	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	516	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	517	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		585
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
483		588
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	592	might perform better.
492		593
493	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
497		608
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
500		611
501	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
502		613
503	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		617
507	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		627
509	=back	628	=back
510		629
511	If one or more of these are or'ed into the flags value, then only these	630	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	631	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	632	here). If none are specified, all backends in C<ev_recommended_backends
514		633	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		634
543	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
544		636
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	638	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
548		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
549	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
550		647
551	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		655
559	Note that certain global state, such as signal state (and installed signal	656	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	657	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
562		659
563	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	667	and C<ev_loop_destroy>.
567		668
568	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
569		670
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
581		681
582	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
585		688
586	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
590	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		703
599	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
600		705
601	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	707	otherwise.
603		708
604	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
605		710
606	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
609		714
610	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
613		733
614	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
615		735
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	737	use.
…		…
626		746
627	=item ev_now_update (loop)	747	=item ev_now_update (loop)
628		748
629	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
632		752
633	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	755	the current time is a good idea.
636		756
637	See also "The special problem of time updates" in the C<ev_timer> section.	757	See also L<The special problem of time updates> in the C<ev_timer> section.
638		758
		759	=item ev_suspend (loop)
		760
		761	=item ev_resume (loop)
		762
		763	These two functions suspend and resume an event loop, for use when the
		764	loop is not used for a while and timeouts should not be processed.
		765
		766	A typical use case would be an interactive program such as a game: When
		767	the user presses C<^Z> to suspend the game and resumes it an hour later it
		768	would be best to handle timeouts as if no time had actually passed while
		769	the program was suspended. This can be achieved by calling C<ev_suspend>
		770	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		771	C<ev_resume> directly afterwards to resume timer processing.
		772
		773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		775	will be rescheduled (that is, they will lose any events that would have
		776	occurred while suspended).
		777
		778	After calling C<ev_suspend> you B<must not> call I<any> function on the
		779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		780	without a previous call to C<ev_suspend>.
		781
		782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		783	event loop time (see C<ev_now_update>).
		784
639	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
640		786
641	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
643	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
644		792
645	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
647		796
648	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	802	beauty.
654		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
658	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
659		814
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
665	iteration of the loop.	820	iteration of the loop.
666		821
667	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
671		826
672	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
673		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	838	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	849	- Queue all expired timers.
690	- Queue all expired periodics.	850	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	852	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
699		863
700	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	865	anymore.
702		866
703	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
707		871
708	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
709		873
710	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		878
715	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
716		880
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
718		883
719	=item ev_ref (loop)	884	=item ev_ref (loop)
720		885
721	=item ev_unref (loop)	886	=item ev_unref (loop)
722		887
723	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
726		891
727	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	895	before stopping it.
730		896
731	As an example, libev itself uses this for its internal signal pipe: It is	897	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	898	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	899	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	900	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	901	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	902	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	903	before, respectively. Note also that libev might stop watchers itself
		904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		905	in the callback).
738		906
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	908	running when nothing else is active.
741		909
742	ev_signal exitsig;	910	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	913	ev_unref (loop);
746		914
747	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
748		916
749	ev_ref (loop);	917	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
771		939
772	By setting a higher I<io collect interval> you allow libev to spend more	940	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	941	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	943	C<ev_timer>) will be not affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
777		947
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	950	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		953
784	Many (busy) programs can usually benefit by setting the I/O collect	954	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	955	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	956	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
789		963
790	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	969	they fire on, say, one-second boundaries only.
796		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
797	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
798		1047
799	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
813		1062
814	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
817		1066
818	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
821		1071
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1073	{
824	ev_io_stop (w);	1074	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
826	}	1076	}
827		1077
828	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
829		1079
830	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
831		1081
832	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
835		1085
836	ev_loop (loop, 0);	1086	ev_run (loop, 0);
837		1087
838	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1090	stack).
841		1091
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1094
845	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1099	and/or writable).
850		1100
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
878		1128
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1130	writable.
881		1131
882	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
883		1133
884	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
885		1135
886	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
887		1137
…		…
905		1155
906	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
907		1157
908	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
909		1159
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
911	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
913	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
914	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
916	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
917		1167
918	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
919		1169
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1171
922	=item C<EV_FORK>	1172	=item C<EV_FORK>
923		1173
924	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1175	C<ev_fork>).
926		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
927	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
928		1182
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
		1184
		1185	=item C<EV_CUSTOM>
		1186
		1187	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1188	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1189
931	=item C<EV_ERROR>	1190	=item C<EV_ERROR>
932		1191
933	An unspecified error has occurred, the watcher has been stopped. This might	1192	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1193	happen because the watcher could not be properly started because libev
…		…
972		1231
973	ev_io w;	1232	ev_io w;
974	ev_init (&w, my_cb);	1233	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1235
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1237
979	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1254
996	Example: Initialise and set an C<ev_io> watcher in one step.	1255	Example: Initialise and set an C<ev_io> watcher in one step.
997		1256
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1258
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1260
1002	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
1004		1263
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1264	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1265	whole section.
1007		1266
1008	ev_io_start (EV_DEFAULT_UC, &w);	1267	ev_io_start (EV_DEFAULT_UC, &w);
1009		1268
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1270
1012	Stops the given watcher if active, and clears the pending status (whether	1271	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1272	the watcher was active or not).
1014		1273
1015	It is possible that stopped watchers are pending - for example,	1274	It is possible that stopped watchers are pending - for example,
…		…
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
1041		1300
1042	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1302	(modulo threads).
1044		1303
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1305
1047	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
1048		1307
1049	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
1054		1313
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1314	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1316
1063	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1318	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1319
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1321	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1322	or might not have been clamped to the valid range.
		1323
		1324	The default priority used by watchers when no priority has been set is
		1325	always C<0>, which is supposed to not be too high and not be too low :).
		1326
		1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1328	priorities.
1072		1329
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1331
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
1085		1342
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1344	callback to be invoked, which can be accomplished with this function.
1088		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
1089	=back	1360	=back
1090
1091		1361
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1093		1363
1094	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
1095	and read at any time: libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
…		…
1141	#include <stddef.h>	1411	#include <stddef.h>
1142		1412
1143	static void	1413	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{	1415	{
1146	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1147	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}	1418	}
1149		1419
1150	static void	1420	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{	1422	{
1153	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1154	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
		1485
		1486	=head2 WATCHER PRIORITY MODELS
		1487
		1488	Many event loops support I<watcher priorities>, which are usually small
		1489	integers that influence the ordering of event callback invocation
		1490	between watchers in some way, all else being equal.
		1491
		1492	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1493	description for the more technical details such as the actual priority
		1494	range.
		1495
		1496	There are two common ways how these these priorities are being interpreted
		1497	by event loops:
		1498
		1499	In the more common lock-out model, higher priorities "lock out" invocation
		1500	of lower priority watchers, which means as long as higher priority
		1501	watchers receive events, lower priority watchers are not being invoked.
		1502
		1503	The less common only-for-ordering model uses priorities solely to order
		1504	callback invocation within a single event loop iteration: Higher priority
		1505	watchers are invoked before lower priority ones, but they all get invoked
		1506	before polling for new events.
		1507
		1508	Libev uses the second (only-for-ordering) model for all its watchers
		1509	except for idle watchers (which use the lock-out model).
		1510
		1511	The rationale behind this is that implementing the lock-out model for
		1512	watchers is not well supported by most kernel interfaces, and most event
		1513	libraries will just poll for the same events again and again as long as
		1514	their callbacks have not been executed, which is very inefficient in the
		1515	common case of one high-priority watcher locking out a mass of lower
		1516	priority ones.
		1517
		1518	Static (ordering) priorities are most useful when you have two or more
		1519	watchers handling the same resource: a typical usage example is having an
		1520	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1521	timeouts. Under load, data might be received while the program handles
		1522	other jobs, but since timers normally get invoked first, the timeout
		1523	handler will be executed before checking for data. In that case, giving
		1524	the timer a lower priority than the I/O watcher ensures that I/O will be
		1525	handled first even under adverse conditions (which is usually, but not
		1526	always, what you want).
		1527
		1528	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1529	will only be executed when no same or higher priority watchers have
		1530	received events, they can be used to implement the "lock-out" model when
		1531	required.
		1532
		1533	For example, to emulate how many other event libraries handle priorities,
		1534	you can associate an C<ev_idle> watcher to each such watcher, and in
		1535	the normal watcher callback, you just start the idle watcher. The real
		1536	processing is done in the idle watcher callback. This causes libev to
		1537	continuously poll and process kernel event data for the watcher, but when
		1538	the lock-out case is known to be rare (which in turn is rare :), this is
		1539	workable.
		1540
		1541	Usually, however, the lock-out model implemented that way will perform
		1542	miserably under the type of load it was designed to handle. In that case,
		1543	it might be preferable to stop the real watcher before starting the
		1544	idle watcher, so the kernel will not have to process the event in case
		1545	the actual processing will be delayed for considerable time.
		1546
		1547	Here is an example of an I/O watcher that should run at a strictly lower
		1548	priority than the default, and which should only process data when no
		1549	other events are pending:
		1550
		1551	ev_idle idle; // actual processing watcher
		1552	ev_io io; // actual event watcher
		1553
		1554	static void
		1555	io_cb (EV_P_ ev_io *w, int revents)
		1556	{
		1557	// stop the I/O watcher, we received the event, but
		1558	// are not yet ready to handle it.
		1559	ev_io_stop (EV_A_ w);
		1560
		1561	// start the idle watcher to handle the actual event.
		1562	// it will not be executed as long as other watchers
		1563	// with the default priority are receiving events.
		1564	ev_idle_start (EV_A_ &idle);
		1565	}
		1566
		1567	static void
		1568	idle_cb (EV_P_ ev_idle *w, int revents)
		1569	{
		1570	// actual processing
		1571	read (STDIN_FILENO, ...);
		1572
		1573	// have to start the I/O watcher again, as
		1574	// we have handled the event
		1575	ev_io_start (EV_P_ &io);
		1576	}
		1577
		1578	// initialisation
		1579	ev_idle_init (&idle, idle_cb);
		1580	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1581	ev_io_start (EV_DEFAULT_ &io);
		1582
		1583	In the "real" world, it might also be beneficial to start a timer, so that
		1584	low-priority connections can not be locked out forever under load. This
		1585	enables your program to keep a lower latency for important connections
		1586	during short periods of high load, while not completely locking out less
		1587	important ones.
1156		1588
1157		1589
1158	=head1 WATCHER TYPES	1590	=head1 WATCHER TYPES
1159		1591
1160	This section describes each watcher in detail, but will not repeat	1592	This section describes each watcher in detail, but will not repeat
…		…
1184	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1185	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1186	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1619	required if you know what you are doing).
1188		1620
1189	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1192
1193	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1197	lot of those (for example Solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1198	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1201		1628
1202	If you cannot run the fd in non-blocking mode (for example you should	1629	If you cannot run the fd in non-blocking mode (for example you should
1203	not play around with an Xlib connection), then you have to separately	1630	not play around with an Xlib connection), then you have to separately
1204	re-test whether a file descriptor is really ready with a known-to-be good	1631	re-test whether a file descriptor is really ready with a known-to-be good
1205	interface such as poll (fortunately in our Xlib example, Xlib already	1632	interface such as poll (fortunately in the case of Xlib, it already does
1206	does this on its own, so its quite safe to use). Some people additionally	1633	this on its own, so its quite safe to use). Some people additionally
1207	use C<SIGALRM> and an interval timer, just to be sure you won't block	1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
1208	indefinitely.	1635	indefinitely.
1209		1636
1210	But really, best use non-blocking mode.	1637	But really, best use non-blocking mode.
1211		1638
…		…
1239		1666
1240	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1244	=head3 The special problem of fork	1704	=head3 The special problem of fork
1245		1705
1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1247	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1248	it in the child.	1708	it in the child if you want to continue to use it in the child.
1249		1709
1250	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1713
1255	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1256		1715
1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1258	when writing to a pipe whose other end has been closed, your program gets	1717	when writing to a pipe whose other end has been closed, your program gets
…		…
1261		1720
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1721	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1722	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1723	somewhere, as that would have given you a big clue).
1265		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1266		1763
1267	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1268		1765
1269	=over 4	1766	=over 4
1270		1767
…		…
1302	...	1799	...
1303	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1801	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1308		1805
1309		1806
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1808
1312	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1814	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1816	monotonic clock option helps a lot here).
1320		1817
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1818	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1819	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1820	might introduce a small delay). If multiple timers become ready during the
		1821	same loop iteration then the ones with earlier time-out values are invoked
		1822	before ones of the same priority with later time-out values (but this is
		1823	no longer true when a callback calls C<ev_run> recursively).
1324		1824
1325	=head3 Be smart about timeouts	1825	=head3 Be smart about timeouts
1326		1826
1327	Many real-world problems involve some kind of timeout, usually for error	1827	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1828	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1872	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1873	member and C<ev_timer_again>.
1374		1874
1375	At start:	1875	At start:
1376		1876
1377	ev_timer_init (timer, callback);	1877	ev_init (timer, callback);
1378	timer->repeat = 60.;	1878	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1879	ev_timer_again (loop, timer);
1380		1880
1381	Each time there is some activity:	1881	Each time there is some activity:
1382		1882
…		…
1414	ev_tstamp timeout = last_activity + 60.;	1914	ev_tstamp timeout = last_activity + 60.;
1415		1915
1416	// if last_activity + 60. is older than now, we did time out	1916	// if last_activity + 60. is older than now, we did time out
1417	if (timeout < now)	1917	if (timeout < now)
1418	{	1918	{
1419	// timeout occured, take action	1919	// timeout occurred, take action
1420	}	1920	}
1421	else	1921	else
1422	{	1922	{
1423	// callback was invoked, but there was some activity, re-arm	1923	// callback was invoked, but there was some activity, re-arm
1424	// the watcher to fire in last_activity + 60, which is	1924	// the watcher to fire in last_activity + 60, which is
…		…
1444		1944
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1945	To start the timer, simply initialise the watcher and set C<last_activity>
1446	to the current time (meaning we just have some activity :), then call the	1946	to the current time (meaning we just have some activity :), then call the
1447	callback, which will "do the right thing" and start the timer:	1947	callback, which will "do the right thing" and start the timer:
1448		1948
1449	ev_timer_init (timer, callback);	1949	ev_init (timer, callback);
1450	last_activity = ev_now (loop);	1950	last_activity = ev_now (loop);
1451	callback (loop, timer, EV_TIMEOUT);	1951	callback (loop, timer, EV_TIMER);
1452		1952
1453	And when there is some activity, simply store the current time in	1953	And when there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1954	C<last_activity>, no libev calls at all:
1455		1955
1456	last_actiivty = ev_now (loop);	1956	last_activity = ev_now (loop);
1457		1957
1458	This technique is slightly more complex, but in most cases where the	1958	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1959	time-out is unlikely to be triggered, much more efficient.
1460		1960
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the	1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1499		1999
1500	=head3 The special problem of time updates	2000	=head3 The special problem of time updates
1501		2001
1502	Establishing the current time is a costly operation (it usually takes at	2002	Establishing the current time is a costly operation (it usually takes at
1503	least two system calls): EV therefore updates its idea of the current	2003	least two system calls): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	2004	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2006	lots of events in one iteration.
1507		2007
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2008	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	2009	time. This is usually the right thing as this timestamp refers to the time
…		…
1515		2015
1516	If the event loop is suspended for a long time, you can also force an	2016	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2018	()>.
1519		2019
		2020	=head3 The special problems of suspended animation
		2021
		2022	When you leave the server world it is quite customary to hit machines that
		2023	can suspend/hibernate - what happens to the clocks during such a suspend?
		2024
		2025	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2026	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2027	to run until the system is suspended, but they will not advance while the
		2028	system is suspended. That means, on resume, it will be as if the program
		2029	was frozen for a few seconds, but the suspend time will not be counted
		2030	towards C<ev_timer> when a monotonic clock source is used. The real time
		2031	clock advanced as expected, but if it is used as sole clocksource, then a
		2032	long suspend would be detected as a time jump by libev, and timers would
		2033	be adjusted accordingly.
		2034
		2035	I would not be surprised to see different behaviour in different between
		2036	operating systems, OS versions or even different hardware.
		2037
		2038	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2039	time jump in the monotonic clocks and the realtime clock. If the program
		2040	is suspended for a very long time, and monotonic clock sources are in use,
		2041	then you can expect C<ev_timer>s to expire as the full suspension time
		2042	will be counted towards the timers. When no monotonic clock source is in
		2043	use, then libev will again assume a timejump and adjust accordingly.
		2044
		2045	It might be beneficial for this latter case to call C<ev_suspend>
		2046	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2047	deterministic behaviour in this case (you can do nothing against
		2048	C<SIGSTOP>).
		2049
1520	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1521		2051
1522	=over 4	2052	=over 4
1523		2053
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2077	If the timer is started but non-repeating, stop it (as if it timed out).
1548		2078
1549	If the timer is repeating, either start it if necessary (with the	2079	If the timer is repeating, either start it if necessary (with the
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2080	C<repeat> value), or reset the running timer to the C<repeat> value.
1551		2081
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1553	usage example.	2083	usage example.
		2084
		2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2086
		2087	Returns the remaining time until a timer fires. If the timer is active,
		2088	then this time is relative to the current event loop time, otherwise it's
		2089	the timeout value currently configured.
		2090
		2091	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2092	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2093	will return C<4>. When the timer expires and is restarted, it will return
		2094	roughly C<7> (likely slightly less as callback invocation takes some time,
		2095	too), and so on.
1554		2096
1555	=item ev_tstamp repeat [read-write]	2097	=item ev_tstamp repeat [read-write]
1556		2098
1557	The current C<repeat> value. Will be used each time the watcher times out	2099	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2100	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2126	}
1585		2127
1586	ev_timer mytimer;	2128	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1590		2132
1591	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1594		2136
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2138	=head2 C<ev_periodic> - to cron or not to cron?
1597		2139
1598	Periodic watchers are also timers of a kind, but they are very versatile	2140	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2141	(and unfortunately a bit complex).
1600		2142
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2144	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2145	(absolute time, the thing you can read on your calender or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2146	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2147	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2148	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2149
		2150	You can tell a periodic watcher to trigger after some specific point
		2151	in time: for example, if you tell a periodic watcher to trigger "in 10
		2152	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2153	not a delay) and then reset your system clock to January of the previous
		2154	year, then it will take a year or more to trigger the event (unlike an
		2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2156	it, as it uses a relative timeout).
		2157
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2158	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2159	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2161	those cannot react to time jumps.
1613		2162
1614	As with timers, the callback is guaranteed to be invoked only when the	2163	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2164	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2165	timers become ready during the same loop iteration then the ones with
		2166	earlier time-out values are invoked before ones with later time-out values
		2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2168
1618	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1619		2170
1620	=over 4	2171	=over 4
1621		2172
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2173	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2174
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2175	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2176
1626	Lots of arguments, lets sort it out... There are basically three modes of	2177	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2178	operation, and we will explain them from simplest to most complex:
1628		2179
1629	=over 4	2180	=over 4
1630		2181
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2182	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2183
1633	In this configuration the watcher triggers an event after the wall clock	2184	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2185	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2186	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2187	will be stopped and invoked when the system clock reaches or surpasses
		2188	this point in time.
1637		2189
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2190	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2191
1640	In this mode the watcher will always be scheduled to time out at the next	2192	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2193	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2194	negative) and then repeat, regardless of any time jumps. The C<offset>
		2195	argument is merely an offset into the C<interval> periods.
1643		2196
1644	This can be used to create timers that do not drift with respect to the	2197	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2198	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2199	hour, on the hour (with respect to UTC):
1647		2200
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2201	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2202
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2203	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2204	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2205	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2206	by 3600.
1654		2207
1655	Another way to think about it (for the mathematically inclined) is that	2208	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2209	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2210	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2211
1659	For numerical stability it is preferable that the C<at> value is near	2212	For numerical stability it is preferable that the C<offset> value is near
1660	C<ev_now ()> (the current time), but there is no range requirement for	2213	C<ev_now ()> (the current time), but there is no range requirement for
1661	this value, and in fact is often specified as zero.	2214	this value, and in fact is often specified as zero.
1662		2215
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2216	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2217	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2218	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2219	millisecond (if the OS supports it and the machine is fast enough).
1667		2220
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2221	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2222
1670	In this mode the values for C<interval> and C<at> are both being	2223	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2224	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2225	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2226	current time as second argument.
1674		2227
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2228	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY other event loop modifications whatsoever>.	2229	or make ANY other event loop modifications whatsoever, unless explicitly
		2230	allowed by documentation here>.
1677		2231
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2232	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2233	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2234	only event loop modification you are allowed to do).
1681		2235
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2265	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2266	program when the crontabs have changed).
1713		2267
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2268	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2269
1716	When active, returns the absolute time that the watcher is supposed to	2270	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2271	to trigger next. This is not the same as the C<offset> argument to
		2272	C<ev_periodic_set>, but indeed works even in interval and manual
		2273	rescheduling modes.
1718		2274
1719	=item ev_tstamp offset [read-write]	2275	=item ev_tstamp offset [read-write]
1720		2276
1721	When repeating, this contains the offset value, otherwise this is the	2277	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2278	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2279	although libev might modify this value for better numerical stability).
1723		2280
1724	Can be modified any time, but changes only take effect when the periodic	2281	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2282	timer fires or C<ev_periodic_again> is being called.
1726		2283
1727	=item ev_tstamp interval [read-write]	2284	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
1746		2303
1747	static void	2304	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2306	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2308	}
1752		2309
1753	ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
…		…
1776		2333
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2335
1779	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2339	normal event processing, like any other event.
1783		2340
1784	If you want signals asynchronously, just use C<sigaction> as you would	2341	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2342	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2343	the signal. You can even use C<ev_async> from a signal handler to
		2344	synchronously wake up an event loop.
1787		2345
1788	You can configure as many watchers as you like per signal. Only when the	2346	You can configure as many watchers as you like for the same signal, but
		2347	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2348	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2349	C<SIGINT> in both the default loop and another loop at the same time. At
		2350	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2351
1789	first watcher gets started will libev actually register a signal handler	2352	When the first watcher gets started will libev actually register something
1790	with the kernel (thus it coexists with your own signal handlers as long as	2353	with the kernel (thus it coexists with your own signal handlers as long as
1791	you don't register any with libev for the same signal). Similarly, when	2354	you don't register any with libev for the same signal).
1792	the last signal watcher for a signal is stopped, libev will reset the
1793	signal handler to SIG_DFL (regardless of what it was set to before).
1794		2355
1795	If possible and supported, libev will install its handlers with	2356	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2358	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2359	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2360	and unblock them in an C<ev_prepare> watcher.
		2361
		2362	=head3 The special problem of inheritance over fork/execve/pthread_create
		2363
		2364	Both the signal mask (C<sigprocmask>) and the signal disposition
		2365	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2366	stopping it again), that is, libev might or might not block the signal,
		2367	and might or might not set or restore the installed signal handler.
		2368
		2369	While this does not matter for the signal disposition (libev never
		2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2371	C<execve>), this matters for the signal mask: many programs do not expect
		2372	certain signals to be blocked.
		2373
		2374	This means that before calling C<exec> (from the child) you should reset
		2375	the signal mask to whatever "default" you expect (all clear is a good
		2376	choice usually).
		2377
		2378	The simplest way to ensure that the signal mask is reset in the child is
		2379	to install a fork handler with C<pthread_atfork> that resets it. That will
		2380	catch fork calls done by libraries (such as the libc) as well.
		2381
		2382	In current versions of libev, the signal will not be blocked indefinitely
		2383	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2384	the window of opportunity for problems, it will not go away, as libev
		2385	I<has> to modify the signal mask, at least temporarily.
		2386
		2387	So I can't stress this enough: I<If you do not reset your signal mask when
		2388	you expect it to be empty, you have a race condition in your code>. This
		2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
1800		2404
1801	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
1802		2406
1803	=over 4	2407	=over 4
1804		2408
…		…
1820	Example: Try to exit cleanly on SIGINT.	2424	Example: Try to exit cleanly on SIGINT.
1821		2425
1822	static void	2426	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2428	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
1826	}	2430	}
1827		2431
1828	ev_signal signal_watcher;	2432	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2434	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2440	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2441	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2442	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2443	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2444	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2445	but forking and registering a watcher a few event loop iterations later or
1842	not.	2446	in the next callback invocation is not.
1843		2447
1844	Only the default event loop is capable of handling signals, and therefore	2448	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2449	you can only register child watchers in the default event loop.
1846		2450
		2451	Due to some design glitches inside libev, child watchers will always be
		2452	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2453	libev)
		2454
1847	=head3 Process Interaction	2455	=head3 Process Interaction
1848		2456
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2457	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2458	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2459	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2460	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2461	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2462	children, even ones not watched.
1855		2463
1856	=head3 Overriding the Built-In Processing	2464	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2474	=head3 Stopping the Child Watcher
1867		2475
1868	Currently, the child watcher never gets stopped, even when the	2476	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2477	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2478	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2479	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2480	problem).
1872		2481
1873	=head3 Watcher-Specific Functions and Data Members	2482	=head3 Watcher-Specific Functions and Data Members
1874		2483
1875	=over 4	2484	=over 4
1876		2485
…		…
2202	// no longer anything immediate to do.	2811	// no longer anything immediate to do.
2203	}	2812	}
2204		2813
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2815	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2816	ev_idle_start (loop, idle_watcher);
2208		2817
2209		2818
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2820
2212	Prepare and check watchers are usually (but not always) used in pairs:	2821	Prepare and check watchers are usually (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2823	afterwards.
2215		2824
2216	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
2218	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
2219	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2221	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2305	struct pollfd fds [nfd];	2914	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	2915	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		2917
2309	/* the callback is illegal, but won't be called as we stop during check */	2918	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	2919	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	2920	ev_timer_start (loop, &tw);
2312		2921
2313	// create one ev_io per pollfd	2922	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	2923	for (int i = 0; i < nfd; ++i)
2315	{	2924	{
…		…
2389		2998
2390	if (timeout >= 0)	2999	if (timeout >= 0)
2391	// create/start timer	3000	// create/start timer
2392		3001
2393	// poll	3002	// poll
2394	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
2395		3004
2396	// stop timer again	3005	// stop timer again
2397	if (timeout >= 0)	3006	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2399		3008
…		…
2477	if you do not want that, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2478		3087
2479	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2480		3089
2481	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3092	appropriate way for embedded loops.
2484		3093
2485	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2486		3095
2487	The embedded event loop.	3096	The embedded event loop.
…		…
2545	event loop blocks next and before C<ev_check> watchers are being called,	3154	event loop blocks next and before C<ev_check> watchers are being called,
2546	and only in the child after the fork. If whoever good citizen calling	3155	and only in the child after the fork. If whoever good citizen calling
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2548	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2549		3158
		3159	=head3 The special problem of life after fork - how is it possible?
		3160
		3161	Most uses of C<fork()> consist of forking, then some simple calls to set
		3162	up/change the process environment, followed by a call to C<exec()>. This
		3163	sequence should be handled by libev without any problems.
		3164
		3165	This changes when the application actually wants to do event handling
		3166	in the child, or both parent in child, in effect "continuing" after the
		3167	fork.
		3168
		3169	The default mode of operation (for libev, with application help to detect
		3170	forks) is to duplicate all the state in the child, as would be expected
		3171	when I<either> the parent I<or> the child process continues.
		3172
		3173	When both processes want to continue using libev, then this is usually the
		3174	wrong result. In that case, usually one process (typically the parent) is
		3175	supposed to continue with all watchers in place as before, while the other
		3176	process typically wants to start fresh, i.e. without any active watchers.
		3177
		3178	The cleanest and most efficient way to achieve that with libev is to
		3179	simply create a new event loop, which of course will be "empty", and
		3180	use that for new watchers. This has the advantage of not touching more
		3181	memory than necessary, and thus avoiding the copy-on-write, and the
		3182	disadvantage of having to use multiple event loops (which do not support
		3183	signal watchers).
		3184
		3185	When this is not possible, or you want to use the default loop for
		3186	other reasons, then in the process that wants to start "fresh", call
		3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3188	Destroying the default loop will "orphan" (not stop) all registered
		3189	watchers, so you have to be careful not to execute code that modifies
		3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
		3192
2550	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2551		3194
2552	=over 4	3195	=over 4
2553		3196
2554	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2555		3198
2556	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3201	really.
2559		3202
2560	=back	3203	=back
2561		3204
2562		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2563	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2564		3247
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2568		3251
2569	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3256
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2579		3264
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2581	just the default loop.	3266	just the default loop.
2582		3267
2583	=head3 Queueing	3268	=head3 Queueing
2584		3269
2585	C<ev_async> does not support queueing of data in any way. The reason	3270	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3271	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3272	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3273	need elaborate support such as pthreads or unportable memory access
		3274	semantics.
2589		3275
2590	That means that if you want to queue data, you have to provide your own	3276	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3277	queue. But at least I can tell you how to implement locking around your
2592	queue:	3278	queue:
2593		3279
…		…
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3369	C<ev_feed_event>, this call is safe to do from other threads, signal or
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2685	section below on what exactly this means).	3371	section below on what exactly this means).
2686		3372
		3373	Note that, as with other watchers in libev, multiple events might get
		3374	compressed into a single callback invocation (another way to look at this
		3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3376	reset when the event loop detects that).
		3377
2687	This call incurs the overhead of a system call only once per loop iteration,	3378	This call incurs the overhead of a system call only once per event loop
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3379	iteration, so while the overhead might be noticeable, it doesn't apply to
2689	calls to C<ev_async_send>.	3380	repeated calls to C<ev_async_send> for the same event loop.
2690		3381
2691	=item bool = ev_async_pending (ev_async *)	3382	=item bool = ev_async_pending (ev_async *)
2692		3383
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3384	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3385	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3388	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3389	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3390	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3391	quickly check whether invoking the loop might be a good idea.
2701		3392
2702	Not that this does I<not> check whether the watcher itself is pending, only	3393	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3394	only whether it has been requested to make this watcher pending: there
		3395	is a time window between the event loop checking and resetting the async
		3396	notification, and the callback being invoked.
2704		3397
2705	=back	3398	=back
2706		3399
2707		3400
2708	=head1 OTHER FUNCTIONS	3401	=head1 OTHER FUNCTIONS
…		…
2725		3418
2726	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3421	repeat = 0) will be started. C<0> is a valid timeout.
2729		3422
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3427	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3428	events precedence.
2736		3429
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3431
2739	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
2740	{	3433	{
2741	if (revents & EV_READ)	3434	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3436	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3437	/* doh, nothing entered */;
2745	}	3438	}
2746		3439
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3441
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3442	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3443
2757	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3445	the given events it.
2759		3446
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
2761		3448
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3450	which is async-safe.
		3451
		3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
2764		3637
2765	=back	3638	=back
2766		3639
2767		3640
2768	=head1 LIBEVENT EMULATION	3641	=head1 LIBEVENT EMULATION
2769		3642
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3643	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3644	emulate the internals of libevent, so here are some usage hints:
2772		3645
2773	=over 4	3646	=over 4
		3647
		3648	=item * Only the libevent-1.4.1-beta API is being emulated.
		3649
		3650	This was the newest libevent version available when libev was implemented,
		3651	and is still mostly unchanged in 2010.
2774		3652
2775	=item * Use it by including <event.h>, as usual.	3653	=item * Use it by including <event.h>, as usual.
2776		3654
2777	=item * The following members are fully supported: ev_base, ev_callback,	3655	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3656	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3662	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3663	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3664	is an ev_pri field.
2787		3665
2788	=item * In libevent, the last base created gets the signals, in libev, the	3666	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3667	base that registered the signal gets the signals.
2790		3668
2791	=item * Other members are not supported.	3669	=item * Other members are not supported.
2792		3670
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3671	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3672	to use the libev header file and library.
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	3691	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	3692	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	3693	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	3694	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		3695
2818	Currently, functions, and static and non-static member functions can be	3696	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	3697	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	3698	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	3699	you need support for other types of functors please contact the author
2822	it).	3700	(preferably after implementing it).
2823		3701
2824	Here is a list of things available in the C<ev> namespace:	3702	Here is a list of things available in the C<ev> namespace:
2825		3703
2826	=over 4	3704	=over 4
2827		3705
…		…
2845		3723
2846	=over 4	3724	=over 4
2847		3725
2848	=item ev::TYPE::TYPE ()	3726	=item ev::TYPE::TYPE ()
2849		3727
2850	=item ev::TYPE::TYPE (struct ev_loop *)	3728	=item ev::TYPE::TYPE (loop)
2851		3729
2852	=item ev::TYPE::~TYPE	3730	=item ev::TYPE::~TYPE
2853		3731
2854	The constructor (optionally) takes an event loop to associate the watcher	3732	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	3733	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	3766	myclass obj;
2889	ev::io iow;	3767	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	3768	iow.set <myclass, &myclass::io_cb> (&obj);
2891		3769
2892	=item w->set (object *)	3770	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		3771
2896	This is a variation of a method callback - leaving out the method to call	3772	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	3773	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	3774	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	3775	the time. Incidentally, you can then also leave out the template argument
…		…
2932	Example: Use a plain function as callback.	3808	Example: Use a plain function as callback.
2933		3809
2934	static void io_cb (ev::io &w, int revents) { }	3810	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	3811	iow.set <io_cb> ();
2936		3812
2937	=item w->set (struct ev_loop *)	3813	=item w->set (loop)
2938		3814
2939	Associates a different C<struct ev_loop> with this watcher. You can only	3815	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	3816	do this when the watcher is inactive (and not pending either).
2941		3817
2942	=item w->set ([arguments])	3818	=item w->set ([arguments])
2943		3819
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3820	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2945	called at least once. Unlike the C counterpart, an active watcher gets	3821	method or a suitable start method must be called at least once. Unlike the
2946	automatically stopped and restarted when reconfiguring it with this	3822	C counterpart, an active watcher gets automatically stopped and restarted
2947	method.	3823	when reconfiguring it with this method.
2948		3824
2949	=item w->start ()	3825	=item w->start ()
2950		3826
2951	Starts the watcher. Note that there is no C<loop> argument, as the	3827	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	3828	constructor already stores the event loop.
2953		3829
		3830	=item w->start ([arguments])
		3831
		3832	Instead of calling C<set> and C<start> methods separately, it is often
		3833	convenient to wrap them in one call. Uses the same type of arguments as
		3834	the configure C<set> method of the watcher.
		3835
2954	=item w->stop ()	3836	=item w->stop ()
2955		3837
2956	Stops the watcher if it is active. Again, no C<loop> argument.	3838	Stops the watcher if it is active. Again, no C<loop> argument.
2957		3839
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3840	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		3852
2971	=back	3853	=back
2972		3854
2973	=back	3855	=back
2974		3856
2975	Example: Define a class with an IO and idle watcher, start one of them in	3857	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	3858	watchers in the constructor.
2977		3859
2978	class myclass	3860	class myclass
2979	{	3861	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	3862	ev::io io ; void io_cb (ev::io &w, int revents);
		3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		3865
2983	myclass (int fd)	3866	myclass (int fd)
2984	{	3867	{
2985	io .set <myclass, &myclass::io_cb > (this);	3868	io .set <myclass, &myclass::io_cb > (this);
		3869	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	3870	idle.set <myclass, &myclass::idle_cb> (this);
2987		3871
2988	io.start (fd, ev::READ);	3872	io.set (fd, ev::WRITE); // configure the watcher
		3873	io.start (); // start it whenever convenient
		3874
		3875	io2.start (fd, ev::READ); // set + start in one call
2989	}	3876	}
2990	};	3877	};
2991		3878
2992		3879
2993	=head1 OTHER LANGUAGE BINDINGS	3880	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	3899	L<http://software.schmorp.de/pkg/EV>.
3013		3900
3014	=item Python	3901	=item Python
3015		3902
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3903	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	3904	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		3905
3023	=item Ruby	3906	=item Ruby
3024		3907
3025	Tony Arcieri has written a ruby extension that offers access to a subset	3908	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	3909	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	3911	L<http://rev.rubyforge.org/>.
3029		3912
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	3913	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	3914	makes rev work even on mingw.
3032		3915
		3916	=item Haskell
		3917
		3918	A haskell binding to libev is available at
		3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3920
3033	=item D	3921	=item D
3034		3922
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3037		3925
3038	=item Ocaml	3926	=item Ocaml
3039		3927
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	3928	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3930
		3931	=item Lua
		3932
		3933	Brian Maher has written a partial interface to libev for lua (at the
		3934	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3935	L<http://github.com/brimworks/lua-ev>.
3042		3936
3043	=back	3937	=back
3044		3938
3045		3939
3046	=head1 MACRO MAGIC	3940	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	3954	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	3955	C<EV_A_> is used when other arguments are following. Example:
3062		3956
3063	ev_unref (EV_A);	3957	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	3958	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	3959	ev_run (EV_A_ 0);
3066		3960
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3961	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	3962	which is often provided by the following macro.
3069		3963
3070	=item C<EV_P>, C<EV_P_>	3964	=item C<EV_P>, C<EV_P_>
…		…
3110	}	4004	}
3111		4005
3112	ev_check check;	4006	ev_check check;
3113	ev_check_init (&check, check_cb);	4007	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4008	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4009	ev_run (EV_DEFAULT_ 0);
3116		4010
3117	=head1 EMBEDDING	4011	=head1 EMBEDDING
3118		4012
3119	Libev can (and often is) directly embedded into host	4013	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4014	applications. Examples of applications that embed it include the Deliantra
…		…
3200	libev.m4	4094	libev.m4
3201		4095
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4096	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4097
3204	Libev can be configured via a variety of preprocessor symbols you have to	4098	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	4099	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4100	the absence of autoconf is documented for every option.
		4101
		4102	Symbols marked with "(h)" do not change the ABI, and can have different
		4103	values when compiling libev vs. including F<ev.h>, so it is permissible
		4104	to redefine them before including F<ev.h> without breaking compatibility
		4105	to a compiled library. All other symbols change the ABI, which means all
		4106	users of libev and the libev code itself must be compiled with compatible
		4107	settings.
3207		4108
3208	=over 4	4109	=over 4
3209		4110
		4111	=item EV_COMPAT3 (h)
		4112
		4113	Backwards compatibility is a major concern for libev. This is why this
		4114	release of libev comes with wrappers for the functions and symbols that
		4115	have been renamed between libev version 3 and 4.
		4116
		4117	You can disable these wrappers (to test compatibility with future
		4118	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4119	sources. This has the additional advantage that you can drop the C<struct>
		4120	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4121	typedef in that case.
		4122
		4123	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4124	and in some even more future version the compatibility code will be
		4125	removed completely.
		4126
3210	=item EV_STANDALONE	4127	=item EV_STANDALONE (h)
3211		4128
3212	Must always be C<1> if you do not use autoconf configuration, which	4129	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	4130	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4131	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	4132	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	4133	F<event.h> that are not directly supported by the libev core alone.
3217		4134
3218	In stanbdalone mode, libev will still try to automatically deduce the	4135	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4136	configuration, but has to be more conservative.
3220		4137
3221	=item EV_USE_MONOTONIC	4138	=item EV_USE_MONOTONIC
3222		4139
3223	If defined to be C<1>, libev will try to detect the availability of the	4140	If defined to be C<1>, libev will try to detect the availability of the
…		…
3288	be used is the winsock select). This means that it will call	4205	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4206	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4207	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4208	on win32. Should not be defined on non-win32 platforms.
3292		4209
3293	=item EV_FD_TO_WIN32_HANDLE	4210	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4211
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4212	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4213	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4214	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4215	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4216	in which case they can provide this function to map fds to socket handles.
		4217
		4218	=item EV_WIN32_HANDLE_TO_FD(handle)
		4219
		4220	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4221	using the standard C<_open_osfhandle> function. For programs implementing
		4222	their own fd to handle mapping, overwriting this function makes it easier
		4223	to do so. This can be done by defining this macro to an appropriate value.
		4224
		4225	=item EV_WIN32_CLOSE_FD(fd)
		4226
		4227	If programs implement their own fd to handle mapping on win32, then this
		4228	macro can be used to override the C<close> function, useful to unregister
		4229	file descriptors again. Note that the replacement function has to close
		4230	the underlying OS handle.
3300		4231
3301	=item EV_USE_POLL	4232	=item EV_USE_POLL
3302		4233
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4234	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4235	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3351	as well as for signal and thread safety in C<ev_async> watchers.	4282	as well as for signal and thread safety in C<ev_async> watchers.
3352		4283
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4284	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4285	(from F<signal.h>), which is usually good enough on most platforms.
3355		4286
3356	=item EV_H	4287	=item EV_H (h)
3357		4288
3358	The name of the F<ev.h> header file used to include it. The default if	4289	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4291	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4292
3362	=item EV_CONFIG_H	4293	=item EV_CONFIG_H (h)
3363		4294
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4297	C<EV_H>, above.
3367		4298
3368	=item EV_EVENT_H	4299	=item EV_EVENT_H (h)
3369		4300
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4302	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4303
3373	=item EV_PROTOTYPES	4304	=item EV_PROTOTYPES (h)
3374		4305
3375	If defined to be C<0>, then F<ev.h> will not define any function	4306	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4307	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4308	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4309	around libev functions.
…		…
3400	fine.	4331	fine.
3401		4332
3402	If your embedding application does not need any priorities, defining these	4333	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4334	both to C<0> will save some memory and CPU.
3404		4335
3405	=item EV_PERIODIC_ENABLE	4336	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4337	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4338	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4339
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4340	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4341	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4342	is not. Disabling watcher types mainly saves code size.
3410		4343
3411	=item EV_IDLE_ENABLE	4344	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4345
3440	If you need to shave off some kilobytes of code at the expense of some	4346	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4347	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4348	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4349	that can be enabled on the platform.
		4350
		4351	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4352	with some broad features you want) and then selectively re-enable
		4353	additional parts you want, for example if you want everything minimal,
		4354	but multiple event loop support, async and child watchers and the poll
		4355	backend, use this:
		4356
		4357	#define EV_FEATURES 0
		4358	#define EV_MULTIPLICITY 1
		4359	#define EV_USE_POLL 1
		4360	#define EV_CHILD_ENABLE 1
		4361	#define EV_ASYNC_ENABLE 1
		4362
		4363	The actual value is a bitset, it can be a combination of the following
		4364	values:
		4365
		4366	=over 4
		4367
		4368	=item C<1> - faster/larger code
		4369
		4370	Use larger code to speed up some operations.
		4371
		4372	Currently this is used to override some inlining decisions (enlarging the
		4373	code size by roughly 30% on amd64).
		4374
		4375	When optimising for size, use of compiler flags such as C<-Os> with
		4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4377	assertions.
		4378
		4379	=item C<2> - faster/larger data structures
		4380
		4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4382	hash table sizes and so on. This will usually further increase code size
		4383	and can additionally have an effect on the size of data structures at
		4384	runtime.
		4385
		4386	=item C<4> - full API configuration
		4387
		4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4389	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4390
		4391	=item C<8> - full API
		4392
		4393	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4394	details on which parts of the API are still available without this
		4395	feature, and do not complain if this subset changes over time.
		4396
		4397	=item C<16> - enable all optional watcher types
		4398
		4399	Enables all optional watcher types. If you want to selectively enable
		4400	only some watcher types other than I/O and timers (e.g. prepare,
		4401	embed, async, child...) you can enable them manually by defining
		4402	C<EV_watchertype_ENABLE> to C<1> instead.
		4403
		4404	=item C<32> - enable all backends
		4405
		4406	This enables all backends - without this feature, you need to enable at
		4407	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4408
		4409	=item C<64> - enable OS-specific "helper" APIs
		4410
		4411	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4412	default.
		4413
		4414	=back
		4415
		4416	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4417	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4418	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4419	watchers, timers and monotonic clock support.
		4420
		4421	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4423	your program might be left out as well - a binary starting a timer and an
		4424	I/O watcher then might come out at only 5Kb.
		4425
		4426	=item EV_AVOID_STDIO
		4427
		4428	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4429	functions (printf, scanf, perror etc.). This will increase the code size
		4430	somewhat, but if your program doesn't otherwise depend on stdio and your
		4431	libc allows it, this avoids linking in the stdio library which is quite
		4432	big.
		4433
		4434	Note that error messages might become less precise when this option is
		4435	enabled.
		4436
		4437	=item EV_NSIG
		4438
		4439	The highest supported signal number, +1 (or, the number of
		4440	signals): Normally, libev tries to deduce the maximum number of signals
		4441	automatically, but sometimes this fails, in which case it can be
		4442	specified. Also, using a lower number than detected (C<32> should be
		4443	good for about any system in existence) can save some memory, as libev
		4444	statically allocates some 12-24 bytes per signal number.
3444		4445
3445	=item EV_PID_HASHSIZE	4446	=item EV_PID_HASHSIZE
3446		4447
3447	C<ev_child> watchers use a small hash table to distribute workload by	4448	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4449	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4450	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4451	might want to increase this value (I<must> be a power of two).
3451		4452
3452	=item EV_INOTIFY_HASHSIZE	4453	=item EV_INOTIFY_HASHSIZE
3453		4454
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4455	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4456	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4457	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4458	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4459	power of two).
3459		4460
3460	=item EV_USE_4HEAP	4461	=item EV_USE_4HEAP
3461		4462
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4463	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4464	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4465	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4466	faster performance with many (thousands) of watchers.
3466		4467
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4468	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4469	will be C<0>.
3469		4470
3470	=item EV_HEAP_CACHE_AT	4471	=item EV_HEAP_CACHE_AT
3471		4472
3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4473	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4474	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4475	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4476	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4477	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4478	noticeably with many (hundreds) of watchers.
3478		4479
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4480	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4481	will be C<0>.
3481		4482
3482	=item EV_VERIFY	4483	=item EV_VERIFY
3483		4484
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4485	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4486	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4487	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4488	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4489	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4490	verification code will be called very frequently, which will slow down
3490	libev considerably.	4491	libev considerably.
3491		4492
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4493	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4494	will be C<0>.
3494		4495
3495	=item EV_COMMON	4496	=item EV_COMMON
3496		4497
3497	By default, all watchers have a C<void *data> member. By redefining	4498	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4499	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4500	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4501	though, and it must be identical each time.
3501		4502
3502	For example, the perl EV module uses something like this:	4503	For example, the perl EV module uses something like this:
3503		4504
…		…
3556	file.	4557	file.
3557		4558
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4559	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	4560	that everybody includes and which overrides some configure choices:
3560		4561
3561	#define EV_MINIMAL 1	4562	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	4563	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	4564	#define EV_PREPARE_ENABLE 1
		4565	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	4566	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	4567	#define EV_CHILD_ENABLE 1
		4568	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	4569	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		4570
3571	#include "ev++.h"	4571	#include "ev++.h"
3572		4572
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		4574
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	4634	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	4635	watcher callback into the event loop interested in the signal.
3636		4636
3637	=back	4637	=back
3638		4638
		4639	See also L<THREAD LOCKING EXAMPLE>.
		4640
3639	=head3 COROUTINES	4641	=head3 COROUTINES
3640		4642
3641	Libev is very accommodating to coroutines ("cooperative threads"):	4643	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	4644	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4645	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	4646	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	4647	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	4648	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		4649
3648	Care has been taken to ensure that libev does not keep local state inside	4650	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4651	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	4652	they do not call any callbacks.
3651		4653
3652	=head2 COMPILER WARNINGS	4654	=head2 COMPILER WARNINGS
3653		4655
3654	Depending on your compiler and compiler settings, you might get no or a	4656	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	4667	maintainable.
3666		4668
3667	And of course, some compiler warnings are just plain stupid, or simply	4669	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	4670	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	4671	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	4672	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	4673	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	4674	such buggy versions.
3673		4675
3674	While libev is written to generate as few warnings as possible,	4676	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	4677	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	4713	I suggest using suppression lists.
3712		4714
3713		4715
3714	=head1 PORTABILITY NOTES	4716	=head1 PORTABILITY NOTES
3715		4717
		4718	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4719
		4720	GNU/Linux is the only common platform that supports 64 bit file/large file
		4721	interfaces but I<disables> them by default.
		4722
		4723	That means that libev compiled in the default environment doesn't support
		4724	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4725
		4726	Unfortunately, many programs try to work around this GNU/Linux issue
		4727	by enabling the large file API, which makes them incompatible with the
		4728	standard libev compiled for their system.
		4729
		4730	Likewise, libev cannot enable the large file API itself as this would
		4731	suddenly make it incompatible to the default compile time environment,
		4732	i.e. all programs not using special compile switches.
		4733
		4734	=head2 OS/X AND DARWIN BUGS
		4735
		4736	The whole thing is a bug if you ask me - basically any system interface
		4737	you touch is broken, whether it is locales, poll, kqueue or even the
		4738	OpenGL drivers.
		4739
		4740	=head3 C<kqueue> is buggy
		4741
		4742	The kqueue syscall is broken in all known versions - most versions support
		4743	only sockets, many support pipes.
		4744
		4745	Libev tries to work around this by not using C<kqueue> by default on this
		4746	rotten platform, but of course you can still ask for it when creating a
		4747	loop - embedding a socket-only kqueue loop into a select-based one is
		4748	probably going to work well.
		4749
		4750	=head3 C<poll> is buggy
		4751
		4752	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4753	implementation by something calling C<kqueue> internally around the 10.5.6
		4754	release, so now C<kqueue> I<and> C<poll> are broken.
		4755
		4756	Libev tries to work around this by not using C<poll> by default on
		4757	this rotten platform, but of course you can still ask for it when creating
		4758	a loop.
		4759
		4760	=head3 C<select> is buggy
		4761
		4762	All that's left is C<select>, and of course Apple found a way to fuck this
		4763	one up as well: On OS/X, C<select> actively limits the number of file
		4764	descriptors you can pass in to 1024 - your program suddenly crashes when
		4765	you use more.
		4766
		4767	There is an undocumented "workaround" for this - defining
		4768	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4769	work on OS/X.
		4770
		4771	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4772
		4773	=head3 C<errno> reentrancy
		4774
		4775	The default compile environment on Solaris is unfortunately so
		4776	thread-unsafe that you can't even use components/libraries compiled
		4777	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4778	defined by default. A valid, if stupid, implementation choice.
		4779
		4780	If you want to use libev in threaded environments you have to make sure
		4781	it's compiled with C<_REENTRANT> defined.
		4782
		4783	=head3 Event port backend
		4784
		4785	The scalable event interface for Solaris is called "event
		4786	ports". Unfortunately, this mechanism is very buggy in all major
		4787	releases. If you run into high CPU usage, your program freezes or you get
		4788	a large number of spurious wakeups, make sure you have all the relevant
		4789	and latest kernel patches applied. No, I don't know which ones, but there
		4790	are multiple ones to apply, and afterwards, event ports actually work
		4791	great.
		4792
		4793	If you can't get it to work, you can try running the program by setting
		4794	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4795	C<select> backends.
		4796
		4797	=head2 AIX POLL BUG
		4798
		4799	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4800	this by trying to avoid the poll backend altogether (i.e. it's not even
		4801	compiled in), which normally isn't a big problem as C<select> works fine
		4802	with large bitsets on AIX, and AIX is dead anyway.
		4803
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4804	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4805
		4806	=head3 General issues
3717		4807
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4808	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	4809	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	4810	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	4812	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4814	as every compielr comes with a slightly differently broken/incompatible
		4815	environment.
3724		4816
3725	Lifting these limitations would basically require the full	4817	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	4818	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	4819	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	4820	also that glib is the slowest event library known to man).
3729		4821
3730	There is no supported compilation method available on windows except	4822	There is no supported compilation method available on windows except
3731	embedding it into other applications.	4823	embedding it into other applications.
		4824
		4825	Sensible signal handling is officially unsupported by Microsoft - libev
		4826	tries its best, but under most conditions, signals will simply not work.
3732		4827
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	4828	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	4829	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	4830	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	4831	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	4836	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	4837	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	4838	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	4839	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	4840	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	4841	(due to Microsoft monopoly games).
3747		4842
3748	A typical way to use libev under windows is to embed it (see the embedding	4843	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	4844	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	4845	of F<ev.h>:
3751		4846
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	4853	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		4854
3760	#include "evwrap.h"	4855	#include "evwrap.h"
3761	#include "ev.c"	4856	#include "ev.c"
3762		4857
3763	=over 4
3764
3765	=item The winsocket select function	4858	=head3 The winsocket C<select> function
3766		4859
3767	The winsocket C<select> function doesn't follow POSIX in that it	4860	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	4861	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	4862	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	4863	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4872	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		4873
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	4874	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	4875	complexity in the O(n²) range when using win32.
3783		4876
3784	=item Limited number of file descriptors	4877	=head3 Limited number of file descriptors
3785		4878
3786	Windows has numerous arbitrary (and low) limits on things.	4879	Windows has numerous arbitrary (and low) limits on things.
3787		4880
3788	Early versions of winsocket's select only supported waiting for a maximum	4881	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	4882	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	4883	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	4884	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	4885	previous thread in each. Sounds great!).
3793		4886
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4887	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	4888	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	4889	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	4890	other interpreters do their own select emulation on windows).
3798		4891
3799	Another limit is the number of file descriptors in the Microsoft runtime	4892	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4893	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	4894	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4895	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	4896	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	4897	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	4898	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	4899	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	4900	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		4901
3813	=head2 PORTABILITY REQUIREMENTS	4902	=head2 PORTABILITY REQUIREMENTS
3814		4903
3815	In addition to a working ISO-C implementation and of course the	4904	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	4905	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	4912	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	4913	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	4914	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	4915	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	4916	calls them using an C<ev_watcher *> internally.
		4917
		4918	=item pointer accesses must be thread-atomic
		4919
		4920	Accessing a pointer value must be atomic, it must both be readable and
		4921	writable in one piece - this is the case on all current architectures.
3828		4922
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	4923	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		4924
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	4925	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4926	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3855	watchers.	4949	watchers.
3856		4950
3857	=item C<double> must hold a time value in seconds with enough accuracy	4951	=item C<double> must hold a time value in seconds with enough accuracy
3858		4952
3859	The type C<double> is used to represent timestamps. It is required to	4953	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	4955	good enough for at least into the year 4000 with millisecond accuracy
		4956	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	4957	implementations using IEEE 754, which is basically all existing ones. With
		4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3863		4959
3864	=back	4960	=back
3865		4961
3866	If you know of other additional requirements drop me a note.	4962	If you know of other additional requirements drop me a note.
3867		4963
…		…
3935	involves iterating over all running async watchers or all signal numbers.	5031	involves iterating over all running async watchers or all signal numbers.
3936		5032
3937	=back	5033	=back
3938		5034
3939		5035
		5036	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5037
		5038	The major version 4 introduced some incompatible changes to the API.
		5039
		5040	At the moment, the C<ev.h> header file provides compatibility definitions
		5041	for all changes, so most programs should still compile. The compatibility
		5042	layer might be removed in later versions of libev, so better update to the
		5043	new API early than late.
		5044
		5045	=over 4
		5046
		5047	=item C<EV_COMPAT3> backwards compatibility mechanism
		5048
		5049	The backward compatibility mechanism can be controlled by
		5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5051	section.
		5052
		5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5054
		5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5056
		5057	ev_loop_destroy (EV_DEFAULT_UC);
		5058	ev_loop_fork (EV_DEFAULT);
		5059
		5060	=item function/symbol renames
		5061
		5062	A number of functions and symbols have been renamed:
		5063
		5064	ev_loop => ev_run
		5065	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5066	EVLOOP_ONESHOT => EVRUN_ONCE
		5067
		5068	ev_unloop => ev_break
		5069	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5070	EVUNLOOP_ONE => EVBREAK_ONE
		5071	EVUNLOOP_ALL => EVBREAK_ALL
		5072
		5073	EV_TIMEOUT => EV_TIMER
		5074
		5075	ev_loop_count => ev_iteration
		5076	ev_loop_depth => ev_depth
		5077	ev_loop_verify => ev_verify
		5078
		5079	Most functions working on C<struct ev_loop> objects don't have an
		5080	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5081	associated constants have been renamed to not collide with the C<struct
		5082	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5083	as all other watcher types. Note that C<ev_loop_fork> is still called
		5084	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5085	typedef.
		5086
		5087	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5088
		5089	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5090	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5091	and work, but the library code will of course be larger.
		5092
		5093	=back
		5094
		5095
		5096	=head1 GLOSSARY
		5097
		5098	=over 4
		5099
		5100	=item active
		5101
		5102	A watcher is active as long as it has been started and not yet stopped.
		5103	See L<WATCHER STATES> for details.
		5104
		5105	=item application
		5106
		5107	In this document, an application is whatever is using libev.
		5108
		5109	=item backend
		5110
		5111	The part of the code dealing with the operating system interfaces.
		5112
		5113	=item callback
		5114
		5115	The address of a function that is called when some event has been
		5116	detected. Callbacks are being passed the event loop, the watcher that
		5117	received the event, and the actual event bitset.
		5118
		5119	=item callback/watcher invocation
		5120
		5121	The act of calling the callback associated with a watcher.
		5122
		5123	=item event
		5124
		5125	A change of state of some external event, such as data now being available
		5126	for reading on a file descriptor, time having passed or simply not having
		5127	any other events happening anymore.
		5128
		5129	In libev, events are represented as single bits (such as C<EV_READ> or
		5130	C<EV_TIMER>).
		5131
		5132	=item event library
		5133
		5134	A software package implementing an event model and loop.
		5135
		5136	=item event loop
		5137
		5138	An entity that handles and processes external events and converts them
		5139	into callback invocations.
		5140
		5141	=item event model
		5142
		5143	The model used to describe how an event loop handles and processes
		5144	watchers and events.
		5145
		5146	=item pending
		5147
		5148	A watcher is pending as soon as the corresponding event has been
		5149	detected. See L<WATCHER STATES> for details.
		5150
		5151	=item real time
		5152
		5153	The physical time that is observed. It is apparently strictly monotonic :)
		5154
		5155	=item wall-clock time
		5156
		5157	The time and date as shown on clocks. Unlike real time, it can actually
		5158	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5159	clock.
		5160
		5161	=item watcher
		5162
		5163	A data structure that describes interest in certain events. Watchers need
		5164	to be started (attached to an event loop) before they can receive events.
		5165
		5166	=back
		5167
3940	=head1 AUTHOR	5168	=head1 AUTHOR
3941		5169
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5171	Magnusson and Emanuele Giaquinta.
3943		5172

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