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Revision 1.264 by root, Wed Aug 19 23:44:51 2009 UTC vs.
Revision 1.431 by root, Fri Nov 22 16:42:10 2013 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	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	78	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	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
118	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
119	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
120	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
121	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
122	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
123	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
134	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	146	time differences (e.g. delays) throughout libev.
136		147
137	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
138		149
139	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	151	and internal errors (bugs).
…		…
164		175
165	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
166		177
167	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
170		182
171	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
172		184
173	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
175	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
176		194
177	=item int ev_version_major ()	195	=item int ev_version_major ()
178		196
179	=item int ev_version_minor ()	197	=item int ev_version_minor ()
180		198
…		…
191	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	211	not a problem.
194		212
195	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
197		216
198	assert (("libev version mismatch",	217	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
201		220
…		…
212	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
214		233
215	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
216		235
217	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
223		243
224	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
225		245
226	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
231		251
232	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
233		253
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
235		255
236	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	285	}
266		286
267	...	287	...
268	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
269		289
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
271		291
272	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	307	}
288		308
289	...	309	...
290	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
291		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
292	=back	325	=back
293		326
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		328
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
299		332
300	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
302	not.	335	do not.
303		336
304	=over 4	337	=over 4
305		338
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		340
308	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
312		351
313	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
314	function.	353	function (or via the C<EV_DEFAULT> macro).
315		354
316	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
319		359
320	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
326		384
327	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		387
330	The following flags are supported:	388	The following flags are supported:
…		…
340		398
341	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
342	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
344	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
345	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
346	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
347		407
348	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
349		409
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	411	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		412
354	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	425	environment variable.
367		426
368	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
369		428
370	When this flag is specified, then libev will not attempt to use the	429	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	431	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		433
375	=item C<EVFLAG_NOSIGNALFD>	434	=item C<EVFLAG_SIGNALFD>
376		435
377	When this flag is specified, then libev will not attempt to use the	436	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is	437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	438	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	439	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
		442
		443	Signalfd will not be used by default as this changes your signal mask, and
		444	there are a lot of shoddy libraries and programs (glib's threadpool for
		445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
382		461
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		463
385	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
386	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	490	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	491	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413		492
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		494
		495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		496	kernels).
		497
416	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
417	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
418	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
419	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
420		502
421	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
422	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
423	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
424	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
425	so on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
426	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
427	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
428	hard to detect.	512	and is of course hard to detect.
429		513
430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
431	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
432	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
433	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
434	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
435	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
436	events to filter out spurious ones, recreating the set when required.	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
		524	not least, it also refuses to work with some file descriptors which work
		525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
437		530
438	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
439	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
440	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
478		571
479	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
480	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
481	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
482	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
483	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
485	cases	578	drops fds silently in similarly hard-to-detect cases.
486		579
487	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
488		581
489	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
490	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
508		601
509	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
510	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
511		604
512	Please note that Solaris event ports can deliver a lot of spurious
513	notifications, so you need to use non-blocking I/O or other means to avoid
514	blocking when no data (or space) is available.
515
516	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
517	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
519	might perform better.	608	might perform better.
520		609
521	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
522	notifications, this backend actually performed fully to specification
523	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
524	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
525		624
526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
527	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
528		627
529	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
530		629
531	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
532	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
533	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
534		633
535	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
536		643
537	=back	644	=back
538		645
539	If one or more of the backend flags are or'ed into the flags value,	646	If one or more of the backend flags are or'ed into the flags value,
540	then only these backends will be tried (in the reverse order as listed	647	then only these backends will be tried (in the reverse order as listed
541	here). If none are specified, all backends in C<ev_recommended_backends	648	here). If none are specified, all backends in C<ev_recommended_backends
542	()> will be tried.	649	()> will be tried.
543		650
544	Example: This is the most typical usage.
545
546	if (!ev_default_loop (0))
547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
548
549	Example: Restrict libev to the select and poll backends, and do not allow
550	environment settings to be taken into account:
551
552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
553
554	Example: Use whatever libev has to offer, but make sure that kqueue is
555	used if available (warning, breaks stuff, best use only with your own
556	private event loop and only if you know the OS supports your types of
557	fds):
558
559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
560
561	=item struct ev_loop *ev_loop_new (unsigned int flags)
562
563	Similar to C<ev_default_loop>, but always creates a new event loop that is
564	always distinct from the default loop. Unlike the default loop, it cannot
565	handle signal and child watchers, and attempts to do so will be greeted by
566	undefined behaviour (or a failed assertion if assertions are enabled).
567
568	Note that this function I<is> thread-safe, and the recommended way to use
569	libev with threads is indeed to create one loop per thread, and using the
570	default loop in the "main" or "initial" thread.
571
572	Example: Try to create a event loop that uses epoll and nothing else.	651	Example: Try to create a event loop that uses epoll and nothing else.
573		652
574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575	if (!epoller)	654	if (!epoller)
576	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
577		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
578	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
579		663
580	Destroys the default loop again (frees all memory and kernel state	664	Destroys an event loop object (frees all memory and kernel state
581	etc.). None of the active event watchers will be stopped in the normal	665	etc.). None of the active event watchers will be stopped in the normal
582	sense, so e.g. C<ev_is_active> might still return true. It is your	666	sense, so e.g. C<ev_is_active> might still return true. It is your
583	responsibility to either stop all watchers cleanly yourself I<before>	667	responsibility to either stop all watchers cleanly yourself I<before>
584	calling this function, or cope with the fact afterwards (which is usually	668	calling this function, or cope with the fact afterwards (which is usually
585	the easiest thing, you can just ignore the watchers and/or C<free ()> them	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
587		671
588	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
589	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
590	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
591		675
592	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
593	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
594	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
595	C<ev_loop_new> and C<ev_loop_destroy>).	683	and C<ev_loop_destroy>.
596		684
597	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
598		686
599	Like C<ev_default_destroy>, but destroys an event loop created by an
600	earlier call to C<ev_loop_new>.
601
602	=item ev_default_fork ()
603
604	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations to
605	to reinitialise the kernel state for backends that have one. Despite the	688	reinitialise the kernel state for backends that have one. Despite the
606	name, you can call it anytime, but it makes most sense after forking, in	689	name, you can call it anytime, but it makes most sense after forking, in
607	the child process (or both child and parent, but that again makes little	690	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
608	sense). You I<must> call it in the child before using any of the libev	691	child before resuming or calling C<ev_run>.
609	functions, and it will only take effect at the next C<ev_loop> iteration.	692
		693	Again, you I<have> to call it on I<any> loop that you want to re-use after
		694	a fork, I<even if you do not plan to use the loop in the parent>. This is
		695	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		696	during fork.
610		697
611	On the other hand, you only need to call this function in the child	698	On the other hand, you only need to call this function in the child
612	process if and only if you want to use the event library in the child. If	699	process if and only if you want to use the event loop in the child. If
613	you just fork+exec, you don't have to call it at all.	700	you just fork+exec or create a new loop in the child, you don't have to
		701	call it at all (in fact, C<epoll> is so badly broken that it makes a
		702	difference, but libev will usually detect this case on its own and do a
		703	costly reset of the backend).
614		704
615	The function itself is quite fast and it's usually not a problem to call	705	The function itself is quite fast and it's usually not a problem to call
616	it just in case after a fork. To make this easy, the function will fit in	706	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		707
		708	Example: Automate calling C<ev_loop_fork> on the default loop when
		709	using pthreads.
		710
		711	static void
		712	post_fork_child (void)
		713	{
		714	ev_loop_fork (EV_DEFAULT);
		715	}
		716
		717	...
619	pthread_atfork (0, 0, ev_default_fork);	718	pthread_atfork (0, 0, post_fork_child);
620
621	=item ev_loop_fork (loop)
622
623	Like C<ev_default_fork>, but acts on an event loop created by
624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
625	after fork that you want to re-use in the child, and how you do this is
626	entirely your own problem.
627		719
628	=item int ev_is_default_loop (loop)	720	=item int ev_is_default_loop (loop)
629		721
630	Returns true when the given loop is, in fact, the default loop, and false	722	Returns true when the given loop is, in fact, the default loop, and false
631	otherwise.	723	otherwise.
632		724
633	=item unsigned int ev_loop_count (loop)	725	=item unsigned int ev_iteration (loop)
634		726
635	Returns the count of loop iterations for the loop, which is identical to	727	Returns the current iteration count for the event loop, which is identical
636	the number of times libev did poll for new events. It starts at C<0> and	728	to the number of times libev did poll for new events. It starts at C<0>
637	happily wraps around with enough iterations.	729	and happily wraps around with enough iterations.
638		730
639	This value can sometimes be useful as a generation counter of sorts (it	731	This value can sometimes be useful as a generation counter of sorts (it
640	"ticks" the number of loop iterations), as it roughly corresponds with	732	"ticks" the number of loop iterations), as it roughly corresponds with
641	C<ev_prepare> and C<ev_check> calls.	733	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		734	prepare and check phases.
642		735
643	=item unsigned int ev_loop_depth (loop)	736	=item unsigned int ev_depth (loop)
644		737
645	Returns the number of times C<ev_loop> was entered minus the number of	738	Returns the number of times C<ev_run> was entered minus the number of
646	times C<ev_loop> was exited, in other words, the recursion depth.	739	times C<ev_run> was exited normally, in other words, the recursion depth.
647		740
648	Outside C<ev_loop>, this number is zero. In a callback, this number is	741	Outside C<ev_run>, this number is zero. In a callback, this number is
649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	742	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
650	in which case it is higher.	743	in which case it is higher.
651		744
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	745	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	etc.), doesn't count as exit.	746	throwing an exception etc.), doesn't count as "exit" - consider this
		747	as a hint to avoid such ungentleman-like behaviour unless it's really
		748	convenient, in which case it is fully supported.
654		749
655	=item unsigned int ev_backend (loop)	750	=item unsigned int ev_backend (loop)
656		751
657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	752	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
658	use.	753	use.
…		…
667		762
668	=item ev_now_update (loop)	763	=item ev_now_update (loop)
669		764
670	Establishes the current time by querying the kernel, updating the time	765	Establishes the current time by querying the kernel, updating the time
671	returned by C<ev_now ()> in the progress. This is a costly operation and	766	returned by C<ev_now ()> in the progress. This is a costly operation and
672	is usually done automatically within C<ev_loop ()>.	767	is usually done automatically within C<ev_run ()>.
673		768
674	This function is rarely useful, but when some event callback runs for a	769	This function is rarely useful, but when some event callback runs for a
675	very long time without entering the event loop, updating libev's idea of	770	very long time without entering the event loop, updating libev's idea of
676	the current time is a good idea.	771	the current time is a good idea.
677		772
678	See also L<The special problem of time updates> in the C<ev_timer> section.	773	See also L</The special problem of time updates> in the C<ev_timer> section.
679		774
680	=item ev_suspend (loop)	775	=item ev_suspend (loop)
681		776
682	=item ev_resume (loop)	777	=item ev_resume (loop)
683		778
684	These two functions suspend and resume a loop, for use when the loop is	779	These two functions suspend and resume an event loop, for use when the
685	not used for a while and timeouts should not be processed.	780	loop is not used for a while and timeouts should not be processed.
686		781
687	A typical use case would be an interactive program such as a game: When	782	A typical use case would be an interactive program such as a game: When
688	the user presses C<^Z> to suspend the game and resumes it an hour later it	783	the user presses C<^Z> to suspend the game and resumes it an hour later it
689	would be best to handle timeouts as if no time had actually passed while	784	would be best to handle timeouts as if no time had actually passed while
690	the program was suspended. This can be achieved by calling C<ev_suspend>	785	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	787	C<ev_resume> directly afterwards to resume timer processing.
693		788
694	Effectively, all C<ev_timer> watchers will be delayed by the time spend	789	Effectively, all C<ev_timer> watchers will be delayed by the time spend
695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	790	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
696	will be rescheduled (that is, they will lose any events that would have	791	will be rescheduled (that is, they will lose any events that would have
697	occured while suspended).	792	occurred while suspended).
698		793
699	After calling C<ev_suspend> you B<must not> call I<any> function on the	794	After calling C<ev_suspend> you B<must not> call I<any> function on the
700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	795	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
701	without a previous call to C<ev_suspend>.	796	without a previous call to C<ev_suspend>.
702		797
703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	798	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
704	event loop time (see C<ev_now_update>).	799	event loop time (see C<ev_now_update>).
705		800
706	=item ev_loop (loop, int flags)	801	=item bool ev_run (loop, int flags)
707		802
708	Finally, this is it, the event handler. This function usually is called	803	Finally, this is it, the event handler. This function usually is called
709	after you initialised all your watchers and you want to start handling	804	after you have initialised all your watchers and you want to start
710	events.	805	handling events. It will ask the operating system for any new events, call
		806	the watcher callbacks, and then repeat the whole process indefinitely: This
		807	is why event loops are called I<loops>.
711		808
712	If the flags argument is specified as C<0>, it will not return until	809	If the flags argument is specified as C<0>, it will keep handling events
713	either no event watchers are active anymore or C<ev_unloop> was called.	810	until either no event watchers are active anymore or C<ev_break> was
		811	called.
714		812
		813	The return value is false if there are no more active watchers (which
		814	usually means "all jobs done" or "deadlock"), and true in all other cases
		815	(which usually means " you should call C<ev_run> again").
		816
715	Please note that an explicit C<ev_unloop> is usually better than	817	Please note that an explicit C<ev_break> is usually better than
716	relying on all watchers to be stopped when deciding when a program has	818	relying on all watchers to be stopped when deciding when a program has
717	finished (especially in interactive programs), but having a program	819	finished (especially in interactive programs), but having a program
718	that automatically loops as long as it has to and no longer by virtue	820	that automatically loops as long as it has to and no longer by virtue
719	of relying on its watchers stopping correctly, that is truly a thing of	821	of relying on its watchers stopping correctly, that is truly a thing of
720	beauty.	822	beauty.
721		823
		824	This function is I<mostly> exception-safe - you can break out of a
		825	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		826	exception and so on. This does not decrement the C<ev_depth> value, nor
		827	will it clear any outstanding C<EVBREAK_ONE> breaks.
		828
722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	829	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
723	those events and any already outstanding ones, but will not block your	830	those events and any already outstanding ones, but will not wait and
724	process in case there are no events and will return after one iteration of	831	block your process in case there are no events and will return after one
725	the loop.	832	iteration of the loop. This is sometimes useful to poll and handle new
		833	events while doing lengthy calculations, to keep the program responsive.
726		834
727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	835	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
728	necessary) and will handle those and any already outstanding ones. It	836	necessary) and will handle those and any already outstanding ones. It
729	will block your process until at least one new event arrives (which could	837	will block your process until at least one new event arrives (which could
730	be an event internal to libev itself, so there is no guarantee that a	838	be an event internal to libev itself, so there is no guarantee that a
731	user-registered callback will be called), and will return after one	839	user-registered callback will be called), and will return after one
732	iteration of the loop.	840	iteration of the loop.
733		841
734	This is useful if you are waiting for some external event in conjunction	842	This is useful if you are waiting for some external event in conjunction
735	with something not expressible using other libev watchers (i.e. "roll your	843	with something not expressible using other libev watchers (i.e. "roll your
736	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	844	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
737	usually a better approach for this kind of thing.	845	usually a better approach for this kind of thing.
738		846
739	Here are the gory details of what C<ev_loop> does:	847	Here are the gory details of what C<ev_run> does (this is for your
		848	understanding, not a guarantee that things will work exactly like this in
		849	future versions):
740		850
		851	- Increment loop depth.
		852	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	853	- Before the first iteration, call any pending watchers.
		854	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	855	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- If a fork was detected (by any means), queue and call all fork watchers.	856	- If a fork was detected (by any means), queue and call all fork watchers.
744	- Queue and call all prepare watchers.	857	- Queue and call all prepare watchers.
		858	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	859	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	860	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	861	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	862	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	863	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	864	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	865	any active watchers at all will result in not sleeping).
752	- Sleep if the I/O and timer collect interval say so.	866	- Sleep if the I/O and timer collect interval say so.
		867	- Increment loop iteration counter.
753	- Block the process, waiting for any events.	868	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	869	- Queue all outstanding I/O (fd) events.
755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	870	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
756	- Queue all expired timers.	871	- Queue all expired timers.
757	- Queue all expired periodics.	872	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	873	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	874	- Queue all check watchers.
760	- Call all queued watchers in reverse order (i.e. check watchers first).	875	- Call all queued watchers in reverse order (i.e. check watchers first).
761	Signals and child watchers are implemented as I/O watchers, and will	876	Signals and child watchers are implemented as I/O watchers, and will
762	be handled here by queueing them when their watcher gets executed.	877	be handled here by queueing them when their watcher gets executed.
763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	878	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
764	were used, or there are no active watchers, return, otherwise	879	were used, or there are no active watchers, goto FINISH, otherwise
765	continue with step *.	880	continue with step LOOP.
		881	FINISH:
		882	- Reset the ev_break status iff it was EVBREAK_ONE.
		883	- Decrement the loop depth.
		884	- Return.
766		885
767	Example: Queue some jobs and then loop until no events are outstanding	886	Example: Queue some jobs and then loop until no events are outstanding
768	anymore.	887	anymore.
769		888
770	... queue jobs here, make sure they register event watchers as long	889	... queue jobs here, make sure they register event watchers as long
771	... as they still have work to do (even an idle watcher will do..)	890	... as they still have work to do (even an idle watcher will do..)
772	ev_loop (my_loop, 0);	891	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	892	... jobs done or somebody called break. yeah!
774		893
775	=item ev_unloop (loop, how)	894	=item ev_break (loop, how)
776		895
777	Can be used to make a call to C<ev_loop> return early (but only after it	896	Can be used to make a call to C<ev_run> return early (but only after it
778	has processed all outstanding events). The C<how> argument must be either	897	has processed all outstanding events). The C<how> argument must be either
779	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	898	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	899	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
781		900
782	This "unloop state" will be cleared when entering C<ev_loop> again.	901	This "break state" will be cleared on the next call to C<ev_run>.
783		902
784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	903	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		904	which case it will have no effect.
785		905
786	=item ev_ref (loop)	906	=item ev_ref (loop)
787		907
788	=item ev_unref (loop)	908	=item ev_unref (loop)
789		909
790	Ref/unref can be used to add or remove a reference count on the event	910	Ref/unref can be used to add or remove a reference count on the event
791	loop: Every watcher keeps one reference, and as long as the reference	911	loop: Every watcher keeps one reference, and as long as the reference
792	count is nonzero, C<ev_loop> will not return on its own.	912	count is nonzero, C<ev_run> will not return on its own.
793		913
794	If you have a watcher you never unregister that should not keep C<ev_loop>	914	This is useful when you have a watcher that you never intend to
795	from returning, call ev_unref() after starting, and ev_ref() before	915	unregister, but that nevertheless should not keep C<ev_run> from
		916	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796	stopping it.	917	before stopping it.
797		918
798	As an example, libev itself uses this for its internal signal pipe: It	919	As an example, libev itself uses this for its internal signal pipe: It
799	is not visible to the libev user and should not keep C<ev_loop> from	920	is not visible to the libev user and should not keep C<ev_run> from
800	exiting if no event watchers registered by it are active. It is also an	921	exiting if no event watchers registered by it are active. It is also an
801	excellent way to do this for generic recurring timers or from within	922	excellent way to do this for generic recurring timers or from within
802	third-party libraries. Just remember to I<unref after start> and I<ref	923	third-party libraries. Just remember to I<unref after start> and I<ref
803	before stop> (but only if the watcher wasn't active before, or was active	924	before stop> (but only if the watcher wasn't active before, or was active
804	before, respectively. Note also that libev might stop watchers itself	925	before, respectively. Note also that libev might stop watchers itself
805	(e.g. non-repeating timers) in which case you have to C<ev_ref>	926	(e.g. non-repeating timers) in which case you have to C<ev_ref>
806	in the callback).	927	in the callback).
807		928
808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	929	Example: Create a signal watcher, but keep it from keeping C<ev_run>
809	running when nothing else is active.	930	running when nothing else is active.
810		931
811	ev_signal exitsig;	932	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	933	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	934	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	935	ev_unref (loop);
815		936
816	Example: For some weird reason, unregister the above signal handler again.	937	Example: For some weird reason, unregister the above signal handler again.
817		938
818	ev_ref (loop);	939	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	940	ev_signal_stop (loop, &exitsig);
…		…
839	overhead for the actual polling but can deliver many events at once.	960	overhead for the actual polling but can deliver many events at once.
840		961
841	By setting a higher I<io collect interval> you allow libev to spend more	962	By setting a higher I<io collect interval> you allow libev to spend more
842	time collecting I/O events, so you can handle more events per iteration,	963	time collecting I/O events, so you can handle more events per iteration,
843	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	964	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
844	C<ev_timer>) will be not affected. Setting this to a non-null value will	965	C<ev_timer>) will not be affected. Setting this to a non-null value will
845	introduce an additional C<ev_sleep ()> call into most loop iterations. The	966	introduce an additional C<ev_sleep ()> call into most loop iterations. The
846	sleep time ensures that libev will not poll for I/O events more often then	967	sleep time ensures that libev will not poll for I/O events more often then
847	once per this interval, on average.	968	once per this interval, on average (as long as the host time resolution is
		969	good enough).
848		970
849	Likewise, by setting a higher I<timeout collect interval> you allow libev	971	Likewise, by setting a higher I<timeout collect interval> you allow libev
850	to spend more time collecting timeouts, at the expense of increased	972	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	973	latency/jitter/inexactness (the watcher callback will be called
852	later). C<ev_io> watchers will not be affected. Setting this to a non-null	974	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
858	usually doesn't make much sense to set it to a lower value than C<0.01>,	980	usually doesn't make much sense to set it to a lower value than C<0.01>,
859	as this approaches the timing granularity of most systems. Note that if	981	as this approaches the timing granularity of most systems. Note that if
860	you do transactions with the outside world and you can't increase the	982	you do transactions with the outside world and you can't increase the
861	parallelity, then this setting will limit your transaction rate (if you	983	parallelity, then this setting will limit your transaction rate (if you
862	need to poll once per transaction and the I/O collect interval is 0.01,	984	need to poll once per transaction and the I/O collect interval is 0.01,
863	then you can't do more than 100 transations per second).	985	then you can't do more than 100 transactions per second).
864		986
865	Setting the I<timeout collect interval> can improve the opportunity for	987	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	988	saving power, as the program will "bundle" timer callback invocations that
867	are "near" in time together, by delaying some, thus reducing the number of	989	are "near" in time together, by delaying some, thus reducing the number of
868	times the process sleeps and wakes up again. Another useful technique to	990	times the process sleeps and wakes up again. Another useful technique to
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	998	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		999
878	=item ev_invoke_pending (loop)	1000	=item ev_invoke_pending (loop)
879		1001
880	This call will simply invoke all pending watchers while resetting their	1002	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	1003	pending state. Normally, C<ev_run> does this automatically when required,
882	but when overriding the invoke callback this call comes handy.	1004	but when overriding the invoke callback this call comes handy. This
		1005	function can be invoked from a watcher - this can be useful for example
		1006	when you want to do some lengthy calculation and want to pass further
		1007	event handling to another thread (you still have to make sure only one
		1008	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
883		1009
884	=item int ev_pending_count (loop)	1010	=item int ev_pending_count (loop)
885		1011
886	Returns the number of pending watchers - zero indicates that no watchers	1012	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1013	are pending.
888		1014
889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1015	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
890		1016
891	This overrides the invoke pending functionality of the loop: Instead of	1017	This overrides the invoke pending functionality of the loop: Instead of
892	invoking all pending watchers when there are any, C<ev_loop> will call	1018	invoking all pending watchers when there are any, C<ev_run> will call
893	this callback instead. This is useful, for example, when you want to	1019	this callback instead. This is useful, for example, when you want to
894	invoke the actual watchers inside another context (another thread etc.).	1020	invoke the actual watchers inside another context (another thread etc.).
895		1021
896	If you want to reset the callback, use C<ev_invoke_pending> as new	1022	If you want to reset the callback, use C<ev_invoke_pending> as new
897	callback.	1023	callback.
898		1024
899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1025	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
900		1026
901	Sometimes you want to share the same loop between multiple threads. This	1027	Sometimes you want to share the same loop between multiple threads. This
902	can be done relatively simply by putting mutex_lock/unlock calls around	1028	can be done relatively simply by putting mutex_lock/unlock calls around
903	each call to a libev function.	1029	each call to a libev function.
904		1030
905	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1031	However, C<ev_run> can run an indefinite time, so it is not feasible
906	wait for it to return. One way around this is to wake up the loop via	1032	to wait for it to return. One way around this is to wake up the event
907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1033	loop via C<ev_break> and C<ev_async_send>, another way is to set these
908	and I<acquire> callbacks on the loop.	1034	I<release> and I<acquire> callbacks on the loop.
909		1035
910	When set, then C<release> will be called just before the thread is	1036	When set, then C<release> will be called just before the thread is
911	suspended waiting for new events, and C<acquire> is called just	1037	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1038	afterwards.
913		1039
…		…
916		1042
917	While event loop modifications are allowed between invocations of	1043	While event loop modifications are allowed between invocations of
918	C<release> and C<acquire> (that's their only purpose after all), no	1044	C<release> and C<acquire> (that's their only purpose after all), no
919	modifications done will affect the event loop, i.e. adding watchers will	1045	modifications done will affect the event loop, i.e. adding watchers will
920	have no effect on the set of file descriptors being watched, or the time	1046	have no effect on the set of file descriptors being watched, or the time
921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1047	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
922	to take note of any changes you made.	1048	to take note of any changes you made.
923		1049
924	In theory, threads executing C<ev_loop> will be async-cancel safe between	1050	In theory, threads executing C<ev_run> will be async-cancel safe between
925	invocations of C<release> and C<acquire>.	1051	invocations of C<release> and C<acquire>.
926		1052
927	See also the locking example in the C<THREADS> section later in this	1053	See also the locking example in the C<THREADS> section later in this
928	document.	1054	document.
929		1055
930	=item ev_set_userdata (loop, void *data)	1056	=item ev_set_userdata (loop, void *data)
931		1057
932	=item ev_userdata (loop)	1058	=item void *ev_userdata (loop)
933		1059
934	Set and retrieve a single C<void *> associated with a loop. When	1060	Set and retrieve a single C<void *> associated with a loop. When
935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1061	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
936	C<0.>	1062	C<0>.
937		1063
938	These two functions can be used to associate arbitrary data with a loop,	1064	These two functions can be used to associate arbitrary data with a loop,
939	and are intended solely for the C<invoke_pending_cb>, C<release> and	1065	and are intended solely for the C<invoke_pending_cb>, C<release> and
940	C<acquire> callbacks described above, but of course can be (ab-)used for	1066	C<acquire> callbacks described above, but of course can be (ab-)used for
941	any other purpose as well.	1067	any other purpose as well.
942		1068
943	=item ev_loop_verify (loop)	1069	=item ev_verify (loop)
944		1070
945	This function only does something when C<EV_VERIFY> support has been	1071	This function only does something when C<EV_VERIFY> support has been
946	compiled in, which is the default for non-minimal builds. It tries to go	1072	compiled in, which is the default for non-minimal builds. It tries to go
947	through all internal structures and checks them for validity. If anything	1073	through all internal structures and checks them for validity. If anything
948	is found to be inconsistent, it will print an error message to standard	1074	is found to be inconsistent, it will print an error message to standard
…		…
959		1085
960	In the following description, uppercase C<TYPE> in names stands for the	1086	In the following description, uppercase C<TYPE> in names stands for the
961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1087	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
962	watchers and C<ev_io_start> for I/O watchers.	1088	watchers and C<ev_io_start> for I/O watchers.
963		1089
964	A watcher is a structure that you create and register to record your	1090	A watcher is an opaque structure that you allocate and register to record
965	interest in some event. For instance, if you want to wait for STDIN to	1091	your interest in some event. To make a concrete example, imagine you want
966	become readable, you would create an C<ev_io> watcher for that:	1092	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1093	for that:
967		1094
968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1095	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
969	{	1096	{
970	ev_io_stop (w);	1097	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1098	ev_break (loop, EVBREAK_ALL);
972	}	1099	}
973		1100
974	struct ev_loop *loop = ev_default_loop (0);	1101	struct ev_loop *loop = ev_default_loop (0);
975		1102
976	ev_io stdin_watcher;	1103	ev_io stdin_watcher;
977		1104
978	ev_init (&stdin_watcher, my_cb);	1105	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1106	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1107	ev_io_start (loop, &stdin_watcher);
981		1108
982	ev_loop (loop, 0);	1109	ev_run (loop, 0);
983		1110
984	As you can see, you are responsible for allocating the memory for your	1111	As you can see, you are responsible for allocating the memory for your
985	watcher structures (and it is I<usually> a bad idea to do this on the	1112	watcher structures (and it is I<usually> a bad idea to do this on the
986	stack).	1113	stack).
987		1114
988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1115	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1116	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
990		1117
991	Each watcher structure must be initialised by a call to C<ev_init	1118	Each watcher structure must be initialised by a call to C<ev_init (watcher
992	(watcher *, callback)>, which expects a callback to be provided. This	1119	*, callback)>, which expects a callback to be provided. This callback is
993	callback gets invoked each time the event occurs (or, in the case of I/O	1120	invoked each time the event occurs (or, in the case of I/O watchers, each
994	watchers, each time the event loop detects that the file descriptor given	1121	time the event loop detects that the file descriptor given is readable
995	is readable and/or writable).	1122	and/or writable).
996		1123
997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1124	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
998	macro to configure it, with arguments specific to the watcher type. There	1125	macro to configure it, with arguments specific to the watcher type. There
999	is also a macro to combine initialisation and setting in one call: C<<	1126	is also a macro to combine initialisation and setting in one call: C<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1127	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1023	=item C<EV_WRITE>	1150	=item C<EV_WRITE>
1024		1151
1025	The file descriptor in the C<ev_io> watcher has become readable and/or	1152	The file descriptor in the C<ev_io> watcher has become readable and/or
1026	writable.	1153	writable.
1027		1154
1028	=item C<EV_TIMEOUT>	1155	=item C<EV_TIMER>
1029		1156
1030	The C<ev_timer> watcher has timed out.	1157	The C<ev_timer> watcher has timed out.
1031		1158
1032	=item C<EV_PERIODIC>	1159	=item C<EV_PERIODIC>
1033		1160
…		…
1051		1178
1052	=item C<EV_PREPARE>	1179	=item C<EV_PREPARE>
1053		1180
1054	=item C<EV_CHECK>	1181	=item C<EV_CHECK>
1055		1182
1056	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1183	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1057	to gather new events, and all C<ev_check> watchers are invoked just after	1184	gather new events, and all C<ev_check> watchers are queued (not invoked)
1058	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1185	just after C<ev_run> has gathered them, but before it queues any callbacks
		1186	for any received events. That means C<ev_prepare> watchers are the last
		1187	watchers invoked before the event loop sleeps or polls for new events, and
		1188	C<ev_check> watchers will be invoked before any other watchers of the same
		1189	or lower priority within an event loop iteration.
		1190
1059	received events. Callbacks of both watcher types can start and stop as	1191	Callbacks of both watcher types can start and stop as many watchers as
1060	many watchers as they want, and all of them will be taken into account	1192	they want, and all of them will be taken into account (for example, a
1061	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1193	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1062	C<ev_loop> from blocking).	1194	blocking).
1063		1195
1064	=item C<EV_EMBED>	1196	=item C<EV_EMBED>
1065		1197
1066	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1198	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1067		1199
1068	=item C<EV_FORK>	1200	=item C<EV_FORK>
1069		1201
1070	The event loop has been resumed in the child process after fork (see	1202	The event loop has been resumed in the child process after fork (see
1071	C<ev_fork>).	1203	C<ev_fork>).
		1204
		1205	=item C<EV_CLEANUP>
		1206
		1207	The event loop is about to be destroyed (see C<ev_cleanup>).
1072		1208
1073	=item C<EV_ASYNC>	1209	=item C<EV_ASYNC>
1074		1210
1075	The given async watcher has been asynchronously notified (see C<ev_async>).	1211	The given async watcher has been asynchronously notified (see C<ev_async>).
1076		1212
…		…
1123		1259
1124	ev_io w;	1260	ev_io w;
1125	ev_init (&w, my_cb);	1261	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1262	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1263
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1264	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1265
1130	This macro initialises the type-specific parts of a watcher. You need to	1266	This macro initialises the type-specific parts of a watcher. You need to
1131	call C<ev_init> at least once before you call this macro, but you can	1267	call C<ev_init> at least once before you call this macro, but you can
1132	call C<ev_TYPE_set> any number of times. You must not, however, call this	1268	call C<ev_TYPE_set> any number of times. You must not, however, call this
1133	macro on a watcher that is active (it can be pending, however, which is a	1269	macro on a watcher that is active (it can be pending, however, which is a
…		…
1146		1282
1147	Example: Initialise and set an C<ev_io> watcher in one step.	1283	Example: Initialise and set an C<ev_io> watcher in one step.
1148		1284
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1286
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1287	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1288
1153	Starts (activates) the given watcher. Only active watchers will receive	1289	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1290	events. If the watcher is already active nothing will happen.
1155		1291
1156	Example: Start the C<ev_io> watcher that is being abused as example in this	1292	Example: Start the C<ev_io> watcher that is being abused as example in this
1157	whole section.	1293	whole section.
1158		1294
1159	ev_io_start (EV_DEFAULT_UC, &w);	1295	ev_io_start (EV_DEFAULT_UC, &w);
1160		1296
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1297	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1298
1163	Stops the given watcher if active, and clears the pending status (whether	1299	Stops the given watcher if active, and clears the pending status (whether
1164	the watcher was active or not).	1300	the watcher was active or not).
1165		1301
1166	It is possible that stopped watchers are pending - for example,	1302	It is possible that stopped watchers are pending - for example,
…		…
1186		1322
1187	=item callback ev_cb (ev_TYPE *watcher)	1323	=item callback ev_cb (ev_TYPE *watcher)
1188		1324
1189	Returns the callback currently set on the watcher.	1325	Returns the callback currently set on the watcher.
1190		1326
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1327	=item ev_set_cb (ev_TYPE *watcher, callback)
1192		1328
1193	Change the callback. You can change the callback at virtually any time	1329	Change the callback. You can change the callback at virtually any time
1194	(modulo threads).	1330	(modulo threads).
1195		1331
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1332	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1333
1198	=item int ev_priority (ev_TYPE *watcher)	1334	=item int ev_priority (ev_TYPE *watcher)
1199		1335
1200	Set and query the priority of the watcher. The priority is a small	1336	Set and query the priority of the watcher. The priority is a small
1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1337	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1214	or might not have been clamped to the valid range.	1350	or might not have been clamped to the valid range.
1215		1351
1216	The default priority used by watchers when no priority has been set is	1352	The default priority used by watchers when no priority has been set is
1217	always C<0>, which is supposed to not be too high and not be too low :).	1353	always C<0>, which is supposed to not be too high and not be too low :).
1218		1354
1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1355	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1220	priorities.	1356	priorities.
1221		1357
1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1358	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1223		1359
1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1360	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1233	watcher isn't pending it does nothing and returns C<0>.	1369	watcher isn't pending it does nothing and returns C<0>.
1234		1370
1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1371	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1236	callback to be invoked, which can be accomplished with this function.	1372	callback to be invoked, which can be accomplished with this function.
1237		1373
		1374	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1375
		1376	Feeds the given event set into the event loop, as if the specified event
		1377	had happened for the specified watcher (which must be a pointer to an
		1378	initialised but not necessarily started event watcher). Obviously you must
		1379	not free the watcher as long as it has pending events.
		1380
		1381	Stopping the watcher, letting libev invoke it, or calling
		1382	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1383	not started in the first place.
		1384
		1385	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1386	functions that do not need a watcher.
		1387
1238	=back	1388	=back
1239		1389
		1390	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1391	OWN COMPOSITE WATCHERS> idioms.
1240		1392
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1393	=head2 WATCHER STATES
1242		1394
1243	Each watcher has, by default, a member C<void *data> that you can change	1395	There are various watcher states mentioned throughout this manual -
1244	and read at any time: libev will completely ignore it. This can be used	1396	active, pending and so on. In this section these states and the rules to
1245	to associate arbitrary data with your watcher. If you need more data and	1397	transition between them will be described in more detail - and while these
1246	don't want to allocate memory and store a pointer to it in that data	1398	rules might look complicated, they usually do "the right thing".
1247	member, you can also "subclass" the watcher type and provide your own
1248	data:
1249		1399
1250	struct my_io	1400	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1401
1258	...	1402	=item initialised
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1403
1262	And since your callback will be called with a pointer to the watcher, you	1404	Before a watcher can be registered with the event loop it has to be
1263	can cast it back to your own type:	1405	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1406	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1264		1407
1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1408	In this state it is simply some block of memory that is suitable for
1266	{	1409	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1410	will - as long as you either keep the memory contents intact, or call
1268	...	1411	C<ev_TYPE_init> again.
1269	}
1270		1412
1271	More interesting and less C-conformant ways of casting your callback type	1413	=item started/running/active
1272	instead have been omitted.
1273		1414
1274	Another common scenario is to use some data structure with multiple	1415	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1275	embedded watchers:	1416	property of the event loop, and is actively waiting for events. While in
		1417	this state it cannot be accessed (except in a few documented ways), moved,
		1418	freed or anything else - the only legal thing is to keep a pointer to it,
		1419	and call libev functions on it that are documented to work on active watchers.
1276		1420
1277	struct my_biggy	1421	=item pending
1278	{
1279	int some_data;
1280	ev_timer t1;
1281	ev_timer t2;
1282	}
1283		1422
1284	In this case getting the pointer to C<my_biggy> is a bit more	1423	If a watcher is active and libev determines that an event it is interested
1285	complicated: Either you store the address of your C<my_biggy> struct	1424	in has occurred (such as a timer expiring), it will become pending. It will
1286	in the C<data> member of the watcher (for woozies), or you need to use	1425	stay in this pending state until either it is stopped or its callback is
1287	some pointer arithmetic using C<offsetof> inside your watchers (for real	1426	about to be invoked, so it is not normally pending inside the watcher
1288	programmers):	1427	callback.
1289		1428
1290	#include <stddef.h>	1429	The watcher might or might not be active while it is pending (for example,
		1430	an expired non-repeating timer can be pending but no longer active). If it
		1431	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1432	but it is still property of the event loop at this time, so cannot be
		1433	moved, freed or reused. And if it is active the rules described in the
		1434	previous item still apply.
1291		1435
1292	static void	1436	It is also possible to feed an event on a watcher that is not active (e.g.
1293	t1_cb (EV_P_ ev_timer *w, int revents)	1437	via C<ev_feed_event>), in which case it becomes pending without being
1294	{	1438	active.
1295	struct my_biggy big = (struct my_biggy *)
1296	(((char *)w) - offsetof (struct my_biggy, t1));
1297	}
1298		1439
1299	static void	1440	=item stopped
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1441
1301	{	1442	A watcher can be stopped implicitly by libev (in which case it might still
1302	struct my_biggy big = (struct my_biggy *)	1443	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1444	latter will clear any pending state the watcher might be in, regardless
1304	}	1445	of whether it was active or not, so stopping a watcher explicitly before
		1446	freeing it is often a good idea.
		1447
		1448	While stopped (and not pending) the watcher is essentially in the
		1449	initialised state, that is, it can be reused, moved, modified in any way
		1450	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1451	it again).
		1452
		1453	=back
1305		1454
1306	=head2 WATCHER PRIORITY MODELS	1455	=head2 WATCHER PRIORITY MODELS
1307		1456
1308	Many event loops support I<watcher priorities>, which are usually small	1457	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1458	integers that influence the ordering of event callback invocation
…		…
1352		1501
1353	For example, to emulate how many other event libraries handle priorities,	1502	For example, to emulate how many other event libraries handle priorities,
1354	you can associate an C<ev_idle> watcher to each such watcher, and in	1503	you can associate an C<ev_idle> watcher to each such watcher, and in
1355	the normal watcher callback, you just start the idle watcher. The real	1504	the normal watcher callback, you just start the idle watcher. The real
1356	processing is done in the idle watcher callback. This causes libev to	1505	processing is done in the idle watcher callback. This causes libev to
1357	continously poll and process kernel event data for the watcher, but when	1506	continuously poll and process kernel event data for the watcher, but when
1358	the lock-out case is known to be rare (which in turn is rare :), this is	1507	the lock-out case is known to be rare (which in turn is rare :), this is
1359	workable.	1508	workable.
1360		1509
1361	Usually, however, the lock-out model implemented that way will perform	1510	Usually, however, the lock-out model implemented that way will perform
1362	miserably under the type of load it was designed to handle. In that case,	1511	miserably under the type of load it was designed to handle. In that case,
…		…
1376	{	1525	{
1377	// stop the I/O watcher, we received the event, but	1526	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1527	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1528	ev_io_stop (EV_A_ w);
1380		1529
1381	// start the idle watcher to ahndle the actual event.	1530	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1531	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1532	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1533	ev_idle_start (EV_A_ &idle);
1385	}	1534	}
1386		1535
…		…
1436	In general you can register as many read and/or write event watchers per	1585	In general you can register as many read and/or write event watchers per
1437	fd as you want (as long as you don't confuse yourself). Setting all file	1586	fd as you want (as long as you don't confuse yourself). Setting all file
1438	descriptors to non-blocking mode is also usually a good idea (but not	1587	descriptors to non-blocking mode is also usually a good idea (but not
1439	required if you know what you are doing).	1588	required if you know what you are doing).
1440		1589
1441	If you cannot use non-blocking mode, then force the use of a
1442	known-to-be-good backend (at the time of this writing, this includes only
1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1444	descriptors for which non-blocking operation makes no sense (such as
1445	files) - libev doesn't guarentee any specific behaviour in that case.
1446
1447	Another thing you have to watch out for is that it is quite easy to	1590	Another thing you have to watch out for is that it is quite easy to
1448	receive "spurious" readiness notifications, that is your callback might	1591	receive "spurious" readiness notifications, that is, your callback might
1449	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1592	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1450	because there is no data. Not only are some backends known to create a	1593	because there is no data. It is very easy to get into this situation even
1451	lot of those (for example Solaris ports), it is very easy to get into	1594	with a relatively standard program structure. Thus it is best to always
1452	this situation even with a relatively standard program structure. Thus	1595	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1596	preferable to a program hanging until some data arrives.
1455		1597
1456	If you cannot run the fd in non-blocking mode (for example you should	1598	If you cannot run the fd in non-blocking mode (for example you should
1457	not play around with an Xlib connection), then you have to separately	1599	not play around with an Xlib connection), then you have to separately
1458	re-test whether a file descriptor is really ready with a known-to-be good	1600	re-test whether a file descriptor is really ready with a known-to-be good
1459	interface such as poll (fortunately in our Xlib example, Xlib already	1601	interface such as poll (fortunately in the case of Xlib, it already does
1460	does this on its own, so its quite safe to use). Some people additionally	1602	this on its own, so its quite safe to use). Some people additionally
1461	use C<SIGALRM> and an interval timer, just to be sure you won't block	1603	use C<SIGALRM> and an interval timer, just to be sure you won't block
1462	indefinitely.	1604	indefinitely.
1463		1605
1464	But really, best use non-blocking mode.	1606	But really, best use non-blocking mode.
1465		1607
…		…
1493		1635
1494	There is no workaround possible except not registering events	1636	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1637	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1638	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		1639
		1640	=head3 The special problem of files
		1641
		1642	Many people try to use C<select> (or libev) on file descriptors
		1643	representing files, and expect it to become ready when their program
		1644	doesn't block on disk accesses (which can take a long time on their own).
		1645
		1646	However, this cannot ever work in the "expected" way - you get a readiness
		1647	notification as soon as the kernel knows whether and how much data is
		1648	there, and in the case of open files, that's always the case, so you
		1649	always get a readiness notification instantly, and your read (or possibly
		1650	write) will still block on the disk I/O.
		1651
		1652	Another way to view it is that in the case of sockets, pipes, character
		1653	devices and so on, there is another party (the sender) that delivers data
		1654	on its own, but in the case of files, there is no such thing: the disk
		1655	will not send data on its own, simply because it doesn't know what you
		1656	wish to read - you would first have to request some data.
		1657
		1658	Since files are typically not-so-well supported by advanced notification
		1659	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1660	to files, even though you should not use it. The reason for this is
		1661	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1662	usually a tty, often a pipe, but also sometimes files or special devices
		1663	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1664	F</dev/urandom>), and even though the file might better be served with
		1665	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1666	it "just works" instead of freezing.
		1667
		1668	So avoid file descriptors pointing to files when you know it (e.g. use
		1669	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1670	when you rarely read from a file instead of from a socket, and want to
		1671	reuse the same code path.
		1672
1498	=head3 The special problem of fork	1673	=head3 The special problem of fork
1499		1674
1500	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1675	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1501	useless behaviour. Libev fully supports fork, but needs to be told about	1676	useless behaviour. Libev fully supports fork, but needs to be told about
1502	it in the child.	1677	it in the child if you want to continue to use it in the child.
1503		1678
1504	To support fork in your programs, you either have to call	1679	To support fork in your child processes, you have to call C<ev_loop_fork
1505	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1680	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1681	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1682
1509	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1510		1684
1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1512	when writing to a pipe whose other end has been closed, your program gets	1686	when writing to a pipe whose other end has been closed, your program gets
…		…
1515		1689
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1690	So when you encounter spurious, unexplained daemon exits, make sure you
1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1691	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1518	somewhere, as that would have given you a big clue).	1692	somewhere, as that would have given you a big clue).
1519		1693
		1694	=head3 The special problem of accept()ing when you can't
		1695
		1696	Many implementations of the POSIX C<accept> function (for example,
		1697	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1698	connection from the pending queue in all error cases.
		1699
		1700	For example, larger servers often run out of file descriptors (because
		1701	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1702	rejecting the connection, leading to libev signalling readiness on
		1703	the next iteration again (the connection still exists after all), and
		1704	typically causing the program to loop at 100% CPU usage.
		1705
		1706	Unfortunately, the set of errors that cause this issue differs between
		1707	operating systems, there is usually little the app can do to remedy the
		1708	situation, and no known thread-safe method of removing the connection to
		1709	cope with overload is known (to me).
		1710
		1711	One of the easiest ways to handle this situation is to just ignore it
		1712	- when the program encounters an overload, it will just loop until the
		1713	situation is over. While this is a form of busy waiting, no OS offers an
		1714	event-based way to handle this situation, so it's the best one can do.
		1715
		1716	A better way to handle the situation is to log any errors other than
		1717	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1718	messages, and continue as usual, which at least gives the user an idea of
		1719	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1720	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1721	usage.
		1722
		1723	If your program is single-threaded, then you could also keep a dummy file
		1724	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1725	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1726	close that fd, and create a new dummy fd. This will gracefully refuse
		1727	clients under typical overload conditions.
		1728
		1729	The last way to handle it is to simply log the error and C<exit>, as
		1730	is often done with C<malloc> failures, but this results in an easy
		1731	opportunity for a DoS attack.
1520		1732
1521	=head3 Watcher-Specific Functions	1733	=head3 Watcher-Specific Functions
1522		1734
1523	=over 4	1735	=over 4
1524		1736
…		…
1556	...	1768	...
1557	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1770	ev_io stdin_readable;
1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1560	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1562		1774
1563		1775
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1777
1566	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1574		1786
1575	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
1576	passed (not I<at>, so on systems with very low-resolution clocks this	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1577	might introduce a small delay). If multiple timers become ready during the	1789	might introduce a small delay, see "the special problem of being too
		1790	early", below). If multiple timers become ready during the same loop
1578	same loop iteration then the ones with earlier time-out values are invoked	1791	iteration then the ones with earlier time-out values are invoked before
1579	before ones of the same priority with later time-out values (but this is	1792	ones of the same priority with later time-out values (but this is no
1580	no longer true when a callback calls C<ev_loop> recursively).	1793	longer true when a callback calls C<ev_run> recursively).
1581		1794
1582	=head3 Be smart about timeouts	1795	=head3 Be smart about timeouts
1583		1796
1584	Many real-world problems involve some kind of timeout, usually for error	1797	Many real-world problems involve some kind of timeout, usually for error
1585	recovery. A typical example is an HTTP request - if the other side hangs,	1798	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1660		1873
1661	In this case, it would be more efficient to leave the C<ev_timer> alone,	1874	In this case, it would be more efficient to leave the C<ev_timer> alone,
1662	but remember the time of last activity, and check for a real timeout only	1875	but remember the time of last activity, and check for a real timeout only
1663	within the callback:	1876	within the callback:
1664		1877
		1878	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	1879	ev_tstamp last_activity; // time of last activity
		1880	ev_timer timer;
1666		1881
1667	static void	1882	static void
1668	callback (EV_P_ ev_timer *w, int revents)	1883	callback (EV_P_ ev_timer *w, int revents)
1669	{	1884	{
1670	ev_tstamp now = ev_now (EV_A);	1885	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	1886	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		1887
1673	// if last_activity + 60. is older than now, we did time out	1888	// if negative, it means we the timeout already occurred
1674	if (timeout < now)	1889	if (after < 0.)
1675	{	1890	{
1676	// timeout occured, take action	1891	// timeout occurred, take action
1677	}	1892	}
1678	else	1893	else
1679	{	1894	{
1680	// callback was invoked, but there was some activity, re-arm	1895	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	1896	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	1897	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	1898	// the timeout can occur.
		1899	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	1900	ev_timer_start (EV_A_ w);
1685	}	1901	}
1686	}	1902	}
1687		1903
1688	To summarise the callback: first calculate the real timeout (defined	1904	To summarise the callback: first calculate in how many seconds the
1689	as "60 seconds after the last activity"), then check if that time has	1905	timeout will occur (by calculating the absolute time when it would occur,
1690	been reached, which means something I<did>, in fact, time out. Otherwise	1906	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1691	the callback was invoked too early (C<timeout> is in the future), so	1907	(EV_A)> from that).
1692	re-schedule the timer to fire at that future time, to see if maybe we have
1693	a timeout then.
1694		1908
1695	Note how C<ev_timer_again> is used, taking advantage of the	1909	If this value is negative, then we are already past the timeout, i.e. we
1696	C<ev_timer_again> optimisation when the timer is already running.	1910	timed out, and need to do whatever is needed in this case.
		1911
		1912	Otherwise, we now the earliest time at which the timeout would trigger,
		1913	and simply start the timer with this timeout value.
		1914
		1915	In other words, each time the callback is invoked it will check whether
		1916	the timeout occurred. If not, it will simply reschedule itself to check
		1917	again at the earliest time it could time out. Rinse. Repeat.
1697		1918
1698	This scheme causes more callback invocations (about one every 60 seconds	1919	This scheme causes more callback invocations (about one every 60 seconds
1699	minus half the average time between activity), but virtually no calls to	1920	minus half the average time between activity), but virtually no calls to
1700	libev to change the timeout.	1921	libev to change the timeout.
1701		1922
1702	To start the timer, simply initialise the watcher and set C<last_activity>	1923	To start the machinery, simply initialise the watcher and set
1703	to the current time (meaning we just have some activity :), then call the	1924	C<last_activity> to the current time (meaning there was some activity just
1704	callback, which will "do the right thing" and start the timer:	1925	now), then call the callback, which will "do the right thing" and start
		1926	the timer:
1705		1927
		1928	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	1929	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	1930	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		1931
1710	And when there is some activity, simply store the current time in	1932	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	1933	C<last_activity>, no libev calls at all:
1712		1934
		1935	if (activity detected)
1713	last_actiivty = ev_now (loop);	1936	last_activity = ev_now (EV_A);
		1937
		1938	When your timeout value changes, then the timeout can be changed by simply
		1939	providing a new value, stopping the timer and calling the callback, which
		1940	will again do the right thing (for example, time out immediately :).
		1941
		1942	timeout = new_value;
		1943	ev_timer_stop (EV_A_ &timer);
		1944	callback (EV_A_ &timer, 0);
1714		1945
1715	This technique is slightly more complex, but in most cases where the	1946	This technique is slightly more complex, but in most cases where the
1716	time-out is unlikely to be triggered, much more efficient.	1947	time-out is unlikely to be triggered, much more efficient.
1717
1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
1719	callback :) - just change the timeout and invoke the callback, which will
1720	fix things for you.
1721		1948
1722	=item 4. Wee, just use a double-linked list for your timeouts.	1949	=item 4. Wee, just use a double-linked list for your timeouts.
1723		1950
1724	If there is not one request, but many thousands (millions...), all	1951	If there is not one request, but many thousands (millions...), all
1725	employing some kind of timeout with the same timeout value, then one can	1952	employing some kind of timeout with the same timeout value, then one can
…		…
1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1979	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1753	rather complicated, but extremely efficient, something that really pays	1980	rather complicated, but extremely efficient, something that really pays
1754	off after the first million or so of active timers, i.e. it's usually	1981	off after the first million or so of active timers, i.e. it's usually
1755	overkill :)	1982	overkill :)
1756		1983
		1984	=head3 The special problem of being too early
		1985
		1986	If you ask a timer to call your callback after three seconds, then
		1987	you expect it to be invoked after three seconds - but of course, this
		1988	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1989	guaranteed to any precision by libev - imagine somebody suspending the
		1990	process with a STOP signal for a few hours for example.
		1991
		1992	So, libev tries to invoke your callback as soon as possible I<after> the
		1993	delay has occurred, but cannot guarantee this.
		1994
		1995	A less obvious failure mode is calling your callback too early: many event
		1996	loops compare timestamps with a "elapsed delay >= requested delay", but
		1997	this can cause your callback to be invoked much earlier than you would
		1998	expect.
		1999
		2000	To see why, imagine a system with a clock that only offers full second
		2001	resolution (think windows if you can't come up with a broken enough OS
		2002	yourself). If you schedule a one-second timer at the time 500.9, then the
		2003	event loop will schedule your timeout to elapse at a system time of 500
		2004	(500.9 truncated to the resolution) + 1, or 501.
		2005
		2006	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2007	501" and invoke the callback 0.1s after it was started, even though a
		2008	one-second delay was requested - this is being "too early", despite best
		2009	intentions.
		2010
		2011	This is the reason why libev will never invoke the callback if the elapsed
		2012	delay equals the requested delay, but only when the elapsed delay is
		2013	larger than the requested delay. In the example above, libev would only invoke
		2014	the callback at system time 502, or 1.1s after the timer was started.
		2015
		2016	So, while libev cannot guarantee that your callback will be invoked
		2017	exactly when requested, it I<can> and I<does> guarantee that the requested
		2018	delay has actually elapsed, or in other words, it always errs on the "too
		2019	late" side of things.
		2020
1757	=head3 The special problem of time updates	2021	=head3 The special problem of time updates
1758		2022
1759	Establishing the current time is a costly operation (it usually takes at	2023	Establishing the current time is a costly operation (it usually takes
1760	least two system calls): EV therefore updates its idea of the current	2024	at least one system call): EV therefore updates its idea of the current
1761	time only before and after C<ev_loop> collects new events, which causes a	2025	time only before and after C<ev_run> collects new events, which causes a
1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2026	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1763	lots of events in one iteration.	2027	lots of events in one iteration.
1764		2028
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2029	The relative timeouts are calculated relative to the C<ev_now ()>
1766	time. This is usually the right thing as this timestamp refers to the time	2030	time. This is usually the right thing as this timestamp refers to the time
…		…
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1772		2036
1773	If the event loop is suspended for a long time, you can also force an	2037	If the event loop is suspended for a long time, you can also force an
1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2038	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1775	()>.	2039	()>.
		2040
		2041	=head3 The special problem of unsynchronised clocks
		2042
		2043	Modern systems have a variety of clocks - libev itself uses the normal
		2044	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2045	jumps).
		2046
		2047	Neither of these clocks is synchronised with each other or any other clock
		2048	on the system, so C<ev_time ()> might return a considerably different time
		2049	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2050	a call to C<gettimeofday> might return a second count that is one higher
		2051	than a directly following call to C<time>.
		2052
		2053	The moral of this is to only compare libev-related timestamps with
		2054	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2055	a second or so.
		2056
		2057	One more problem arises due to this lack of synchronisation: if libev uses
		2058	the system monotonic clock and you compare timestamps from C<ev_time>
		2059	or C<ev_now> from when you started your timer and when your callback is
		2060	invoked, you will find that sometimes the callback is a bit "early".
		2061
		2062	This is because C<ev_timer>s work in real time, not wall clock time, so
		2063	libev makes sure your callback is not invoked before the delay happened,
		2064	I<measured according to the real time>, not the system clock.
		2065
		2066	If your timeouts are based on a physical timescale (e.g. "time out this
		2067	connection after 100 seconds") then this shouldn't bother you as it is
		2068	exactly the right behaviour.
		2069
		2070	If you want to compare wall clock/system timestamps to your timers, then
		2071	you need to use C<ev_periodic>s, as these are based on the wall clock
		2072	time, where your comparisons will always generate correct results.
1776		2073
1777	=head3 The special problems of suspended animation	2074	=head3 The special problems of suspended animation
1778		2075
1779	When you leave the server world it is quite customary to hit machines that	2076	When you leave the server world it is quite customary to hit machines that
1780	can suspend/hibernate - what happens to the clocks during such a suspend?	2077	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1824	keep up with the timer (because it takes longer than those 10 seconds to	2121	keep up with the timer (because it takes longer than those 10 seconds to
1825	do stuff) the timer will not fire more than once per event loop iteration.	2122	do stuff) the timer will not fire more than once per event loop iteration.
1826		2123
1827	=item ev_timer_again (loop, ev_timer *)	2124	=item ev_timer_again (loop, ev_timer *)
1828		2125
1829	This will act as if the timer timed out and restart it again if it is	2126	This will act as if the timer timed out, and restarts it again if it is
1830	repeating. The exact semantics are:	2127	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2128	timeout to the C<repeat> value and calling C<ev_timer_start>.
1831		2129
		2130	The exact semantics are as in the following rules, all of which will be
		2131	applied to the watcher:
		2132
		2133	=over 4
		2134
1832	If the timer is pending, its pending status is cleared.	2135	=item If the timer is pending, the pending status is always cleared.
1833		2136
1834	If the timer is started but non-repeating, stop it (as if it timed out).	2137	=item If the timer is started but non-repeating, stop it (as if it timed
		2138	out, without invoking it).
1835		2139
1836	If the timer is repeating, either start it if necessary (with the	2140	=item If the timer is repeating, make the C<repeat> value the new timeout
1837	C<repeat> value), or reset the running timer to the C<repeat> value.	2141	and start the timer, if necessary.
1838		2142
		2143	=back
		2144
1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2145	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1840	usage example.	2146	usage example.
1841		2147
1842	=item ev_timer_remaining (loop, ev_timer *)	2148	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2149
1844	Returns the remaining time until a timer fires. If the timer is active,	2150	Returns the remaining time until a timer fires. If the timer is active,
1845	then this time is relative to the current event loop time, otherwise it's	2151	then this time is relative to the current event loop time, otherwise it's
1846	the timeout value currently configured.	2152	the timeout value currently configured.
1847		2153
1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2154	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2155	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1850	will return C<4>. When the timer expires and is restarted, it will return	2156	will return C<4>. When the timer expires and is restarted, it will return
1851	roughly C<7> (likely slightly less as callback invocation takes some time,	2157	roughly C<7> (likely slightly less as callback invocation takes some time,
1852	too), and so on.	2158	too), and so on.
1853		2159
1854	=item ev_tstamp repeat [read-write]	2160	=item ev_tstamp repeat [read-write]
…		…
1883	}	2189	}
1884		2190
1885	ev_timer mytimer;	2191	ev_timer mytimer;
1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2192	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1887	ev_timer_again (&mytimer); /* start timer */	2193	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2194	ev_run (loop, 0);
1889		2195
1890	// and in some piece of code that gets executed on any "activity":	2196	// and in some piece of code that gets executed on any "activity":
1891	// reset the timeout to start ticking again at 10 seconds	2197	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2198	ev_timer_again (&mytimer);
1893		2199
…		…
1919		2225
1920	As with timers, the callback is guaranteed to be invoked only when the	2226	As with timers, the callback is guaranteed to be invoked only when the
1921	point in time where it is supposed to trigger has passed. If multiple	2227	point in time where it is supposed to trigger has passed. If multiple
1922	timers become ready during the same loop iteration then the ones with	2228	timers become ready during the same loop iteration then the ones with
1923	earlier time-out values are invoked before ones with later time-out values	2229	earlier time-out values are invoked before ones with later time-out values
1924	(but this is no longer true when a callback calls C<ev_loop> recursively).	2230	(but this is no longer true when a callback calls C<ev_run> recursively).
1925		2231
1926	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1927		2233
1928	=over 4	2234	=over 4
1929		2235
…		…
1964		2270
1965	Another way to think about it (for the mathematically inclined) is that	2271	Another way to think about it (for the mathematically inclined) is that
1966	C<ev_periodic> will try to run the callback in this mode at the next possible	2272	C<ev_periodic> will try to run the callback in this mode at the next possible
1967	time where C<time = offset (mod interval)>, regardless of any time jumps.	2273	time where C<time = offset (mod interval)>, regardless of any time jumps.
1968		2274
1969	For numerical stability it is preferable that the C<offset> value is near	2275	The C<interval> I<MUST> be positive, and for numerical stability, the
1970	C<ev_now ()> (the current time), but there is no range requirement for	2276	interval value should be higher than C<1/8192> (which is around 100
1971	this value, and in fact is often specified as zero.	2277	microseconds) and C<offset> should be higher than C<0> and should have
		2278	at most a similar magnitude as the current time (say, within a factor of
		2279	ten). Typical values for offset are, in fact, C<0> or something between
		2280	C<0> and C<interval>, which is also the recommended range.
1972		2281
1973	Note also that there is an upper limit to how often a timer can fire (CPU	2282	Note also that there is an upper limit to how often a timer can fire (CPU
1974	speed for example), so if C<interval> is very small then timing stability	2283	speed for example), so if C<interval> is very small then timing stability
1975	will of course deteriorate. Libev itself tries to be exact to be about one	2284	will of course deteriorate. Libev itself tries to be exact to be about one
1976	millisecond (if the OS supports it and the machine is fast enough).	2285	millisecond (if the OS supports it and the machine is fast enough).
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2366	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2367	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2368	potentially a lot of jitter, but good long-term stability.
2060		2369
2061	static void	2370	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2371	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2372	{
2064	... its now a full hour (UTC, or TAI or whatever your clock follows)	2373	... its now a full hour (UTC, or TAI or whatever your clock follows)
2065	}	2374	}
2066		2375
2067	ev_periodic hourly_tick;	2376	ev_periodic hourly_tick;
…		…
2090		2399
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2400	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2401
2093	Signal watchers will trigger an event when the process receives a specific	2402	Signal watchers will trigger an event when the process receives a specific
2094	signal one or more times. Even though signals are very asynchronous, libev	2403	signal one or more times. Even though signals are very asynchronous, libev
2095	will try it's best to deliver signals synchronously, i.e. as part of the	2404	will try its best to deliver signals synchronously, i.e. as part of the
2096	normal event processing, like any other event.	2405	normal event processing, like any other event.
2097		2406
2098	If you want signals to be delivered truly asynchronously, just use	2407	If you want signals to be delivered truly asynchronously, just use
2099	C<sigaction> as you would do without libev and forget about sharing	2408	C<sigaction> as you would do without libev and forget about sharing
2100	the signal. You can even use C<ev_async> from a signal handler to	2409	the signal. You can even use C<ev_async> from a signal handler to
…		…
2104	only within the same loop, i.e. you can watch for C<SIGINT> in your	2413	only within the same loop, i.e. you can watch for C<SIGINT> in your
2105	default loop and for C<SIGIO> in another loop, but you cannot watch for	2414	default loop and for C<SIGIO> in another loop, but you cannot watch for
2106	C<SIGINT> in both the default loop and another loop at the same time. At	2415	C<SIGINT> in both the default loop and another loop at the same time. At
2107	the moment, C<SIGCHLD> is permanently tied to the default loop.	2416	the moment, C<SIGCHLD> is permanently tied to the default loop.
2108		2417
2109	When the first watcher gets started will libev actually register something	2418	Only after the first watcher for a signal is started will libev actually
2110	with the kernel (thus it coexists with your own signal handlers as long as	2419	register something with the kernel. It thus coexists with your own signal
2111	you don't register any with libev for the same signal).	2420	handlers as long as you don't register any with libev for the same signal.
2112
2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
2115	sotpping it again), that is, libev might or might not block the signal,
2116	and might or might not set or restore the installed signal handler.
2117		2421
2118	If possible and supported, libev will install its handlers with	2422	If possible and supported, libev will install its handlers with
2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2423	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2120	not be unduly interrupted. If you have a problem with system calls getting	2424	not be unduly interrupted. If you have a problem with system calls getting
2121	interrupted by signals you can block all signals in an C<ev_check> watcher	2425	interrupted by signals you can block all signals in an C<ev_check> watcher
2122	and unblock them in an C<ev_prepare> watcher.	2426	and unblock them in an C<ev_prepare> watcher.
2123		2427
		2428	=head3 The special problem of inheritance over fork/execve/pthread_create
		2429
		2430	Both the signal mask (C<sigprocmask>) and the signal disposition
		2431	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2432	stopping it again), that is, libev might or might not block the signal,
		2433	and might or might not set or restore the installed signal handler (but
		2434	see C<EVFLAG_NOSIGMASK>).
		2435
		2436	While this does not matter for the signal disposition (libev never
		2437	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2438	C<execve>), this matters for the signal mask: many programs do not expect
		2439	certain signals to be blocked.
		2440
		2441	This means that before calling C<exec> (from the child) you should reset
		2442	the signal mask to whatever "default" you expect (all clear is a good
		2443	choice usually).
		2444
		2445	The simplest way to ensure that the signal mask is reset in the child is
		2446	to install a fork handler with C<pthread_atfork> that resets it. That will
		2447	catch fork calls done by libraries (such as the libc) as well.
		2448
		2449	In current versions of libev, the signal will not be blocked indefinitely
		2450	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2451	the window of opportunity for problems, it will not go away, as libev
		2452	I<has> to modify the signal mask, at least temporarily.
		2453
		2454	So I can't stress this enough: I<If you do not reset your signal mask when
		2455	you expect it to be empty, you have a race condition in your code>. This
		2456	is not a libev-specific thing, this is true for most event libraries.
		2457
		2458	=head3 The special problem of threads signal handling
		2459
		2460	POSIX threads has problematic signal handling semantics, specifically,
		2461	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2462	threads in a process block signals, which is hard to achieve.
		2463
		2464	When you want to use sigwait (or mix libev signal handling with your own
		2465	for the same signals), you can tackle this problem by globally blocking
		2466	all signals before creating any threads (or creating them with a fully set
		2467	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2468	loops. Then designate one thread as "signal receiver thread" which handles
		2469	these signals. You can pass on any signals that libev might be interested
		2470	in by calling C<ev_feed_signal>.
		2471
2124	=head3 Watcher-Specific Functions and Data Members	2472	=head3 Watcher-Specific Functions and Data Members
2125		2473
2126	=over 4	2474	=over 4
2127		2475
2128	=item ev_signal_init (ev_signal *, callback, int signum)	2476	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2143	Example: Try to exit cleanly on SIGINT.	2491	Example: Try to exit cleanly on SIGINT.
2144		2492
2145	static void	2493	static void
2146	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2494	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2147	{	2495	{
2148	ev_unloop (loop, EVUNLOOP_ALL);	2496	ev_break (loop, EVBREAK_ALL);
2149	}	2497	}
2150		2498
2151	ev_signal signal_watcher;	2499	ev_signal signal_watcher;
2152	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2500	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2153	ev_signal_start (loop, &signal_watcher);	2501	ev_signal_start (loop, &signal_watcher);
…		…
2262		2610
2263	=head2 C<ev_stat> - did the file attributes just change?	2611	=head2 C<ev_stat> - did the file attributes just change?
2264		2612
2265	This watches a file system path for attribute changes. That is, it calls	2613	This watches a file system path for attribute changes. That is, it calls
2266	C<stat> on that path in regular intervals (or when the OS says it changed)	2614	C<stat> on that path in regular intervals (or when the OS says it changed)
2267	and sees if it changed compared to the last time, invoking the callback if	2615	and sees if it changed compared to the last time, invoking the callback
2268	it did.	2616	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2617	happen after the watcher has been started will be reported.
2269		2618
2270	The path does not need to exist: changing from "path exists" to "path does	2619	The path does not need to exist: changing from "path exists" to "path does
2271	not exist" is a status change like any other. The condition "path does not	2620	not exist" is a status change like any other. The condition "path does not
2272	exist" (or more correctly "path cannot be stat'ed") is signified by the	2621	exist" (or more correctly "path cannot be stat'ed") is signified by the
2273	C<st_nlink> field being zero (which is otherwise always forced to be at	2622	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2503	Apart from keeping your process non-blocking (which is a useful	2852	Apart from keeping your process non-blocking (which is a useful
2504	effect on its own sometimes), idle watchers are a good place to do	2853	effect on its own sometimes), idle watchers are a good place to do
2505	"pseudo-background processing", or delay processing stuff to after the	2854	"pseudo-background processing", or delay processing stuff to after the
2506	event loop has handled all outstanding events.	2855	event loop has handled all outstanding events.
2507		2856
		2857	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2858
		2859	As long as there is at least one active idle watcher, libev will never
		2860	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2861	For this to work, the idle watcher doesn't need to be invoked at all - the
		2862	lowest priority will do.
		2863
		2864	This mode of operation can be useful together with an C<ev_check> watcher,
		2865	to do something on each event loop iteration - for example to balance load
		2866	between different connections.
		2867
		2868	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2869	example.
		2870
2508	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
2509		2872
2510	=over 4	2873	=over 4
2511		2874
2512	=item ev_idle_init (ev_idle *, callback)	2875	=item ev_idle_init (ev_idle *, callback)
…		…
2523	callback, free it. Also, use no error checking, as usual.	2886	callback, free it. Also, use no error checking, as usual.
2524		2887
2525	static void	2888	static void
2526	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2889	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2527	{	2890	{
		2891	// stop the watcher
		2892	ev_idle_stop (loop, w);
		2893
		2894	// now we can free it
2528	free (w);	2895	free (w);
		2896
2529	// now do something you wanted to do when the program has	2897	// now do something you wanted to do when the program has
2530	// no longer anything immediate to do.	2898	// no longer anything immediate to do.
2531	}	2899	}
2532		2900
2533	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2901	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2535	ev_idle_start (loop, idle_watcher);	2903	ev_idle_start (loop, idle_watcher);
2536		2904
2537		2905
2538	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2906	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2539		2907
2540	Prepare and check watchers are usually (but not always) used in pairs:	2908	Prepare and check watchers are often (but not always) used in pairs:
2541	prepare watchers get invoked before the process blocks and check watchers	2909	prepare watchers get invoked before the process blocks and check watchers
2542	afterwards.	2910	afterwards.
2543		2911
2544	You I<must not> call C<ev_loop> or similar functions that enter	2912	You I<must not> call C<ev_run> or similar functions that enter
2545	the current event loop from either C<ev_prepare> or C<ev_check>	2913	the current event loop from either C<ev_prepare> or C<ev_check>
2546	watchers. Other loops than the current one are fine, however. The	2914	watchers. Other loops than the current one are fine, however. The
2547	rationale behind this is that you do not need to check for recursion in	2915	rationale behind this is that you do not need to check for recursion in
2548	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2916	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2549	C<ev_check> so if you have one watcher of each kind they will always be	2917	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2573	with priority higher than or equal to the event loop and one coroutine	2941	with priority higher than or equal to the event loop and one coroutine
2574	of lower priority, but only once, using idle watchers to keep the event	2942	of lower priority, but only once, using idle watchers to keep the event
2575	loop from blocking if lower-priority coroutines are active, thus mapping	2943	loop from blocking if lower-priority coroutines are active, thus mapping
2576	low-priority coroutines to idle/background tasks).	2944	low-priority coroutines to idle/background tasks).
2577		2945
2578	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2946	When used for this purpose, it is recommended to give C<ev_check> watchers
2579	priority, to ensure that they are being run before any other watchers	2947	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2580	after the poll (this doesn't matter for C<ev_prepare> watchers).	2948	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2949	watchers).
2581		2950
2582	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2951	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2583	activate ("feed") events into libev. While libev fully supports this, they	2952	activate ("feed") events into libev. While libev fully supports this, they
2584	might get executed before other C<ev_check> watchers did their job. As	2953	might get executed before other C<ev_check> watchers did their job. As
2585	C<ev_check> watchers are often used to embed other (non-libev) event	2954	C<ev_check> watchers are often used to embed other (non-libev) event
2586	loops those other event loops might be in an unusable state until their	2955	loops those other event loops might be in an unusable state until their
2587	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2956	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2588	others).	2957	others).
		2958
		2959	=head3 Abusing an C<ev_check> watcher for its side-effect
		2960
		2961	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2962	useful because they are called once per event loop iteration. For
		2963	example, if you want to handle a large number of connections fairly, you
		2964	normally only do a bit of work for each active connection, and if there
		2965	is more work to do, you wait for the next event loop iteration, so other
		2966	connections have a chance of making progress.
		2967
		2968	Using an C<ev_check> watcher is almost enough: it will be called on the
		2969	next event loop iteration. However, that isn't as soon as possible -
		2970	without external events, your C<ev_check> watcher will not be invoked.
		2971
		2972	This is where C<ev_idle> watchers come in handy - all you need is a
		2973	single global idle watcher that is active as long as you have one active
		2974	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2975	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2976	invoked. Neither watcher alone can do that.
2589		2977
2590	=head3 Watcher-Specific Functions and Data Members	2978	=head3 Watcher-Specific Functions and Data Members
2591		2979
2592	=over 4	2980	=over 4
2593		2981
…		…
2717		3105
2718	if (timeout >= 0)	3106	if (timeout >= 0)
2719	// create/start timer	3107	// create/start timer
2720		3108
2721	// poll	3109	// poll
2722	ev_loop (EV_A_ 0);	3110	ev_run (EV_A_ 0);
2723		3111
2724	// stop timer again	3112	// stop timer again
2725	if (timeout >= 0)	3113	if (timeout >= 0)
2726	ev_timer_stop (EV_A_ &to);	3114	ev_timer_stop (EV_A_ &to);
2727		3115
…		…
2794		3182
2795	=over 4	3183	=over 4
2796		3184
2797	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2798		3186
2799	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3187	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2800		3188
2801	Configures the watcher to embed the given loop, which must be	3189	Configures the watcher to embed the given loop, which must be
2802	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3190	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2803	invoked automatically, otherwise it is the responsibility of the callback	3191	invoked automatically, otherwise it is the responsibility of the callback
2804	to invoke it (it will continue to be called until the sweep has been done,	3192	to invoke it (it will continue to be called until the sweep has been done,
2805	if you do not want that, you need to temporarily stop the embed watcher).	3193	if you do not want that, you need to temporarily stop the embed watcher).
2806		3194
2807	=item ev_embed_sweep (loop, ev_embed *)	3195	=item ev_embed_sweep (loop, ev_embed *)
2808		3196
2809	Make a single, non-blocking sweep over the embedded loop. This works	3197	Make a single, non-blocking sweep over the embedded loop. This works
2810	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3198	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2811	appropriate way for embedded loops.	3199	appropriate way for embedded loops.
2812		3200
2813	=item struct ev_loop *other [read-only]	3201	=item struct ev_loop *other [read-only]
2814		3202
2815	The embedded event loop.	3203	The embedded event loop.
…		…
2867		3255
2868	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3256	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2869		3257
2870	Fork watchers are called when a C<fork ()> was detected (usually because	3258	Fork watchers are called when a C<fork ()> was detected (usually because
2871	whoever is a good citizen cared to tell libev about it by calling	3259	whoever is a good citizen cared to tell libev about it by calling
2872	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3260	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2873	event loop blocks next and before C<ev_check> watchers are being called,	3261	and before C<ev_check> watchers are being called, and only in the child
2874	and only in the child after the fork. If whoever good citizen calling	3262	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2875	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3263	and calls it in the wrong process, the fork handlers will be invoked, too,
2876	handlers will be invoked, too, of course.	3264	of course.
2877		3265
2878	=head3 The special problem of life after fork - how is it possible?	3266	=head3 The special problem of life after fork - how is it possible?
2879		3267
2880	Most uses of C<fork()> consist of forking, then some simple calls to ste	3268	Most uses of C<fork()> consist of forking, then some simple calls to set
2881	up/change the process environment, followed by a call to C<exec()>. This	3269	up/change the process environment, followed by a call to C<exec()>. This
2882	sequence should be handled by libev without any problems.	3270	sequence should be handled by libev without any problems.
2883		3271
2884	This changes when the application actually wants to do event handling	3272	This changes when the application actually wants to do event handling
2885	in the child, or both parent in child, in effect "continuing" after the	3273	in the child, or both parent in child, in effect "continuing" after the
…		…
2901	disadvantage of having to use multiple event loops (which do not support	3289	disadvantage of having to use multiple event loops (which do not support
2902	signal watchers).	3290	signal watchers).
2903		3291
2904	When this is not possible, or you want to use the default loop for	3292	When this is not possible, or you want to use the default loop for
2905	other reasons, then in the process that wants to start "fresh", call	3293	other reasons, then in the process that wants to start "fresh", call
2906	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3294	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2907	the default loop will "orphan" (not stop) all registered watchers, so you	3295	Destroying the default loop will "orphan" (not stop) all registered
2908	have to be careful not to execute code that modifies those watchers. Note	3296	watchers, so you have to be careful not to execute code that modifies
2909	also that in that case, you have to re-register any signal watchers.	3297	those watchers. Note also that in that case, you have to re-register any
		3298	signal watchers.
2910		3299
2911	=head3 Watcher-Specific Functions and Data Members	3300	=head3 Watcher-Specific Functions and Data Members
2912		3301
2913	=over 4	3302	=over 4
2914		3303
2915	=item ev_fork_init (ev_signal *, callback)	3304	=item ev_fork_init (ev_fork *, callback)
2916		3305
2917	Initialises and configures the fork watcher - it has no parameters of any	3306	Initialises and configures the fork watcher - it has no parameters of any
2918	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3307	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2919	believe me.	3308	really.
2920		3309
2921	=back	3310	=back
2922		3311
2923		3312
		3313	=head2 C<ev_cleanup> - even the best things end
		3314
		3315	Cleanup watchers are called just before the event loop is being destroyed
		3316	by a call to C<ev_loop_destroy>.
		3317
		3318	While there is no guarantee that the event loop gets destroyed, cleanup
		3319	watchers provide a convenient method to install cleanup hooks for your
		3320	program, worker threads and so on - you just to make sure to destroy the
		3321	loop when you want them to be invoked.
		3322
		3323	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3324	all other watchers, they do not keep a reference to the event loop (which
		3325	makes a lot of sense if you think about it). Like all other watchers, you
		3326	can call libev functions in the callback, except C<ev_cleanup_start>.
		3327
		3328	=head3 Watcher-Specific Functions and Data Members
		3329
		3330	=over 4
		3331
		3332	=item ev_cleanup_init (ev_cleanup *, callback)
		3333
		3334	Initialises and configures the cleanup watcher - it has no parameters of
		3335	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3336	pointless, I assure you.
		3337
		3338	=back
		3339
		3340	Example: Register an atexit handler to destroy the default loop, so any
		3341	cleanup functions are called.
		3342
		3343	static void
		3344	program_exits (void)
		3345	{
		3346	ev_loop_destroy (EV_DEFAULT_UC);
		3347	}
		3348
		3349	...
		3350	atexit (program_exits);
		3351
		3352
2924	=head2 C<ev_async> - how to wake up another event loop	3353	=head2 C<ev_async> - how to wake up an event loop
2925		3354
2926	In general, you cannot use an C<ev_loop> from multiple threads or other	3355	In general, you cannot use an C<ev_loop> from multiple threads or other
2927	asynchronous sources such as signal handlers (as opposed to multiple event	3356	asynchronous sources such as signal handlers (as opposed to multiple event
2928	loops - those are of course safe to use in different threads).	3357	loops - those are of course safe to use in different threads).
2929		3358
2930	Sometimes, however, you need to wake up another event loop you do not	3359	Sometimes, however, you need to wake up an event loop you do not control,
2931	control, for example because it belongs to another thread. This is what	3360	for example because it belongs to another thread. This is what C<ev_async>
2932	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3361	watchers do: as long as the C<ev_async> watcher is active, you can signal
2933	can signal it by calling C<ev_async_send>, which is thread- and signal	3362	it by calling C<ev_async_send>, which is thread- and signal safe.
2934	safe.
2935		3363
2936	This functionality is very similar to C<ev_signal> watchers, as signals,	3364	This functionality is very similar to C<ev_signal> watchers, as signals,
2937	too, are asynchronous in nature, and signals, too, will be compressed	3365	too, are asynchronous in nature, and signals, too, will be compressed
2938	(i.e. the number of callback invocations may be less than the number of	3366	(i.e. the number of callback invocations may be less than the number of
2939	C<ev_async_sent> calls).	3367	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2940		3368	of "global async watchers" by using a watcher on an otherwise unused
2941	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3369	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2942	just the default loop.	3370	even without knowing which loop owns the signal.
2943		3371
2944	=head3 Queueing	3372	=head3 Queueing
2945		3373
2946	C<ev_async> does not support queueing of data in any way. The reason	3374	C<ev_async> does not support queueing of data in any way. The reason
2947	is that the author does not know of a simple (or any) algorithm for a	3375	is that the author does not know of a simple (or any) algorithm for a
2948	multiple-writer-single-reader queue that works in all cases and doesn't	3376	multiple-writer-single-reader queue that works in all cases and doesn't
2949	need elaborate support such as pthreads.	3377	need elaborate support such as pthreads or unportable memory access
		3378	semantics.
2950		3379
2951	That means that if you want to queue data, you have to provide your own	3380	That means that if you want to queue data, you have to provide your own
2952	queue. But at least I can tell you how to implement locking around your	3381	queue. But at least I can tell you how to implement locking around your
2953	queue:	3382	queue:
2954		3383
…		…
3038	trust me.	3467	trust me.
3039		3468
3040	=item ev_async_send (loop, ev_async *)	3469	=item ev_async_send (loop, ev_async *)
3041		3470
3042	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3043	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3472	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3473	returns.
		3474
3044	C<ev_feed_event>, this call is safe to do from other threads, signal or	3475	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3045	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3476	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3046	section below on what exactly this means).	3477	embedding section below on what exactly this means).
3047		3478
3048	Note that, as with other watchers in libev, multiple events might get	3479	Note that, as with other watchers in libev, multiple events might get
3049	compressed into a single callback invocation (another way to look at this	3480	compressed into a single callback invocation (another way to look at
3050	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3481	this is that C<ev_async> watchers are level-triggered: they are set on
3051	reset when the event loop detects that).	3482	C<ev_async_send>, reset when the event loop detects that).
3052		3483
3053	This call incurs the overhead of a system call only once per event loop	3484	This call incurs the overhead of at most one extra system call per event
3054	iteration, so while the overhead might be noticeable, it doesn't apply to	3485	loop iteration, if the event loop is blocked, and no syscall at all if
3055	repeated calls to C<ev_async_send> for the same event loop.	3486	the event loop (or your program) is processing events. That means that
		3487	repeated calls are basically free (there is no need to avoid calls for
		3488	performance reasons) and that the overhead becomes smaller (typically
		3489	zero) under load.
3056		3490
3057	=item bool = ev_async_pending (ev_async *)	3491	=item bool = ev_async_pending (ev_async *)
3058		3492
3059	Returns a non-zero value when C<ev_async_send> has been called on the	3493	Returns a non-zero value when C<ev_async_send> has been called on the
3060	watcher but the event has not yet been processed (or even noted) by the	3494	watcher but the event has not yet been processed (or even noted) by the
…		…
3093		3527
3094	If C<timeout> is less than 0, then no timeout watcher will be	3528	If C<timeout> is less than 0, then no timeout watcher will be
3095	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3529	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3096	repeat = 0) will be started. C<0> is a valid timeout.	3530	repeat = 0) will be started. C<0> is a valid timeout.
3097		3531
3098	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3532	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3099	passed an C<revents> set like normal event callbacks (a combination of	3533	passed an C<revents> set like normal event callbacks (a combination of
3100	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3534	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3101	value passed to C<ev_once>. Note that it is possible to receive I<both>	3535	value passed to C<ev_once>. Note that it is possible to receive I<both>
3102	a timeout and an io event at the same time - you probably should give io	3536	a timeout and an io event at the same time - you probably should give io
3103	events precedence.	3537	events precedence.
3104		3538
3105	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3539	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3106		3540
3107	static void stdin_ready (int revents, void *arg)	3541	static void stdin_ready (int revents, void *arg)
3108	{	3542	{
3109	if (revents & EV_READ)	3543	if (revents & EV_READ)
3110	/* stdin might have data for us, joy! */;	3544	/* stdin might have data for us, joy! */;
3111	else if (revents & EV_TIMEOUT)	3545	else if (revents & EV_TIMER)
3112	/* doh, nothing entered */;	3546	/* doh, nothing entered */;
3113	}	3547	}
3114		3548
3115	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3549	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3116		3550
3117	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3118
3119	Feeds the given event set into the event loop, as if the specified event
3120	had happened for the specified watcher (which must be a pointer to an
3121	initialised but not necessarily started event watcher).
3122
3123	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3551	=item ev_feed_fd_event (loop, int fd, int revents)
3124		3552
3125	Feed an event on the given fd, as if a file descriptor backend detected	3553	Feed an event on the given fd, as if a file descriptor backend detected
3126	the given events it.	3554	the given events.
3127		3555
3128	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3556	=item ev_feed_signal_event (loop, int signum)
3129		3557
3130	Feed an event as if the given signal occurred (C<loop> must be the default	3558	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3131	loop!).	3559	which is async-safe.
3132		3560
3133	=back	3561	=back
		3562
		3563
		3564	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3565
		3566	This section explains some common idioms that are not immediately
		3567	obvious. Note that examples are sprinkled over the whole manual, and this
		3568	section only contains stuff that wouldn't fit anywhere else.
		3569
		3570	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3571
		3572	Each watcher has, by default, a C<void *data> member that you can read
		3573	or modify at any time: libev will completely ignore it. This can be used
		3574	to associate arbitrary data with your watcher. If you need more data and
		3575	don't want to allocate memory separately and store a pointer to it in that
		3576	data member, you can also "subclass" the watcher type and provide your own
		3577	data:
		3578
		3579	struct my_io
		3580	{
		3581	ev_io io;
		3582	int otherfd;
		3583	void *somedata;
		3584	struct whatever *mostinteresting;
		3585	};
		3586
		3587	...
		3588	struct my_io w;
		3589	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3590
		3591	And since your callback will be called with a pointer to the watcher, you
		3592	can cast it back to your own type:
		3593
		3594	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3595	{
		3596	struct my_io *w = (struct my_io *)w_;
		3597	...
		3598	}
		3599
		3600	More interesting and less C-conformant ways of casting your callback
		3601	function type instead have been omitted.
		3602
		3603	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3604
		3605	Another common scenario is to use some data structure with multiple
		3606	embedded watchers, in effect creating your own watcher that combines
		3607	multiple libev event sources into one "super-watcher":
		3608
		3609	struct my_biggy
		3610	{
		3611	int some_data;
		3612	ev_timer t1;
		3613	ev_timer t2;
		3614	}
		3615
		3616	In this case getting the pointer to C<my_biggy> is a bit more
		3617	complicated: Either you store the address of your C<my_biggy> struct in
		3618	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3619	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3620	real programmers):
		3621
		3622	#include <stddef.h>
		3623
		3624	static void
		3625	t1_cb (EV_P_ ev_timer *w, int revents)
		3626	{
		3627	struct my_biggy big = (struct my_biggy *)
		3628	(((char *)w) - offsetof (struct my_biggy, t1));
		3629	}
		3630
		3631	static void
		3632	t2_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t2));
		3636	}
		3637
		3638	=head2 AVOIDING FINISHING BEFORE RETURNING
		3639
		3640	Often you have structures like this in event-based programs:
		3641
		3642	callback ()
		3643	{
		3644	free (request);
		3645	}
		3646
		3647	request = start_new_request (..., callback);
		3648
		3649	The intent is to start some "lengthy" operation. The C<request> could be
		3650	used to cancel the operation, or do other things with it.
		3651
		3652	It's not uncommon to have code paths in C<start_new_request> that
		3653	immediately invoke the callback, for example, to report errors. Or you add
		3654	some caching layer that finds that it can skip the lengthy aspects of the
		3655	operation and simply invoke the callback with the result.
		3656
		3657	The problem here is that this will happen I<before> C<start_new_request>
		3658	has returned, so C<request> is not set.
		3659
		3660	Even if you pass the request by some safer means to the callback, you
		3661	might want to do something to the request after starting it, such as
		3662	canceling it, which probably isn't working so well when the callback has
		3663	already been invoked.
		3664
		3665	A common way around all these issues is to make sure that
		3666	C<start_new_request> I<always> returns before the callback is invoked. If
		3667	C<start_new_request> immediately knows the result, it can artificially
		3668	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3669	example, or more sneakily, by reusing an existing (stopped) watcher and
		3670	pushing it into the pending queue:
		3671
		3672	ev_set_cb (watcher, callback);
		3673	ev_feed_event (EV_A_ watcher, 0);
		3674
		3675	This way, C<start_new_request> can safely return before the callback is
		3676	invoked, while not delaying callback invocation too much.
		3677
		3678	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3679
		3680	Often (especially in GUI toolkits) there are places where you have
		3681	I<modal> interaction, which is most easily implemented by recursively
		3682	invoking C<ev_run>.
		3683
		3684	This brings the problem of exiting - a callback might want to finish the
		3685	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3686	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3687	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3688	other combination: In these cases, a simple C<ev_break> will not work.
		3689
		3690	The solution is to maintain "break this loop" variable for each C<ev_run>
		3691	invocation, and use a loop around C<ev_run> until the condition is
		3692	triggered, using C<EVRUN_ONCE>:
		3693
		3694	// main loop
		3695	int exit_main_loop = 0;
		3696
		3697	while (!exit_main_loop)
		3698	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3699
		3700	// in a modal watcher
		3701	int exit_nested_loop = 0;
		3702
		3703	while (!exit_nested_loop)
		3704	ev_run (EV_A_ EVRUN_ONCE);
		3705
		3706	To exit from any of these loops, just set the corresponding exit variable:
		3707
		3708	// exit modal loop
		3709	exit_nested_loop = 1;
		3710
		3711	// exit main program, after modal loop is finished
		3712	exit_main_loop = 1;
		3713
		3714	// exit both
		3715	exit_main_loop = exit_nested_loop = 1;
		3716
		3717	=head2 THREAD LOCKING EXAMPLE
		3718
		3719	Here is a fictitious example of how to run an event loop in a different
		3720	thread from where callbacks are being invoked and watchers are
		3721	created/added/removed.
		3722
		3723	For a real-world example, see the C<EV::Loop::Async> perl module,
		3724	which uses exactly this technique (which is suited for many high-level
		3725	languages).
		3726
		3727	The example uses a pthread mutex to protect the loop data, a condition
		3728	variable to wait for callback invocations, an async watcher to notify the
		3729	event loop thread and an unspecified mechanism to wake up the main thread.
		3730
		3731	First, you need to associate some data with the event loop:
		3732
		3733	typedef struct {
		3734	mutex_t lock; /* global loop lock */
		3735	ev_async async_w;
		3736	thread_t tid;
		3737	cond_t invoke_cv;
		3738	} userdata;
		3739
		3740	void prepare_loop (EV_P)
		3741	{
		3742	// for simplicity, we use a static userdata struct.
		3743	static userdata u;
		3744
		3745	ev_async_init (&u->async_w, async_cb);
		3746	ev_async_start (EV_A_ &u->async_w);
		3747
		3748	pthread_mutex_init (&u->lock, 0);
		3749	pthread_cond_init (&u->invoke_cv, 0);
		3750
		3751	// now associate this with the loop
		3752	ev_set_userdata (EV_A_ u);
		3753	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3754	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3755
		3756	// then create the thread running ev_run
		3757	pthread_create (&u->tid, 0, l_run, EV_A);
		3758	}
		3759
		3760	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3761	solely to wake up the event loop so it takes notice of any new watchers
		3762	that might have been added:
		3763
		3764	static void
		3765	async_cb (EV_P_ ev_async *w, int revents)
		3766	{
		3767	// just used for the side effects
		3768	}
		3769
		3770	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3771	protecting the loop data, respectively.
		3772
		3773	static void
		3774	l_release (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777	pthread_mutex_unlock (&u->lock);
		3778	}
		3779
		3780	static void
		3781	l_acquire (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_lock (&u->lock);
		3785	}
		3786
		3787	The event loop thread first acquires the mutex, and then jumps straight
		3788	into C<ev_run>:
		3789
		3790	void *
		3791	l_run (void *thr_arg)
		3792	{
		3793	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3794
		3795	l_acquire (EV_A);
		3796	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3797	ev_run (EV_A_ 0);
		3798	l_release (EV_A);
		3799
		3800	return 0;
		3801	}
		3802
		3803	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3804	signal the main thread via some unspecified mechanism (signals? pipe
		3805	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3806	have been called (in a while loop because a) spurious wakeups are possible
		3807	and b) skipping inter-thread-communication when there are no pending
		3808	watchers is very beneficial):
		3809
		3810	static void
		3811	l_invoke (EV_P)
		3812	{
		3813	userdata *u = ev_userdata (EV_A);
		3814
		3815	while (ev_pending_count (EV_A))
		3816	{
		3817	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3818	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3819	}
		3820	}
		3821
		3822	Now, whenever the main thread gets told to invoke pending watchers, it
		3823	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3824	thread to continue:
		3825
		3826	static void
		3827	real_invoke_pending (EV_P)
		3828	{
		3829	userdata *u = ev_userdata (EV_A);
		3830
		3831	pthread_mutex_lock (&u->lock);
		3832	ev_invoke_pending (EV_A);
		3833	pthread_cond_signal (&u->invoke_cv);
		3834	pthread_mutex_unlock (&u->lock);
		3835	}
		3836
		3837	Whenever you want to start/stop a watcher or do other modifications to an
		3838	event loop, you will now have to lock:
		3839
		3840	ev_timer timeout_watcher;
		3841	userdata *u = ev_userdata (EV_A);
		3842
		3843	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3844
		3845	pthread_mutex_lock (&u->lock);
		3846	ev_timer_start (EV_A_ &timeout_watcher);
		3847	ev_async_send (EV_A_ &u->async_w);
		3848	pthread_mutex_unlock (&u->lock);
		3849
		3850	Note that sending the C<ev_async> watcher is required because otherwise
		3851	an event loop currently blocking in the kernel will have no knowledge
		3852	about the newly added timer. By waking up the loop it will pick up any new
		3853	watchers in the next event loop iteration.
		3854
		3855	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3856
		3857	While the overhead of a callback that e.g. schedules a thread is small, it
		3858	is still an overhead. If you embed libev, and your main usage is with some
		3859	kind of threads or coroutines, you might want to customise libev so that
		3860	doesn't need callbacks anymore.
		3861
		3862	Imagine you have coroutines that you can switch to using a function
		3863	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3864	and that due to some magic, the currently active coroutine is stored in a
		3865	global called C<current_coro>. Then you can build your own "wait for libev
		3866	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3867	the differing C<;> conventions):
		3868
		3869	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3870	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3871
		3872	That means instead of having a C callback function, you store the
		3873	coroutine to switch to in each watcher, and instead of having libev call
		3874	your callback, you instead have it switch to that coroutine.
		3875
		3876	A coroutine might now wait for an event with a function called
		3877	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3878	matter when, or whether the watcher is active or not when this function is
		3879	called):
		3880
		3881	void
		3882	wait_for_event (ev_watcher *w)
		3883	{
		3884	ev_set_cb (w, current_coro);
		3885	switch_to (libev_coro);
		3886	}
		3887
		3888	That basically suspends the coroutine inside C<wait_for_event> and
		3889	continues the libev coroutine, which, when appropriate, switches back to
		3890	this or any other coroutine.
		3891
		3892	You can do similar tricks if you have, say, threads with an event queue -
		3893	instead of storing a coroutine, you store the queue object and instead of
		3894	switching to a coroutine, you push the watcher onto the queue and notify
		3895	any waiters.
		3896
		3897	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3898	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3899
		3900	// my_ev.h
		3901	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3902	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3903	#include "../libev/ev.h"
		3904
		3905	// my_ev.c
		3906	#define EV_H "my_ev.h"
		3907	#include "../libev/ev.c"
		3908
		3909	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3910	F<my_ev.c> into your project. When properly specifying include paths, you
		3911	can even use F<ev.h> as header file name directly.
3134		3912
3135		3913
3136	=head1 LIBEVENT EMULATION	3914	=head1 LIBEVENT EMULATION
3137		3915
3138	Libev offers a compatibility emulation layer for libevent. It cannot	3916	Libev offers a compatibility emulation layer for libevent. It cannot
3139	emulate the internals of libevent, so here are some usage hints:	3917	emulate the internals of libevent, so here are some usage hints:
3140		3918
3141	=over 4	3919	=over 4
		3920
		3921	=item * Only the libevent-1.4.1-beta API is being emulated.
		3922
		3923	This was the newest libevent version available when libev was implemented,
		3924	and is still mostly unchanged in 2010.
3142		3925
3143	=item * Use it by including <event.h>, as usual.	3926	=item * Use it by including <event.h>, as usual.
3144		3927
3145	=item * The following members are fully supported: ev_base, ev_callback,	3928	=item * The following members are fully supported: ev_base, ev_callback,
3146	ev_arg, ev_fd, ev_res, ev_events.	3929	ev_arg, ev_fd, ev_res, ev_events.
…		…
3152	=item * Priorities are not currently supported. Initialising priorities	3935	=item * Priorities are not currently supported. Initialising priorities
3153	will fail and all watchers will have the same priority, even though there	3936	will fail and all watchers will have the same priority, even though there
3154	is an ev_pri field.	3937	is an ev_pri field.
3155		3938
3156	=item * In libevent, the last base created gets the signals, in libev, the	3939	=item * In libevent, the last base created gets the signals, in libev, the
3157	first base created (== the default loop) gets the signals.	3940	base that registered the signal gets the signals.
3158		3941
3159	=item * Other members are not supported.	3942	=item * Other members are not supported.
3160		3943
3161	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3944	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3162	to use the libev header file and library.	3945	to use the libev header file and library.
3163		3946
3164	=back	3947	=back
3165		3948
3166	=head1 C++ SUPPORT	3949	=head1 C++ SUPPORT
		3950
		3951	=head2 C API
		3952
		3953	The normal C API should work fine when used from C++: both ev.h and the
		3954	libev sources can be compiled as C++. Therefore, code that uses the C API
		3955	will work fine.
		3956
		3957	Proper exception specifications might have to be added to callbacks passed
		3958	to libev: exceptions may be thrown only from watcher callbacks, all
		3959	other callbacks (allocator, syserr, loop acquire/release and periodic
		3960	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3961	()> specification. If you have code that needs to be compiled as both C
		3962	and C++ you can use the C<EV_THROW> macro for this:
		3963
		3964	static void
		3965	fatal_error (const char *msg) EV_THROW
		3966	{
		3967	perror (msg);
		3968	abort ();
		3969	}
		3970
		3971	...
		3972	ev_set_syserr_cb (fatal_error);
		3973
		3974	The only API functions that can currently throw exceptions are C<ev_run>,
		3975	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3976	because it runs cleanup watchers).
		3977
		3978	Throwing exceptions in watcher callbacks is only supported if libev itself
		3979	is compiled with a C++ compiler or your C and C++ environments allow
		3980	throwing exceptions through C libraries (most do).
		3981
		3982	=head2 C++ API
3167		3983
3168	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3984	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3169	you to use some convenience methods to start/stop watchers and also change	3985	you to use some convenience methods to start/stop watchers and also change
3170	the callback model to a model using method callbacks on objects.	3986	the callback model to a model using method callbacks on objects.
3171		3987
3172	To use it,	3988	To use it,
3173		3989
3174	#include <ev++.h>	3990	#include <ev++.h>
3175		3991
3176	This automatically includes F<ev.h> and puts all of its definitions (many	3992	This automatically includes F<ev.h> and puts all of its definitions (many
3177	of them macros) into the global namespace. All C++ specific things are	3993	of them macros) into the global namespace. All C++ specific things are
3178	put into the C<ev> namespace. It should support all the same embedding	3994	put into the C<ev> namespace. It should support all the same embedding
…		…
3181	Care has been taken to keep the overhead low. The only data member the C++	3997	Care has been taken to keep the overhead low. The only data member the C++
3182	classes add (compared to plain C-style watchers) is the event loop pointer	3998	classes add (compared to plain C-style watchers) is the event loop pointer
3183	that the watcher is associated with (or no additional members at all if	3999	that the watcher is associated with (or no additional members at all if
3184	you disable C<EV_MULTIPLICITY> when embedding libev).	4000	you disable C<EV_MULTIPLICITY> when embedding libev).
3185		4001
3186	Currently, functions, and static and non-static member functions can be	4002	Currently, functions, static and non-static member functions and classes
3187	used as callbacks. Other types should be easy to add as long as they only	4003	with C<operator ()> can be used as callbacks. Other types should be easy
3188	need one additional pointer for context. If you need support for other	4004	to add as long as they only need one additional pointer for context. If
3189	types of functors please contact the author (preferably after implementing	4005	you need support for other types of functors please contact the author
3190	it).	4006	(preferably after implementing it).
		4007
		4008	For all this to work, your C++ compiler either has to use the same calling
		4009	conventions as your C compiler (for static member functions), or you have
		4010	to embed libev and compile libev itself as C++.
3191		4011
3192	Here is a list of things available in the C<ev> namespace:	4012	Here is a list of things available in the C<ev> namespace:
3193		4013
3194	=over 4	4014	=over 4
3195		4015
…		…
3205	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4025	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3206		4026
3207	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4027	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3208	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4028	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3209	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4029	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3210	defines by many implementations.	4030	defined by many implementations.
3211		4031
3212	All of those classes have these methods:	4032	All of those classes have these methods:
3213		4033
3214	=over 4	4034	=over 4
3215		4035
3216	=item ev::TYPE::TYPE ()	4036	=item ev::TYPE::TYPE ()
3217		4037
3218	=item ev::TYPE::TYPE (struct ev_loop *)	4038	=item ev::TYPE::TYPE (loop)
3219		4039
3220	=item ev::TYPE::~TYPE	4040	=item ev::TYPE::~TYPE
3221		4041
3222	The constructor (optionally) takes an event loop to associate the watcher	4042	The constructor (optionally) takes an event loop to associate the watcher
3223	with. If it is omitted, it will use C<EV_DEFAULT>.	4043	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3256	myclass obj;	4076	myclass obj;
3257	ev::io iow;	4077	ev::io iow;
3258	iow.set <myclass, &myclass::io_cb> (&obj);	4078	iow.set <myclass, &myclass::io_cb> (&obj);
3259		4079
3260	=item w->set (object *)	4080	=item w->set (object *)
3261
3262	This is an B<experimental> feature that might go away in a future version.
3263		4081
3264	This is a variation of a method callback - leaving out the method to call	4082	This is a variation of a method callback - leaving out the method to call
3265	will default the method to C<operator ()>, which makes it possible to use	4083	will default the method to C<operator ()>, which makes it possible to use
3266	functor objects without having to manually specify the C<operator ()> all	4084	functor objects without having to manually specify the C<operator ()> all
3267	the time. Incidentally, you can then also leave out the template argument	4085	the time. Incidentally, you can then also leave out the template argument
…		…
3300	Example: Use a plain function as callback.	4118	Example: Use a plain function as callback.
3301		4119
3302	static void io_cb (ev::io &w, int revents) { }	4120	static void io_cb (ev::io &w, int revents) { }
3303	iow.set <io_cb> ();	4121	iow.set <io_cb> ();
3304		4122
3305	=item w->set (struct ev_loop *)	4123	=item w->set (loop)
3306		4124
3307	Associates a different C<struct ev_loop> with this watcher. You can only	4125	Associates a different C<struct ev_loop> with this watcher. You can only
3308	do this when the watcher is inactive (and not pending either).	4126	do this when the watcher is inactive (and not pending either).
3309		4127
3310	=item w->set ([arguments])	4128	=item w->set ([arguments])
3311		4129
3312	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4130	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4131	with the same arguments. Either this method or a suitable start method
3313	called at least once. Unlike the C counterpart, an active watcher gets	4132	must be called at least once. Unlike the C counterpart, an active watcher
3314	automatically stopped and restarted when reconfiguring it with this	4133	gets automatically stopped and restarted when reconfiguring it with this
3315	method.	4134	method.
		4135
		4136	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4137	clashing with the C<set (loop)> method.
3316		4138
3317	=item w->start ()	4139	=item w->start ()
3318		4140
3319	Starts the watcher. Note that there is no C<loop> argument, as the	4141	Starts the watcher. Note that there is no C<loop> argument, as the
3320	constructor already stores the event loop.	4142	constructor already stores the event loop.
3321		4143
		4144	=item w->start ([arguments])
		4145
		4146	Instead of calling C<set> and C<start> methods separately, it is often
		4147	convenient to wrap them in one call. Uses the same type of arguments as
		4148	the configure C<set> method of the watcher.
		4149
3322	=item w->stop ()	4150	=item w->stop ()
3323		4151
3324	Stops the watcher if it is active. Again, no C<loop> argument.	4152	Stops the watcher if it is active. Again, no C<loop> argument.
3325		4153
3326	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4154	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3338		4166
3339	=back	4167	=back
3340		4168
3341	=back	4169	=back
3342		4170
3343	Example: Define a class with an IO and idle watcher, start one of them in	4171	Example: Define a class with two I/O and idle watchers, start the I/O
3344	the constructor.	4172	watchers in the constructor.
3345		4173
3346	class myclass	4174	class myclass
3347	{	4175	{
3348	ev::io io ; void io_cb (ev::io &w, int revents);	4176	ev::io io ; void io_cb (ev::io &w, int revents);
		4177	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3349	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4178	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3350		4179
3351	myclass (int fd)	4180	myclass (int fd)
3352	{	4181	{
3353	io .set <myclass, &myclass::io_cb > (this);	4182	io .set <myclass, &myclass::io_cb > (this);
		4183	io2 .set <myclass, &myclass::io2_cb > (this);
3354	idle.set <myclass, &myclass::idle_cb> (this);	4184	idle.set <myclass, &myclass::idle_cb> (this);
3355		4185
3356	io.start (fd, ev::READ);	4186	io.set (fd, ev::WRITE); // configure the watcher
		4187	io.start (); // start it whenever convenient
		4188
		4189	io2.start (fd, ev::READ); // set + start in one call
3357	}	4190	}
3358	};	4191	};
3359		4192
3360		4193
3361	=head1 OTHER LANGUAGE BINDINGS	4194	=head1 OTHER LANGUAGE BINDINGS
…		…
3400	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4233	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3401		4234
3402	=item D	4235	=item D
3403		4236
3404	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4237	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3405	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4238	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3406		4239
3407	=item Ocaml	4240	=item Ocaml
3408		4241
3409	Erkki Seppala has written Ocaml bindings for libev, to be found at	4242	Erkki Seppala has written Ocaml bindings for libev, to be found at
3410	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4243	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3411		4244
3412	=item Lua	4245	=item Lua
3413		4246
3414	Brian Maher has written a partial interface to libev	4247	Brian Maher has written a partial interface to libev for lua (at the
3415	for lua (only C<ev_io> and C<ev_timer>), to be found at	4248	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3416	L<http://github.com/brimworks/lua-ev>.	4249	L<http://github.com/brimworks/lua-ev>.
		4250
		4251	=item Javascript
		4252
		4253	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4254
		4255	=item Others
		4256
		4257	There are others, and I stopped counting.
3417		4258
3418	=back	4259	=back
3419		4260
3420		4261
3421	=head1 MACRO MAGIC	4262	=head1 MACRO MAGIC
…		…
3435	loop argument"). The C<EV_A> form is used when this is the sole argument,	4276	loop argument"). The C<EV_A> form is used when this is the sole argument,
3436	C<EV_A_> is used when other arguments are following. Example:	4277	C<EV_A_> is used when other arguments are following. Example:
3437		4278
3438	ev_unref (EV_A);	4279	ev_unref (EV_A);
3439	ev_timer_add (EV_A_ watcher);	4280	ev_timer_add (EV_A_ watcher);
3440	ev_loop (EV_A_ 0);	4281	ev_run (EV_A_ 0);
3441		4282
3442	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4283	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3443	which is often provided by the following macro.	4284	which is often provided by the following macro.
3444		4285
3445	=item C<EV_P>, C<EV_P_>	4286	=item C<EV_P>, C<EV_P_>
…		…
3458	suitable for use with C<EV_A>.	4299	suitable for use with C<EV_A>.
3459		4300
3460	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4301	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3461		4302
3462	Similar to the other two macros, this gives you the value of the default	4303	Similar to the other two macros, this gives you the value of the default
3463	loop, if multiple loops are supported ("ev loop default").	4304	loop, if multiple loops are supported ("ev loop default"). The default loop
		4305	will be initialised if it isn't already initialised.
		4306
		4307	For non-multiplicity builds, these macros do nothing, so you always have
		4308	to initialise the loop somewhere.
3464		4309
3465	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4310	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3466		4311
3467	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4312	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3468	default loop has been initialised (C<UC> == unchecked). Their behaviour	4313	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3485	}	4330	}
3486		4331
3487	ev_check check;	4332	ev_check check;
3488	ev_check_init (&check, check_cb);	4333	ev_check_init (&check, check_cb);
3489	ev_check_start (EV_DEFAULT_ &check);	4334	ev_check_start (EV_DEFAULT_ &check);
3490	ev_loop (EV_DEFAULT_ 0);	4335	ev_run (EV_DEFAULT_ 0);
3491		4336
3492	=head1 EMBEDDING	4337	=head1 EMBEDDING
3493		4338
3494	Libev can (and often is) directly embedded into host	4339	Libev can (and often is) directly embedded into host
3495	applications. Examples of applications that embed it include the Deliantra	4340	applications. Examples of applications that embed it include the Deliantra
…		…
3575	libev.m4	4420	libev.m4
3576		4421
3577	=head2 PREPROCESSOR SYMBOLS/MACROS	4422	=head2 PREPROCESSOR SYMBOLS/MACROS
3578		4423
3579	Libev can be configured via a variety of preprocessor symbols you have to	4424	Libev can be configured via a variety of preprocessor symbols you have to
3580	define before including any of its files. The default in the absence of	4425	define before including (or compiling) any of its files. The default in
3581	autoconf is documented for every option.	4426	the absence of autoconf is documented for every option.
		4427
		4428	Symbols marked with "(h)" do not change the ABI, and can have different
		4429	values when compiling libev vs. including F<ev.h>, so it is permissible
		4430	to redefine them before including F<ev.h> without breaking compatibility
		4431	to a compiled library. All other symbols change the ABI, which means all
		4432	users of libev and the libev code itself must be compiled with compatible
		4433	settings.
3582		4434
3583	=over 4	4435	=over 4
3584		4436
		4437	=item EV_COMPAT3 (h)
		4438
		4439	Backwards compatibility is a major concern for libev. This is why this
		4440	release of libev comes with wrappers for the functions and symbols that
		4441	have been renamed between libev version 3 and 4.
		4442
		4443	You can disable these wrappers (to test compatibility with future
		4444	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4445	sources. This has the additional advantage that you can drop the C<struct>
		4446	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4447	typedef in that case.
		4448
		4449	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4450	and in some even more future version the compatibility code will be
		4451	removed completely.
		4452
3585	=item EV_STANDALONE	4453	=item EV_STANDALONE (h)
3586		4454
3587	Must always be C<1> if you do not use autoconf configuration, which	4455	Must always be C<1> if you do not use autoconf configuration, which
3588	keeps libev from including F<config.h>, and it also defines dummy	4456	keeps libev from including F<config.h>, and it also defines dummy
3589	implementations for some libevent functions (such as logging, which is not	4457	implementations for some libevent functions (such as logging, which is not
3590	supported). It will also not define any of the structs usually found in	4458	supported). It will also not define any of the structs usually found in
3591	F<event.h> that are not directly supported by the libev core alone.	4459	F<event.h> that are not directly supported by the libev core alone.
3592		4460
3593	In standalone mode, libev will still try to automatically deduce the	4461	In standalone mode, libev will still try to automatically deduce the
3594	configuration, but has to be more conservative.	4462	configuration, but has to be more conservative.
		4463
		4464	=item EV_USE_FLOOR
		4465
		4466	If defined to be C<1>, libev will use the C<floor ()> function for its
		4467	periodic reschedule calculations, otherwise libev will fall back on a
		4468	portable (slower) implementation. If you enable this, you usually have to
		4469	link against libm or something equivalent. Enabling this when the C<floor>
		4470	function is not available will fail, so the safe default is to not enable
		4471	this.
3595		4472
3596	=item EV_USE_MONOTONIC	4473	=item EV_USE_MONOTONIC
3597		4474
3598	If defined to be C<1>, libev will try to detect the availability of the	4475	If defined to be C<1>, libev will try to detect the availability of the
3599	monotonic clock option at both compile time and runtime. Otherwise no	4476	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3684		4561
3685	If programs implement their own fd to handle mapping on win32, then this	4562	If programs implement their own fd to handle mapping on win32, then this
3686	macro can be used to override the C<close> function, useful to unregister	4563	macro can be used to override the C<close> function, useful to unregister
3687	file descriptors again. Note that the replacement function has to close	4564	file descriptors again. Note that the replacement function has to close
3688	the underlying OS handle.	4565	the underlying OS handle.
		4566
		4567	=item EV_USE_WSASOCKET
		4568
		4569	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4570	communication socket, which works better in some environments. Otherwise,
		4571	the normal C<socket> function will be used, which works better in other
		4572	environments.
3689		4573
3690	=item EV_USE_POLL	4574	=item EV_USE_POLL
3691		4575
3692	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4576	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3693	backend. Otherwise it will be enabled on non-win32 platforms. It	4577	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3729	If defined to be C<1>, libev will compile in support for the Linux inotify	4613	If defined to be C<1>, libev will compile in support for the Linux inotify
3730	interface to speed up C<ev_stat> watchers. Its actual availability will	4614	interface to speed up C<ev_stat> watchers. Its actual availability will
3731	be detected at runtime. If undefined, it will be enabled if the headers	4615	be detected at runtime. If undefined, it will be enabled if the headers
3732	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4616	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3733		4617
		4618	=item EV_NO_SMP
		4619
		4620	If defined to be C<1>, libev will assume that memory is always coherent
		4621	between threads, that is, threads can be used, but threads never run on
		4622	different cpus (or different cpu cores). This reduces dependencies
		4623	and makes libev faster.
		4624
		4625	=item EV_NO_THREADS
		4626
		4627	If defined to be C<1>, libev will assume that it will never be called from
		4628	different threads (that includes signal handlers), which is a stronger
		4629	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4630	libev faster.
		4631
3734	=item EV_ATOMIC_T	4632	=item EV_ATOMIC_T
3735		4633
3736	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4634	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3737	access is atomic with respect to other threads or signal contexts. No such	4635	access is atomic with respect to other threads or signal contexts. No
3738	type is easily found in the C language, so you can provide your own type	4636	such type is easily found in the C language, so you can provide your own
3739	that you know is safe for your purposes. It is used both for signal handler "locking"	4637	type that you know is safe for your purposes. It is used both for signal
3740	as well as for signal and thread safety in C<ev_async> watchers.	4638	handler "locking" as well as for signal and thread safety in C<ev_async>
		4639	watchers.
3741		4640
3742	In the absence of this define, libev will use C<sig_atomic_t volatile>	4641	In the absence of this define, libev will use C<sig_atomic_t volatile>
3743	(from F<signal.h>), which is usually good enough on most platforms.	4642	(from F<signal.h>), which is usually good enough on most platforms.
3744		4643
3745	=item EV_H	4644	=item EV_H (h)
3746		4645
3747	The name of the F<ev.h> header file used to include it. The default if	4646	The name of the F<ev.h> header file used to include it. The default if
3748	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4647	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3749	used to virtually rename the F<ev.h> header file in case of conflicts.	4648	used to virtually rename the F<ev.h> header file in case of conflicts.
3750		4649
3751	=item EV_CONFIG_H	4650	=item EV_CONFIG_H (h)
3752		4651
3753	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4652	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3754	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4653	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3755	C<EV_H>, above.	4654	C<EV_H>, above.
3756		4655
3757	=item EV_EVENT_H	4656	=item EV_EVENT_H (h)
3758		4657
3759	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4658	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3760	of how the F<event.h> header can be found, the default is C<"event.h">.	4659	of how the F<event.h> header can be found, the default is C<"event.h">.
3761		4660
3762	=item EV_PROTOTYPES	4661	=item EV_PROTOTYPES (h)
3763		4662
3764	If defined to be C<0>, then F<ev.h> will not define any function	4663	If defined to be C<0>, then F<ev.h> will not define any function
3765	prototypes, but still define all the structs and other symbols. This is	4664	prototypes, but still define all the structs and other symbols. This is
3766	occasionally useful if you want to provide your own wrapper functions	4665	occasionally useful if you want to provide your own wrapper functions
3767	around libev functions.	4666	around libev functions.
…		…
3772	will have the C<struct ev_loop *> as first argument, and you can create	4671	will have the C<struct ev_loop *> as first argument, and you can create
3773	additional independent event loops. Otherwise there will be no support	4672	additional independent event loops. Otherwise there will be no support
3774	for multiple event loops and there is no first event loop pointer	4673	for multiple event loops and there is no first event loop pointer
3775	argument. Instead, all functions act on the single default loop.	4674	argument. Instead, all functions act on the single default loop.
3776		4675
		4676	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4677	default loop when multiplicity is switched off - you always have to
		4678	initialise the loop manually in this case.
		4679
3777	=item EV_MINPRI	4680	=item EV_MINPRI
3778		4681
3779	=item EV_MAXPRI	4682	=item EV_MAXPRI
3780		4683
3781	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4684	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3789	fine.	4692	fine.
3790		4693
3791	If your embedding application does not need any priorities, defining these	4694	If your embedding application does not need any priorities, defining these
3792	both to C<0> will save some memory and CPU.	4695	both to C<0> will save some memory and CPU.
3793		4696
3794	=item EV_PERIODIC_ENABLE	4697	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4698	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4699	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3795		4700
3796	If undefined or defined to be C<1>, then periodic timers are supported. If	4701	If undefined or defined to be C<1> (and the platform supports it), then
3797	defined to be C<0>, then they are not. Disabling them saves a few kB of	4702	the respective watcher type is supported. If defined to be C<0>, then it
3798	code.	4703	is not. Disabling watcher types mainly saves code size.
3799		4704
3800	=item EV_IDLE_ENABLE	4705	=item EV_FEATURES
3801
3802	If undefined or defined to be C<1>, then idle watchers are supported. If
3803	defined to be C<0>, then they are not. Disabling them saves a few kB of
3804	code.
3805
3806	=item EV_EMBED_ENABLE
3807
3808	If undefined or defined to be C<1>, then embed watchers are supported. If
3809	defined to be C<0>, then they are not. Embed watchers rely on most other
3810	watcher types, which therefore must not be disabled.
3811
3812	=item EV_STAT_ENABLE
3813
3814	If undefined or defined to be C<1>, then stat watchers are supported. If
3815	defined to be C<0>, then they are not.
3816
3817	=item EV_FORK_ENABLE
3818
3819	If undefined or defined to be C<1>, then fork watchers are supported. If
3820	defined to be C<0>, then they are not.
3821
3822	=item EV_ASYNC_ENABLE
3823
3824	If undefined or defined to be C<1>, then async watchers are supported. If
3825	defined to be C<0>, then they are not.
3826
3827	=item EV_MINIMAL
3828		4706
3829	If you need to shave off some kilobytes of code at the expense of some	4707	If you need to shave off some kilobytes of code at the expense of some
3830	speed (but with the full API), define this symbol to C<1>. Currently this	4708	speed (but with the full API), you can define this symbol to request
3831	is used to override some inlining decisions, saves roughly 30% code size	4709	certain subsets of functionality. The default is to enable all features
3832	on amd64. It also selects a much smaller 2-heap for timer management over	4710	that can be enabled on the platform.
3833	the default 4-heap.
3834		4711
3835	You can save even more by disabling watcher types you do not need	4712	A typical way to use this symbol is to define it to C<0> (or to a bitset
3836	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4713	with some broad features you want) and then selectively re-enable
3837	(C<-DNDEBUG>) will usually reduce code size a lot.	4714	additional parts you want, for example if you want everything minimal,
		4715	but multiple event loop support, async and child watchers and the poll
		4716	backend, use this:
3838		4717
3839	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4718	#define EV_FEATURES 0
3840	provide a bare-bones event library. See C<ev.h> for details on what parts	4719	#define EV_MULTIPLICITY 1
3841	of the API are still available, and do not complain if this subset changes	4720	#define EV_USE_POLL 1
3842	over time.	4721	#define EV_CHILD_ENABLE 1
		4722	#define EV_ASYNC_ENABLE 1
		4723
		4724	The actual value is a bitset, it can be a combination of the following
		4725	values (by default, all of these are enabled):
		4726
		4727	=over 4
		4728
		4729	=item C<1> - faster/larger code
		4730
		4731	Use larger code to speed up some operations.
		4732
		4733	Currently this is used to override some inlining decisions (enlarging the
		4734	code size by roughly 30% on amd64).
		4735
		4736	When optimising for size, use of compiler flags such as C<-Os> with
		4737	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4738	assertions.
		4739
		4740	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4741	(e.g. gcc with C<-Os>).
		4742
		4743	=item C<2> - faster/larger data structures
		4744
		4745	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4746	hash table sizes and so on. This will usually further increase code size
		4747	and can additionally have an effect on the size of data structures at
		4748	runtime.
		4749
		4750	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4751	(e.g. gcc with C<-Os>).
		4752
		4753	=item C<4> - full API configuration
		4754
		4755	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4756	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4757
		4758	=item C<8> - full API
		4759
		4760	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4761	details on which parts of the API are still available without this
		4762	feature, and do not complain if this subset changes over time.
		4763
		4764	=item C<16> - enable all optional watcher types
		4765
		4766	Enables all optional watcher types. If you want to selectively enable
		4767	only some watcher types other than I/O and timers (e.g. prepare,
		4768	embed, async, child...) you can enable them manually by defining
		4769	C<EV_watchertype_ENABLE> to C<1> instead.
		4770
		4771	=item C<32> - enable all backends
		4772
		4773	This enables all backends - without this feature, you need to enable at
		4774	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4775
		4776	=item C<64> - enable OS-specific "helper" APIs
		4777
		4778	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4779	default.
		4780
		4781	=back
		4782
		4783	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4784	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4785	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4786	watchers, timers and monotonic clock support.
		4787
		4788	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4789	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4790	your program might be left out as well - a binary starting a timer and an
		4791	I/O watcher then might come out at only 5Kb.
		4792
		4793	=item EV_API_STATIC
		4794
		4795	If this symbol is defined (by default it is not), then all identifiers
		4796	will have static linkage. This means that libev will not export any
		4797	identifiers, and you cannot link against libev anymore. This can be useful
		4798	when you embed libev, only want to use libev functions in a single file,
		4799	and do not want its identifiers to be visible.
		4800
		4801	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4802	wants to use libev.
		4803
		4804	This option only works when libev is compiled with a C compiler, as C++
		4805	doesn't support the required declaration syntax.
		4806
		4807	=item EV_AVOID_STDIO
		4808
		4809	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4810	functions (printf, scanf, perror etc.). This will increase the code size
		4811	somewhat, but if your program doesn't otherwise depend on stdio and your
		4812	libc allows it, this avoids linking in the stdio library which is quite
		4813	big.
		4814
		4815	Note that error messages might become less precise when this option is
		4816	enabled.
3843		4817
3844	=item EV_NSIG	4818	=item EV_NSIG
3845		4819
3846	The highest supported signal number, +1 (or, the number of	4820	The highest supported signal number, +1 (or, the number of
3847	signals): Normally, libev tries to deduce the maximum number of signals	4821	signals): Normally, libev tries to deduce the maximum number of signals
3848	automatically, but sometimes this fails, in which case it can be	4822	automatically, but sometimes this fails, in which case it can be
3849	specified. Also, using a lower number than detected (C<32> should be	4823	specified. Also, using a lower number than detected (C<32> should be
3850	good for about any system in existance) can save some memory, as libev	4824	good for about any system in existence) can save some memory, as libev
3851	statically allocates some 12-24 bytes per signal number.	4825	statically allocates some 12-24 bytes per signal number.
3852		4826
3853	=item EV_PID_HASHSIZE	4827	=item EV_PID_HASHSIZE
3854		4828
3855	C<ev_child> watchers use a small hash table to distribute workload by	4829	C<ev_child> watchers use a small hash table to distribute workload by
3856	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4830	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3857	than enough. If you need to manage thousands of children you might want to	4831	usually more than enough. If you need to manage thousands of children you
3858	increase this value (I<must> be a power of two).	4832	might want to increase this value (I<must> be a power of two).
3859		4833
3860	=item EV_INOTIFY_HASHSIZE	4834	=item EV_INOTIFY_HASHSIZE
3861		4835
3862	C<ev_stat> watchers use a small hash table to distribute workload by	4836	C<ev_stat> watchers use a small hash table to distribute workload by
3863	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4837	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3864	usually more than enough. If you need to manage thousands of C<ev_stat>	4838	disabled), usually more than enough. If you need to manage thousands of
3865	watchers you might want to increase this value (I<must> be a power of	4839	C<ev_stat> watchers you might want to increase this value (I<must> be a
3866	two).	4840	power of two).
3867		4841
3868	=item EV_USE_4HEAP	4842	=item EV_USE_4HEAP
3869		4843
3870	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4844	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3871	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4845	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3872	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4846	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3873	faster performance with many (thousands) of watchers.	4847	faster performance with many (thousands) of watchers.
3874		4848
3875	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4849	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3876	(disabled).	4850	will be C<0>.
3877		4851
3878	=item EV_HEAP_CACHE_AT	4852	=item EV_HEAP_CACHE_AT
3879		4853
3880	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4854	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3881	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4855	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3882	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4856	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3883	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4857	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3884	but avoids random read accesses on heap changes. This improves performance	4858	but avoids random read accesses on heap changes. This improves performance
3885	noticeably with many (hundreds) of watchers.	4859	noticeably with many (hundreds) of watchers.
3886		4860
3887	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4861	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3888	(disabled).	4862	will be C<0>.
3889		4863
3890	=item EV_VERIFY	4864	=item EV_VERIFY
3891		4865
3892	Controls how much internal verification (see C<ev_loop_verify ()>) will	4866	Controls how much internal verification (see C<ev_verify ()>) will
3893	be done: If set to C<0>, no internal verification code will be compiled	4867	be done: If set to C<0>, no internal verification code will be compiled
3894	in. If set to C<1>, then verification code will be compiled in, but not	4868	in. If set to C<1>, then verification code will be compiled in, but not
3895	called. If set to C<2>, then the internal verification code will be	4869	called. If set to C<2>, then the internal verification code will be
3896	called once per loop, which can slow down libev. If set to C<3>, then the	4870	called once per loop, which can slow down libev. If set to C<3>, then the
3897	verification code will be called very frequently, which will slow down	4871	verification code will be called very frequently, which will slow down
3898	libev considerably.	4872	libev considerably.
3899		4873
3900	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4874	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3901	C<0>.	4875	will be C<0>.
3902		4876
3903	=item EV_COMMON	4877	=item EV_COMMON
3904		4878
3905	By default, all watchers have a C<void *data> member. By redefining	4879	By default, all watchers have a C<void *data> member. By redefining
3906	this macro to a something else you can include more and other types of	4880	this macro to something else you can include more and other types of
3907	members. You have to define it each time you include one of the files,	4881	members. You have to define it each time you include one of the files,
3908	though, and it must be identical each time.	4882	though, and it must be identical each time.
3909		4883
3910	For example, the perl EV module uses something like this:	4884	For example, the perl EV module uses something like this:
3911		4885
…		…
3964	file.	4938	file.
3965		4939
3966	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4940	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3967	that everybody includes and which overrides some configure choices:	4941	that everybody includes and which overrides some configure choices:
3968		4942
3969	#define EV_MINIMAL 1	4943	#define EV_FEATURES 8
3970	#define EV_USE_POLL 0	4944	#define EV_USE_SELECT 1
3971	#define EV_MULTIPLICITY 0
3972	#define EV_PERIODIC_ENABLE 0	4945	#define EV_PREPARE_ENABLE 1
		4946	#define EV_IDLE_ENABLE 1
3973	#define EV_STAT_ENABLE 0	4947	#define EV_SIGNAL_ENABLE 1
3974	#define EV_FORK_ENABLE 0	4948	#define EV_CHILD_ENABLE 1
		4949	#define EV_USE_STDEXCEPT 0
3975	#define EV_CONFIG_H <config.h>	4950	#define EV_CONFIG_H <config.h>
3976	#define EV_MINPRI 0
3977	#define EV_MAXPRI 0
3978		4951
3979	#include "ev++.h"	4952	#include "ev++.h"
3980		4953
3981	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4954	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3982		4955
3983	#include "ev_cpp.h"	4956	#include "ev_cpp.h"
3984	#include "ev.c"	4957	#include "ev.c"
3985		4958
3986	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4959	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3987		4960
3988	=head2 THREADS AND COROUTINES	4961	=head2 THREADS AND COROUTINES
3989		4962
3990	=head3 THREADS	4963	=head3 THREADS
3991		4964
…		…
4042	default loop and triggering an C<ev_async> watcher from the default loop	5015	default loop and triggering an C<ev_async> watcher from the default loop
4043	watcher callback into the event loop interested in the signal.	5016	watcher callback into the event loop interested in the signal.
4044		5017
4045	=back	5018	=back
4046		5019
4047	=head4 THREAD LOCKING EXAMPLE	5020	See also L</THREAD LOCKING EXAMPLE>.
4048
4049	Here is a fictitious example of how to run an event loop in a different
4050	thread than where callbacks are being invoked and watchers are
4051	created/added/removed.
4052
4053	For a real-world example, see the C<EV::Loop::Async> perl module,
4054	which uses exactly this technique (which is suited for many high-level
4055	languages).
4056
4057	The example uses a pthread mutex to protect the loop data, a condition
4058	variable to wait for callback invocations, an async watcher to notify the
4059	event loop thread and an unspecified mechanism to wake up the main thread.
4060
4061	First, you need to associate some data with the event loop:
4062
4063	typedef struct {
4064	mutex_t lock; /* global loop lock */
4065	ev_async async_w;
4066	thread_t tid;
4067	cond_t invoke_cv;
4068	} userdata;
4069
4070	void prepare_loop (EV_P)
4071	{
4072	// for simplicity, we use a static userdata struct.
4073	static userdata u;
4074
4075	ev_async_init (&u->async_w, async_cb);
4076	ev_async_start (EV_A_ &u->async_w);
4077
4078	pthread_mutex_init (&u->lock, 0);
4079	pthread_cond_init (&u->invoke_cv, 0);
4080
4081	// now associate this with the loop
4082	ev_set_userdata (EV_A_ u);
4083	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4084	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4085
4086	// then create the thread running ev_loop
4087	pthread_create (&u->tid, 0, l_run, EV_A);
4088	}
4089
4090	The callback for the C<ev_async> watcher does nothing: the watcher is used
4091	solely to wake up the event loop so it takes notice of any new watchers
4092	that might have been added:
4093
4094	static void
4095	async_cb (EV_P_ ev_async *w, int revents)
4096	{
4097	// just used for the side effects
4098	}
4099
4100	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4101	protecting the loop data, respectively.
4102
4103	static void
4104	l_release (EV_P)
4105	{
4106	userdata *u = ev_userdata (EV_A);
4107	pthread_mutex_unlock (&u->lock);
4108	}
4109
4110	static void
4111	l_acquire (EV_P)
4112	{
4113	userdata *u = ev_userdata (EV_A);
4114	pthread_mutex_lock (&u->lock);
4115	}
4116
4117	The event loop thread first acquires the mutex, and then jumps straight
4118	into C<ev_loop>:
4119
4120	void *
4121	l_run (void *thr_arg)
4122	{
4123	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4124
4125	l_acquire (EV_A);
4126	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4127	ev_loop (EV_A_ 0);
4128	l_release (EV_A);
4129
4130	return 0;
4131	}
4132
4133	Instead of invoking all pending watchers, the C<l_invoke> callback will
4134	signal the main thread via some unspecified mechanism (signals? pipe
4135	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4136	have been called (in a while loop because a) spurious wakeups are possible
4137	and b) skipping inter-thread-communication when there are no pending
4138	watchers is very beneficial):
4139
4140	static void
4141	l_invoke (EV_P)
4142	{
4143	userdata *u = ev_userdata (EV_A);
4144
4145	while (ev_pending_count (EV_A))
4146	{
4147	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4148	pthread_cond_wait (&u->invoke_cv, &u->lock);
4149	}
4150	}
4151
4152	Now, whenever the main thread gets told to invoke pending watchers, it
4153	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4154	thread to continue:
4155
4156	static void
4157	real_invoke_pending (EV_P)
4158	{
4159	userdata *u = ev_userdata (EV_A);
4160
4161	pthread_mutex_lock (&u->lock);
4162	ev_invoke_pending (EV_A);
4163	pthread_cond_signal (&u->invoke_cv);
4164	pthread_mutex_unlock (&u->lock);
4165	}
4166
4167	Whenever you want to start/stop a watcher or do other modifications to an
4168	event loop, you will now have to lock:
4169
4170	ev_timer timeout_watcher;
4171	userdata *u = ev_userdata (EV_A);
4172
4173	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4174
4175	pthread_mutex_lock (&u->lock);
4176	ev_timer_start (EV_A_ &timeout_watcher);
4177	ev_async_send (EV_A_ &u->async_w);
4178	pthread_mutex_unlock (&u->lock);
4179
4180	Note that sending the C<ev_async> watcher is required because otherwise
4181	an event loop currently blocking in the kernel will have no knowledge
4182	about the newly added timer. By waking up the loop it will pick up any new
4183	watchers in the next event loop iteration.
4184		5021
4185	=head3 COROUTINES	5022	=head3 COROUTINES
4186		5023
4187	Libev is very accommodating to coroutines ("cooperative threads"):	5024	Libev is very accommodating to coroutines ("cooperative threads"):
4188	libev fully supports nesting calls to its functions from different	5025	libev fully supports nesting calls to its functions from different
4189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5026	coroutines (e.g. you can call C<ev_run> on the same loop from two
4190	different coroutines, and switch freely between both coroutines running	5027	different coroutines, and switch freely between both coroutines running
4191	the loop, as long as you don't confuse yourself). The only exception is	5028	the loop, as long as you don't confuse yourself). The only exception is
4192	that you must not do this from C<ev_periodic> reschedule callbacks.	5029	that you must not do this from C<ev_periodic> reschedule callbacks.
4193		5030
4194	Care has been taken to ensure that libev does not keep local state inside	5031	Care has been taken to ensure that libev does not keep local state inside
4195	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5032	C<ev_run>, and other calls do not usually allow for coroutine switches as
4196	they do not call any callbacks.	5033	they do not call any callbacks.
4197		5034
4198	=head2 COMPILER WARNINGS	5035	=head2 COMPILER WARNINGS
4199		5036
4200	Depending on your compiler and compiler settings, you might get no or a	5037	Depending on your compiler and compiler settings, you might get no or a
…		…
4211	maintainable.	5048	maintainable.
4212		5049
4213	And of course, some compiler warnings are just plain stupid, or simply	5050	And of course, some compiler warnings are just plain stupid, or simply
4214	wrong (because they don't actually warn about the condition their message	5051	wrong (because they don't actually warn about the condition their message
4215	seems to warn about). For example, certain older gcc versions had some	5052	seems to warn about). For example, certain older gcc versions had some
4216	warnings that resulted an extreme number of false positives. These have	5053	warnings that resulted in an extreme number of false positives. These have
4217	been fixed, but some people still insist on making code warn-free with	5054	been fixed, but some people still insist on making code warn-free with
4218	such buggy versions.	5055	such buggy versions.
4219		5056
4220	While libev is written to generate as few warnings as possible,	5057	While libev is written to generate as few warnings as possible,
4221	"warn-free" code is not a goal, and it is recommended not to build libev	5058	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4257	I suggest using suppression lists.	5094	I suggest using suppression lists.
4258		5095
4259		5096
4260	=head1 PORTABILITY NOTES	5097	=head1 PORTABILITY NOTES
4261		5098
		5099	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5100
		5101	GNU/Linux is the only common platform that supports 64 bit file/large file
		5102	interfaces but I<disables> them by default.
		5103
		5104	That means that libev compiled in the default environment doesn't support
		5105	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5106
		5107	Unfortunately, many programs try to work around this GNU/Linux issue
		5108	by enabling the large file API, which makes them incompatible with the
		5109	standard libev compiled for their system.
		5110
		5111	Likewise, libev cannot enable the large file API itself as this would
		5112	suddenly make it incompatible to the default compile time environment,
		5113	i.e. all programs not using special compile switches.
		5114
		5115	=head2 OS/X AND DARWIN BUGS
		5116
		5117	The whole thing is a bug if you ask me - basically any system interface
		5118	you touch is broken, whether it is locales, poll, kqueue or even the
		5119	OpenGL drivers.
		5120
		5121	=head3 C<kqueue> is buggy
		5122
		5123	The kqueue syscall is broken in all known versions - most versions support
		5124	only sockets, many support pipes.
		5125
		5126	Libev tries to work around this by not using C<kqueue> by default on this
		5127	rotten platform, but of course you can still ask for it when creating a
		5128	loop - embedding a socket-only kqueue loop into a select-based one is
		5129	probably going to work well.
		5130
		5131	=head3 C<poll> is buggy
		5132
		5133	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5134	implementation by something calling C<kqueue> internally around the 10.5.6
		5135	release, so now C<kqueue> I<and> C<poll> are broken.
		5136
		5137	Libev tries to work around this by not using C<poll> by default on
		5138	this rotten platform, but of course you can still ask for it when creating
		5139	a loop.
		5140
		5141	=head3 C<select> is buggy
		5142
		5143	All that's left is C<select>, and of course Apple found a way to fuck this
		5144	one up as well: On OS/X, C<select> actively limits the number of file
		5145	descriptors you can pass in to 1024 - your program suddenly crashes when
		5146	you use more.
		5147
		5148	There is an undocumented "workaround" for this - defining
		5149	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5150	work on OS/X.
		5151
		5152	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5153
		5154	=head3 C<errno> reentrancy
		5155
		5156	The default compile environment on Solaris is unfortunately so
		5157	thread-unsafe that you can't even use components/libraries compiled
		5158	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5159	defined by default. A valid, if stupid, implementation choice.
		5160
		5161	If you want to use libev in threaded environments you have to make sure
		5162	it's compiled with C<_REENTRANT> defined.
		5163
		5164	=head3 Event port backend
		5165
		5166	The scalable event interface for Solaris is called "event
		5167	ports". Unfortunately, this mechanism is very buggy in all major
		5168	releases. If you run into high CPU usage, your program freezes or you get
		5169	a large number of spurious wakeups, make sure you have all the relevant
		5170	and latest kernel patches applied. No, I don't know which ones, but there
		5171	are multiple ones to apply, and afterwards, event ports actually work
		5172	great.
		5173
		5174	If you can't get it to work, you can try running the program by setting
		5175	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5176	C<select> backends.
		5177
		5178	=head2 AIX POLL BUG
		5179
		5180	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5181	this by trying to avoid the poll backend altogether (i.e. it's not even
		5182	compiled in), which normally isn't a big problem as C<select> works fine
		5183	with large bitsets on AIX, and AIX is dead anyway.
		5184
4262	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5185	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5186
		5187	=head3 General issues
4263		5188
4264	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5189	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4265	requires, and its I/O model is fundamentally incompatible with the POSIX	5190	requires, and its I/O model is fundamentally incompatible with the POSIX
4266	model. Libev still offers limited functionality on this platform in	5191	model. Libev still offers limited functionality on this platform in
4267	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5192	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4268	descriptors. This only applies when using Win32 natively, not when using	5193	descriptors. This only applies when using Win32 natively, not when using
4269	e.g. cygwin.	5194	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5195	as every compiler comes with a slightly differently broken/incompatible
		5196	environment.
4270		5197
4271	Lifting these limitations would basically require the full	5198	Lifting these limitations would basically require the full
4272	re-implementation of the I/O system. If you are into these kinds of	5199	re-implementation of the I/O system. If you are into this kind of thing,
4273	things, then note that glib does exactly that for you in a very portable	5200	then note that glib does exactly that for you in a very portable way (note
4274	way (note also that glib is the slowest event library known to man).	5201	also that glib is the slowest event library known to man).
4275		5202
4276	There is no supported compilation method available on windows except	5203	There is no supported compilation method available on windows except
4277	embedding it into other applications.	5204	embedding it into other applications.
4278		5205
4279	Sensible signal handling is officially unsupported by Microsoft - libev	5206	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4307	you do I<not> compile the F<ev.c> or any other embedded source files!):	5234	you do I<not> compile the F<ev.c> or any other embedded source files!):
4308		5235
4309	#include "evwrap.h"	5236	#include "evwrap.h"
4310	#include "ev.c"	5237	#include "ev.c"
4311		5238
4312	=over 4
4313
4314	=item The winsocket select function	5239	=head3 The winsocket C<select> function
4315		5240
4316	The winsocket C<select> function doesn't follow POSIX in that it	5241	The winsocket C<select> function doesn't follow POSIX in that it
4317	requires socket I<handles> and not socket I<file descriptors> (it is	5242	requires socket I<handles> and not socket I<file descriptors> (it is
4318	also extremely buggy). This makes select very inefficient, and also	5243	also extremely buggy). This makes select very inefficient, and also
4319	requires a mapping from file descriptors to socket handles (the Microsoft	5244	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4328	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5253	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4329		5254
4330	Note that winsockets handling of fd sets is O(n), so you can easily get a	5255	Note that winsockets handling of fd sets is O(n), so you can easily get a
4331	complexity in the O(n²) range when using win32.	5256	complexity in the O(n²) range when using win32.
4332		5257
4333	=item Limited number of file descriptors	5258	=head3 Limited number of file descriptors
4334		5259
4335	Windows has numerous arbitrary (and low) limits on things.	5260	Windows has numerous arbitrary (and low) limits on things.
4336		5261
4337	Early versions of winsocket's select only supported waiting for a maximum	5262	Early versions of winsocket's select only supported waiting for a maximum
4338	of C<64> handles (probably owning to the fact that all windows kernels	5263	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4353	runtime libraries. This might get you to about C<512> or C<2048> sockets	5278	runtime libraries. This might get you to about C<512> or C<2048> sockets
4354	(depending on windows version and/or the phase of the moon). To get more,	5279	(depending on windows version and/or the phase of the moon). To get more,
4355	you need to wrap all I/O functions and provide your own fd management, but	5280	you need to wrap all I/O functions and provide your own fd management, but
4356	the cost of calling select (O(n²)) will likely make this unworkable.	5281	the cost of calling select (O(n²)) will likely make this unworkable.
4357		5282
4358	=back
4359
4360	=head2 PORTABILITY REQUIREMENTS	5283	=head2 PORTABILITY REQUIREMENTS
4361		5284
4362	In addition to a working ISO-C implementation and of course the	5285	In addition to a working ISO-C implementation and of course the
4363	backend-specific APIs, libev relies on a few additional extensions:	5286	backend-specific APIs, libev relies on a few additional extensions:
4364		5287
…		…
4370	Libev assumes not only that all watcher pointers have the same internal	5293	Libev assumes not only that all watcher pointers have the same internal
4371	structure (guaranteed by POSIX but not by ISO C for example), but it also	5294	structure (guaranteed by POSIX but not by ISO C for example), but it also
4372	assumes that the same (machine) code can be used to call any watcher	5295	assumes that the same (machine) code can be used to call any watcher
4373	callback: The watcher callbacks have different type signatures, but libev	5296	callback: The watcher callbacks have different type signatures, but libev
4374	calls them using an C<ev_watcher *> internally.	5297	calls them using an C<ev_watcher *> internally.
		5298
		5299	=item pointer accesses must be thread-atomic
		5300
		5301	Accessing a pointer value must be atomic, it must both be readable and
		5302	writable in one piece - this is the case on all current architectures.
4375		5303
4376	=item C<sig_atomic_t volatile> must be thread-atomic as well	5304	=item C<sig_atomic_t volatile> must be thread-atomic as well
4377		5305
4378	The type C<sig_atomic_t volatile> (or whatever is defined as	5306	The type C<sig_atomic_t volatile> (or whatever is defined as
4379	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5307	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4388	thread" or will block signals process-wide, both behaviours would	5316	thread" or will block signals process-wide, both behaviours would
4389	be compatible with libev. Interaction between C<sigprocmask> and	5317	be compatible with libev. Interaction between C<sigprocmask> and
4390	C<pthread_sigmask> could complicate things, however.	5318	C<pthread_sigmask> could complicate things, however.
4391		5319
4392	The most portable way to handle signals is to block signals in all threads	5320	The most portable way to handle signals is to block signals in all threads
4393	except the initial one, and run the default loop in the initial thread as	5321	except the initial one, and run the signal handling loop in the initial
4394	well.	5322	thread as well.
4395		5323
4396	=item C<long> must be large enough for common memory allocation sizes	5324	=item C<long> must be large enough for common memory allocation sizes
4397		5325
4398	To improve portability and simplify its API, libev uses C<long> internally	5326	To improve portability and simplify its API, libev uses C<long> internally
4399	instead of C<size_t> when allocating its data structures. On non-POSIX	5327	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4402	watchers.	5330	watchers.
4403		5331
4404	=item C<double> must hold a time value in seconds with enough accuracy	5332	=item C<double> must hold a time value in seconds with enough accuracy
4405		5333
4406	The type C<double> is used to represent timestamps. It is required to	5334	The type C<double> is used to represent timestamps. It is required to
4407	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5335	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4408	enough for at least into the year 4000. This requirement is fulfilled by	5336	good enough for at least into the year 4000 with millisecond accuracy
		5337	(the design goal for libev). This requirement is overfulfilled by
4409	implementations implementing IEEE 754, which is basically all existing	5338	implementations using IEEE 754, which is basically all existing ones.
		5339
4410	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5340	With IEEE 754 doubles, you get microsecond accuracy until at least the
4411	2200.	5341	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5342	is either obsolete or somebody patched it to use C<long double> or
		5343	something like that, just kidding).
4412		5344
4413	=back	5345	=back
4414		5346
4415	If you know of other additional requirements drop me a note.	5347	If you know of other additional requirements drop me a note.
4416		5348
…		…
4478	=item Processing ev_async_send: O(number_of_async_watchers)	5410	=item Processing ev_async_send: O(number_of_async_watchers)
4479		5411
4480	=item Processing signals: O(max_signal_number)	5412	=item Processing signals: O(max_signal_number)
4481		5413
4482	Sending involves a system call I<iff> there were no other C<ev_async_send>	5414	Sending involves a system call I<iff> there were no other C<ev_async_send>
4483	calls in the current loop iteration. Checking for async and signal events	5415	calls in the current loop iteration and the loop is currently
		5416	blocked. Checking for async and signal events involves iterating over all
4484	involves iterating over all running async watchers or all signal numbers.	5417	running async watchers or all signal numbers.
4485		5418
4486	=back	5419	=back
4487		5420
4488		5421
		5422	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5423
		5424	The major version 4 introduced some incompatible changes to the API.
		5425
		5426	At the moment, the C<ev.h> header file provides compatibility definitions
		5427	for all changes, so most programs should still compile. The compatibility
		5428	layer might be removed in later versions of libev, so better update to the
		5429	new API early than late.
		5430
		5431	=over 4
		5432
		5433	=item C<EV_COMPAT3> backwards compatibility mechanism
		5434
		5435	The backward compatibility mechanism can be controlled by
		5436	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5437	section.
		5438
		5439	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5440
		5441	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5442
		5443	ev_loop_destroy (EV_DEFAULT_UC);
		5444	ev_loop_fork (EV_DEFAULT);
		5445
		5446	=item function/symbol renames
		5447
		5448	A number of functions and symbols have been renamed:
		5449
		5450	ev_loop => ev_run
		5451	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5452	EVLOOP_ONESHOT => EVRUN_ONCE
		5453
		5454	ev_unloop => ev_break
		5455	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5456	EVUNLOOP_ONE => EVBREAK_ONE
		5457	EVUNLOOP_ALL => EVBREAK_ALL
		5458
		5459	EV_TIMEOUT => EV_TIMER
		5460
		5461	ev_loop_count => ev_iteration
		5462	ev_loop_depth => ev_depth
		5463	ev_loop_verify => ev_verify
		5464
		5465	Most functions working on C<struct ev_loop> objects don't have an
		5466	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5467	associated constants have been renamed to not collide with the C<struct
		5468	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5469	as all other watcher types. Note that C<ev_loop_fork> is still called
		5470	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5471	typedef.
		5472
		5473	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5474
		5475	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5476	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5477	and work, but the library code will of course be larger.
		5478
		5479	=back
		5480
		5481
4489	=head1 GLOSSARY	5482	=head1 GLOSSARY
4490		5483
4491	=over 4	5484	=over 4
4492		5485
4493	=item active	5486	=item active
4494		5487
4495	A watcher is active as long as it has been started (has been attached to	5488	A watcher is active as long as it has been started and not yet stopped.
4496	an event loop) but not yet stopped (disassociated from the event loop).	5489	See L</WATCHER STATES> for details.
4497		5490
4498	=item application	5491	=item application
4499		5492
4500	In this document, an application is whatever is using libev.	5493	In this document, an application is whatever is using libev.
		5494
		5495	=item backend
		5496
		5497	The part of the code dealing with the operating system interfaces.
4501		5498
4502	=item callback	5499	=item callback
4503		5500
4504	The address of a function that is called when some event has been	5501	The address of a function that is called when some event has been
4505	detected. Callbacks are being passed the event loop, the watcher that	5502	detected. Callbacks are being passed the event loop, the watcher that
4506	received the event, and the actual event bitset.	5503	received the event, and the actual event bitset.
4507		5504
4508	=item callback invocation	5505	=item callback/watcher invocation
4509		5506
4510	The act of calling the callback associated with a watcher.	5507	The act of calling the callback associated with a watcher.
4511		5508
4512	=item event	5509	=item event
4513		5510
4514	A change of state of some external event, such as data now being available	5511	A change of state of some external event, such as data now being available
4515	for reading on a file descriptor, time having passed or simply not having	5512	for reading on a file descriptor, time having passed or simply not having
4516	any other events happening anymore.	5513	any other events happening anymore.
4517		5514
4518	In libev, events are represented as single bits (such as C<EV_READ> or	5515	In libev, events are represented as single bits (such as C<EV_READ> or
4519	C<EV_TIMEOUT>).	5516	C<EV_TIMER>).
4520		5517
4521	=item event library	5518	=item event library
4522		5519
4523	A software package implementing an event model and loop.	5520	A software package implementing an event model and loop.
4524		5521
…		…
4532	The model used to describe how an event loop handles and processes	5529	The model used to describe how an event loop handles and processes
4533	watchers and events.	5530	watchers and events.
4534		5531
4535	=item pending	5532	=item pending
4536		5533
4537	A watcher is pending as soon as the corresponding event has been detected,	5534	A watcher is pending as soon as the corresponding event has been
4538	and stops being pending as soon as the watcher will be invoked or its	5535	detected. See L</WATCHER STATES> for details.
4539	pending status is explicitly cleared by the application.
4540
4541	A watcher can be pending, but not active. Stopping a watcher also clears
4542	its pending status.
4543		5536
4544	=item real time	5537	=item real time
4545		5538
4546	The physical time that is observed. It is apparently strictly monotonic :)	5539	The physical time that is observed. It is apparently strictly monotonic :)
4547		5540
4548	=item wall-clock time	5541	=item wall-clock time
4549		5542
4550	The time and date as shown on clocks. Unlike real time, it can actually	5543	The time and date as shown on clocks. Unlike real time, it can actually
4551	be wrong and jump forwards and backwards, e.g. when the you adjust your	5544	be wrong and jump forwards and backwards, e.g. when you adjust your
4552	clock.	5545	clock.
4553		5546
4554	=item watcher	5547	=item watcher
4555		5548
4556	A data structure that describes interest in certain events. Watchers need	5549	A data structure that describes interest in certain events. Watchers need
4557	to be started (attached to an event loop) before they can receive events.	5550	to be started (attached to an event loop) before they can receive events.
4558		5551
4559	=item watcher invocation
4560
4561	The act of calling the callback associated with a watcher.
4562
4563	=back	5552	=back
4564		5553
4565	=head1 AUTHOR	5554	=head1 AUTHOR
4566		5555
4567	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5556	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5557	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4568		5558

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