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Revision 1.438 by root, Tue Jan 12 05:52:44 2016 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
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	without a system call and thus I<very> fast, but my GNU/Linux system also has
359	C<pthread_atfork> which is even faster).	418	C<pthread_atfork> which is even faster).
360		419
361	The big advantage of this flag is that you can forget about fork (and	420	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	421	forget about forgetting to tell libev about forking, although you still
363	flag.	422	have to ignore C<SIGPIPE>) when you use this flag.
364		423
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	424	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
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
605	to reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
606	name, you can call it anytime, but it makes most sense after forking, in	689	the name, you can call it anytime you are allowed to start or stop
607	the child process (or both child and parent, but that again makes little	690	watchers (except inside an C<ev_prepare> callback), but it makes most
608	sense). You I<must> call it in the child before using any of the libev	691	sense after forking, in the child process. You I<must> call it (or use
609	functions, and it will only take effect at the next C<ev_loop> iteration.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		693
		694	In addition, if you want to reuse a loop (via this function or
		695	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		696
		697	Again, you I<have> to call it on I<any> loop that you want to re-use after
		698	a fork, I<even if you do not plan to use the loop in the parent>. This is
		699	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		700	during fork.
610		701
611	On the other hand, you only need to call this function in the child	702	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	703	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.	704	you just fork+exec or create a new loop in the child, you don't have to
		705	call it at all (in fact, C<epoll> is so badly broken that it makes a
		706	difference, but libev will usually detect this case on its own and do a
		707	costly reset of the backend).
614		708
615	The function itself is quite fast and it's usually not a problem to call	709	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	710	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		711
		712	Example: Automate calling C<ev_loop_fork> on the default loop when
		713	using pthreads.
		714
		715	static void
		716	post_fork_child (void)
		717	{
		718	ev_loop_fork (EV_DEFAULT);
		719	}
		720
		721	...
619	pthread_atfork (0, 0, ev_default_fork);	722	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		723
628	=item int ev_is_default_loop (loop)	724	=item int ev_is_default_loop (loop)
629		725
630	Returns true when the given loop is, in fact, the default loop, and false	726	Returns true when the given loop is, in fact, the default loop, and false
631	otherwise.	727	otherwise.
632		728
633	=item unsigned int ev_loop_count (loop)	729	=item unsigned int ev_iteration (loop)
634		730
635	Returns the count of loop iterations for the loop, which is identical to	731	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	732	to the number of times libev did poll for new events. It starts at C<0>
637	happily wraps around with enough iterations.	733	and happily wraps around with enough iterations.
638		734
639	This value can sometimes be useful as a generation counter of sorts (it	735	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	736	"ticks" the number of loop iterations), as it roughly corresponds with
641	C<ev_prepare> and C<ev_check> calls.	737	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		738	prepare and check phases.
642		739
643	=item unsigned int ev_loop_depth (loop)	740	=item unsigned int ev_depth (loop)
644		741
645	Returns the number of times C<ev_loop> was entered minus the number of	742	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.	743	times C<ev_run> was exited normally, in other words, the recursion depth.
647		744
648	Outside C<ev_loop>, this number is zero. In a callback, this number is	745	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),	746	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
650	in which case it is higher.	747	in which case it is higher.
651		748
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	749	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	etc.), doesn't count as exit.	750	throwing an exception etc.), doesn't count as "exit" - consider this
		751	as a hint to avoid such ungentleman-like behaviour unless it's really
		752	convenient, in which case it is fully supported.
654		753
655	=item unsigned int ev_backend (loop)	754	=item unsigned int ev_backend (loop)
656		755
657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	756	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
658	use.	757	use.
…		…
667		766
668	=item ev_now_update (loop)	767	=item ev_now_update (loop)
669		768
670	Establishes the current time by querying the kernel, updating the time	769	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	770	returned by C<ev_now ()> in the progress. This is a costly operation and
672	is usually done automatically within C<ev_loop ()>.	771	is usually done automatically within C<ev_run ()>.
673		772
674	This function is rarely useful, but when some event callback runs for a	773	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	774	very long time without entering the event loop, updating libev's idea of
676	the current time is a good idea.	775	the current time is a good idea.
677		776
678	See also L<The special problem of time updates> in the C<ev_timer> section.	777	See also L</The special problem of time updates> in the C<ev_timer> section.
679		778
680	=item ev_suspend (loop)	779	=item ev_suspend (loop)
681		780
682	=item ev_resume (loop)	781	=item ev_resume (loop)
683		782
684	These two functions suspend and resume a loop, for use when the loop is	783	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.	784	loop is not used for a while and timeouts should not be processed.
686		785
687	A typical use case would be an interactive program such as a game: When	786	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	787	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	788	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>	789	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	791	C<ev_resume> directly afterwards to resume timer processing.
693		792
694	Effectively, all C<ev_timer> watchers will be delayed by the time spend	793	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	794	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	795	will be rescheduled (that is, they will lose any events that would have
697	occured while suspended).	796	occurred while suspended).
698		797
699	After calling C<ev_suspend> you B<must not> call I<any> function on the	798	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>	799	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>.	800	without a previous call to C<ev_suspend>.
702		801
703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	802	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
704	event loop time (see C<ev_now_update>).	803	event loop time (see C<ev_now_update>).
705		804
706	=item ev_loop (loop, int flags)	805	=item bool ev_run (loop, int flags)
707		806
708	Finally, this is it, the event handler. This function usually is called	807	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	808	after you have initialised all your watchers and you want to start
710	events.	809	handling events. It will ask the operating system for any new events, call
		810	the watcher callbacks, and then repeat the whole process indefinitely: This
		811	is why event loops are called I<loops>.
711		812
712	If the flags argument is specified as C<0>, it will not return until	813	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.	814	until either no event watchers are active anymore or C<ev_break> was
		815	called.
714		816
		817	The return value is false if there are no more active watchers (which
		818	usually means "all jobs done" or "deadlock"), and true in all other cases
		819	(which usually means " you should call C<ev_run> again").
		820
715	Please note that an explicit C<ev_unloop> is usually better than	821	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	822	relying on all watchers to be stopped when deciding when a program has
717	finished (especially in interactive programs), but having a program	823	finished (especially in interactive programs), but having a program
718	that automatically loops as long as it has to and no longer by virtue	824	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	825	of relying on its watchers stopping correctly, that is truly a thing of
720	beauty.	826	beauty.
721		827
		828	This function is I<mostly> exception-safe - you can break out of a
		829	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		830	exception and so on. This does not decrement the C<ev_depth> value, nor
		831	will it clear any outstanding C<EVBREAK_ONE> breaks.
		832
722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	833	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	834	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	835	block your process in case there are no events and will return after one
725	the loop.	836	iteration of the loop. This is sometimes useful to poll and handle new
		837	events while doing lengthy calculations, to keep the program responsive.
726		838
727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	839	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	840	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	841	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	842	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	843	user-registered callback will be called), and will return after one
732	iteration of the loop.	844	iteration of the loop.
733		845
734	This is useful if you are waiting for some external event in conjunction	846	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	847	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	848	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.	849	usually a better approach for this kind of thing.
738		850
739	Here are the gory details of what C<ev_loop> does:	851	Here are the gory details of what C<ev_run> does (this is for your
		852	understanding, not a guarantee that things will work exactly like this in
		853	future versions):
740		854
		855	- Increment loop depth.
		856	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	857	- Before the first iteration, call any pending watchers.
		858	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	859	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- If a fork was detected (by any means), queue and call all fork watchers.	860	- If a fork was detected (by any means), queue and call all fork watchers.
744	- Queue and call all prepare watchers.	861	- Queue and call all prepare watchers.
		862	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	863	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	864	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	865	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	866	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	867	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	868	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	869	any active watchers at all will result in not sleeping).
752	- Sleep if the I/O and timer collect interval say so.	870	- Sleep if the I/O and timer collect interval say so.
		871	- Increment loop iteration counter.
753	- Block the process, waiting for any events.	872	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	873	- Queue all outstanding I/O (fd) events.
755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	874	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
756	- Queue all expired timers.	875	- Queue all expired timers.
757	- Queue all expired periodics.	876	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	877	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	878	- Queue all check watchers.
760	- Call all queued watchers in reverse order (i.e. check watchers first).	879	- 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	880	Signals and child watchers are implemented as I/O watchers, and will
762	be handled here by queueing them when their watcher gets executed.	881	be handled here by queueing them when their watcher gets executed.
763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	882	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
764	were used, or there are no active watchers, return, otherwise	883	were used, or there are no active watchers, goto FINISH, otherwise
765	continue with step *.	884	continue with step LOOP.
		885	FINISH:
		886	- Reset the ev_break status iff it was EVBREAK_ONE.
		887	- Decrement the loop depth.
		888	- Return.
766		889
767	Example: Queue some jobs and then loop until no events are outstanding	890	Example: Queue some jobs and then loop until no events are outstanding
768	anymore.	891	anymore.
769		892
770	... queue jobs here, make sure they register event watchers as long	893	... 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..)	894	... as they still have work to do (even an idle watcher will do..)
772	ev_loop (my_loop, 0);	895	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	896	... jobs done or somebody called break. yeah!
774		897
775	=item ev_unloop (loop, how)	898	=item ev_break (loop, how)
776		899
777	Can be used to make a call to C<ev_loop> return early (but only after it	900	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	901	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	902	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.	903	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
781		904
782	This "unloop state" will be cleared when entering C<ev_loop> again.	905	This "break state" will be cleared on the next call to C<ev_run>.
783		906
784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	907	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		908	which case it will have no effect.
785		909
786	=item ev_ref (loop)	910	=item ev_ref (loop)
787		911
788	=item ev_unref (loop)	912	=item ev_unref (loop)
789		913
790	Ref/unref can be used to add or remove a reference count on the event	914	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	915	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.	916	count is nonzero, C<ev_run> will not return on its own.
793		917
794	If you have a watcher you never unregister that should not keep C<ev_loop>	918	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	919	unregister, but that nevertheless should not keep C<ev_run> from
		920	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796	stopping it.	921	before stopping it.
797		922
798	As an example, libev itself uses this for its internal signal pipe: It	923	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	924	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	925	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	926	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	927	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	928	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	929	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>	930	(e.g. non-repeating timers) in which case you have to C<ev_ref>
806	in the callback).	931	in the callback).
807		932
808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	933	Example: Create a signal watcher, but keep it from keeping C<ev_run>
809	running when nothing else is active.	934	running when nothing else is active.
810		935
811	ev_signal exitsig;	936	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	937	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	938	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	939	ev_unref (loop);
815		940
816	Example: For some weird reason, unregister the above signal handler again.	941	Example: For some weird reason, unregister the above signal handler again.
817		942
818	ev_ref (loop);	943	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	944	ev_signal_stop (loop, &exitsig);
…		…
839	overhead for the actual polling but can deliver many events at once.	964	overhead for the actual polling but can deliver many events at once.
840		965
841	By setting a higher I<io collect interval> you allow libev to spend more	966	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,	967	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	968	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	969	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	970	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	971	sleep time ensures that libev will not poll for I/O events more often then
847	once per this interval, on average.	972	once per this interval, on average (as long as the host time resolution is
		973	good enough).
848		974
849	Likewise, by setting a higher I<timeout collect interval> you allow libev	975	Likewise, by setting a higher I<timeout collect interval> you allow libev
850	to spend more time collecting timeouts, at the expense of increased	976	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	977	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	978	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>,	984	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	985	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	986	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	987	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,	988	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).	989	then you can't do more than 100 transactions per second).
864		990
865	Setting the I<timeout collect interval> can improve the opportunity for	991	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	992	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	993	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	994	times the process sleeps and wakes up again. Another useful technique to
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1002	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		1003
878	=item ev_invoke_pending (loop)	1004	=item ev_invoke_pending (loop)
879		1005
880	This call will simply invoke all pending watchers while resetting their	1006	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	1007	pending state. Normally, C<ev_run> does this automatically when required,
882	but when overriding the invoke callback this call comes handy.	1008	but when overriding the invoke callback this call comes handy. This
		1009	function can be invoked from a watcher - this can be useful for example
		1010	when you want to do some lengthy calculation and want to pass further
		1011	event handling to another thread (you still have to make sure only one
		1012	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
883		1013
884	=item int ev_pending_count (loop)	1014	=item int ev_pending_count (loop)
885		1015
886	Returns the number of pending watchers - zero indicates that no watchers	1016	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1017	are pending.
888		1018
889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1019	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
890		1020
891	This overrides the invoke pending functionality of the loop: Instead of	1021	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	1022	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	1023	this callback instead. This is useful, for example, when you want to
894	invoke the actual watchers inside another context (another thread etc.).	1024	invoke the actual watchers inside another context (another thread etc.).
895		1025
896	If you want to reset the callback, use C<ev_invoke_pending> as new	1026	If you want to reset the callback, use C<ev_invoke_pending> as new
897	callback.	1027	callback.
898		1028
899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1029	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
900		1030
901	Sometimes you want to share the same loop between multiple threads. This	1031	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	1032	can be done relatively simply by putting mutex_lock/unlock calls around
903	each call to a libev function.	1033	each call to a libev function.
904		1034
905	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1035	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	1036	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>	1037	loop via C<ev_break> and C<ev_async_send>, another way is to set these
908	and I<acquire> callbacks on the loop.	1038	I<release> and I<acquire> callbacks on the loop.
909		1039
910	When set, then C<release> will be called just before the thread is	1040	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	1041	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1042	afterwards.
913		1043
…		…
916		1046
917	While event loop modifications are allowed between invocations of	1047	While event loop modifications are allowed between invocations of
918	C<release> and C<acquire> (that's their only purpose after all), no	1048	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	1049	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	1050	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	1051	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.	1052	to take note of any changes you made.
923		1053
924	In theory, threads executing C<ev_loop> will be async-cancel safe between	1054	In theory, threads executing C<ev_run> will be async-cancel safe between
925	invocations of C<release> and C<acquire>.	1055	invocations of C<release> and C<acquire>.
926		1056
927	See also the locking example in the C<THREADS> section later in this	1057	See also the locking example in the C<THREADS> section later in this
928	document.	1058	document.
929		1059
930	=item ev_set_userdata (loop, void *data)	1060	=item ev_set_userdata (loop, void *data)
931		1061
932	=item ev_userdata (loop)	1062	=item void *ev_userdata (loop)
933		1063
934	Set and retrieve a single C<void *> associated with a loop. When	1064	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	1065	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
936	C<0.>	1066	C<0>.
937		1067
938	These two functions can be used to associate arbitrary data with a loop,	1068	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	1069	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	1070	C<acquire> callbacks described above, but of course can be (ab-)used for
941	any other purpose as well.	1071	any other purpose as well.
942		1072
943	=item ev_loop_verify (loop)	1073	=item ev_verify (loop)
944		1074
945	This function only does something when C<EV_VERIFY> support has been	1075	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	1076	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	1077	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	1078	is found to be inconsistent, it will print an error message to standard
…		…
959		1089
960	In the following description, uppercase C<TYPE> in names stands for the	1090	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	1091	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.	1092	watchers and C<ev_io_start> for I/O watchers.
963		1093
964	A watcher is a structure that you create and register to record your	1094	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	1095	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:	1096	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1097	for that:
967		1098
968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
969	{	1100	{
970	ev_io_stop (w);	1101	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1102	ev_break (loop, EVBREAK_ALL);
972	}	1103	}
973		1104
974	struct ev_loop *loop = ev_default_loop (0);	1105	struct ev_loop *loop = ev_default_loop (0);
975		1106
976	ev_io stdin_watcher;	1107	ev_io stdin_watcher;
977		1108
978	ev_init (&stdin_watcher, my_cb);	1109	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1110	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1111	ev_io_start (loop, &stdin_watcher);
981		1112
982	ev_loop (loop, 0);	1113	ev_run (loop, 0);
983		1114
984	As you can see, you are responsible for allocating the memory for your	1115	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	1116	watcher structures (and it is I<usually> a bad idea to do this on the
986	stack).	1117	stack).
987		1118
988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1119	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).	1120	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
990		1121
991	Each watcher structure must be initialised by a call to C<ev_init	1122	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	1123	*, 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	1124	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	1125	time the event loop detects that the file descriptor given is readable
995	is readable and/or writable).	1126	and/or writable).
996		1127
997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1128	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	1129	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<<	1130	is also a macro to combine initialisation and setting in one call: C<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1131	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1023	=item C<EV_WRITE>	1154	=item C<EV_WRITE>
1024		1155
1025	The file descriptor in the C<ev_io> watcher has become readable and/or	1156	The file descriptor in the C<ev_io> watcher has become readable and/or
1026	writable.	1157	writable.
1027		1158
1028	=item C<EV_TIMEOUT>	1159	=item C<EV_TIMER>
1029		1160
1030	The C<ev_timer> watcher has timed out.	1161	The C<ev_timer> watcher has timed out.
1031		1162
1032	=item C<EV_PERIODIC>	1163	=item C<EV_PERIODIC>
1033		1164
…		…
1051		1182
1052	=item C<EV_PREPARE>	1183	=item C<EV_PREPARE>
1053		1184
1054	=item C<EV_CHECK>	1185	=item C<EV_CHECK>
1055		1186
1056	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1187	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	1188	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	1189	just after C<ev_run> has gathered them, but before it queues any callbacks
		1190	for any received events. That means C<ev_prepare> watchers are the last
		1191	watchers invoked before the event loop sleeps or polls for new events, and
		1192	C<ev_check> watchers will be invoked before any other watchers of the same
		1193	or lower priority within an event loop iteration.
		1194
1059	received events. Callbacks of both watcher types can start and stop as	1195	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	1196	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	1197	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1062	C<ev_loop> from blocking).	1198	blocking).
1063		1199
1064	=item C<EV_EMBED>	1200	=item C<EV_EMBED>
1065		1201
1066	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1202	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1067		1203
1068	=item C<EV_FORK>	1204	=item C<EV_FORK>
1069		1205
1070	The event loop has been resumed in the child process after fork (see	1206	The event loop has been resumed in the child process after fork (see
1071	C<ev_fork>).	1207	C<ev_fork>).
		1208
		1209	=item C<EV_CLEANUP>
		1210
		1211	The event loop is about to be destroyed (see C<ev_cleanup>).
1072		1212
1073	=item C<EV_ASYNC>	1213	=item C<EV_ASYNC>
1074		1214
1075	The given async watcher has been asynchronously notified (see C<ev_async>).	1215	The given async watcher has been asynchronously notified (see C<ev_async>).
1076		1216
…		…
1123		1263
1124	ev_io w;	1264	ev_io w;
1125	ev_init (&w, my_cb);	1265	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1266	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1267
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1268	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1269
1130	This macro initialises the type-specific parts of a watcher. You need to	1270	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	1271	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	1272	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	1273	macro on a watcher that is active (it can be pending, however, which is a
…		…
1146		1286
1147	Example: Initialise and set an C<ev_io> watcher in one step.	1287	Example: Initialise and set an C<ev_io> watcher in one step.
1148		1288
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1289	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1290
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1291	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1292
1153	Starts (activates) the given watcher. Only active watchers will receive	1293	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1294	events. If the watcher is already active nothing will happen.
1155		1295
1156	Example: Start the C<ev_io> watcher that is being abused as example in this	1296	Example: Start the C<ev_io> watcher that is being abused as example in this
1157	whole section.	1297	whole section.
1158		1298
1159	ev_io_start (EV_DEFAULT_UC, &w);	1299	ev_io_start (EV_DEFAULT_UC, &w);
1160		1300
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1301	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1302
1163	Stops the given watcher if active, and clears the pending status (whether	1303	Stops the given watcher if active, and clears the pending status (whether
1164	the watcher was active or not).	1304	the watcher was active or not).
1165		1305
1166	It is possible that stopped watchers are pending - for example,	1306	It is possible that stopped watchers are pending - for example,
…		…
1186		1326
1187	=item callback ev_cb (ev_TYPE *watcher)	1327	=item callback ev_cb (ev_TYPE *watcher)
1188		1328
1189	Returns the callback currently set on the watcher.	1329	Returns the callback currently set on the watcher.
1190		1330
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1331	=item ev_set_cb (ev_TYPE *watcher, callback)
1192		1332
1193	Change the callback. You can change the callback at virtually any time	1333	Change the callback. You can change the callback at virtually any time
1194	(modulo threads).	1334	(modulo threads).
1195		1335
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1336	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1337
1198	=item int ev_priority (ev_TYPE *watcher)	1338	=item int ev_priority (ev_TYPE *watcher)
1199		1339
1200	Set and query the priority of the watcher. The priority is a small	1340	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>	1341	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1214	or might not have been clamped to the valid range.	1354	or might not have been clamped to the valid range.
1215		1355
1216	The default priority used by watchers when no priority has been set is	1356	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 :).	1357	always C<0>, which is supposed to not be too high and not be too low :).
1218		1358
1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1359	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1220	priorities.	1360	priorities.
1221		1361
1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1362	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1223		1363
1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1364	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>.	1373	watcher isn't pending it does nothing and returns C<0>.
1234		1374
1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1375	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.	1376	callback to be invoked, which can be accomplished with this function.
1237		1377
		1378	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1379
		1380	Feeds the given event set into the event loop, as if the specified event
		1381	had happened for the specified watcher (which must be a pointer to an
		1382	initialised but not necessarily started event watcher). Obviously you must
		1383	not free the watcher as long as it has pending events.
		1384
		1385	Stopping the watcher, letting libev invoke it, or calling
		1386	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1387	not started in the first place.
		1388
		1389	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1390	functions that do not need a watcher.
		1391
1238	=back	1392	=back
1239		1393
		1394	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1395	OWN COMPOSITE WATCHERS> idioms.
1240		1396
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1397	=head2 WATCHER STATES
1242		1398
1243	Each watcher has, by default, a member C<void *data> that you can change	1399	There are various watcher states mentioned throughout this manual -
1244	and read at any time: libev will completely ignore it. This can be used	1400	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	1401	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	1402	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		1403
1250	struct my_io	1404	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1405
1258	...	1406	=item initialised
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1407
1262	And since your callback will be called with a pointer to the watcher, you	1408	Before a watcher can be registered with the event loop it has to be
1263	can cast it back to your own type:	1409	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1410	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1264		1411
1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1412	In this state it is simply some block of memory that is suitable for
1266	{	1413	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1414	will - as long as you either keep the memory contents intact, or call
1268	...	1415	C<ev_TYPE_init> again.
1269	}
1270		1416
1271	More interesting and less C-conformant ways of casting your callback type	1417	=item started/running/active
1272	instead have been omitted.
1273		1418
1274	Another common scenario is to use some data structure with multiple	1419	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1275	embedded watchers:	1420	property of the event loop, and is actively waiting for events. While in
		1421	this state it cannot be accessed (except in a few documented ways), moved,
		1422	freed or anything else - the only legal thing is to keep a pointer to it,
		1423	and call libev functions on it that are documented to work on active watchers.
1276		1424
1277	struct my_biggy	1425	=item pending
1278	{
1279	int some_data;
1280	ev_timer t1;
1281	ev_timer t2;
1282	}
1283		1426
1284	In this case getting the pointer to C<my_biggy> is a bit more	1427	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	1428	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	1429	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	1430	about to be invoked, so it is not normally pending inside the watcher
1288	programmers):	1431	callback.
1289		1432
1290	#include <stddef.h>	1433	The watcher might or might not be active while it is pending (for example,
		1434	an expired non-repeating timer can be pending but no longer active). If it
		1435	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1436	but it is still property of the event loop at this time, so cannot be
		1437	moved, freed or reused. And if it is active the rules described in the
		1438	previous item still apply.
1291		1439
1292	static void	1440	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)	1441	via C<ev_feed_event>), in which case it becomes pending without being
1294	{	1442	active.
1295	struct my_biggy big = (struct my_biggy *)
1296	(((char *)w) - offsetof (struct my_biggy, t1));
1297	}
1298		1443
1299	static void	1444	=item stopped
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1445
1301	{	1446	A watcher can be stopped implicitly by libev (in which case it might still
1302	struct my_biggy big = (struct my_biggy *)	1447	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1448	latter will clear any pending state the watcher might be in, regardless
1304	}	1449	of whether it was active or not, so stopping a watcher explicitly before
		1450	freeing it is often a good idea.
		1451
		1452	While stopped (and not pending) the watcher is essentially in the
		1453	initialised state, that is, it can be reused, moved, modified in any way
		1454	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1455	it again).
		1456
		1457	=back
1305		1458
1306	=head2 WATCHER PRIORITY MODELS	1459	=head2 WATCHER PRIORITY MODELS
1307		1460
1308	Many event loops support I<watcher priorities>, which are usually small	1461	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1462	integers that influence the ordering of event callback invocation
…		…
1352		1505
1353	For example, to emulate how many other event libraries handle priorities,	1506	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	1507	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	1508	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	1509	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	1510	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	1511	the lock-out case is known to be rare (which in turn is rare :), this is
1359	workable.	1512	workable.
1360		1513
1361	Usually, however, the lock-out model implemented that way will perform	1514	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,	1515	miserably under the type of load it was designed to handle. In that case,
…		…
1376	{	1529	{
1377	// stop the I/O watcher, we received the event, but	1530	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1531	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1532	ev_io_stop (EV_A_ w);
1380		1533
1381	// start the idle watcher to ahndle the actual event.	1534	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1535	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1536	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1537	ev_idle_start (EV_A_ &idle);
1385	}	1538	}
1386		1539
…		…
1436	In general you can register as many read and/or write event watchers per	1589	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	1590	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	1591	descriptors to non-blocking mode is also usually a good idea (but not
1439	required if you know what you are doing).	1592	required if you know what you are doing).
1440		1593
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	1594	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	1595	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	1596	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	1597	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	1598	with a relatively standard program structure. Thus it is best to always
1452	this situation even with a relatively standard program structure. Thus	1599	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.	1600	preferable to a program hanging until some data arrives.
1455		1601
1456	If you cannot run the fd in non-blocking mode (for example you should	1602	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	1603	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	1604	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	1605	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	1606	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	1607	use C<SIGALRM> and an interval timer, just to be sure you won't block
1462	indefinitely.	1608	indefinitely.
1463		1609
1464	But really, best use non-blocking mode.	1610	But really, best use non-blocking mode.
1465		1611
…		…
1493		1639
1494	There is no workaround possible except not registering events	1640	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1641	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1642	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		1643
		1644	=head3 The special problem of files
		1645
		1646	Many people try to use C<select> (or libev) on file descriptors
		1647	representing files, and expect it to become ready when their program
		1648	doesn't block on disk accesses (which can take a long time on their own).
		1649
		1650	However, this cannot ever work in the "expected" way - you get a readiness
		1651	notification as soon as the kernel knows whether and how much data is
		1652	there, and in the case of open files, that's always the case, so you
		1653	always get a readiness notification instantly, and your read (or possibly
		1654	write) will still block on the disk I/O.
		1655
		1656	Another way to view it is that in the case of sockets, pipes, character
		1657	devices and so on, there is another party (the sender) that delivers data
		1658	on its own, but in the case of files, there is no such thing: the disk
		1659	will not send data on its own, simply because it doesn't know what you
		1660	wish to read - you would first have to request some data.
		1661
		1662	Since files are typically not-so-well supported by advanced notification
		1663	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1664	to files, even though you should not use it. The reason for this is
		1665	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1666	usually a tty, often a pipe, but also sometimes files or special devices
		1667	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1668	F</dev/urandom>), and even though the file might better be served with
		1669	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1670	it "just works" instead of freezing.
		1671
		1672	So avoid file descriptors pointing to files when you know it (e.g. use
		1673	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1674	when you rarely read from a file instead of from a socket, and want to
		1675	reuse the same code path.
		1676
1498	=head3 The special problem of fork	1677	=head3 The special problem of fork
1499		1678
1500	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1679	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	1680	useless behaviour. Libev fully supports fork, but needs to be told about
1502	it in the child.	1681	it in the child if you want to continue to use it in the child.
1503		1682
1504	To support fork in your programs, you either have to call	1683	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,	1684	()> 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	1685	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1686
1509	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1510		1688
1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1689	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	1690	when writing to a pipe whose other end has been closed, your program gets
…		…
1515		1693
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1694	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	1695	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).	1696	somewhere, as that would have given you a big clue).
1519		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1520		1736
1521	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1522		1738
1523	=over 4	1739	=over 4
1524		1740
…		…
1556	...	1772	...
1557	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1774	ev_io stdin_readable;
1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1560	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1562		1778
1563		1779
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1781
1566	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1574		1790
1575	The callback is guaranteed to be invoked only I<after> its timeout has	1791	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	1792	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	1793	might introduce a small delay, see "the special problem of being too
		1794	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	1795	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	1796	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).	1797	longer true when a callback calls C<ev_run> recursively).
1581		1798
1582	=head3 Be smart about timeouts	1799	=head3 Be smart about timeouts
1583		1800
1584	Many real-world problems involve some kind of timeout, usually for error	1801	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,	1802	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1660		1877
1661	In this case, it would be more efficient to leave the C<ev_timer> alone,	1878	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	1879	but remember the time of last activity, and check for a real timeout only
1663	within the callback:	1880	within the callback:
1664		1881
		1882	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	1883	ev_tstamp last_activity; // time of last activity
		1884	ev_timer timer;
1666		1885
1667	static void	1886	static void
1668	callback (EV_P_ ev_timer *w, int revents)	1887	callback (EV_P_ ev_timer *w, int revents)
1669	{	1888	{
1670	ev_tstamp now = ev_now (EV_A);	1889	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	1890	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		1891
1673	// if last_activity + 60. is older than now, we did time out	1892	// if negative, it means we the timeout already occurred
1674	if (timeout < now)	1893	if (after < 0.)
1675	{	1894	{
1676	// timeout occured, take action	1895	// timeout occurred, take action
1677	}	1896	}
1678	else	1897	else
1679	{	1898	{
1680	// callback was invoked, but there was some activity, re-arm	1899	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	1900	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	1901	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	1902	// the timeout can occur.
		1903	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	1904	ev_timer_start (EV_A_ w);
1685	}	1905	}
1686	}	1906	}
1687		1907
1688	To summarise the callback: first calculate the real timeout (defined	1908	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	1909	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	1910	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	1911	(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		1912
1695	Note how C<ev_timer_again> is used, taking advantage of the	1913	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.	1914	timed out, and need to do whatever is needed in this case.
		1915
		1916	Otherwise, we now the earliest time at which the timeout would trigger,
		1917	and simply start the timer with this timeout value.
		1918
		1919	In other words, each time the callback is invoked it will check whether
		1920	the timeout occurred. If not, it will simply reschedule itself to check
		1921	again at the earliest time it could time out. Rinse. Repeat.
1697		1922
1698	This scheme causes more callback invocations (about one every 60 seconds	1923	This scheme causes more callback invocations (about one every 60 seconds
1699	minus half the average time between activity), but virtually no calls to	1924	minus half the average time between activity), but virtually no calls to
1700	libev to change the timeout.	1925	libev to change the timeout.
1701		1926
1702	To start the timer, simply initialise the watcher and set C<last_activity>	1927	To start the machinery, simply initialise the watcher and set
1703	to the current time (meaning we just have some activity :), then call the	1928	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:	1929	now), then call the callback, which will "do the right thing" and start
		1930	the timer:
1705		1931
		1932	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	1933	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	1934	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		1935
1710	And when there is some activity, simply store the current time in	1936	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	1937	C<last_activity>, no libev calls at all:
1712		1938
		1939	if (activity detected)
1713	last_actiivty = ev_now (loop);	1940	last_activity = ev_now (EV_A);
		1941
		1942	When your timeout value changes, then the timeout can be changed by simply
		1943	providing a new value, stopping the timer and calling the callback, which
		1944	will again do the right thing (for example, time out immediately :).
		1945
		1946	timeout = new_value;
		1947	ev_timer_stop (EV_A_ &timer);
		1948	callback (EV_A_ &timer, 0);
1714		1949
1715	This technique is slightly more complex, but in most cases where the	1950	This technique is slightly more complex, but in most cases where the
1716	time-out is unlikely to be triggered, much more efficient.	1951	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		1952
1722	=item 4. Wee, just use a double-linked list for your timeouts.	1953	=item 4. Wee, just use a double-linked list for your timeouts.
1723		1954
1724	If there is not one request, but many thousands (millions...), all	1955	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	1956	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	1983	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	1984	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	1985	off after the first million or so of active timers, i.e. it's usually
1755	overkill :)	1986	overkill :)
1756		1987
		1988	=head3 The special problem of being too early
		1989
		1990	If you ask a timer to call your callback after three seconds, then
		1991	you expect it to be invoked after three seconds - but of course, this
		1992	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1993	guaranteed to any precision by libev - imagine somebody suspending the
		1994	process with a STOP signal for a few hours for example.
		1995
		1996	So, libev tries to invoke your callback as soon as possible I<after> the
		1997	delay has occurred, but cannot guarantee this.
		1998
		1999	A less obvious failure mode is calling your callback too early: many event
		2000	loops compare timestamps with a "elapsed delay >= requested delay", but
		2001	this can cause your callback to be invoked much earlier than you would
		2002	expect.
		2003
		2004	To see why, imagine a system with a clock that only offers full second
		2005	resolution (think windows if you can't come up with a broken enough OS
		2006	yourself). If you schedule a one-second timer at the time 500.9, then the
		2007	event loop will schedule your timeout to elapse at a system time of 500
		2008	(500.9 truncated to the resolution) + 1, or 501.
		2009
		2010	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2011	501" and invoke the callback 0.1s after it was started, even though a
		2012	one-second delay was requested - this is being "too early", despite best
		2013	intentions.
		2014
		2015	This is the reason why libev will never invoke the callback if the elapsed
		2016	delay equals the requested delay, but only when the elapsed delay is
		2017	larger than the requested delay. In the example above, libev would only invoke
		2018	the callback at system time 502, or 1.1s after the timer was started.
		2019
		2020	So, while libev cannot guarantee that your callback will be invoked
		2021	exactly when requested, it I<can> and I<does> guarantee that the requested
		2022	delay has actually elapsed, or in other words, it always errs on the "too
		2023	late" side of things.
		2024
1757	=head3 The special problem of time updates	2025	=head3 The special problem of time updates
1758		2026
1759	Establishing the current time is a costly operation (it usually takes at	2027	Establishing the current time is a costly operation (it usually takes
1760	least two system calls): EV therefore updates its idea of the current	2028	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	2029	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	2030	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1763	lots of events in one iteration.	2031	lots of events in one iteration.
1764		2032
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2033	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	2034	time. This is usually the right thing as this timestamp refers to the time
1767	of the event triggering whatever timeout you are modifying/starting. If	2035	of the event triggering whatever timeout you are modifying/starting. If
1768	you suspect event processing to be delayed and you I<need> to base the	2036	you suspect event processing to be delayed and you I<need> to base the
1769	timeout on the current time, use something like this to adjust for this:	2037	timeout on the current time, use something like the following to adjust
		2038	for it:
1770		2039
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2040	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1772		2041
1773	If the event loop is suspended for a long time, you can also force an	2042	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	2043	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1775	()>.	2044	()>, although that will push the event time of all outstanding events
		2045	further into the future.
		2046
		2047	=head3 The special problem of unsynchronised clocks
		2048
		2049	Modern systems have a variety of clocks - libev itself uses the normal
		2050	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2051	jumps).
		2052
		2053	Neither of these clocks is synchronised with each other or any other clock
		2054	on the system, so C<ev_time ()> might return a considerably different time
		2055	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2056	a call to C<gettimeofday> might return a second count that is one higher
		2057	than a directly following call to C<time>.
		2058
		2059	The moral of this is to only compare libev-related timestamps with
		2060	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2061	a second or so.
		2062
		2063	One more problem arises due to this lack of synchronisation: if libev uses
		2064	the system monotonic clock and you compare timestamps from C<ev_time>
		2065	or C<ev_now> from when you started your timer and when your callback is
		2066	invoked, you will find that sometimes the callback is a bit "early".
		2067
		2068	This is because C<ev_timer>s work in real time, not wall clock time, so
		2069	libev makes sure your callback is not invoked before the delay happened,
		2070	I<measured according to the real time>, not the system clock.
		2071
		2072	If your timeouts are based on a physical timescale (e.g. "time out this
		2073	connection after 100 seconds") then this shouldn't bother you as it is
		2074	exactly the right behaviour.
		2075
		2076	If you want to compare wall clock/system timestamps to your timers, then
		2077	you need to use C<ev_periodic>s, as these are based on the wall clock
		2078	time, where your comparisons will always generate correct results.
1776		2079
1777	=head3 The special problems of suspended animation	2080	=head3 The special problems of suspended animation
1778		2081
1779	When you leave the server world it is quite customary to hit machines that	2082	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?	2083	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	2127	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.	2128	do stuff) the timer will not fire more than once per event loop iteration.
1826		2129
1827	=item ev_timer_again (loop, ev_timer *)	2130	=item ev_timer_again (loop, ev_timer *)
1828		2131
1829	This will act as if the timer timed out and restart it again if it is	2132	This will act as if the timer timed out, and restarts it again if it is
1830	repeating. The exact semantics are:	2133	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2134	timeout to the C<repeat> value and calling C<ev_timer_start>.
1831		2135
		2136	The exact semantics are as in the following rules, all of which will be
		2137	applied to the watcher:
		2138
		2139	=over 4
		2140
1832	If the timer is pending, its pending status is cleared.	2141	=item If the timer is pending, the pending status is always cleared.
1833		2142
1834	If the timer is started but non-repeating, stop it (as if it timed out).	2143	=item If the timer is started but non-repeating, stop it (as if it timed
		2144	out, without invoking it).
1835		2145
1836	If the timer is repeating, either start it if necessary (with the	2146	=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.	2147	and start the timer, if necessary.
1838		2148
		2149	=back
		2150
1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2151	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1840	usage example.	2152	usage example.
1841		2153
1842	=item ev_timer_remaining (loop, ev_timer *)	2154	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2155
1844	Returns the remaining time until a timer fires. If the timer is active,	2156	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	2157	then this time is relative to the current event loop time, otherwise it's
1846	the timeout value currently configured.	2158	the timeout value currently configured.
1847		2159
1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2160	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>	2161	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	2162	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,	2163	roughly C<7> (likely slightly less as callback invocation takes some time,
1852	too), and so on.	2164	too), and so on.
1853		2165
1854	=item ev_tstamp repeat [read-write]	2166	=item ev_tstamp repeat [read-write]
…		…
1883	}	2195	}
1884		2196
1885	ev_timer mytimer;	2197	ev_timer mytimer;
1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2198	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1887	ev_timer_again (&mytimer); /* start timer */	2199	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2200	ev_run (loop, 0);
1889		2201
1890	// and in some piece of code that gets executed on any "activity":	2202	// and in some piece of code that gets executed on any "activity":
1891	// reset the timeout to start ticking again at 10 seconds	2203	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2204	ev_timer_again (&mytimer);
1893		2205
…		…
1897	Periodic watchers are also timers of a kind, but they are very versatile	2209	Periodic watchers are also timers of a kind, but they are very versatile
1898	(and unfortunately a bit complex).	2210	(and unfortunately a bit complex).
1899		2211
1900	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2212	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1901	relative time, the physical time that passes) but on wall clock time	2213	relative time, the physical time that passes) but on wall clock time
1902	(absolute time, the thing you can read on your calender or clock). The	2214	(absolute time, the thing you can read on your calendar or clock). The
1903	difference is that wall clock time can run faster or slower than real	2215	difference is that wall clock time can run faster or slower than real
1904	time, and time jumps are not uncommon (e.g. when you adjust your	2216	time, and time jumps are not uncommon (e.g. when you adjust your
1905	wrist-watch).	2217	wrist-watch).
1906		2218
1907	You can tell a periodic watcher to trigger after some specific point	2219	You can tell a periodic watcher to trigger after some specific point
…		…
1919		2231
1920	As with timers, the callback is guaranteed to be invoked only when the	2232	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	2233	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	2234	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	2235	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).	2236	(but this is no longer true when a callback calls C<ev_run> recursively).
1925		2237
1926	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1927		2239
1928	=over 4	2240	=over 4
1929		2241
…		…
1964		2276
1965	Another way to think about it (for the mathematically inclined) is that	2277	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	2278	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.	2279	time where C<time = offset (mod interval)>, regardless of any time jumps.
1968		2280
1969	For numerical stability it is preferable that the C<offset> value is near	2281	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	2282	interval value should be higher than C<1/8192> (which is around 100
1971	this value, and in fact is often specified as zero.	2283	microseconds) and C<offset> should be higher than C<0> and should have
		2284	at most a similar magnitude as the current time (say, within a factor of
		2285	ten). Typical values for offset are, in fact, C<0> or something between
		2286	C<0> and C<interval>, which is also the recommended range.
1972		2287
1973	Note also that there is an upper limit to how often a timer can fire (CPU	2288	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	2289	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	2290	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).	2291	millisecond (if the OS supports it and the machine is fast enough).
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2372	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2373	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2374	potentially a lot of jitter, but good long-term stability.
2060		2375
2061	static void	2376	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2377	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2378	{
2064	... its now a full hour (UTC, or TAI or whatever your clock follows)	2379	... its now a full hour (UTC, or TAI or whatever your clock follows)
2065	}	2380	}
2066		2381
2067	ev_periodic hourly_tick;	2382	ev_periodic hourly_tick;
…		…
2084		2399
2085	ev_periodic hourly_tick;	2400	ev_periodic hourly_tick;
2086	ev_periodic_init (&hourly_tick, clock_cb,	2401	ev_periodic_init (&hourly_tick, clock_cb,
2087	fmod (ev_now (loop), 3600.), 3600., 0);	2402	fmod (ev_now (loop), 3600.), 3600., 0);
2088	ev_periodic_start (loop, &hourly_tick);	2403	ev_periodic_start (loop, &hourly_tick);
2089		2404
2090		2405
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2406	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2407
2093	Signal watchers will trigger an event when the process receives a specific	2408	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	2409	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	2410	will try its best to deliver signals synchronously, i.e. as part of the
2096	normal event processing, like any other event.	2411	normal event processing, like any other event.
2097		2412
2098	If you want signals to be delivered truly asynchronously, just use	2413	If you want signals to be delivered truly asynchronously, just use
2099	C<sigaction> as you would do without libev and forget about sharing	2414	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	2415	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	2419	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	2420	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	2421	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.	2422	the moment, C<SIGCHLD> is permanently tied to the default loop.
2108		2423
2109	When the first watcher gets started will libev actually register something	2424	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	2425	register something with the kernel. It thus coexists with your own signal
2111	you don't register any with libev for the same signal).	2426	handlers as long as you don't register any with libev for the same signal.
2112		2427
2113	If possible and supported, libev will install its handlers with	2428	If possible and supported, libev will install its handlers with
2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2429	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2115	not be unduly interrupted. If you have a problem with system calls getting	2430	not be unduly interrupted. If you have a problem with system calls getting
2116	interrupted by signals you can block all signals in an C<ev_check> watcher	2431	interrupted by signals you can block all signals in an C<ev_check> watcher
2117	and unblock them in an C<ev_prepare> watcher.	2432	and unblock them in an C<ev_prepare> watcher.
2118		2433
2119	=head3 The special problem of inheritance over execve	2434	=head3 The special problem of inheritance over fork/execve/pthread_create
2120		2435
2121	Both the signal mask (C<sigprocmask>) and the signal disposition	2436	Both the signal mask (C<sigprocmask>) and the signal disposition
2122	(C<sigaction>) are unspecified after starting a signal watcher (and after	2437	(C<sigaction>) are unspecified after starting a signal watcher (and after
2123	stopping it again), that is, libev might or might not block the signal,	2438	stopping it again), that is, libev might or might not block the signal,
2124	and might or might not set or restore the installed signal handler.	2439	and might or might not set or restore the installed signal handler (but
		2440	see C<EVFLAG_NOSIGMASK>).
2125		2441
2126	While this does not matter for the signal disposition (libev never	2442	While this does not matter for the signal disposition (libev never
2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2443	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2128	C<execve>), this matters for the signal mask: many programs do not expect	2444	C<execve>), this matters for the signal mask: many programs do not expect
2129	many signals to be blocked.	2445	certain signals to be blocked.
2130		2446
2131	This means that before calling C<exec> (from the child) you should reset	2447	This means that before calling C<exec> (from the child) you should reset
2132	the signal mask to whatever "default" you expect (all clear is a good	2448	the signal mask to whatever "default" you expect (all clear is a good
2133	choice usually).	2449	choice usually).
2134		2450
		2451	The simplest way to ensure that the signal mask is reset in the child is
		2452	to install a fork handler with C<pthread_atfork> that resets it. That will
		2453	catch fork calls done by libraries (such as the libc) as well.
		2454
		2455	In current versions of libev, the signal will not be blocked indefinitely
		2456	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2457	the window of opportunity for problems, it will not go away, as libev
		2458	I<has> to modify the signal mask, at least temporarily.
		2459
		2460	So I can't stress this enough: I<If you do not reset your signal mask when
		2461	you expect it to be empty, you have a race condition in your code>. This
		2462	is not a libev-specific thing, this is true for most event libraries.
		2463
		2464	=head3 The special problem of threads signal handling
		2465
		2466	POSIX threads has problematic signal handling semantics, specifically,
		2467	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2468	threads in a process block signals, which is hard to achieve.
		2469
		2470	When you want to use sigwait (or mix libev signal handling with your own
		2471	for the same signals), you can tackle this problem by globally blocking
		2472	all signals before creating any threads (or creating them with a fully set
		2473	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2474	loops. Then designate one thread as "signal receiver thread" which handles
		2475	these signals. You can pass on any signals that libev might be interested
		2476	in by calling C<ev_feed_signal>.
		2477
2135	=head3 Watcher-Specific Functions and Data Members	2478	=head3 Watcher-Specific Functions and Data Members
2136		2479
2137	=over 4	2480	=over 4
2138		2481
2139	=item ev_signal_init (ev_signal *, callback, int signum)	2482	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2154	Example: Try to exit cleanly on SIGINT.	2497	Example: Try to exit cleanly on SIGINT.
2155		2498
2156	static void	2499	static void
2157	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2500	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2158	{	2501	{
2159	ev_unloop (loop, EVUNLOOP_ALL);	2502	ev_break (loop, EVBREAK_ALL);
2160	}	2503	}
2161		2504
2162	ev_signal signal_watcher;	2505	ev_signal signal_watcher;
2163	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2506	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2164	ev_signal_start (loop, &signal_watcher);	2507	ev_signal_start (loop, &signal_watcher);
…		…
2273		2616
2274	=head2 C<ev_stat> - did the file attributes just change?	2617	=head2 C<ev_stat> - did the file attributes just change?
2275		2618
2276	This watches a file system path for attribute changes. That is, it calls	2619	This watches a file system path for attribute changes. That is, it calls
2277	C<stat> on that path in regular intervals (or when the OS says it changed)	2620	C<stat> on that path in regular intervals (or when the OS says it changed)
2278	and sees if it changed compared to the last time, invoking the callback if	2621	and sees if it changed compared to the last time, invoking the callback
2279	it did.	2622	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2623	happen after the watcher has been started will be reported.
2280		2624
2281	The path does not need to exist: changing from "path exists" to "path does	2625	The path does not need to exist: changing from "path exists" to "path does
2282	not exist" is a status change like any other. The condition "path does not	2626	not exist" is a status change like any other. The condition "path does not
2283	exist" (or more correctly "path cannot be stat'ed") is signified by the	2627	exist" (or more correctly "path cannot be stat'ed") is signified by the
2284	C<st_nlink> field being zero (which is otherwise always forced to be at	2628	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2514	Apart from keeping your process non-blocking (which is a useful	2858	Apart from keeping your process non-blocking (which is a useful
2515	effect on its own sometimes), idle watchers are a good place to do	2859	effect on its own sometimes), idle watchers are a good place to do
2516	"pseudo-background processing", or delay processing stuff to after the	2860	"pseudo-background processing", or delay processing stuff to after the
2517	event loop has handled all outstanding events.	2861	event loop has handled all outstanding events.
2518		2862
		2863	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2864
		2865	As long as there is at least one active idle watcher, libev will never
		2866	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2867	For this to work, the idle watcher doesn't need to be invoked at all - the
		2868	lowest priority will do.
		2869
		2870	This mode of operation can be useful together with an C<ev_check> watcher,
		2871	to do something on each event loop iteration - for example to balance load
		2872	between different connections.
		2873
		2874	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2875	example.
		2876
2519	=head3 Watcher-Specific Functions and Data Members	2877	=head3 Watcher-Specific Functions and Data Members
2520		2878
2521	=over 4	2879	=over 4
2522		2880
2523	=item ev_idle_init (ev_idle *, callback)	2881	=item ev_idle_init (ev_idle *, callback)
…		…
2534	callback, free it. Also, use no error checking, as usual.	2892	callback, free it. Also, use no error checking, as usual.
2535		2893
2536	static void	2894	static void
2537	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2895	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2538	{	2896	{
		2897	// stop the watcher
		2898	ev_idle_stop (loop, w);
		2899
		2900	// now we can free it
2539	free (w);	2901	free (w);
		2902
2540	// now do something you wanted to do when the program has	2903	// now do something you wanted to do when the program has
2541	// no longer anything immediate to do.	2904	// no longer anything immediate to do.
2542	}	2905	}
2543		2906
2544	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2907	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2546	ev_idle_start (loop, idle_watcher);	2909	ev_idle_start (loop, idle_watcher);
2547		2910
2548		2911
2549	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2912	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2550		2913
2551	Prepare and check watchers are usually (but not always) used in pairs:	2914	Prepare and check watchers are often (but not always) used in pairs:
2552	prepare watchers get invoked before the process blocks and check watchers	2915	prepare watchers get invoked before the process blocks and check watchers
2553	afterwards.	2916	afterwards.
2554		2917
2555	You I<must not> call C<ev_loop> or similar functions that enter	2918	You I<must not> call C<ev_run> (or similar functions that enter the
2556	the current event loop from either C<ev_prepare> or C<ev_check>	2919	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2557	watchers. Other loops than the current one are fine, however. The	2920	C<ev_check> watchers. Other loops than the current one are fine,
2558	rationale behind this is that you do not need to check for recursion in	2921	however. The rationale behind this is that you do not need to check
2559	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2922	for recursion in those watchers, i.e. the sequence will always be
2560	C<ev_check> so if you have one watcher of each kind they will always be	2923	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2561	called in pairs bracketing the blocking call.	2924	kind they will always be called in pairs bracketing the blocking call.
2562		2925
2563	Their main purpose is to integrate other event mechanisms into libev and	2926	Their main purpose is to integrate other event mechanisms into libev and
2564	their use is somewhat advanced. They could be used, for example, to track	2927	their use is somewhat advanced. They could be used, for example, to track
2565	variable changes, implement your own watchers, integrate net-snmp or a	2928	variable changes, implement your own watchers, integrate net-snmp or a
2566	coroutine library and lots more. They are also occasionally useful if	2929	coroutine library and lots more. They are also occasionally useful if
…		…
2584	with priority higher than or equal to the event loop and one coroutine	2947	with priority higher than or equal to the event loop and one coroutine
2585	of lower priority, but only once, using idle watchers to keep the event	2948	of lower priority, but only once, using idle watchers to keep the event
2586	loop from blocking if lower-priority coroutines are active, thus mapping	2949	loop from blocking if lower-priority coroutines are active, thus mapping
2587	low-priority coroutines to idle/background tasks).	2950	low-priority coroutines to idle/background tasks).
2588		2951
2589	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2952	When used for this purpose, it is recommended to give C<ev_check> watchers
2590	priority, to ensure that they are being run before any other watchers	2953	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2591	after the poll (this doesn't matter for C<ev_prepare> watchers).	2954	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2955	watchers).
2592		2956
2593	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2957	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2594	activate ("feed") events into libev. While libev fully supports this, they	2958	activate ("feed") events into libev. While libev fully supports this, they
2595	might get executed before other C<ev_check> watchers did their job. As	2959	might get executed before other C<ev_check> watchers did their job. As
2596	C<ev_check> watchers are often used to embed other (non-libev) event	2960	C<ev_check> watchers are often used to embed other (non-libev) event
2597	loops those other event loops might be in an unusable state until their	2961	loops those other event loops might be in an unusable state until their
2598	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2962	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2599	others).	2963	others).
		2964
		2965	=head3 Abusing an C<ev_check> watcher for its side-effect
		2966
		2967	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2968	useful because they are called once per event loop iteration. For
		2969	example, if you want to handle a large number of connections fairly, you
		2970	normally only do a bit of work for each active connection, and if there
		2971	is more work to do, you wait for the next event loop iteration, so other
		2972	connections have a chance of making progress.
		2973
		2974	Using an C<ev_check> watcher is almost enough: it will be called on the
		2975	next event loop iteration. However, that isn't as soon as possible -
		2976	without external events, your C<ev_check> watcher will not be invoked.
		2977
		2978	This is where C<ev_idle> watchers come in handy - all you need is a
		2979	single global idle watcher that is active as long as you have one active
		2980	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2981	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2982	invoked. Neither watcher alone can do that.
2600		2983
2601	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2602		2985
2603	=over 4	2986	=over 4
2604		2987
…		…
2728		3111
2729	if (timeout >= 0)	3112	if (timeout >= 0)
2730	// create/start timer	3113	// create/start timer
2731		3114
2732	// poll	3115	// poll
2733	ev_loop (EV_A_ 0);	3116	ev_run (EV_A_ 0);
2734		3117
2735	// stop timer again	3118	// stop timer again
2736	if (timeout >= 0)	3119	if (timeout >= 0)
2737	ev_timer_stop (EV_A_ &to);	3120	ev_timer_stop (EV_A_ &to);
2738		3121
…		…
2805		3188
2806	=over 4	3189	=over 4
2807		3190
2808	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3191	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2809		3192
2810	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3193	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2811		3194
2812	Configures the watcher to embed the given loop, which must be	3195	Configures the watcher to embed the given loop, which must be
2813	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3196	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2814	invoked automatically, otherwise it is the responsibility of the callback	3197	invoked automatically, otherwise it is the responsibility of the callback
2815	to invoke it (it will continue to be called until the sweep has been done,	3198	to invoke it (it will continue to be called until the sweep has been done,
2816	if you do not want that, you need to temporarily stop the embed watcher).	3199	if you do not want that, you need to temporarily stop the embed watcher).
2817		3200
2818	=item ev_embed_sweep (loop, ev_embed *)	3201	=item ev_embed_sweep (loop, ev_embed *)
2819		3202
2820	Make a single, non-blocking sweep over the embedded loop. This works	3203	Make a single, non-blocking sweep over the embedded loop. This works
2821	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3204	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2822	appropriate way for embedded loops.	3205	appropriate way for embedded loops.
2823		3206
2824	=item struct ev_loop *other [read-only]	3207	=item struct ev_loop *other [read-only]
2825		3208
2826	The embedded event loop.	3209	The embedded event loop.
…		…
2836	used).	3219	used).
2837		3220
2838	struct ev_loop *loop_hi = ev_default_init (0);	3221	struct ev_loop *loop_hi = ev_default_init (0);
2839	struct ev_loop *loop_lo = 0;	3222	struct ev_loop *loop_lo = 0;
2840	ev_embed embed;	3223	ev_embed embed;
2841		3224
2842	// see if there is a chance of getting one that works	3225	// see if there is a chance of getting one that works
2843	// (remember that a flags value of 0 means autodetection)	3226	// (remember that a flags value of 0 means autodetection)
2844	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3227	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2845	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3228	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2846	: 0;	3229	: 0;
…		…
2860	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3243	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2861		3244
2862	struct ev_loop *loop = ev_default_init (0);	3245	struct ev_loop *loop = ev_default_init (0);
2863	struct ev_loop *loop_socket = 0;	3246	struct ev_loop *loop_socket = 0;
2864	ev_embed embed;	3247	ev_embed embed;
2865		3248
2866	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3249	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2867	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3250	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2868	{	3251	{
2869	ev_embed_init (&embed, 0, loop_socket);	3252	ev_embed_init (&embed, 0, loop_socket);
2870	ev_embed_start (loop, &embed);	3253	ev_embed_start (loop, &embed);
…		…
2878		3261
2879	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3262	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2880		3263
2881	Fork watchers are called when a C<fork ()> was detected (usually because	3264	Fork watchers are called when a C<fork ()> was detected (usually because
2882	whoever is a good citizen cared to tell libev about it by calling	3265	whoever is a good citizen cared to tell libev about it by calling
2883	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3266	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2884	event loop blocks next and before C<ev_check> watchers are being called,	3267	and before C<ev_check> watchers are being called, and only in the child
2885	and only in the child after the fork. If whoever good citizen calling	3268	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2886	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3269	and calls it in the wrong process, the fork handlers will be invoked, too,
2887	handlers will be invoked, too, of course.	3270	of course.
2888		3271
2889	=head3 The special problem of life after fork - how is it possible?	3272	=head3 The special problem of life after fork - how is it possible?
2890		3273
2891	Most uses of C<fork()> consist of forking, then some simple calls to ste	3274	Most uses of C<fork ()> consist of forking, then some simple calls to set
2892	up/change the process environment, followed by a call to C<exec()>. This	3275	up/change the process environment, followed by a call to C<exec()>. This
2893	sequence should be handled by libev without any problems.	3276	sequence should be handled by libev without any problems.
2894		3277
2895	This changes when the application actually wants to do event handling	3278	This changes when the application actually wants to do event handling
2896	in the child, or both parent in child, in effect "continuing" after the	3279	in the child, or both parent in child, in effect "continuing" after the
…		…
2912	disadvantage of having to use multiple event loops (which do not support	3295	disadvantage of having to use multiple event loops (which do not support
2913	signal watchers).	3296	signal watchers).
2914		3297
2915	When this is not possible, or you want to use the default loop for	3298	When this is not possible, or you want to use the default loop for
2916	other reasons, then in the process that wants to start "fresh", call	3299	other reasons, then in the process that wants to start "fresh", call
2917	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3300	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2918	the default loop will "orphan" (not stop) all registered watchers, so you	3301	Destroying the default loop will "orphan" (not stop) all registered
2919	have to be careful not to execute code that modifies those watchers. Note	3302	watchers, so you have to be careful not to execute code that modifies
2920	also that in that case, you have to re-register any signal watchers.	3303	those watchers. Note also that in that case, you have to re-register any
		3304	signal watchers.
2921		3305
2922	=head3 Watcher-Specific Functions and Data Members	3306	=head3 Watcher-Specific Functions and Data Members
2923		3307
2924	=over 4	3308	=over 4
2925		3309
2926	=item ev_fork_init (ev_signal *, callback)	3310	=item ev_fork_init (ev_fork *, callback)
2927		3311
2928	Initialises and configures the fork watcher - it has no parameters of any	3312	Initialises and configures the fork watcher - it has no parameters of any
2929	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3313	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2930	believe me.	3314	really.
2931		3315
2932	=back	3316	=back
2933		3317
2934		3318
		3319	=head2 C<ev_cleanup> - even the best things end
		3320
		3321	Cleanup watchers are called just before the event loop is being destroyed
		3322	by a call to C<ev_loop_destroy>.
		3323
		3324	While there is no guarantee that the event loop gets destroyed, cleanup
		3325	watchers provide a convenient method to install cleanup hooks for your
		3326	program, worker threads and so on - you just to make sure to destroy the
		3327	loop when you want them to be invoked.
		3328
		3329	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3330	all other watchers, they do not keep a reference to the event loop (which
		3331	makes a lot of sense if you think about it). Like all other watchers, you
		3332	can call libev functions in the callback, except C<ev_cleanup_start>.
		3333
		3334	=head3 Watcher-Specific Functions and Data Members
		3335
		3336	=over 4
		3337
		3338	=item ev_cleanup_init (ev_cleanup *, callback)
		3339
		3340	Initialises and configures the cleanup watcher - it has no parameters of
		3341	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3342	pointless, I assure you.
		3343
		3344	=back
		3345
		3346	Example: Register an atexit handler to destroy the default loop, so any
		3347	cleanup functions are called.
		3348
		3349	static void
		3350	program_exits (void)
		3351	{
		3352	ev_loop_destroy (EV_DEFAULT_UC);
		3353	}
		3354
		3355	...
		3356	atexit (program_exits);
		3357
		3358
2935	=head2 C<ev_async> - how to wake up another event loop	3359	=head2 C<ev_async> - how to wake up an event loop
2936		3360
2937	In general, you cannot use an C<ev_loop> from multiple threads or other	3361	In general, you cannot use an C<ev_loop> from multiple threads or other
2938	asynchronous sources such as signal handlers (as opposed to multiple event	3362	asynchronous sources such as signal handlers (as opposed to multiple event
2939	loops - those are of course safe to use in different threads).	3363	loops - those are of course safe to use in different threads).
2940		3364
2941	Sometimes, however, you need to wake up another event loop you do not	3365	Sometimes, however, you need to wake up an event loop you do not control,
2942	control, for example because it belongs to another thread. This is what	3366	for example because it belongs to another thread. This is what C<ev_async>
2943	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3367	watchers do: as long as the C<ev_async> watcher is active, you can signal
2944	can signal it by calling C<ev_async_send>, which is thread- and signal	3368	it by calling C<ev_async_send>, which is thread- and signal safe.
2945	safe.
2946		3369
2947	This functionality is very similar to C<ev_signal> watchers, as signals,	3370	This functionality is very similar to C<ev_signal> watchers, as signals,
2948	too, are asynchronous in nature, and signals, too, will be compressed	3371	too, are asynchronous in nature, and signals, too, will be compressed
2949	(i.e. the number of callback invocations may be less than the number of	3372	(i.e. the number of callback invocations may be less than the number of
2950	C<ev_async_sent> calls).	3373	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2951		3374	of "global async watchers" by using a watcher on an otherwise unused
2952	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3375	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2953	just the default loop.	3376	even without knowing which loop owns the signal.
2954		3377
2955	=head3 Queueing	3378	=head3 Queueing
2956		3379
2957	C<ev_async> does not support queueing of data in any way. The reason	3380	C<ev_async> does not support queueing of data in any way. The reason
2958	is that the author does not know of a simple (or any) algorithm for a	3381	is that the author does not know of a simple (or any) algorithm for a
2959	multiple-writer-single-reader queue that works in all cases and doesn't	3382	multiple-writer-single-reader queue that works in all cases and doesn't
2960	need elaborate support such as pthreads.	3383	need elaborate support such as pthreads or unportable memory access
		3384	semantics.
2961		3385
2962	That means that if you want to queue data, you have to provide your own	3386	That means that if you want to queue data, you have to provide your own
2963	queue. But at least I can tell you how to implement locking around your	3387	queue. But at least I can tell you how to implement locking around your
2964	queue:	3388	queue:
2965		3389
…		…
3049	trust me.	3473	trust me.
3050		3474
3051	=item ev_async_send (loop, ev_async *)	3475	=item ev_async_send (loop, ev_async *)
3052		3476
3053	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3477	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3054	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3478	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3479	returns.
		3480
3055	C<ev_feed_event>, this call is safe to do from other threads, signal or	3481	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3056	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3482	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3057	section below on what exactly this means).	3483	embedding section below on what exactly this means).
3058		3484
3059	Note that, as with other watchers in libev, multiple events might get	3485	Note that, as with other watchers in libev, multiple events might get
3060	compressed into a single callback invocation (another way to look at this	3486	compressed into a single callback invocation (another way to look at
3061	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3487	this is that C<ev_async> watchers are level-triggered: they are set on
3062	reset when the event loop detects that).	3488	C<ev_async_send>, reset when the event loop detects that).
3063		3489
3064	This call incurs the overhead of a system call only once per event loop	3490	This call incurs the overhead of at most one extra system call per event
3065	iteration, so while the overhead might be noticeable, it doesn't apply to	3491	loop iteration, if the event loop is blocked, and no syscall at all if
3066	repeated calls to C<ev_async_send> for the same event loop.	3492	the event loop (or your program) is processing events. That means that
		3493	repeated calls are basically free (there is no need to avoid calls for
		3494	performance reasons) and that the overhead becomes smaller (typically
		3495	zero) under load.
3067		3496
3068	=item bool = ev_async_pending (ev_async *)	3497	=item bool = ev_async_pending (ev_async *)
3069		3498
3070	Returns a non-zero value when C<ev_async_send> has been called on the	3499	Returns a non-zero value when C<ev_async_send> has been called on the
3071	watcher but the event has not yet been processed (or even noted) by the	3500	watcher but the event has not yet been processed (or even noted) by the
…		…
3104		3533
3105	If C<timeout> is less than 0, then no timeout watcher will be	3534	If C<timeout> is less than 0, then no timeout watcher will be
3106	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3535	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3107	repeat = 0) will be started. C<0> is a valid timeout.	3536	repeat = 0) will be started. C<0> is a valid timeout.
3108		3537
3109	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3538	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3110	passed an C<revents> set like normal event callbacks (a combination of	3539	passed an C<revents> set like normal event callbacks (a combination of
3111	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3540	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3112	value passed to C<ev_once>. Note that it is possible to receive I<both>	3541	value passed to C<ev_once>. Note that it is possible to receive I<both>
3113	a timeout and an io event at the same time - you probably should give io	3542	a timeout and an io event at the same time - you probably should give io
3114	events precedence.	3543	events precedence.
3115		3544
3116	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3545	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3117		3546
3118	static void stdin_ready (int revents, void *arg)	3547	static void stdin_ready (int revents, void *arg)
3119	{	3548	{
3120	if (revents & EV_READ)	3549	if (revents & EV_READ)
3121	/* stdin might have data for us, joy! */;	3550	/* stdin might have data for us, joy! */;
3122	else if (revents & EV_TIMEOUT)	3551	else if (revents & EV_TIMER)
3123	/* doh, nothing entered */;	3552	/* doh, nothing entered */;
3124	}	3553	}
3125		3554
3126	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3555	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3127		3556
3128	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3129
3130	Feeds the given event set into the event loop, as if the specified event
3131	had happened for the specified watcher (which must be a pointer to an
3132	initialised but not necessarily started event watcher).
3133
3134	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3557	=item ev_feed_fd_event (loop, int fd, int revents)
3135		3558
3136	Feed an event on the given fd, as if a file descriptor backend detected	3559	Feed an event on the given fd, as if a file descriptor backend detected
3137	the given events it.	3560	the given events.
3138		3561
3139	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3562	=item ev_feed_signal_event (loop, int signum)
3140		3563
3141	Feed an event as if the given signal occurred (C<loop> must be the default	3564	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3142	loop!).	3565	which is async-safe.
3143		3566
3144	=back	3567	=back
		3568
		3569
		3570	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3571
		3572	This section explains some common idioms that are not immediately
		3573	obvious. Note that examples are sprinkled over the whole manual, and this
		3574	section only contains stuff that wouldn't fit anywhere else.
		3575
		3576	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3577
		3578	Each watcher has, by default, a C<void *data> member that you can read
		3579	or modify at any time: libev will completely ignore it. This can be used
		3580	to associate arbitrary data with your watcher. If you need more data and
		3581	don't want to allocate memory separately and store a pointer to it in that
		3582	data member, you can also "subclass" the watcher type and provide your own
		3583	data:
		3584
		3585	struct my_io
		3586	{
		3587	ev_io io;
		3588	int otherfd;
		3589	void *somedata;
		3590	struct whatever *mostinteresting;
		3591	};
		3592
		3593	...
		3594	struct my_io w;
		3595	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3596
		3597	And since your callback will be called with a pointer to the watcher, you
		3598	can cast it back to your own type:
		3599
		3600	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3601	{
		3602	struct my_io *w = (struct my_io *)w_;
		3603	...
		3604	}
		3605
		3606	More interesting and less C-conformant ways of casting your callback
		3607	function type instead have been omitted.
		3608
		3609	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3610
		3611	Another common scenario is to use some data structure with multiple
		3612	embedded watchers, in effect creating your own watcher that combines
		3613	multiple libev event sources into one "super-watcher":
		3614
		3615	struct my_biggy
		3616	{
		3617	int some_data;
		3618	ev_timer t1;
		3619	ev_timer t2;
		3620	}
		3621
		3622	In this case getting the pointer to C<my_biggy> is a bit more
		3623	complicated: Either you store the address of your C<my_biggy> struct in
		3624	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3625	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3626	real programmers):
		3627
		3628	#include <stddef.h>
		3629
		3630	static void
		3631	t1_cb (EV_P_ ev_timer *w, int revents)
		3632	{
		3633	struct my_biggy big = (struct my_biggy *)
		3634	(((char *)w) - offsetof (struct my_biggy, t1));
		3635	}
		3636
		3637	static void
		3638	t2_cb (EV_P_ ev_timer *w, int revents)
		3639	{
		3640	struct my_biggy big = (struct my_biggy *)
		3641	(((char *)w) - offsetof (struct my_biggy, t2));
		3642	}
		3643
		3644	=head2 AVOIDING FINISHING BEFORE RETURNING
		3645
		3646	Often you have structures like this in event-based programs:
		3647
		3648	callback ()
		3649	{
		3650	free (request);
		3651	}
		3652
		3653	request = start_new_request (..., callback);
		3654
		3655	The intent is to start some "lengthy" operation. The C<request> could be
		3656	used to cancel the operation, or do other things with it.
		3657
		3658	It's not uncommon to have code paths in C<start_new_request> that
		3659	immediately invoke the callback, for example, to report errors. Or you add
		3660	some caching layer that finds that it can skip the lengthy aspects of the
		3661	operation and simply invoke the callback with the result.
		3662
		3663	The problem here is that this will happen I<before> C<start_new_request>
		3664	has returned, so C<request> is not set.
		3665
		3666	Even if you pass the request by some safer means to the callback, you
		3667	might want to do something to the request after starting it, such as
		3668	canceling it, which probably isn't working so well when the callback has
		3669	already been invoked.
		3670
		3671	A common way around all these issues is to make sure that
		3672	C<start_new_request> I<always> returns before the callback is invoked. If
		3673	C<start_new_request> immediately knows the result, it can artificially
		3674	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3675	example, or more sneakily, by reusing an existing (stopped) watcher and
		3676	pushing it into the pending queue:
		3677
		3678	ev_set_cb (watcher, callback);
		3679	ev_feed_event (EV_A_ watcher, 0);
		3680
		3681	This way, C<start_new_request> can safely return before the callback is
		3682	invoked, while not delaying callback invocation too much.
		3683
		3684	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3685
		3686	Often (especially in GUI toolkits) there are places where you have
		3687	I<modal> interaction, which is most easily implemented by recursively
		3688	invoking C<ev_run>.
		3689
		3690	This brings the problem of exiting - a callback might want to finish the
		3691	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3692	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3693	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3694	other combination: In these cases, a simple C<ev_break> will not work.
		3695
		3696	The solution is to maintain "break this loop" variable for each C<ev_run>
		3697	invocation, and use a loop around C<ev_run> until the condition is
		3698	triggered, using C<EVRUN_ONCE>:
		3699
		3700	// main loop
		3701	int exit_main_loop = 0;
		3702
		3703	while (!exit_main_loop)
		3704	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3705
		3706	// in a modal watcher
		3707	int exit_nested_loop = 0;
		3708
		3709	while (!exit_nested_loop)
		3710	ev_run (EV_A_ EVRUN_ONCE);
		3711
		3712	To exit from any of these loops, just set the corresponding exit variable:
		3713
		3714	// exit modal loop
		3715	exit_nested_loop = 1;
		3716
		3717	// exit main program, after modal loop is finished
		3718	exit_main_loop = 1;
		3719
		3720	// exit both
		3721	exit_main_loop = exit_nested_loop = 1;
		3722
		3723	=head2 THREAD LOCKING EXAMPLE
		3724
		3725	Here is a fictitious example of how to run an event loop in a different
		3726	thread from where callbacks are being invoked and watchers are
		3727	created/added/removed.
		3728
		3729	For a real-world example, see the C<EV::Loop::Async> perl module,
		3730	which uses exactly this technique (which is suited for many high-level
		3731	languages).
		3732
		3733	The example uses a pthread mutex to protect the loop data, a condition
		3734	variable to wait for callback invocations, an async watcher to notify the
		3735	event loop thread and an unspecified mechanism to wake up the main thread.
		3736
		3737	First, you need to associate some data with the event loop:
		3738
		3739	typedef struct {
		3740	mutex_t lock; /* global loop lock */
		3741	ev_async async_w;
		3742	thread_t tid;
		3743	cond_t invoke_cv;
		3744	} userdata;
		3745
		3746	void prepare_loop (EV_P)
		3747	{
		3748	// for simplicity, we use a static userdata struct.
		3749	static userdata u;
		3750
		3751	ev_async_init (&u->async_w, async_cb);
		3752	ev_async_start (EV_A_ &u->async_w);
		3753
		3754	pthread_mutex_init (&u->lock, 0);
		3755	pthread_cond_init (&u->invoke_cv, 0);
		3756
		3757	// now associate this with the loop
		3758	ev_set_userdata (EV_A_ u);
		3759	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3760	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3761
		3762	// then create the thread running ev_run
		3763	pthread_create (&u->tid, 0, l_run, EV_A);
		3764	}
		3765
		3766	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3767	solely to wake up the event loop so it takes notice of any new watchers
		3768	that might have been added:
		3769
		3770	static void
		3771	async_cb (EV_P_ ev_async *w, int revents)
		3772	{
		3773	// just used for the side effects
		3774	}
		3775
		3776	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3777	protecting the loop data, respectively.
		3778
		3779	static void
		3780	l_release (EV_P)
		3781	{
		3782	userdata *u = ev_userdata (EV_A);
		3783	pthread_mutex_unlock (&u->lock);
		3784	}
		3785
		3786	static void
		3787	l_acquire (EV_P)
		3788	{
		3789	userdata *u = ev_userdata (EV_A);
		3790	pthread_mutex_lock (&u->lock);
		3791	}
		3792
		3793	The event loop thread first acquires the mutex, and then jumps straight
		3794	into C<ev_run>:
		3795
		3796	void *
		3797	l_run (void *thr_arg)
		3798	{
		3799	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3800
		3801	l_acquire (EV_A);
		3802	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3803	ev_run (EV_A_ 0);
		3804	l_release (EV_A);
		3805
		3806	return 0;
		3807	}
		3808
		3809	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3810	signal the main thread via some unspecified mechanism (signals? pipe
		3811	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3812	have been called (in a while loop because a) spurious wakeups are possible
		3813	and b) skipping inter-thread-communication when there are no pending
		3814	watchers is very beneficial):
		3815
		3816	static void
		3817	l_invoke (EV_P)
		3818	{
		3819	userdata *u = ev_userdata (EV_A);
		3820
		3821	while (ev_pending_count (EV_A))
		3822	{
		3823	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3824	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3825	}
		3826	}
		3827
		3828	Now, whenever the main thread gets told to invoke pending watchers, it
		3829	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3830	thread to continue:
		3831
		3832	static void
		3833	real_invoke_pending (EV_P)
		3834	{
		3835	userdata *u = ev_userdata (EV_A);
		3836
		3837	pthread_mutex_lock (&u->lock);
		3838	ev_invoke_pending (EV_A);
		3839	pthread_cond_signal (&u->invoke_cv);
		3840	pthread_mutex_unlock (&u->lock);
		3841	}
		3842
		3843	Whenever you want to start/stop a watcher or do other modifications to an
		3844	event loop, you will now have to lock:
		3845
		3846	ev_timer timeout_watcher;
		3847	userdata *u = ev_userdata (EV_A);
		3848
		3849	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3850
		3851	pthread_mutex_lock (&u->lock);
		3852	ev_timer_start (EV_A_ &timeout_watcher);
		3853	ev_async_send (EV_A_ &u->async_w);
		3854	pthread_mutex_unlock (&u->lock);
		3855
		3856	Note that sending the C<ev_async> watcher is required because otherwise
		3857	an event loop currently blocking in the kernel will have no knowledge
		3858	about the newly added timer. By waking up the loop it will pick up any new
		3859	watchers in the next event loop iteration.
		3860
		3861	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3862
		3863	While the overhead of a callback that e.g. schedules a thread is small, it
		3864	is still an overhead. If you embed libev, and your main usage is with some
		3865	kind of threads or coroutines, you might want to customise libev so that
		3866	doesn't need callbacks anymore.
		3867
		3868	Imagine you have coroutines that you can switch to using a function
		3869	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3870	and that due to some magic, the currently active coroutine is stored in a
		3871	global called C<current_coro>. Then you can build your own "wait for libev
		3872	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3873	the differing C<;> conventions):
		3874
		3875	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3876	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3877
		3878	That means instead of having a C callback function, you store the
		3879	coroutine to switch to in each watcher, and instead of having libev call
		3880	your callback, you instead have it switch to that coroutine.
		3881
		3882	A coroutine might now wait for an event with a function called
		3883	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3884	matter when, or whether the watcher is active or not when this function is
		3885	called):
		3886
		3887	void
		3888	wait_for_event (ev_watcher *w)
		3889	{
		3890	ev_set_cb (w, current_coro);
		3891	switch_to (libev_coro);
		3892	}
		3893
		3894	That basically suspends the coroutine inside C<wait_for_event> and
		3895	continues the libev coroutine, which, when appropriate, switches back to
		3896	this or any other coroutine.
		3897
		3898	You can do similar tricks if you have, say, threads with an event queue -
		3899	instead of storing a coroutine, you store the queue object and instead of
		3900	switching to a coroutine, you push the watcher onto the queue and notify
		3901	any waiters.
		3902
		3903	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3904	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3905
		3906	// my_ev.h
		3907	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3908	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3909	#include "../libev/ev.h"
		3910
		3911	// my_ev.c
		3912	#define EV_H "my_ev.h"
		3913	#include "../libev/ev.c"
		3914
		3915	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3916	F<my_ev.c> into your project. When properly specifying include paths, you
		3917	can even use F<ev.h> as header file name directly.
3145		3918
3146		3919
3147	=head1 LIBEVENT EMULATION	3920	=head1 LIBEVENT EMULATION
3148		3921
3149	Libev offers a compatibility emulation layer for libevent. It cannot	3922	Libev offers a compatibility emulation layer for libevent. It cannot
3150	emulate the internals of libevent, so here are some usage hints:	3923	emulate the internals of libevent, so here are some usage hints:
3151		3924
3152	=over 4	3925	=over 4
		3926
		3927	=item * Only the libevent-1.4.1-beta API is being emulated.
		3928
		3929	This was the newest libevent version available when libev was implemented,
		3930	and is still mostly unchanged in 2010.
3153		3931
3154	=item * Use it by including <event.h>, as usual.	3932	=item * Use it by including <event.h>, as usual.
3155		3933
3156	=item * The following members are fully supported: ev_base, ev_callback,	3934	=item * The following members are fully supported: ev_base, ev_callback,
3157	ev_arg, ev_fd, ev_res, ev_events.	3935	ev_arg, ev_fd, ev_res, ev_events.
…		…
3163	=item * Priorities are not currently supported. Initialising priorities	3941	=item * Priorities are not currently supported. Initialising priorities
3164	will fail and all watchers will have the same priority, even though there	3942	will fail and all watchers will have the same priority, even though there
3165	is an ev_pri field.	3943	is an ev_pri field.
3166		3944
3167	=item * In libevent, the last base created gets the signals, in libev, the	3945	=item * In libevent, the last base created gets the signals, in libev, the
3168	first base created (== the default loop) gets the signals.	3946	base that registered the signal gets the signals.
3169		3947
3170	=item * Other members are not supported.	3948	=item * Other members are not supported.
3171		3949
3172	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3950	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3173	to use the libev header file and library.	3951	to use the libev header file and library.
3174		3952
3175	=back	3953	=back
3176		3954
3177	=head1 C++ SUPPORT	3955	=head1 C++ SUPPORT
		3956
		3957	=head2 C API
		3958
		3959	The normal C API should work fine when used from C++: both ev.h and the
		3960	libev sources can be compiled as C++. Therefore, code that uses the C API
		3961	will work fine.
		3962
		3963	Proper exception specifications might have to be added to callbacks passed
		3964	to libev: exceptions may be thrown only from watcher callbacks, all
		3965	other callbacks (allocator, syserr, loop acquire/release and periodic
		3966	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3967	()> specification. If you have code that needs to be compiled as both C
		3968	and C++ you can use the C<EV_THROW> macro for this:
		3969
		3970	static void
		3971	fatal_error (const char *msg) EV_THROW
		3972	{
		3973	perror (msg);
		3974	abort ();
		3975	}
		3976
		3977	...
		3978	ev_set_syserr_cb (fatal_error);
		3979
		3980	The only API functions that can currently throw exceptions are C<ev_run>,
		3981	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3982	because it runs cleanup watchers).
		3983
		3984	Throwing exceptions in watcher callbacks is only supported if libev itself
		3985	is compiled with a C++ compiler or your C and C++ environments allow
		3986	throwing exceptions through C libraries (most do).
		3987
		3988	=head2 C++ API
3178		3989
3179	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3990	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3180	you to use some convenience methods to start/stop watchers and also change	3991	you to use some convenience methods to start/stop watchers and also change
3181	the callback model to a model using method callbacks on objects.	3992	the callback model to a model using method callbacks on objects.
3182		3993
3183	To use it,	3994	To use it,
3184		3995
3185	#include <ev++.h>	3996	#include <ev++.h>
3186		3997
3187	This automatically includes F<ev.h> and puts all of its definitions (many	3998	This automatically includes F<ev.h> and puts all of its definitions (many
3188	of them macros) into the global namespace. All C++ specific things are	3999	of them macros) into the global namespace. All C++ specific things are
3189	put into the C<ev> namespace. It should support all the same embedding	4000	put into the C<ev> namespace. It should support all the same embedding
…		…
3192	Care has been taken to keep the overhead low. The only data member the C++	4003	Care has been taken to keep the overhead low. The only data member the C++
3193	classes add (compared to plain C-style watchers) is the event loop pointer	4004	classes add (compared to plain C-style watchers) is the event loop pointer
3194	that the watcher is associated with (or no additional members at all if	4005	that the watcher is associated with (or no additional members at all if
3195	you disable C<EV_MULTIPLICITY> when embedding libev).	4006	you disable C<EV_MULTIPLICITY> when embedding libev).
3196		4007
3197	Currently, functions, and static and non-static member functions can be	4008	Currently, functions, static and non-static member functions and classes
3198	used as callbacks. Other types should be easy to add as long as they only	4009	with C<operator ()> can be used as callbacks. Other types should be easy
3199	need one additional pointer for context. If you need support for other	4010	to add as long as they only need one additional pointer for context. If
3200	types of functors please contact the author (preferably after implementing	4011	you need support for other types of functors please contact the author
3201	it).	4012	(preferably after implementing it).
		4013
		4014	For all this to work, your C++ compiler either has to use the same calling
		4015	conventions as your C compiler (for static member functions), or you have
		4016	to embed libev and compile libev itself as C++.
3202		4017
3203	Here is a list of things available in the C<ev> namespace:	4018	Here is a list of things available in the C<ev> namespace:
3204		4019
3205	=over 4	4020	=over 4
3206		4021
…		…
3216	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4031	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3217		4032
3218	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4033	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3219	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4034	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3220	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4035	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3221	defines by many implementations.	4036	defined by many implementations.
3222		4037
3223	All of those classes have these methods:	4038	All of those classes have these methods:
3224		4039
3225	=over 4	4040	=over 4
3226		4041
3227	=item ev::TYPE::TYPE ()	4042	=item ev::TYPE::TYPE ()
3228		4043
3229	=item ev::TYPE::TYPE (struct ev_loop *)	4044	=item ev::TYPE::TYPE (loop)
3230		4045
3231	=item ev::TYPE::~TYPE	4046	=item ev::TYPE::~TYPE
3232		4047
3233	The constructor (optionally) takes an event loop to associate the watcher	4048	The constructor (optionally) takes an event loop to associate the watcher
3234	with. If it is omitted, it will use C<EV_DEFAULT>.	4049	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3267	myclass obj;	4082	myclass obj;
3268	ev::io iow;	4083	ev::io iow;
3269	iow.set <myclass, &myclass::io_cb> (&obj);	4084	iow.set <myclass, &myclass::io_cb> (&obj);
3270		4085
3271	=item w->set (object *)	4086	=item w->set (object *)
3272
3273	This is an B<experimental> feature that might go away in a future version.
3274		4087
3275	This is a variation of a method callback - leaving out the method to call	4088	This is a variation of a method callback - leaving out the method to call
3276	will default the method to C<operator ()>, which makes it possible to use	4089	will default the method to C<operator ()>, which makes it possible to use
3277	functor objects without having to manually specify the C<operator ()> all	4090	functor objects without having to manually specify the C<operator ()> all
3278	the time. Incidentally, you can then also leave out the template argument	4091	the time. Incidentally, you can then also leave out the template argument
…		…
3290	void operator() (ev::io &w, int revents)	4103	void operator() (ev::io &w, int revents)
3291	{	4104	{
3292	...	4105	...
3293	}	4106	}
3294	}	4107	}
3295		4108
3296	myfunctor f;	4109	myfunctor f;
3297		4110
3298	ev::io w;	4111	ev::io w;
3299	w.set (&f);	4112	w.set (&f);
3300		4113
…		…
3311	Example: Use a plain function as callback.	4124	Example: Use a plain function as callback.
3312		4125
3313	static void io_cb (ev::io &w, int revents) { }	4126	static void io_cb (ev::io &w, int revents) { }
3314	iow.set <io_cb> ();	4127	iow.set <io_cb> ();
3315		4128
3316	=item w->set (struct ev_loop *)	4129	=item w->set (loop)
3317		4130
3318	Associates a different C<struct ev_loop> with this watcher. You can only	4131	Associates a different C<struct ev_loop> with this watcher. You can only
3319	do this when the watcher is inactive (and not pending either).	4132	do this when the watcher is inactive (and not pending either).
3320		4133
3321	=item w->set ([arguments])	4134	=item w->set ([arguments])
3322		4135
3323	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4136	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4137	with the same arguments. Either this method or a suitable start method
3324	called at least once. Unlike the C counterpart, an active watcher gets	4138	must be called at least once. Unlike the C counterpart, an active watcher
3325	automatically stopped and restarted when reconfiguring it with this	4139	gets automatically stopped and restarted when reconfiguring it with this
3326	method.	4140	method.
		4141
		4142	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4143	clashing with the C<set (loop)> method.
3327		4144
3328	=item w->start ()	4145	=item w->start ()
3329		4146
3330	Starts the watcher. Note that there is no C<loop> argument, as the	4147	Starts the watcher. Note that there is no C<loop> argument, as the
3331	constructor already stores the event loop.	4148	constructor already stores the event loop.
3332		4149
		4150	=item w->start ([arguments])
		4151
		4152	Instead of calling C<set> and C<start> methods separately, it is often
		4153	convenient to wrap them in one call. Uses the same type of arguments as
		4154	the configure C<set> method of the watcher.
		4155
3333	=item w->stop ()	4156	=item w->stop ()
3334		4157
3335	Stops the watcher if it is active. Again, no C<loop> argument.	4158	Stops the watcher if it is active. Again, no C<loop> argument.
3336		4159
3337	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4160	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3349		4172
3350	=back	4173	=back
3351		4174
3352	=back	4175	=back
3353		4176
3354	Example: Define a class with an IO and idle watcher, start one of them in	4177	Example: Define a class with two I/O and idle watchers, start the I/O
3355	the constructor.	4178	watchers in the constructor.
3356		4179
3357	class myclass	4180	class myclass
3358	{	4181	{
3359	ev::io io ; void io_cb (ev::io &w, int revents);	4182	ev::io io ; void io_cb (ev::io &w, int revents);
		4183	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3360	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3361		4185
3362	myclass (int fd)	4186	myclass (int fd)
3363	{	4187	{
3364	io .set <myclass, &myclass::io_cb > (this);	4188	io .set <myclass, &myclass::io_cb > (this);
		4189	io2 .set <myclass, &myclass::io2_cb > (this);
3365	idle.set <myclass, &myclass::idle_cb> (this);	4190	idle.set <myclass, &myclass::idle_cb> (this);
3366		4191
3367	io.start (fd, ev::READ);	4192	io.set (fd, ev::WRITE); // configure the watcher
		4193	io.start (); // start it whenever convenient
		4194
		4195	io2.start (fd, ev::READ); // set + start in one call
3368	}	4196	}
3369	};	4197	};
3370		4198
3371		4199
3372	=head1 OTHER LANGUAGE BINDINGS	4200	=head1 OTHER LANGUAGE BINDINGS
…		…
3411	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4239	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3412		4240
3413	=item D	4241	=item D
3414		4242
3415	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4243	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3416	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4244	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3417		4245
3418	=item Ocaml	4246	=item Ocaml
3419		4247
3420	Erkki Seppala has written Ocaml bindings for libev, to be found at	4248	Erkki Seppala has written Ocaml bindings for libev, to be found at
3421	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4249	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3422		4250
3423	=item Lua	4251	=item Lua
3424		4252
3425	Brian Maher has written a partial interface to libev	4253	Brian Maher has written a partial interface to libev for lua (at the
3426	for lua (only C<ev_io> and C<ev_timer>), to be found at	4254	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3427	L<http://github.com/brimworks/lua-ev>.	4255	L<http://github.com/brimworks/lua-ev>.
		4256
		4257	=item Javascript
		4258
		4259	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4260
		4261	=item Others
		4262
		4263	There are others, and I stopped counting.
3428		4264
3429	=back	4265	=back
3430		4266
3431		4267
3432	=head1 MACRO MAGIC	4268	=head1 MACRO MAGIC
…		…
3446	loop argument"). The C<EV_A> form is used when this is the sole argument,	4282	loop argument"). The C<EV_A> form is used when this is the sole argument,
3447	C<EV_A_> is used when other arguments are following. Example:	4283	C<EV_A_> is used when other arguments are following. Example:
3448		4284
3449	ev_unref (EV_A);	4285	ev_unref (EV_A);
3450	ev_timer_add (EV_A_ watcher);	4286	ev_timer_add (EV_A_ watcher);
3451	ev_loop (EV_A_ 0);	4287	ev_run (EV_A_ 0);
3452		4288
3453	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4289	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3454	which is often provided by the following macro.	4290	which is often provided by the following macro.
3455		4291
3456	=item C<EV_P>, C<EV_P_>	4292	=item C<EV_P>, C<EV_P_>
…		…
3469	suitable for use with C<EV_A>.	4305	suitable for use with C<EV_A>.
3470		4306
3471	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4307	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3472		4308
3473	Similar to the other two macros, this gives you the value of the default	4309	Similar to the other two macros, this gives you the value of the default
3474	loop, if multiple loops are supported ("ev loop default").	4310	loop, if multiple loops are supported ("ev loop default"). The default loop
		4311	will be initialised if it isn't already initialised.
		4312
		4313	For non-multiplicity builds, these macros do nothing, so you always have
		4314	to initialise the loop somewhere.
3475		4315
3476	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4316	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3477		4317
3478	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4318	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3479	default loop has been initialised (C<UC> == unchecked). Their behaviour	4319	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3496	}	4336	}
3497		4337
3498	ev_check check;	4338	ev_check check;
3499	ev_check_init (&check, check_cb);	4339	ev_check_init (&check, check_cb);
3500	ev_check_start (EV_DEFAULT_ &check);	4340	ev_check_start (EV_DEFAULT_ &check);
3501	ev_loop (EV_DEFAULT_ 0);	4341	ev_run (EV_DEFAULT_ 0);
3502		4342
3503	=head1 EMBEDDING	4343	=head1 EMBEDDING
3504		4344
3505	Libev can (and often is) directly embedded into host	4345	Libev can (and often is) directly embedded into host
3506	applications. Examples of applications that embed it include the Deliantra	4346	applications. Examples of applications that embed it include the Deliantra
…		…
3586	libev.m4	4426	libev.m4
3587		4427
3588	=head2 PREPROCESSOR SYMBOLS/MACROS	4428	=head2 PREPROCESSOR SYMBOLS/MACROS
3589		4429
3590	Libev can be configured via a variety of preprocessor symbols you have to	4430	Libev can be configured via a variety of preprocessor symbols you have to
3591	define before including any of its files. The default in the absence of	4431	define before including (or compiling) any of its files. The default in
3592	autoconf is documented for every option.	4432	the absence of autoconf is documented for every option.
		4433
		4434	Symbols marked with "(h)" do not change the ABI, and can have different
		4435	values when compiling libev vs. including F<ev.h>, so it is permissible
		4436	to redefine them before including F<ev.h> without breaking compatibility
		4437	to a compiled library. All other symbols change the ABI, which means all
		4438	users of libev and the libev code itself must be compiled with compatible
		4439	settings.
3593		4440
3594	=over 4	4441	=over 4
3595		4442
		4443	=item EV_COMPAT3 (h)
		4444
		4445	Backwards compatibility is a major concern for libev. This is why this
		4446	release of libev comes with wrappers for the functions and symbols that
		4447	have been renamed between libev version 3 and 4.
		4448
		4449	You can disable these wrappers (to test compatibility with future
		4450	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4451	sources. This has the additional advantage that you can drop the C<struct>
		4452	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4453	typedef in that case.
		4454
		4455	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4456	and in some even more future version the compatibility code will be
		4457	removed completely.
		4458
3596	=item EV_STANDALONE	4459	=item EV_STANDALONE (h)
3597		4460
3598	Must always be C<1> if you do not use autoconf configuration, which	4461	Must always be C<1> if you do not use autoconf configuration, which
3599	keeps libev from including F<config.h>, and it also defines dummy	4462	keeps libev from including F<config.h>, and it also defines dummy
3600	implementations for some libevent functions (such as logging, which is not	4463	implementations for some libevent functions (such as logging, which is not
3601	supported). It will also not define any of the structs usually found in	4464	supported). It will also not define any of the structs usually found in
3602	F<event.h> that are not directly supported by the libev core alone.	4465	F<event.h> that are not directly supported by the libev core alone.
3603		4466
3604	In standalone mode, libev will still try to automatically deduce the	4467	In standalone mode, libev will still try to automatically deduce the
3605	configuration, but has to be more conservative.	4468	configuration, but has to be more conservative.
		4469
		4470	=item EV_USE_FLOOR
		4471
		4472	If defined to be C<1>, libev will use the C<floor ()> function for its
		4473	periodic reschedule calculations, otherwise libev will fall back on a
		4474	portable (slower) implementation. If you enable this, you usually have to
		4475	link against libm or something equivalent. Enabling this when the C<floor>
		4476	function is not available will fail, so the safe default is to not enable
		4477	this.
3606		4478
3607	=item EV_USE_MONOTONIC	4479	=item EV_USE_MONOTONIC
3608		4480
3609	If defined to be C<1>, libev will try to detect the availability of the	4481	If defined to be C<1>, libev will try to detect the availability of the
3610	monotonic clock option at both compile time and runtime. Otherwise no	4482	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3695		4567
3696	If programs implement their own fd to handle mapping on win32, then this	4568	If programs implement their own fd to handle mapping on win32, then this
3697	macro can be used to override the C<close> function, useful to unregister	4569	macro can be used to override the C<close> function, useful to unregister
3698	file descriptors again. Note that the replacement function has to close	4570	file descriptors again. Note that the replacement function has to close
3699	the underlying OS handle.	4571	the underlying OS handle.
		4572
		4573	=item EV_USE_WSASOCKET
		4574
		4575	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4576	communication socket, which works better in some environments. Otherwise,
		4577	the normal C<socket> function will be used, which works better in other
		4578	environments.
3700		4579
3701	=item EV_USE_POLL	4580	=item EV_USE_POLL
3702		4581
3703	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4582	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3704	backend. Otherwise it will be enabled on non-win32 platforms. It	4583	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3740	If defined to be C<1>, libev will compile in support for the Linux inotify	4619	If defined to be C<1>, libev will compile in support for the Linux inotify
3741	interface to speed up C<ev_stat> watchers. Its actual availability will	4620	interface to speed up C<ev_stat> watchers. Its actual availability will
3742	be detected at runtime. If undefined, it will be enabled if the headers	4621	be detected at runtime. If undefined, it will be enabled if the headers
3743	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4622	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3744		4623
		4624	=item EV_NO_SMP
		4625
		4626	If defined to be C<1>, libev will assume that memory is always coherent
		4627	between threads, that is, threads can be used, but threads never run on
		4628	different cpus (or different cpu cores). This reduces dependencies
		4629	and makes libev faster.
		4630
		4631	=item EV_NO_THREADS
		4632
		4633	If defined to be C<1>, libev will assume that it will never be called from
		4634	different threads (that includes signal handlers), which is a stronger
		4635	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4636	libev faster.
		4637
3745	=item EV_ATOMIC_T	4638	=item EV_ATOMIC_T
3746		4639
3747	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4640	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3748	access is atomic with respect to other threads or signal contexts. No such	4641	access is atomic with respect to other threads or signal contexts. No
3749	type is easily found in the C language, so you can provide your own type	4642	such type is easily found in the C language, so you can provide your own
3750	that you know is safe for your purposes. It is used both for signal handler "locking"	4643	type that you know is safe for your purposes. It is used both for signal
3751	as well as for signal and thread safety in C<ev_async> watchers.	4644	handler "locking" as well as for signal and thread safety in C<ev_async>
		4645	watchers.
3752		4646
3753	In the absence of this define, libev will use C<sig_atomic_t volatile>	4647	In the absence of this define, libev will use C<sig_atomic_t volatile>
3754	(from F<signal.h>), which is usually good enough on most platforms.	4648	(from F<signal.h>), which is usually good enough on most platforms.
3755		4649
3756	=item EV_H	4650	=item EV_H (h)
3757		4651
3758	The name of the F<ev.h> header file used to include it. The default if	4652	The name of the F<ev.h> header file used to include it. The default if
3759	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4653	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3760	used to virtually rename the F<ev.h> header file in case of conflicts.	4654	used to virtually rename the F<ev.h> header file in case of conflicts.
3761		4655
3762	=item EV_CONFIG_H	4656	=item EV_CONFIG_H (h)
3763		4657
3764	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4658	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3765	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4659	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3766	C<EV_H>, above.	4660	C<EV_H>, above.
3767		4661
3768	=item EV_EVENT_H	4662	=item EV_EVENT_H (h)
3769		4663
3770	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4664	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3771	of how the F<event.h> header can be found, the default is C<"event.h">.	4665	of how the F<event.h> header can be found, the default is C<"event.h">.
3772		4666
3773	=item EV_PROTOTYPES	4667	=item EV_PROTOTYPES (h)
3774		4668
3775	If defined to be C<0>, then F<ev.h> will not define any function	4669	If defined to be C<0>, then F<ev.h> will not define any function
3776	prototypes, but still define all the structs and other symbols. This is	4670	prototypes, but still define all the structs and other symbols. This is
3777	occasionally useful if you want to provide your own wrapper functions	4671	occasionally useful if you want to provide your own wrapper functions
3778	around libev functions.	4672	around libev functions.
…		…
3783	will have the C<struct ev_loop *> as first argument, and you can create	4677	will have the C<struct ev_loop *> as first argument, and you can create
3784	additional independent event loops. Otherwise there will be no support	4678	additional independent event loops. Otherwise there will be no support
3785	for multiple event loops and there is no first event loop pointer	4679	for multiple event loops and there is no first event loop pointer
3786	argument. Instead, all functions act on the single default loop.	4680	argument. Instead, all functions act on the single default loop.
3787		4681
		4682	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4683	default loop when multiplicity is switched off - you always have to
		4684	initialise the loop manually in this case.
		4685
3788	=item EV_MINPRI	4686	=item EV_MINPRI
3789		4687
3790	=item EV_MAXPRI	4688	=item EV_MAXPRI
3791		4689
3792	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4690	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3800	fine.	4698	fine.
3801		4699
3802	If your embedding application does not need any priorities, defining these	4700	If your embedding application does not need any priorities, defining these
3803	both to C<0> will save some memory and CPU.	4701	both to C<0> will save some memory and CPU.
3804		4702
3805	=item EV_PERIODIC_ENABLE	4703	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4704	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4705	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3806		4706
3807	If undefined or defined to be C<1>, then periodic timers are supported. If	4707	If undefined or defined to be C<1> (and the platform supports it), then
3808	defined to be C<0>, then they are not. Disabling them saves a few kB of	4708	the respective watcher type is supported. If defined to be C<0>, then it
3809	code.	4709	is not. Disabling watcher types mainly saves code size.
3810		4710
3811	=item EV_IDLE_ENABLE	4711	=item EV_FEATURES
3812
3813	If undefined or defined to be C<1>, then idle watchers are supported. If
3814	defined to be C<0>, then they are not. Disabling them saves a few kB of
3815	code.
3816
3817	=item EV_EMBED_ENABLE
3818
3819	If undefined or defined to be C<1>, then embed watchers are supported. If
3820	defined to be C<0>, then they are not. Embed watchers rely on most other
3821	watcher types, which therefore must not be disabled.
3822
3823	=item EV_STAT_ENABLE
3824
3825	If undefined or defined to be C<1>, then stat watchers are supported. If
3826	defined to be C<0>, then they are not.
3827
3828	=item EV_FORK_ENABLE
3829
3830	If undefined or defined to be C<1>, then fork watchers are supported. If
3831	defined to be C<0>, then they are not.
3832
3833	=item EV_ASYNC_ENABLE
3834
3835	If undefined or defined to be C<1>, then async watchers are supported. If
3836	defined to be C<0>, then they are not.
3837
3838	=item EV_MINIMAL
3839		4712
3840	If you need to shave off some kilobytes of code at the expense of some	4713	If you need to shave off some kilobytes of code at the expense of some
3841	speed (but with the full API), define this symbol to C<1>. Currently this	4714	speed (but with the full API), you can define this symbol to request
3842	is used to override some inlining decisions, saves roughly 30% code size	4715	certain subsets of functionality. The default is to enable all features
3843	on amd64. It also selects a much smaller 2-heap for timer management over	4716	that can be enabled on the platform.
3844	the default 4-heap.
3845		4717
3846	You can save even more by disabling watcher types you do not need	4718	A typical way to use this symbol is to define it to C<0> (or to a bitset
3847	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4719	with some broad features you want) and then selectively re-enable
3848	(C<-DNDEBUG>) will usually reduce code size a lot.	4720	additional parts you want, for example if you want everything minimal,
		4721	but multiple event loop support, async and child watchers and the poll
		4722	backend, use this:
3849		4723
3850	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4724	#define EV_FEATURES 0
3851	provide a bare-bones event library. See C<ev.h> for details on what parts	4725	#define EV_MULTIPLICITY 1
3852	of the API are still available, and do not complain if this subset changes	4726	#define EV_USE_POLL 1
3853	over time.	4727	#define EV_CHILD_ENABLE 1
		4728	#define EV_ASYNC_ENABLE 1
		4729
		4730	The actual value is a bitset, it can be a combination of the following
		4731	values (by default, all of these are enabled):
		4732
		4733	=over 4
		4734
		4735	=item C<1> - faster/larger code
		4736
		4737	Use larger code to speed up some operations.
		4738
		4739	Currently this is used to override some inlining decisions (enlarging the
		4740	code size by roughly 30% on amd64).
		4741
		4742	When optimising for size, use of compiler flags such as C<-Os> with
		4743	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4744	assertions.
		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
		4748
		4749	=item C<2> - faster/larger data structures
		4750
		4751	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4752	hash table sizes and so on. This will usually further increase code size
		4753	and can additionally have an effect on the size of data structures at
		4754	runtime.
		4755
		4756	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4757	(e.g. gcc with C<-Os>).
		4758
		4759	=item C<4> - full API configuration
		4760
		4761	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4762	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4763
		4764	=item C<8> - full API
		4765
		4766	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4767	details on which parts of the API are still available without this
		4768	feature, and do not complain if this subset changes over time.
		4769
		4770	=item C<16> - enable all optional watcher types
		4771
		4772	Enables all optional watcher types. If you want to selectively enable
		4773	only some watcher types other than I/O and timers (e.g. prepare,
		4774	embed, async, child...) you can enable them manually by defining
		4775	C<EV_watchertype_ENABLE> to C<1> instead.
		4776
		4777	=item C<32> - enable all backends
		4778
		4779	This enables all backends - without this feature, you need to enable at
		4780	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4781
		4782	=item C<64> - enable OS-specific "helper" APIs
		4783
		4784	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4785	default.
		4786
		4787	=back
		4788
		4789	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4790	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4791	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4792	watchers, timers and monotonic clock support.
		4793
		4794	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4795	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4796	your program might be left out as well - a binary starting a timer and an
		4797	I/O watcher then might come out at only 5Kb.
		4798
		4799	=item EV_API_STATIC
		4800
		4801	If this symbol is defined (by default it is not), then all identifiers
		4802	will have static linkage. This means that libev will not export any
		4803	identifiers, and you cannot link against libev anymore. This can be useful
		4804	when you embed libev, only want to use libev functions in a single file,
		4805	and do not want its identifiers to be visible.
		4806
		4807	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4808	wants to use libev.
		4809
		4810	This option only works when libev is compiled with a C compiler, as C++
		4811	doesn't support the required declaration syntax.
		4812
		4813	=item EV_AVOID_STDIO
		4814
		4815	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4816	functions (printf, scanf, perror etc.). This will increase the code size
		4817	somewhat, but if your program doesn't otherwise depend on stdio and your
		4818	libc allows it, this avoids linking in the stdio library which is quite
		4819	big.
		4820
		4821	Note that error messages might become less precise when this option is
		4822	enabled.
3854		4823
3855	=item EV_NSIG	4824	=item EV_NSIG
3856		4825
3857	The highest supported signal number, +1 (or, the number of	4826	The highest supported signal number, +1 (or, the number of
3858	signals): Normally, libev tries to deduce the maximum number of signals	4827	signals): Normally, libev tries to deduce the maximum number of signals
3859	automatically, but sometimes this fails, in which case it can be	4828	automatically, but sometimes this fails, in which case it can be
3860	specified. Also, using a lower number than detected (C<32> should be	4829	specified. Also, using a lower number than detected (C<32> should be
3861	good for about any system in existance) can save some memory, as libev	4830	good for about any system in existence) can save some memory, as libev
3862	statically allocates some 12-24 bytes per signal number.	4831	statically allocates some 12-24 bytes per signal number.
3863		4832
3864	=item EV_PID_HASHSIZE	4833	=item EV_PID_HASHSIZE
3865		4834
3866	C<ev_child> watchers use a small hash table to distribute workload by	4835	C<ev_child> watchers use a small hash table to distribute workload by
3867	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4836	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3868	than enough. If you need to manage thousands of children you might want to	4837	usually more than enough. If you need to manage thousands of children you
3869	increase this value (I<must> be a power of two).	4838	might want to increase this value (I<must> be a power of two).
3870		4839
3871	=item EV_INOTIFY_HASHSIZE	4840	=item EV_INOTIFY_HASHSIZE
3872		4841
3873	C<ev_stat> watchers use a small hash table to distribute workload by	4842	C<ev_stat> watchers use a small hash table to distribute workload by
3874	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4843	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3875	usually more than enough. If you need to manage thousands of C<ev_stat>	4844	disabled), usually more than enough. If you need to manage thousands of
3876	watchers you might want to increase this value (I<must> be a power of	4845	C<ev_stat> watchers you might want to increase this value (I<must> be a
3877	two).	4846	power of two).
3878		4847
3879	=item EV_USE_4HEAP	4848	=item EV_USE_4HEAP
3880		4849
3881	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4850	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3882	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4851	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3883	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4852	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3884	faster performance with many (thousands) of watchers.	4853	faster performance with many (thousands) of watchers.
3885		4854
3886	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4855	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3887	(disabled).	4856	will be C<0>.
3888		4857
3889	=item EV_HEAP_CACHE_AT	4858	=item EV_HEAP_CACHE_AT
3890		4859
3891	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4860	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3892	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4861	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3893	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4862	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3894	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4863	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3895	but avoids random read accesses on heap changes. This improves performance	4864	but avoids random read accesses on heap changes. This improves performance
3896	noticeably with many (hundreds) of watchers.	4865	noticeably with many (hundreds) of watchers.
3897		4866
3898	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4867	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3899	(disabled).	4868	will be C<0>.
3900		4869
3901	=item EV_VERIFY	4870	=item EV_VERIFY
3902		4871
3903	Controls how much internal verification (see C<ev_loop_verify ()>) will	4872	Controls how much internal verification (see C<ev_verify ()>) will
3904	be done: If set to C<0>, no internal verification code will be compiled	4873	be done: If set to C<0>, no internal verification code will be compiled
3905	in. If set to C<1>, then verification code will be compiled in, but not	4874	in. If set to C<1>, then verification code will be compiled in, but not
3906	called. If set to C<2>, then the internal verification code will be	4875	called. If set to C<2>, then the internal verification code will be
3907	called once per loop, which can slow down libev. If set to C<3>, then the	4876	called once per loop, which can slow down libev. If set to C<3>, then the
3908	verification code will be called very frequently, which will slow down	4877	verification code will be called very frequently, which will slow down
3909	libev considerably.	4878	libev considerably.
3910		4879
3911	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4880	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3912	C<0>.	4881	will be C<0>.
3913		4882
3914	=item EV_COMMON	4883	=item EV_COMMON
3915		4884
3916	By default, all watchers have a C<void *data> member. By redefining	4885	By default, all watchers have a C<void *data> member. By redefining
3917	this macro to a something else you can include more and other types of	4886	this macro to something else you can include more and other types of
3918	members. You have to define it each time you include one of the files,	4887	members. You have to define it each time you include one of the files,
3919	though, and it must be identical each time.	4888	though, and it must be identical each time.
3920		4889
3921	For example, the perl EV module uses something like this:	4890	For example, the perl EV module uses something like this:
3922		4891
…		…
3975	file.	4944	file.
3976		4945
3977	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4946	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3978	that everybody includes and which overrides some configure choices:	4947	that everybody includes and which overrides some configure choices:
3979		4948
3980	#define EV_MINIMAL 1	4949	#define EV_FEATURES 8
3981	#define EV_USE_POLL 0	4950	#define EV_USE_SELECT 1
3982	#define EV_MULTIPLICITY 0
3983	#define EV_PERIODIC_ENABLE 0	4951	#define EV_PREPARE_ENABLE 1
		4952	#define EV_IDLE_ENABLE 1
3984	#define EV_STAT_ENABLE 0	4953	#define EV_SIGNAL_ENABLE 1
3985	#define EV_FORK_ENABLE 0	4954	#define EV_CHILD_ENABLE 1
		4955	#define EV_USE_STDEXCEPT 0
3986	#define EV_CONFIG_H <config.h>	4956	#define EV_CONFIG_H <config.h>
3987	#define EV_MINPRI 0
3988	#define EV_MAXPRI 0
3989		4957
3990	#include "ev++.h"	4958	#include "ev++.h"
3991		4959
3992	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3993		4961
3994	#include "ev_cpp.h"	4962	#include "ev_cpp.h"
3995	#include "ev.c"	4963	#include "ev.c"
3996		4964
3997	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4965	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3998		4966
3999	=head2 THREADS AND COROUTINES	4967	=head2 THREADS AND COROUTINES
4000		4968
4001	=head3 THREADS	4969	=head3 THREADS
4002		4970
…		…
4053	default loop and triggering an C<ev_async> watcher from the default loop	5021	default loop and triggering an C<ev_async> watcher from the default loop
4054	watcher callback into the event loop interested in the signal.	5022	watcher callback into the event loop interested in the signal.
4055		5023
4056	=back	5024	=back
4057		5025
4058	=head4 THREAD LOCKING EXAMPLE	5026	See also L</THREAD LOCKING EXAMPLE>.
4059
4060	Here is a fictitious example of how to run an event loop in a different
4061	thread than where callbacks are being invoked and watchers are
4062	created/added/removed.
4063
4064	For a real-world example, see the C<EV::Loop::Async> perl module,
4065	which uses exactly this technique (which is suited for many high-level
4066	languages).
4067
4068	The example uses a pthread mutex to protect the loop data, a condition
4069	variable to wait for callback invocations, an async watcher to notify the
4070	event loop thread and an unspecified mechanism to wake up the main thread.
4071
4072	First, you need to associate some data with the event loop:
4073
4074	typedef struct {
4075	mutex_t lock; /* global loop lock */
4076	ev_async async_w;
4077	thread_t tid;
4078	cond_t invoke_cv;
4079	} userdata;
4080
4081	void prepare_loop (EV_P)
4082	{
4083	// for simplicity, we use a static userdata struct.
4084	static userdata u;
4085
4086	ev_async_init (&u->async_w, async_cb);
4087	ev_async_start (EV_A_ &u->async_w);
4088
4089	pthread_mutex_init (&u->lock, 0);
4090	pthread_cond_init (&u->invoke_cv, 0);
4091
4092	// now associate this with the loop
4093	ev_set_userdata (EV_A_ u);
4094	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4095	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4096
4097	// then create the thread running ev_loop
4098	pthread_create (&u->tid, 0, l_run, EV_A);
4099	}
4100
4101	The callback for the C<ev_async> watcher does nothing: the watcher is used
4102	solely to wake up the event loop so it takes notice of any new watchers
4103	that might have been added:
4104
4105	static void
4106	async_cb (EV_P_ ev_async *w, int revents)
4107	{
4108	// just used for the side effects
4109	}
4110
4111	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4112	protecting the loop data, respectively.
4113
4114	static void
4115	l_release (EV_P)
4116	{
4117	userdata *u = ev_userdata (EV_A);
4118	pthread_mutex_unlock (&u->lock);
4119	}
4120
4121	static void
4122	l_acquire (EV_P)
4123	{
4124	userdata *u = ev_userdata (EV_A);
4125	pthread_mutex_lock (&u->lock);
4126	}
4127
4128	The event loop thread first acquires the mutex, and then jumps straight
4129	into C<ev_loop>:
4130
4131	void *
4132	l_run (void *thr_arg)
4133	{
4134	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4135
4136	l_acquire (EV_A);
4137	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4138	ev_loop (EV_A_ 0);
4139	l_release (EV_A);
4140
4141	return 0;
4142	}
4143
4144	Instead of invoking all pending watchers, the C<l_invoke> callback will
4145	signal the main thread via some unspecified mechanism (signals? pipe
4146	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4147	have been called (in a while loop because a) spurious wakeups are possible
4148	and b) skipping inter-thread-communication when there are no pending
4149	watchers is very beneficial):
4150
4151	static void
4152	l_invoke (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155
4156	while (ev_pending_count (EV_A))
4157	{
4158	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4159	pthread_cond_wait (&u->invoke_cv, &u->lock);
4160	}
4161	}
4162
4163	Now, whenever the main thread gets told to invoke pending watchers, it
4164	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4165	thread to continue:
4166
4167	static void
4168	real_invoke_pending (EV_P)
4169	{
4170	userdata *u = ev_userdata (EV_A);
4171
4172	pthread_mutex_lock (&u->lock);
4173	ev_invoke_pending (EV_A);
4174	pthread_cond_signal (&u->invoke_cv);
4175	pthread_mutex_unlock (&u->lock);
4176	}
4177
4178	Whenever you want to start/stop a watcher or do other modifications to an
4179	event loop, you will now have to lock:
4180
4181	ev_timer timeout_watcher;
4182	userdata *u = ev_userdata (EV_A);
4183
4184	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4185
4186	pthread_mutex_lock (&u->lock);
4187	ev_timer_start (EV_A_ &timeout_watcher);
4188	ev_async_send (EV_A_ &u->async_w);
4189	pthread_mutex_unlock (&u->lock);
4190
4191	Note that sending the C<ev_async> watcher is required because otherwise
4192	an event loop currently blocking in the kernel will have no knowledge
4193	about the newly added timer. By waking up the loop it will pick up any new
4194	watchers in the next event loop iteration.
4195		5027
4196	=head3 COROUTINES	5028	=head3 COROUTINES
4197		5029
4198	Libev is very accommodating to coroutines ("cooperative threads"):	5030	Libev is very accommodating to coroutines ("cooperative threads"):
4199	libev fully supports nesting calls to its functions from different	5031	libev fully supports nesting calls to its functions from different
4200	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5032	coroutines (e.g. you can call C<ev_run> on the same loop from two
4201	different coroutines, and switch freely between both coroutines running	5033	different coroutines, and switch freely between both coroutines running
4202	the loop, as long as you don't confuse yourself). The only exception is	5034	the loop, as long as you don't confuse yourself). The only exception is
4203	that you must not do this from C<ev_periodic> reschedule callbacks.	5035	that you must not do this from C<ev_periodic> reschedule callbacks.
4204		5036
4205	Care has been taken to ensure that libev does not keep local state inside	5037	Care has been taken to ensure that libev does not keep local state inside
4206	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5038	C<ev_run>, and other calls do not usually allow for coroutine switches as
4207	they do not call any callbacks.	5039	they do not call any callbacks.
4208		5040
4209	=head2 COMPILER WARNINGS	5041	=head2 COMPILER WARNINGS
4210		5042
4211	Depending on your compiler and compiler settings, you might get no or a	5043	Depending on your compiler and compiler settings, you might get no or a
…		…
4222	maintainable.	5054	maintainable.
4223		5055
4224	And of course, some compiler warnings are just plain stupid, or simply	5056	And of course, some compiler warnings are just plain stupid, or simply
4225	wrong (because they don't actually warn about the condition their message	5057	wrong (because they don't actually warn about the condition their message
4226	seems to warn about). For example, certain older gcc versions had some	5058	seems to warn about). For example, certain older gcc versions had some
4227	warnings that resulted an extreme number of false positives. These have	5059	warnings that resulted in an extreme number of false positives. These have
4228	been fixed, but some people still insist on making code warn-free with	5060	been fixed, but some people still insist on making code warn-free with
4229	such buggy versions.	5061	such buggy versions.
4230		5062
4231	While libev is written to generate as few warnings as possible,	5063	While libev is written to generate as few warnings as possible,
4232	"warn-free" code is not a goal, and it is recommended not to build libev	5064	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4268	I suggest using suppression lists.	5100	I suggest using suppression lists.
4269		5101
4270		5102
4271	=head1 PORTABILITY NOTES	5103	=head1 PORTABILITY NOTES
4272		5104
		5105	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5106
		5107	GNU/Linux is the only common platform that supports 64 bit file/large file
		5108	interfaces but I<disables> them by default.
		5109
		5110	That means that libev compiled in the default environment doesn't support
		5111	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5112
		5113	Unfortunately, many programs try to work around this GNU/Linux issue
		5114	by enabling the large file API, which makes them incompatible with the
		5115	standard libev compiled for their system.
		5116
		5117	Likewise, libev cannot enable the large file API itself as this would
		5118	suddenly make it incompatible to the default compile time environment,
		5119	i.e. all programs not using special compile switches.
		5120
		5121	=head2 OS/X AND DARWIN BUGS
		5122
		5123	The whole thing is a bug if you ask me - basically any system interface
		5124	you touch is broken, whether it is locales, poll, kqueue or even the
		5125	OpenGL drivers.
		5126
		5127	=head3 C<kqueue> is buggy
		5128
		5129	The kqueue syscall is broken in all known versions - most versions support
		5130	only sockets, many support pipes.
		5131
		5132	Libev tries to work around this by not using C<kqueue> by default on this
		5133	rotten platform, but of course you can still ask for it when creating a
		5134	loop - embedding a socket-only kqueue loop into a select-based one is
		5135	probably going to work well.
		5136
		5137	=head3 C<poll> is buggy
		5138
		5139	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5140	implementation by something calling C<kqueue> internally around the 10.5.6
		5141	release, so now C<kqueue> I<and> C<poll> are broken.
		5142
		5143	Libev tries to work around this by not using C<poll> by default on
		5144	this rotten platform, but of course you can still ask for it when creating
		5145	a loop.
		5146
		5147	=head3 C<select> is buggy
		5148
		5149	All that's left is C<select>, and of course Apple found a way to fuck this
		5150	one up as well: On OS/X, C<select> actively limits the number of file
		5151	descriptors you can pass in to 1024 - your program suddenly crashes when
		5152	you use more.
		5153
		5154	There is an undocumented "workaround" for this - defining
		5155	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5156	work on OS/X.
		5157
		5158	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5159
		5160	=head3 C<errno> reentrancy
		5161
		5162	The default compile environment on Solaris is unfortunately so
		5163	thread-unsafe that you can't even use components/libraries compiled
		5164	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5165	defined by default. A valid, if stupid, implementation choice.
		5166
		5167	If you want to use libev in threaded environments you have to make sure
		5168	it's compiled with C<_REENTRANT> defined.
		5169
		5170	=head3 Event port backend
		5171
		5172	The scalable event interface for Solaris is called "event
		5173	ports". Unfortunately, this mechanism is very buggy in all major
		5174	releases. If you run into high CPU usage, your program freezes or you get
		5175	a large number of spurious wakeups, make sure you have all the relevant
		5176	and latest kernel patches applied. No, I don't know which ones, but there
		5177	are multiple ones to apply, and afterwards, event ports actually work
		5178	great.
		5179
		5180	If you can't get it to work, you can try running the program by setting
		5181	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5182	C<select> backends.
		5183
		5184	=head2 AIX POLL BUG
		5185
		5186	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5187	this by trying to avoid the poll backend altogether (i.e. it's not even
		5188	compiled in), which normally isn't a big problem as C<select> works fine
		5189	with large bitsets on AIX, and AIX is dead anyway.
		5190
4273	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5191	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5192
		5193	=head3 General issues
4274		5194
4275	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5195	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4276	requires, and its I/O model is fundamentally incompatible with the POSIX	5196	requires, and its I/O model is fundamentally incompatible with the POSIX
4277	model. Libev still offers limited functionality on this platform in	5197	model. Libev still offers limited functionality on this platform in
4278	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5198	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4279	descriptors. This only applies when using Win32 natively, not when using	5199	descriptors. This only applies when using Win32 natively, not when using
4280	e.g. cygwin.	5200	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5201	as every compiler comes with a slightly differently broken/incompatible
		5202	environment.
4281		5203
4282	Lifting these limitations would basically require the full	5204	Lifting these limitations would basically require the full
4283	re-implementation of the I/O system. If you are into these kinds of	5205	re-implementation of the I/O system. If you are into this kind of thing,
4284	things, then note that glib does exactly that for you in a very portable	5206	then note that glib does exactly that for you in a very portable way (note
4285	way (note also that glib is the slowest event library known to man).	5207	also that glib is the slowest event library known to man).
4286		5208
4287	There is no supported compilation method available on windows except	5209	There is no supported compilation method available on windows except
4288	embedding it into other applications.	5210	embedding it into other applications.
4289		5211
4290	Sensible signal handling is officially unsupported by Microsoft - libev	5212	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4318	you do I<not> compile the F<ev.c> or any other embedded source files!):	5240	you do I<not> compile the F<ev.c> or any other embedded source files!):
4319		5241
4320	#include "evwrap.h"	5242	#include "evwrap.h"
4321	#include "ev.c"	5243	#include "ev.c"
4322		5244
4323	=over 4
4324
4325	=item The winsocket select function	5245	=head3 The winsocket C<select> function
4326		5246
4327	The winsocket C<select> function doesn't follow POSIX in that it	5247	The winsocket C<select> function doesn't follow POSIX in that it
4328	requires socket I<handles> and not socket I<file descriptors> (it is	5248	requires socket I<handles> and not socket I<file descriptors> (it is
4329	also extremely buggy). This makes select very inefficient, and also	5249	also extremely buggy). This makes select very inefficient, and also
4330	requires a mapping from file descriptors to socket handles (the Microsoft	5250	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4339	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5259	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4340		5260
4341	Note that winsockets handling of fd sets is O(n), so you can easily get a	5261	Note that winsockets handling of fd sets is O(n), so you can easily get a
4342	complexity in the O(n²) range when using win32.	5262	complexity in the O(n²) range when using win32.
4343		5263
4344	=item Limited number of file descriptors	5264	=head3 Limited number of file descriptors
4345		5265
4346	Windows has numerous arbitrary (and low) limits on things.	5266	Windows has numerous arbitrary (and low) limits on things.
4347		5267
4348	Early versions of winsocket's select only supported waiting for a maximum	5268	Early versions of winsocket's select only supported waiting for a maximum
4349	of C<64> handles (probably owning to the fact that all windows kernels	5269	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4364	runtime libraries. This might get you to about C<512> or C<2048> sockets	5284	runtime libraries. This might get you to about C<512> or C<2048> sockets
4365	(depending on windows version and/or the phase of the moon). To get more,	5285	(depending on windows version and/or the phase of the moon). To get more,
4366	you need to wrap all I/O functions and provide your own fd management, but	5286	you need to wrap all I/O functions and provide your own fd management, but
4367	the cost of calling select (O(n²)) will likely make this unworkable.	5287	the cost of calling select (O(n²)) will likely make this unworkable.
4368		5288
4369	=back
4370
4371	=head2 PORTABILITY REQUIREMENTS	5289	=head2 PORTABILITY REQUIREMENTS
4372		5290
4373	In addition to a working ISO-C implementation and of course the	5291	In addition to a working ISO-C implementation and of course the
4374	backend-specific APIs, libev relies on a few additional extensions:	5292	backend-specific APIs, libev relies on a few additional extensions:
4375		5293
…		…
4381	Libev assumes not only that all watcher pointers have the same internal	5299	Libev assumes not only that all watcher pointers have the same internal
4382	structure (guaranteed by POSIX but not by ISO C for example), but it also	5300	structure (guaranteed by POSIX but not by ISO C for example), but it also
4383	assumes that the same (machine) code can be used to call any watcher	5301	assumes that the same (machine) code can be used to call any watcher
4384	callback: The watcher callbacks have different type signatures, but libev	5302	callback: The watcher callbacks have different type signatures, but libev
4385	calls them using an C<ev_watcher *> internally.	5303	calls them using an C<ev_watcher *> internally.
		5304
		5305	=item pointer accesses must be thread-atomic
		5306
		5307	Accessing a pointer value must be atomic, it must both be readable and
		5308	writable in one piece - this is the case on all current architectures.
4386		5309
4387	=item C<sig_atomic_t volatile> must be thread-atomic as well	5310	=item C<sig_atomic_t volatile> must be thread-atomic as well
4388		5311
4389	The type C<sig_atomic_t volatile> (or whatever is defined as	5312	The type C<sig_atomic_t volatile> (or whatever is defined as
4390	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5313	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4399	thread" or will block signals process-wide, both behaviours would	5322	thread" or will block signals process-wide, both behaviours would
4400	be compatible with libev. Interaction between C<sigprocmask> and	5323	be compatible with libev. Interaction between C<sigprocmask> and
4401	C<pthread_sigmask> could complicate things, however.	5324	C<pthread_sigmask> could complicate things, however.
4402		5325
4403	The most portable way to handle signals is to block signals in all threads	5326	The most portable way to handle signals is to block signals in all threads
4404	except the initial one, and run the default loop in the initial thread as	5327	except the initial one, and run the signal handling loop in the initial
4405	well.	5328	thread as well.
4406		5329
4407	=item C<long> must be large enough for common memory allocation sizes	5330	=item C<long> must be large enough for common memory allocation sizes
4408		5331
4409	To improve portability and simplify its API, libev uses C<long> internally	5332	To improve portability and simplify its API, libev uses C<long> internally
4410	instead of C<size_t> when allocating its data structures. On non-POSIX	5333	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4413	watchers.	5336	watchers.
4414		5337
4415	=item C<double> must hold a time value in seconds with enough accuracy	5338	=item C<double> must hold a time value in seconds with enough accuracy
4416		5339
4417	The type C<double> is used to represent timestamps. It is required to	5340	The type C<double> is used to represent timestamps. It is required to
4418	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5341	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4419	enough for at least into the year 4000. This requirement is fulfilled by	5342	good enough for at least into the year 4000 with millisecond accuracy
		5343	(the design goal for libev). This requirement is overfulfilled by
4420	implementations implementing IEEE 754, which is basically all existing	5344	implementations using IEEE 754, which is basically all existing ones.
		5345
4421	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5346	With IEEE 754 doubles, you get microsecond accuracy until at least the
4422	2200.	5347	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5348	is either obsolete or somebody patched it to use C<long double> or
		5349	something like that, just kidding).
4423		5350
4424	=back	5351	=back
4425		5352
4426	If you know of other additional requirements drop me a note.	5353	If you know of other additional requirements drop me a note.
4427		5354
…		…
4489	=item Processing ev_async_send: O(number_of_async_watchers)	5416	=item Processing ev_async_send: O(number_of_async_watchers)
4490		5417
4491	=item Processing signals: O(max_signal_number)	5418	=item Processing signals: O(max_signal_number)
4492		5419
4493	Sending involves a system call I<iff> there were no other C<ev_async_send>	5420	Sending involves a system call I<iff> there were no other C<ev_async_send>
4494	calls in the current loop iteration. Checking for async and signal events	5421	calls in the current loop iteration and the loop is currently
		5422	blocked. Checking for async and signal events involves iterating over all
4495	involves iterating over all running async watchers or all signal numbers.	5423	running async watchers or all signal numbers.
4496		5424
4497	=back	5425	=back
4498		5426
4499		5427
		5428	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5429
		5430	The major version 4 introduced some incompatible changes to the API.
		5431
		5432	At the moment, the C<ev.h> header file provides compatibility definitions
		5433	for all changes, so most programs should still compile. The compatibility
		5434	layer might be removed in later versions of libev, so better update to the
		5435	new API early than late.
		5436
		5437	=over 4
		5438
		5439	=item C<EV_COMPAT3> backwards compatibility mechanism
		5440
		5441	The backward compatibility mechanism can be controlled by
		5442	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5443	section.
		5444
		5445	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5446
		5447	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5448
		5449	ev_loop_destroy (EV_DEFAULT_UC);
		5450	ev_loop_fork (EV_DEFAULT);
		5451
		5452	=item function/symbol renames
		5453
		5454	A number of functions and symbols have been renamed:
		5455
		5456	ev_loop => ev_run
		5457	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5458	EVLOOP_ONESHOT => EVRUN_ONCE
		5459
		5460	ev_unloop => ev_break
		5461	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5462	EVUNLOOP_ONE => EVBREAK_ONE
		5463	EVUNLOOP_ALL => EVBREAK_ALL
		5464
		5465	EV_TIMEOUT => EV_TIMER
		5466
		5467	ev_loop_count => ev_iteration
		5468	ev_loop_depth => ev_depth
		5469	ev_loop_verify => ev_verify
		5470
		5471	Most functions working on C<struct ev_loop> objects don't have an
		5472	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5473	associated constants have been renamed to not collide with the C<struct
		5474	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5475	as all other watcher types. Note that C<ev_loop_fork> is still called
		5476	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5477	typedef.
		5478
		5479	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5480
		5481	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5482	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5483	and work, but the library code will of course be larger.
		5484
		5485	=back
		5486
		5487
4500	=head1 GLOSSARY	5488	=head1 GLOSSARY
4501		5489
4502	=over 4	5490	=over 4
4503		5491
4504	=item active	5492	=item active
4505		5493
4506	A watcher is active as long as it has been started (has been attached to	5494	A watcher is active as long as it has been started and not yet stopped.
4507	an event loop) but not yet stopped (disassociated from the event loop).	5495	See L</WATCHER STATES> for details.
4508		5496
4509	=item application	5497	=item application
4510		5498
4511	In this document, an application is whatever is using libev.	5499	In this document, an application is whatever is using libev.
		5500
		5501	=item backend
		5502
		5503	The part of the code dealing with the operating system interfaces.
4512		5504
4513	=item callback	5505	=item callback
4514		5506
4515	The address of a function that is called when some event has been	5507	The address of a function that is called when some event has been
4516	detected. Callbacks are being passed the event loop, the watcher that	5508	detected. Callbacks are being passed the event loop, the watcher that
4517	received the event, and the actual event bitset.	5509	received the event, and the actual event bitset.
4518		5510
4519	=item callback invocation	5511	=item callback/watcher invocation
4520		5512
4521	The act of calling the callback associated with a watcher.	5513	The act of calling the callback associated with a watcher.
4522		5514
4523	=item event	5515	=item event
4524		5516
4525	A change of state of some external event, such as data now being available	5517	A change of state of some external event, such as data now being available
4526	for reading on a file descriptor, time having passed or simply not having	5518	for reading on a file descriptor, time having passed or simply not having
4527	any other events happening anymore.	5519	any other events happening anymore.
4528		5520
4529	In libev, events are represented as single bits (such as C<EV_READ> or	5521	In libev, events are represented as single bits (such as C<EV_READ> or
4530	C<EV_TIMEOUT>).	5522	C<EV_TIMER>).
4531		5523
4532	=item event library	5524	=item event library
4533		5525
4534	A software package implementing an event model and loop.	5526	A software package implementing an event model and loop.
4535		5527
…		…
4543	The model used to describe how an event loop handles and processes	5535	The model used to describe how an event loop handles and processes
4544	watchers and events.	5536	watchers and events.
4545		5537
4546	=item pending	5538	=item pending
4547		5539
4548	A watcher is pending as soon as the corresponding event has been detected,	5540	A watcher is pending as soon as the corresponding event has been
4549	and stops being pending as soon as the watcher will be invoked or its	5541	detected. See L</WATCHER STATES> for details.
4550	pending status is explicitly cleared by the application.
4551
4552	A watcher can be pending, but not active. Stopping a watcher also clears
4553	its pending status.
4554		5542
4555	=item real time	5543	=item real time
4556		5544
4557	The physical time that is observed. It is apparently strictly monotonic :)	5545	The physical time that is observed. It is apparently strictly monotonic :)
4558		5546
4559	=item wall-clock time	5547	=item wall-clock time
4560		5548
4561	The time and date as shown on clocks. Unlike real time, it can actually	5549	The time and date as shown on clocks. Unlike real time, it can actually
4562	be wrong and jump forwards and backwards, e.g. when the you adjust your	5550	be wrong and jump forwards and backwards, e.g. when you adjust your
4563	clock.	5551	clock.
4564		5552
4565	=item watcher	5553	=item watcher
4566		5554
4567	A data structure that describes interest in certain events. Watchers need	5555	A data structure that describes interest in certain events. Watchers need
4568	to be started (attached to an event loop) before they can receive events.	5556	to be started (attached to an event loop) before they can receive events.
4569		5557
4570	=item watcher invocation
4571
4572	The act of calling the callback associated with a watcher.
4573
4574	=back	5558	=back
4575		5559
4576	=head1 AUTHOR	5560	=head1 AUTHOR
4577		5561
4578	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5562	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5563	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4579		5564

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