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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
132	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
133	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
169		180
170	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
171		182
172	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
173	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
174	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
175		192
176	=item int ev_version_major ()	193	=item int ev_version_major ()
177		194
178	=item int ev_version_minor ()	195	=item int ev_version_minor ()
179		196
…		…
190	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	209	not a problem.
193		210
194	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
196		214
197	assert (("libev version mismatch",	215	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
200		218
…		…
211	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
213		231
214	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
215		233
216	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
222		241
223	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
224		243
225	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
230		249
231	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
232		251
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		253
235	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
237	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
238	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
264	}	283	}
265		284
266	...	285	...
267	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
268		287
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		289
271	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
274	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	305	}
287		306
288	...	307	...
289	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
290		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
291	=back	323	=back
292		324
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		326
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
298		330
299	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
301	not.	333	do not.
302		334
303	=over 4	335	=over 4
304		336
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		338
307	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
311		349
312	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
313	function.	351	function (or via the C<EV_DEFAULT> macro).
314		352
315	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
318		357
319	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
325		382
326	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		385
329	The following flags are supported:	386	The following flags are supported:
…		…
344	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
345	around bugs.	402	around bugs.
346		403
347	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
348		405
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
350	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		408
353	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
354	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
355	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
365	environment variable.	421	environment variable.
366		422
367	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
368		424
369	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
371	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
373		429
374	=item C<EVFLAG_NOSIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
375		431
376	When this flag is specified, then libev will not attempt to use the	432	When this flag is specified, then libev will attempt to use the
377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
378	probably only useful to work around any bugs in libev. Consequently, this	434	delivers signals synchronously, which makes it both faster and might make
379	flag might go away once the signalfd functionality is considered stable,	435	it possible to get the queued signal data. It can also simplify signal
380	so it's useful mostly in environment variables and not in program code.	436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
381		457
382	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
383		459
384	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
385	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
410	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
411	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
412		488
413	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
414		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
415	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
416	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
417	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
418	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
419		498
420	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
421	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
422	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
423	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
424	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
425	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
426	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
427	hard to detect.	508	and is of course hard to detect.
428		509
429	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
430	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
431	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
432	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
433	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
434	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
435	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
436		526
437	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
438	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
439	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
440	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
477		567
478	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
479	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
480	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
481	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
482	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
483	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
484	cases	574	drops fds silently in similarly hard-to-detect cases
485		575
486	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
487		577
488	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
489	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
506	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
507		597
508	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
509	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
510		600
511	Please note that Solaris event ports can deliver a lot of spurious
512	notifications, so you need to use non-blocking I/O or other means to avoid
513	blocking when no data (or space) is available.
514
515	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
516	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
517	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
518	might perform better.	604	might perform better.
519		605
520	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
521	notifications, this backend actually performed fully to specification
522	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
523	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
524		620
525	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
526	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
527		623
528	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
529		625
530	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
531	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
532	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
533		629
534	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
535		639
536	=back	640	=back
537		641
538	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
539	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
540	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
541	()> will be tried.	645	()> will be tried.
542		646
543	Example: This is the most typical usage.
544
545	if (!ev_default_loop (0))
546	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
547
548	Example: Restrict libev to the select and poll backends, and do not allow
549	environment settings to be taken into account:
550
551	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
552
553	Example: Use whatever libev has to offer, but make sure that kqueue is
554	used if available (warning, breaks stuff, best use only with your own
555	private event loop and only if you know the OS supports your types of
556	fds):
557
558	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
559
560	=item struct ev_loop *ev_loop_new (unsigned int flags)
561
562	Similar to C<ev_default_loop>, but always creates a new event loop that is
563	always distinct from the default loop. Unlike the default loop, it cannot
564	handle signal and child watchers, and attempts to do so will be greeted by
565	undefined behaviour (or a failed assertion if assertions are enabled).
566
567	Note that this function I<is> thread-safe, and the recommended way to use
568	libev with threads is indeed to create one loop per thread, and using the
569	default loop in the "main" or "initial" thread.
570
571	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
572		648
573	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
574	if (!epoller)	650	if (!epoller)
575	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
576		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
577	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
578		659
579	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
580	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
581	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
582	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
583	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
584	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
586		667
587	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
588	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
589	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
590		671
591	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
592	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
593	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
594	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
595		680
596	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
597		682
598	Like C<ev_default_destroy>, but destroys an event loop created by an
599	earlier call to C<ev_loop_new>.
600
601	=item ev_default_fork ()
602
603	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
604	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
605	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
606	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
607	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
608	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
609		693
610	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
611	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
612	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
613		700
614	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
615	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
616	quite nicely into a call to C<pthread_atfork>:
617		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
618	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
619
620	=item ev_loop_fork (loop)
621
622	Like C<ev_default_fork>, but acts on an event loop created by
623	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
624	after fork that you want to re-use in the child, and how you do this is
625	entirely your own problem.
626		715
627	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
628		717
629	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
630	otherwise.	719	otherwise.
631		720
632	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
633		722
634	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
635	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
636	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
637		726
638	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
639	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
640	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
641		731
642	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
643		733
644	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
645	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
646		736
647	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
648	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
649	in which case it is higher.	739	in which case it is higher.
650		740
651	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
652	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
653		745
654	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
655		747
656	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
657	use.	749	use.
…		…
666		758
667	=item ev_now_update (loop)	759	=item ev_now_update (loop)
668		760
669	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
670	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
671	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
672		764
673	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
674	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
675	the current time is a good idea.	767	the current time is a good idea.
676		768
…		…
678		770
679	=item ev_suspend (loop)	771	=item ev_suspend (loop)
680		772
681	=item ev_resume (loop)	773	=item ev_resume (loop)
682		774
683	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
684	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
685		777
686	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
687	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
688	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
689	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
691	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
692		784
693	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
694	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
695	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
696	occured while suspended).	788	occurred while suspended).
697		789
698	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
699	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
700	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
701		793
702	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
703	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
704		796
705	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
706		798
707	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
708	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
709	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
710		804
711	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
712	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
713		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
714	Please note that an explicit C<ev_unloop> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
715	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
716	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
717	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
718	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
719	beauty.	818	beauty.
720		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
721	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
722	those events and any already outstanding ones, but will not block your	826	those events and any already outstanding ones, but will not wait and
723	process in case there are no events and will return after one iteration of	827	block your process in case there are no events and will return after one
724	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
725		830
726	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
727	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
728	will block your process until at least one new event arrives (which could	833	will block your process until at least one new event arrives (which could
729	be an event internal to libev itself, so there is no guarantee that a	834	be an event internal to libev itself, so there is no guarantee that a
730	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
731	iteration of the loop.	836	iteration of the loop.
732		837
733	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
734	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
735	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
736	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
737		842
738	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
739		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
740	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
741	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
742	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
743	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
744	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
745	as to not disturb the other process.	856	as to not disturb the other process.
746	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
747	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
748	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
749	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
750	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
751	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
752	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
753	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
754	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
755	- Queue all expired timers.	867	- Queue all expired timers.
756	- Queue all expired periodics.	868	- Queue all expired periodics.
757	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
758	- Queue all check watchers.	870	- Queue all check watchers.
759	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- Call all queued watchers in reverse order (i.e. check watchers first).
760	Signals and child watchers are implemented as I/O watchers, and will	872	Signals and child watchers are implemented as I/O watchers, and will
761	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
762	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
763	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
764	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
765		881
766	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
767	anymore.	883	anymore.
768		884
769	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
770	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
771	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
772	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
773		889
774	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
775		891
776	Can be used to make a call to C<ev_loop> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
777	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
778	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
779	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
780		896
781	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
782		898
783	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
784		901
785	=item ev_ref (loop)	902	=item ev_ref (loop)
786		903
787	=item ev_unref (loop)	904	=item ev_unref (loop)
788		905
789	Ref/unref can be used to add or remove a reference count on the event	906	Ref/unref can be used to add or remove a reference count on the event
790	loop: Every watcher keeps one reference, and as long as the reference	907	loop: Every watcher keeps one reference, and as long as the reference
791	count is nonzero, C<ev_loop> will not return on its own.	908	count is nonzero, C<ev_run> will not return on its own.
792		909
793	If you have a watcher you never unregister that should not keep C<ev_loop>	910	This is useful when you have a watcher that you never intend to
794	from returning, call ev_unref() after starting, and ev_ref() before	911	unregister, but that nevertheless should not keep C<ev_run> from
		912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
795	stopping it.	913	before stopping it.
796		914
797	As an example, libev itself uses this for its internal signal pipe: It	915	As an example, libev itself uses this for its internal signal pipe: It
798	is not visible to the libev user and should not keep C<ev_loop> from	916	is not visible to the libev user and should not keep C<ev_run> from
799	exiting if no event watchers registered by it are active. It is also an	917	exiting if no event watchers registered by it are active. It is also an
800	excellent way to do this for generic recurring timers or from within	918	excellent way to do this for generic recurring timers or from within
801	third-party libraries. Just remember to I<unref after start> and I<ref	919	third-party libraries. Just remember to I<unref after start> and I<ref
802	before stop> (but only if the watcher wasn't active before, or was active	920	before stop> (but only if the watcher wasn't active before, or was active
803	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
804	(e.g. non-repeating timers) in which case you have to C<ev_ref>	922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
805	in the callback).	923	in the callback).
806		924
807	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
808	running when nothing else is active.	926	running when nothing else is active.
809		927
810	ev_signal exitsig;	928	ev_signal exitsig;
811	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
812	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
813	evf_unref (loop);	931	ev_unref (loop);
814		932
815	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
816		934
817	ev_ref (loop);	935	ev_ref (loop);
818	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
838	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
839		957
840	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
841	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
842	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
843	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
844	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
845	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
846	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
847		966
848	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
849	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
850	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
851	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
857	usually doesn't make much sense to set it to a lower value than C<0.01>,	976	usually doesn't make much sense to set it to a lower value than C<0.01>,
858	as this approaches the timing granularity of most systems. Note that if	977	as this approaches the timing granularity of most systems. Note that if
859	you do transactions with the outside world and you can't increase the	978	you do transactions with the outside world and you can't increase the
860	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
861	need to poll once per transaction and the I/O collect interval is 0.01,	980	need to poll once per transaction and the I/O collect interval is 0.01,
862	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
863		982
864	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
865	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
866	are "near" in time together, by delaying some, thus reducing the number of	985	are "near" in time together, by delaying some, thus reducing the number of
867	times the process sleeps and wakes up again. Another useful technique to	986	times the process sleeps and wakes up again. Another useful technique to
…		…
875	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
876		995
877	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
878		997
879	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
880	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
881	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
882		1005
883	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
884		1007
885	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
886	are pending.	1009	are pending.
887		1010
888	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
889		1012
890	This overrides the invoke pending functionality of the loop: Instead of	1013	This overrides the invoke pending functionality of the loop: Instead of
891	invoking all pending watchers when there are any, C<ev_loop> will call	1014	invoking all pending watchers when there are any, C<ev_run> will call
892	this callback instead. This is useful, for example, when you want to	1015	this callback instead. This is useful, for example, when you want to
893	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
894		1017
895	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
896	callback.	1019	callback.
897		1020
898	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
899		1022
900	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
901	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
902	each call to a libev function.	1025	each call to a libev function.
903		1026
904	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
905	wait for it to return. One way around this is to wake up the loop via	1028	to wait for it to return. One way around this is to wake up the event
906	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
907	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
908		1031
909	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
910	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
911	afterwards.	1034	afterwards.
912		1035
…		…
915		1038
916	While event loop modifications are allowed between invocations of	1039	While event loop modifications are allowed between invocations of
917	C<release> and C<acquire> (that's their only purpose after all), no	1040	C<release> and C<acquire> (that's their only purpose after all), no
918	modifications done will affect the event loop, i.e. adding watchers will	1041	modifications done will affect the event loop, i.e. adding watchers will
919	have no effect on the set of file descriptors being watched, or the time	1042	have no effect on the set of file descriptors being watched, or the time
920	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
921	to take note of any changes you made.	1044	to take note of any changes you made.
922		1045
923	In theory, threads executing C<ev_loop> will be async-cancel safe between	1046	In theory, threads executing C<ev_run> will be async-cancel safe between
924	invocations of C<release> and C<acquire>.	1047	invocations of C<release> and C<acquire>.
925		1048
926	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
927	document.	1050	document.
928		1051
929	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
930		1053
931	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
932		1055
933	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
934	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
935	C<0.>	1058	C<0>.
936		1059
937	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
938	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
939	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
940	any other purpose as well.	1063	any other purpose as well.
941		1064
942	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
943		1066
944	This function only does something when C<EV_VERIFY> support has been	1067	This function only does something when C<EV_VERIFY> support has been
945	compiled in, which is the default for non-minimal builds. It tries to go	1068	compiled in, which is the default for non-minimal builds. It tries to go
946	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
947	is found to be inconsistent, it will print an error message to standard	1070	is found to be inconsistent, it will print an error message to standard
…		…
958		1081
959	In the following description, uppercase C<TYPE> in names stands for the	1082	In the following description, uppercase C<TYPE> in names stands for the
960	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
961	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
962		1085
963	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
964	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
965	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
966		1090
967	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
968	{	1092	{
969	ev_io_stop (w);	1093	ev_io_stop (w);
970	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
971	}	1095	}
972		1096
973	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
974		1098
975	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
976		1100
977	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
978	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
979	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
980		1104
981	ev_loop (loop, 0);	1105	ev_run (loop, 0);
982		1106
983	As you can see, you are responsible for allocating the memory for your	1107	As you can see, you are responsible for allocating the memory for your
984	watcher structures (and it is I<usually> a bad idea to do this on the	1108	watcher structures (and it is I<usually> a bad idea to do this on the
985	stack).	1109	stack).
986		1110
987	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
988	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
989		1113
990	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
991	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
992	callback gets invoked each time the event occurs (or, in the case of I/O	1116	invoked each time the event occurs (or, in the case of I/O watchers, each
993	watchers, each time the event loop detects that the file descriptor given	1117	time the event loop detects that the file descriptor given is readable
994	is readable and/or writable).	1118	and/or writable).
995		1119
996	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
997	macro to configure it, with arguments specific to the watcher type. There	1121	macro to configure it, with arguments specific to the watcher type. There
998	is also a macro to combine initialisation and setting in one call: C<<	1122	is also a macro to combine initialisation and setting in one call: C<<
999	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1022	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
1023		1147
1024	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
1025	writable.	1149	writable.
1026		1150
1027	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
1028		1152
1029	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
1030		1154
1031	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
1032		1156
…		…
1050		1174
1051	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1052		1176
1053	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1054		1178
1055	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1056	to gather new events, and all C<ev_check> watchers are invoked just after	1180	to gather new events, and all C<ev_check> watchers are invoked just after
1057	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	C<ev_run> has gathered them, but before it invokes any callbacks for any
1058	received events. Callbacks of both watcher types can start and stop as	1182	received events. Callbacks of both watcher types can start and stop as
1059	many watchers as they want, and all of them will be taken into account	1183	many watchers as they want, and all of them will be taken into account
1060	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1184	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1061	C<ev_loop> from blocking).	1185	C<ev_run> from blocking).
1062		1186
1063	=item C<EV_EMBED>	1187	=item C<EV_EMBED>
1064		1188
1065	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1189	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1066		1190
1067	=item C<EV_FORK>	1191	=item C<EV_FORK>
1068		1192
1069	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
1070	C<ev_fork>).	1194	C<ev_fork>).
		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
1071		1199
1072	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1073		1201
1074	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
1075		1203
…		…
1122		1250
1123	ev_io w;	1251	ev_io w;
1124	ev_init (&w, my_cb);	1252	ev_init (&w, my_cb);
1125	ev_io_set (&w, STDIN_FILENO, EV_READ);	1253	ev_io_set (&w, STDIN_FILENO, EV_READ);
1126		1254
1127	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1255	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1128		1256
1129	This macro initialises the type-specific parts of a watcher. You need to	1257	This macro initialises the type-specific parts of a watcher. You need to
1130	call C<ev_init> at least once before you call this macro, but you can	1258	call C<ev_init> at least once before you call this macro, but you can
1131	call C<ev_TYPE_set> any number of times. You must not, however, call this	1259	call C<ev_TYPE_set> any number of times. You must not, however, call this
1132	macro on a watcher that is active (it can be pending, however, which is a	1260	macro on a watcher that is active (it can be pending, however, which is a
…		…
1145		1273
1146	Example: Initialise and set an C<ev_io> watcher in one step.	1274	Example: Initialise and set an C<ev_io> watcher in one step.
1147		1275
1148	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1276	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1149		1277
1150	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1278	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1151		1279
1152	Starts (activates) the given watcher. Only active watchers will receive	1280	Starts (activates) the given watcher. Only active watchers will receive
1153	events. If the watcher is already active nothing will happen.	1281	events. If the watcher is already active nothing will happen.
1154		1282
1155	Example: Start the C<ev_io> watcher that is being abused as example in this	1283	Example: Start the C<ev_io> watcher that is being abused as example in this
1156	whole section.	1284	whole section.
1157		1285
1158	ev_io_start (EV_DEFAULT_UC, &w);	1286	ev_io_start (EV_DEFAULT_UC, &w);
1159		1287
1160	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1288	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1161		1289
1162	Stops the given watcher if active, and clears the pending status (whether	1290	Stops the given watcher if active, and clears the pending status (whether
1163	the watcher was active or not).	1291	the watcher was active or not).
1164		1292
1165	It is possible that stopped watchers are pending - for example,	1293	It is possible that stopped watchers are pending - for example,
…		…
1190	=item ev_cb_set (ev_TYPE *watcher, callback)	1318	=item ev_cb_set (ev_TYPE *watcher, callback)
1191		1319
1192	Change the callback. You can change the callback at virtually any time	1320	Change the callback. You can change the callback at virtually any time
1193	(modulo threads).	1321	(modulo threads).
1194		1322
1195	=item ev_set_priority (ev_TYPE *watcher, priority)	1323	=item ev_set_priority (ev_TYPE *watcher, int priority)
1196		1324
1197	=item int ev_priority (ev_TYPE *watcher)	1325	=item int ev_priority (ev_TYPE *watcher)
1198		1326
1199	Set and query the priority of the watcher. The priority is a small	1327	Set and query the priority of the watcher. The priority is a small
1200	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1328	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1232	watcher isn't pending it does nothing and returns C<0>.	1360	watcher isn't pending it does nothing and returns C<0>.
1233		1361
1234	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1362	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1235	callback to be invoked, which can be accomplished with this function.	1363	callback to be invoked, which can be accomplished with this function.
1236		1364
		1365	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1366
		1367	Feeds the given event set into the event loop, as if the specified event
		1368	had happened for the specified watcher (which must be a pointer to an
		1369	initialised but not necessarily started event watcher). Obviously you must
		1370	not free the watcher as long as it has pending events.
		1371
		1372	Stopping the watcher, letting libev invoke it, or calling
		1373	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1374	not started in the first place.
		1375
		1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1377	functions that do not need a watcher.
		1378
1237	=back	1379	=back
1238		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
1239		1383
1240	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1384	=head2 WATCHER STATES
1241		1385
1242	Each watcher has, by default, a member C<void *data> that you can change	1386	There are various watcher states mentioned throughout this manual -
1243	and read at any time: libev will completely ignore it. This can be used	1387	active, pending and so on. In this section these states and the rules to
1244	to associate arbitrary data with your watcher. If you need more data and	1388	transition between them will be described in more detail - and while these
1245	don't want to allocate memory and store a pointer to it in that data	1389	rules might look complicated, they usually do "the right thing".
1246	member, you can also "subclass" the watcher type and provide your own
1247	data:
1248		1390
1249	struct my_io	1391	=over 4
1250	{
1251	ev_io io;
1252	int otherfd;
1253	void *somedata;
1254	struct whatever *mostinteresting;
1255	};
1256		1392
1257	...	1393	=item initialiased
1258	struct my_io w;
1259	ev_io_init (&w.io, my_cb, fd, EV_READ);
1260		1394
1261	And since your callback will be called with a pointer to the watcher, you	1395	Before a watcher can be registered with the event loop it has to be
1262	can cast it back to your own type:	1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1263		1398
1264	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1399	In this state it is simply some block of memory that is suitable for
1265	{	1400	use in an event loop. It can be moved around, freed, reused etc. at
1266	struct my_io *w = (struct my_io *)w_;	1401	will - as long as you either keep the memory contents intact, or call
1267	...	1402	C<ev_TYPE_init> again.
1268	}
1269		1403
1270	More interesting and less C-conformant ways of casting your callback type	1404	=item started/running/active
1271	instead have been omitted.
1272		1405
1273	Another common scenario is to use some data structure with multiple	1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1274	embedded watchers:	1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
1275		1411
1276	struct my_biggy	1412	=item pending
1277	{
1278	int some_data;
1279	ev_timer t1;
1280	ev_timer t2;
1281	}
1282		1413
1283	In this case getting the pointer to C<my_biggy> is a bit more	1414	If a watcher is active and libev determines that an event it is interested
1284	complicated: Either you store the address of your C<my_biggy> struct	1415	in has occurred (such as a timer expiring), it will become pending. It will
1285	in the C<data> member of the watcher (for woozies), or you need to use	1416	stay in this pending state until either it is stopped or its callback is
1286	some pointer arithmetic using C<offsetof> inside your watchers (for real	1417	about to be invoked, so it is not normally pending inside the watcher
1287	programmers):	1418	callback.
1288		1419
1289	#include <stddef.h>	1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
1290		1426
1291	static void	1427	It is also possible to feed an event on a watcher that is not active (e.g.
1292	t1_cb (EV_P_ ev_timer *w, int revents)	1428	via C<ev_feed_event>), in which case it becomes pending without being
1293	{	1429	active.
1294	struct my_biggy big = (struct my_biggy *)
1295	(((char *)w) - offsetof (struct my_biggy, t1));
1296	}
1297		1430
1298	static void	1431	=item stopped
1299	t2_cb (EV_P_ ev_timer *w, int revents)	1432
1300	{	1433	A watcher can be stopped implicitly by libev (in which case it might still
1301	struct my_biggy big = (struct my_biggy *)	1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1302	(((char *)w) - offsetof (struct my_biggy, t2));	1435	latter will clear any pending state the watcher might be in, regardless
1303	}	1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is, it can be reused, moved, modified in any way
		1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
		1443
		1444	=back
1304		1445
1305	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1306		1447
1307	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1308	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1351		1492
1352	For example, to emulate how many other event libraries handle priorities,	1493	For example, to emulate how many other event libraries handle priorities,
1353	you can associate an C<ev_idle> watcher to each such watcher, and in	1494	you can associate an C<ev_idle> watcher to each such watcher, and in
1354	the normal watcher callback, you just start the idle watcher. The real	1495	the normal watcher callback, you just start the idle watcher. The real
1355	processing is done in the idle watcher callback. This causes libev to	1496	processing is done in the idle watcher callback. This causes libev to
1356	continously poll and process kernel event data for the watcher, but when	1497	continuously poll and process kernel event data for the watcher, but when
1357	the lock-out case is known to be rare (which in turn is rare :), this is	1498	the lock-out case is known to be rare (which in turn is rare :), this is
1358	workable.	1499	workable.
1359		1500
1360	Usually, however, the lock-out model implemented that way will perform	1501	Usually, however, the lock-out model implemented that way will perform
1361	miserably under the type of load it was designed to handle. In that case,	1502	miserably under the type of load it was designed to handle. In that case,
…		…
1375	{	1516	{
1376	// stop the I/O watcher, we received the event, but	1517	// stop the I/O watcher, we received the event, but
1377	// are not yet ready to handle it.	1518	// are not yet ready to handle it.
1378	ev_io_stop (EV_A_ w);	1519	ev_io_stop (EV_A_ w);
1379		1520
1380	// start the idle watcher to ahndle the actual event.	1521	// start the idle watcher to handle the actual event.
1381	// it will not be executed as long as other watchers	1522	// it will not be executed as long as other watchers
1382	// with the default priority are receiving events.	1523	// with the default priority are receiving events.
1383	ev_idle_start (EV_A_ &idle);	1524	ev_idle_start (EV_A_ &idle);
1384	}	1525	}
1385		1526
…		…
1435	In general you can register as many read and/or write event watchers per	1576	In general you can register as many read and/or write event watchers per
1436	fd as you want (as long as you don't confuse yourself). Setting all file	1577	fd as you want (as long as you don't confuse yourself). Setting all file
1437	descriptors to non-blocking mode is also usually a good idea (but not	1578	descriptors to non-blocking mode is also usually a good idea (but not
1438	required if you know what you are doing).	1579	required if you know what you are doing).
1439		1580
1440	If you cannot use non-blocking mode, then force the use of a
1441	known-to-be-good backend (at the time of this writing, this includes only
1442	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1443	descriptors for which non-blocking operation makes no sense (such as
1444	files) - libev doesn't guarentee any specific behaviour in that case.
1445
1446	Another thing you have to watch out for is that it is quite easy to	1581	Another thing you have to watch out for is that it is quite easy to
1447	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1448	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1583	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1449	because there is no data. Not only are some backends known to create a	1584	because there is no data. It is very easy to get into this situation even
1450	lot of those (for example Solaris ports), it is very easy to get into	1585	with a relatively standard program structure. Thus it is best to always
1451	this situation even with a relatively standard program structure. Thus	1586	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1452	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1453	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1454		1588
1455	If you cannot run the fd in non-blocking mode (for example you should	1589	If you cannot run the fd in non-blocking mode (for example you should
1456	not play around with an Xlib connection), then you have to separately	1590	not play around with an Xlib connection), then you have to separately
1457	re-test whether a file descriptor is really ready with a known-to-be good	1591	re-test whether a file descriptor is really ready with a known-to-be good
1458	interface such as poll (fortunately in our Xlib example, Xlib already	1592	interface such as poll (fortunately in the case of Xlib, it already does
1459	does this on its own, so its quite safe to use). Some people additionally	1593	this on its own, so its quite safe to use). Some people additionally
1460	use C<SIGALRM> and an interval timer, just to be sure you won't block	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1461	indefinitely.	1595	indefinitely.
1462		1596
1463	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1464		1598
…		…
1492		1626
1493	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1494	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1495	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1496		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1497	=head3 The special problem of fork	1664	=head3 The special problem of fork
1498		1665
1499	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1500	useless behaviour. Libev fully supports fork, but needs to be told about	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1501	it in the child.	1668	it in the child if you want to continue to use it in the child.
1502		1669
1503	To support fork in your programs, you either have to call	1670	To support fork in your child processes, you have to call C<ev_loop_fork
1504	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1671	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1505	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1506	C<EVBACKEND_POLL>.
1507		1673
1508	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1509		1675
1510	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1511	when writing to a pipe whose other end has been closed, your program gets	1677	when writing to a pipe whose other end has been closed, your program gets
…		…
1514		1680
1515	So when you encounter spurious, unexplained daemon exits, make sure you	1681	So when you encounter spurious, unexplained daemon exits, make sure you
1516	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1682	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1517	somewhere, as that would have given you a big clue).	1683	somewhere, as that would have given you a big clue).
1518		1684
		1685	=head3 The special problem of accept()ing when you can't
		1686
		1687	Many implementations of the POSIX C<accept> function (for example,
		1688	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1689	connection from the pending queue in all error cases.
		1690
		1691	For example, larger servers often run out of file descriptors (because
		1692	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1693	rejecting the connection, leading to libev signalling readiness on
		1694	the next iteration again (the connection still exists after all), and
		1695	typically causing the program to loop at 100% CPU usage.
		1696
		1697	Unfortunately, the set of errors that cause this issue differs between
		1698	operating systems, there is usually little the app can do to remedy the
		1699	situation, and no known thread-safe method of removing the connection to
		1700	cope with overload is known (to me).
		1701
		1702	One of the easiest ways to handle this situation is to just ignore it
		1703	- when the program encounters an overload, it will just loop until the
		1704	situation is over. While this is a form of busy waiting, no OS offers an
		1705	event-based way to handle this situation, so it's the best one can do.
		1706
		1707	A better way to handle the situation is to log any errors other than
		1708	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1709	messages, and continue as usual, which at least gives the user an idea of
		1710	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1711	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1712	usage.
		1713
		1714	If your program is single-threaded, then you could also keep a dummy file
		1715	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1716	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1717	close that fd, and create a new dummy fd. This will gracefully refuse
		1718	clients under typical overload conditions.
		1719
		1720	The last way to handle it is to simply log the error and C<exit>, as
		1721	is often done with C<malloc> failures, but this results in an easy
		1722	opportunity for a DoS attack.
1519		1723
1520	=head3 Watcher-Specific Functions	1724	=head3 Watcher-Specific Functions
1521		1725
1522	=over 4	1726	=over 4
1523		1727
…		…
1555	...	1759	...
1556	struct ev_loop *loop = ev_default_init (0);	1760	struct ev_loop *loop = ev_default_init (0);
1557	ev_io stdin_readable;	1761	ev_io stdin_readable;
1558	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1762	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1559	ev_io_start (loop, &stdin_readable);	1763	ev_io_start (loop, &stdin_readable);
1560	ev_loop (loop, 0);	1764	ev_run (loop, 0);
1561		1765
1562		1766
1563	=head2 C<ev_timer> - relative and optionally repeating timeouts	1767	=head2 C<ev_timer> - relative and optionally repeating timeouts
1564		1768
1565	Timer watchers are simple relative timers that generate an event after a	1769	Timer watchers are simple relative timers that generate an event after a
…		…
1571	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1572	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1573		1777
1574	The callback is guaranteed to be invoked only I<after> its timeout has	1778	The callback is guaranteed to be invoked only I<after> its timeout has
1575	passed (not I<at>, so on systems with very low-resolution clocks this	1779	passed (not I<at>, so on systems with very low-resolution clocks this
1576	might introduce a small delay). If multiple timers become ready during the	1780	might introduce a small delay, see "the special problem of being too
		1781	early", below). If multiple timers become ready during the same loop
1577	same loop iteration then the ones with earlier time-out values are invoked	1782	iteration then the ones with earlier time-out values are invoked before
1578	before ones of the same priority with later time-out values (but this is	1783	ones of the same priority with later time-out values (but this is no
1579	no longer true when a callback calls C<ev_loop> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1580		1785
1581	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1582		1787
1583	Many real-world problems involve some kind of timeout, usually for error	1788	Many real-world problems involve some kind of timeout, usually for error
1584	recovery. A typical example is an HTTP request - if the other side hangs,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1659		1864
1660	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	In this case, it would be more efficient to leave the C<ev_timer> alone,
1661	but remember the time of last activity, and check for a real timeout only	1866	but remember the time of last activity, and check for a real timeout only
1662	within the callback:	1867	within the callback:
1663		1868
		1869	ev_tstamp timeout = 60.;
1664	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1665		1872
1666	static void	1873	static void
1667	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1668	{	1875	{
1669	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1670	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1671		1878
1672	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occurred
1673	if (timeout < now)	1880	if (after < 0.)
1674	{	1881	{
1675	// timeout occured, take action	1882	// timeout occurred, take action
1676	}	1883	}
1677	else	1884	else
1678	{	1885	{
1679	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1680	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1681	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1682	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1683	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1684	}	1892	}
1685	}	1893	}
1686		1894
1687	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1688	as "60 seconds after the last activity"), then check if that time has	1896	timeout will occur (by calculating the absolute time when it would occur,
1689	been reached, which means something I<did>, in fact, time out. Otherwise	1897	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1690	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1691	re-schedule the timer to fire at that future time, to see if maybe we have
1692	a timeout then.
1693		1899
1694	Note how C<ev_timer_again> is used, taking advantage of the	1900	If this value is negative, then we are already past the timeout, i.e. we
1695	C<ev_timer_again> optimisation when the timer is already running.	1901	timed out, and need to do whatever is needed in this case.
		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout occurred. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1696		1909
1697	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1698	minus half the average time between activity), but virtually no calls to	1911	minus half the average time between activity), but virtually no calls to
1699	libev to change the timeout.	1912	libev to change the timeout.
1700		1913
1701	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1702	to the current time (meaning we just have some activity :), then call the	1915	C<last_activity> to the current time (meaning there was some activity just
1703	callback, which will "do the right thing" and start the timer:	1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1704		1918
		1919	last_activity = ev_now (EV_A);
1705	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1706	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1707	callback (loop, timer, EV_TIMEOUT);
1708		1922
1709	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1710	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1711		1925
		1926	if (activity detected)
1712	last_actiivty = ev_now (loop);	1927	last_activity = ev_now (EV_A);
		1928
		1929	When your timeout value changes, then the timeout can be changed by simply
		1930	providing a new value, stopping the timer and calling the callback, which
		1931	will again do the right thing (for example, time out immediately :).
		1932
		1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1713		1936
1714	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1715	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1716
1717	Changing the timeout is trivial as well (if it isn't hard-coded in the
1718	callback :) - just change the timeout and invoke the callback, which will
1719	fix things for you.
1720		1939
1721	=item 4. Wee, just use a double-linked list for your timeouts.	1940	=item 4. Wee, just use a double-linked list for your timeouts.
1722		1941
1723	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1724	employing some kind of timeout with the same timeout value, then one can	1943	employing some kind of timeout with the same timeout value, then one can
…		…
1751	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1970	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1752	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1753	off after the first million or so of active timers, i.e. it's usually	1972	off after the first million or so of active timers, i.e. it's usually
1754	overkill :)	1973	overkill :)
1755		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1756	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1757		2013
1758	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1759	least two system calls): EV therefore updates its idea of the current	2015	at least one system call): EV therefore updates its idea of the current
1760	time only before and after C<ev_loop> collects new events, which causes a	2016	time only before and after C<ev_run> collects new events, which causes a
1761	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1762	lots of events in one iteration.	2018	lots of events in one iteration.
1763		2019
1764	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
1765	time. This is usually the right thing as this timestamp refers to the time	2021	time. This is usually the right thing as this timestamp refers to the time
…		…
1770	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1771		2027
1772	If the event loop is suspended for a long time, you can also force an	2028	If the event loop is suspended for a long time, you can also force an
1773	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1774	()>.	2030	()>.
		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
1775		2064
1776	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1777		2066
1778	When you leave the server world it is quite customary to hit machines that	2067	When you leave the server world it is quite customary to hit machines that
1779	can suspend/hibernate - what happens to the clocks during such a suspend?	2068	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1823	keep up with the timer (because it takes longer than those 10 seconds to	2112	keep up with the timer (because it takes longer than those 10 seconds to
1824	do stuff) the timer will not fire more than once per event loop iteration.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1825		2114
1826	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1827		2116
1828	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1829	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1830		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1831	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1832		2127
1833	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1834		2130
1835	If the timer is repeating, either start it if necessary (with the	2131	=item If the timer is repeating, make the C<repeat> value the new timeout
1836	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1837		2135
1838	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1839	usage example.	2137	usage example.
1840		2138
1841	=item ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1842		2140
1843	Returns the remaining time until a timer fires. If the timer is active,	2141	Returns the remaining time until a timer fires. If the timer is active,
1844	then this time is relative to the current event loop time, otherwise it's	2142	then this time is relative to the current event loop time, otherwise it's
1845	the timeout value currently configured.	2143	the timeout value currently configured.
1846		2144
1847	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2145	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1848	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2146	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1849	will return C<4>. When the timer expires and is restarted, it will return	2147	will return C<4>. When the timer expires and is restarted, it will return
1850	roughly C<7> (likely slightly less as callback invocation takes some time,	2148	roughly C<7> (likely slightly less as callback invocation takes some time,
1851	too), and so on.	2149	too), and so on.
1852		2150
1853	=item ev_tstamp repeat [read-write]	2151	=item ev_tstamp repeat [read-write]
…		…
1882	}	2180	}
1883		2181
1884	ev_timer mytimer;	2182	ev_timer mytimer;
1885	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2183	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1886	ev_timer_again (&mytimer); /* start timer */	2184	ev_timer_again (&mytimer); /* start timer */
1887	ev_loop (loop, 0);	2185	ev_run (loop, 0);
1888		2186
1889	// and in some piece of code that gets executed on any "activity":	2187	// and in some piece of code that gets executed on any "activity":
1890	// reset the timeout to start ticking again at 10 seconds	2188	// reset the timeout to start ticking again at 10 seconds
1891	ev_timer_again (&mytimer);	2189	ev_timer_again (&mytimer);
1892		2190
…		…
1918		2216
1919	As with timers, the callback is guaranteed to be invoked only when the	2217	As with timers, the callback is guaranteed to be invoked only when the
1920	point in time where it is supposed to trigger has passed. If multiple	2218	point in time where it is supposed to trigger has passed. If multiple
1921	timers become ready during the same loop iteration then the ones with	2219	timers become ready during the same loop iteration then the ones with
1922	earlier time-out values are invoked before ones with later time-out values	2220	earlier time-out values are invoked before ones with later time-out values
1923	(but this is no longer true when a callback calls C<ev_loop> recursively).	2221	(but this is no longer true when a callback calls C<ev_run> recursively).
1924		2222
1925	=head3 Watcher-Specific Functions and Data Members	2223	=head3 Watcher-Specific Functions and Data Members
1926		2224
1927	=over 4	2225	=over 4
1928		2226
…		…
1963		2261
1964	Another way to think about it (for the mathematically inclined) is that	2262	Another way to think about it (for the mathematically inclined) is that
1965	C<ev_periodic> will try to run the callback in this mode at the next possible	2263	C<ev_periodic> will try to run the callback in this mode at the next possible
1966	time where C<time = offset (mod interval)>, regardless of any time jumps.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
1967		2265
1968	For numerical stability it is preferable that the C<offset> value is near	2266	The C<interval> I<MUST> be positive, and for numerical stability, the
1969	C<ev_now ()> (the current time), but there is no range requirement for	2267	interval value should be higher than C<1/8192> (which is around 100
1970	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
1971		2272
1972	Note also that there is an upper limit to how often a timer can fire (CPU	2273	Note also that there is an upper limit to how often a timer can fire (CPU
1973	speed for example), so if C<interval> is very small then timing stability	2274	speed for example), so if C<interval> is very small then timing stability
1974	will of course deteriorate. Libev itself tries to be exact to be about one	2275	will of course deteriorate. Libev itself tries to be exact to be about one
1975	millisecond (if the OS supports it and the machine is fast enough).	2276	millisecond (if the OS supports it and the machine is fast enough).
…		…
2056	Example: Call a callback every hour, or, more precisely, whenever the	2357	Example: Call a callback every hour, or, more precisely, whenever the
2057	system time is divisible by 3600. The callback invocation times have	2358	system time is divisible by 3600. The callback invocation times have
2058	potentially a lot of jitter, but good long-term stability.	2359	potentially a lot of jitter, but good long-term stability.
2059		2360
2060	static void	2361	static void
2061	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2362	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2062	{	2363	{
2063	... its now a full hour (UTC, or TAI or whatever your clock follows)	2364	... its now a full hour (UTC, or TAI or whatever your clock follows)
2064	}	2365	}
2065		2366
2066	ev_periodic hourly_tick;	2367	ev_periodic hourly_tick;
…		…
2089		2390
2090	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2091		2392
2092	Signal watchers will trigger an event when the process receives a specific	2393	Signal watchers will trigger an event when the process receives a specific
2093	signal one or more times. Even though signals are very asynchronous, libev	2394	signal one or more times. Even though signals are very asynchronous, libev
2094	will try it's best to deliver signals synchronously, i.e. as part of the	2395	will try its best to deliver signals synchronously, i.e. as part of the
2095	normal event processing, like any other event.	2396	normal event processing, like any other event.
2096		2397
2097	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2098	C<sigaction> as you would do without libev and forget about sharing	2399	C<sigaction> as you would do without libev and forget about sharing
2099	the signal. You can even use C<ev_async> from a signal handler to	2400	the signal. You can even use C<ev_async> from a signal handler to
…		…
2107		2408
2108	When the first watcher gets started will libev actually register something	2409	When the first watcher gets started will libev actually register something
2109	with the kernel (thus it coexists with your own signal handlers as long as	2410	with the kernel (thus it coexists with your own signal handlers as long as
2110	you don't register any with libev for the same signal).	2411	you don't register any with libev for the same signal).
2111		2412
2112	Both the signal mask state (C<sigprocmask>) and the signal handler state
2113	(C<sigaction>) are unspecified after starting a signal watcher (and after
2114	sotpping it again), that is, libev might or might not block the signal,
2115	and might or might not set or restore the installed signal handler.
2116
2117	If possible and supported, libev will install its handlers with	2413	If possible and supported, libev will install its handlers with
2118	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2414	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2119	not be unduly interrupted. If you have a problem with system calls getting	2415	not be unduly interrupted. If you have a problem with system calls getting
2120	interrupted by signals you can block all signals in an C<ev_check> watcher	2416	interrupted by signals you can block all signals in an C<ev_check> watcher
2121	and unblock them in an C<ev_prepare> watcher.	2417	and unblock them in an C<ev_prepare> watcher.
2122		2418
		2419	=head3 The special problem of inheritance over fork/execve/pthread_create
		2420
		2421	Both the signal mask (C<sigprocmask>) and the signal disposition
		2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2423	stopping it again), that is, libev might or might not block the signal,
		2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
		2426
		2427	While this does not matter for the signal disposition (libev never
		2428	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2429	C<execve>), this matters for the signal mask: many programs do not expect
		2430	certain signals to be blocked.
		2431
		2432	This means that before calling C<exec> (from the child) you should reset
		2433	the signal mask to whatever "default" you expect (all clear is a good
		2434	choice usually).
		2435
		2436	The simplest way to ensure that the signal mask is reset in the child is
		2437	to install a fork handler with C<pthread_atfork> that resets it. That will
		2438	catch fork calls done by libraries (such as the libc) as well.
		2439
		2440	In current versions of libev, the signal will not be blocked indefinitely
		2441	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2442	the window of opportunity for problems, it will not go away, as libev
		2443	I<has> to modify the signal mask, at least temporarily.
		2444
		2445	So I can't stress this enough: I<If you do not reset your signal mask when
		2446	you expect it to be empty, you have a race condition in your code>. This
		2447	is not a libev-specific thing, this is true for most event libraries.
		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
		2462
2123	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2124		2464
2125	=over 4	2465	=over 4
2126		2466
2127	=item ev_signal_init (ev_signal *, callback, int signum)	2467	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2142	Example: Try to exit cleanly on SIGINT.	2482	Example: Try to exit cleanly on SIGINT.
2143		2483
2144	static void	2484	static void
2145	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2485	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2146	{	2486	{
2147	ev_unloop (loop, EVUNLOOP_ALL);	2487	ev_break (loop, EVBREAK_ALL);
2148	}	2488	}
2149		2489
2150	ev_signal signal_watcher;	2490	ev_signal signal_watcher;
2151	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2491	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2152	ev_signal_start (loop, &signal_watcher);	2492	ev_signal_start (loop, &signal_watcher);
…		…
2538		2878
2539	Prepare and check watchers are usually (but not always) used in pairs:	2879	Prepare and check watchers are usually (but not always) used in pairs:
2540	prepare watchers get invoked before the process blocks and check watchers	2880	prepare watchers get invoked before the process blocks and check watchers
2541	afterwards.	2881	afterwards.
2542		2882
2543	You I<must not> call C<ev_loop> or similar functions that enter	2883	You I<must not> call C<ev_run> or similar functions that enter
2544	the current event loop from either C<ev_prepare> or C<ev_check>	2884	the current event loop from either C<ev_prepare> or C<ev_check>
2545	watchers. Other loops than the current one are fine, however. The	2885	watchers. Other loops than the current one are fine, however. The
2546	rationale behind this is that you do not need to check for recursion in	2886	rationale behind this is that you do not need to check for recursion in
2547	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2887	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2548	C<ev_check> so if you have one watcher of each kind they will always be	2888	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2716		3056
2717	if (timeout >= 0)	3057	if (timeout >= 0)
2718	// create/start timer	3058	// create/start timer
2719		3059
2720	// poll	3060	// poll
2721	ev_loop (EV_A_ 0);	3061	ev_run (EV_A_ 0);
2722		3062
2723	// stop timer again	3063	// stop timer again
2724	if (timeout >= 0)	3064	if (timeout >= 0)
2725	ev_timer_stop (EV_A_ &to);	3065	ev_timer_stop (EV_A_ &to);
2726		3066
…		…
2804	if you do not want that, you need to temporarily stop the embed watcher).	3144	if you do not want that, you need to temporarily stop the embed watcher).
2805		3145
2806	=item ev_embed_sweep (loop, ev_embed *)	3146	=item ev_embed_sweep (loop, ev_embed *)
2807		3147
2808	Make a single, non-blocking sweep over the embedded loop. This works	3148	Make a single, non-blocking sweep over the embedded loop. This works
2809	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3149	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2810	appropriate way for embedded loops.	3150	appropriate way for embedded loops.
2811		3151
2812	=item struct ev_loop *other [read-only]	3152	=item struct ev_loop *other [read-only]
2813		3153
2814	The embedded event loop.	3154	The embedded event loop.
…		…
2874	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3214	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2875	handlers will be invoked, too, of course.	3215	handlers will be invoked, too, of course.
2876		3216
2877	=head3 The special problem of life after fork - how is it possible?	3217	=head3 The special problem of life after fork - how is it possible?
2878		3218
2879	Most uses of C<fork()> consist of forking, then some simple calls to ste	3219	Most uses of C<fork()> consist of forking, then some simple calls to set
2880	up/change the process environment, followed by a call to C<exec()>. This	3220	up/change the process environment, followed by a call to C<exec()>. This
2881	sequence should be handled by libev without any problems.	3221	sequence should be handled by libev without any problems.
2882		3222
2883	This changes when the application actually wants to do event handling	3223	This changes when the application actually wants to do event handling
2884	in the child, or both parent in child, in effect "continuing" after the	3224	in the child, or both parent in child, in effect "continuing" after the
…		…
2900	disadvantage of having to use multiple event loops (which do not support	3240	disadvantage of having to use multiple event loops (which do not support
2901	signal watchers).	3241	signal watchers).
2902		3242
2903	When this is not possible, or you want to use the default loop for	3243	When this is not possible, or you want to use the default loop for
2904	other reasons, then in the process that wants to start "fresh", call	3244	other reasons, then in the process that wants to start "fresh", call
2905	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3245	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2906	the default loop will "orphan" (not stop) all registered watchers, so you	3246	Destroying the default loop will "orphan" (not stop) all registered
2907	have to be careful not to execute code that modifies those watchers. Note	3247	watchers, so you have to be careful not to execute code that modifies
2908	also that in that case, you have to re-register any signal watchers.	3248	those watchers. Note also that in that case, you have to re-register any
		3249	signal watchers.
2909		3250
2910	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
2911		3252
2912	=over 4	3253	=over 4
2913		3254
2914	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
2915		3256
2916	Initialises and configures the fork watcher - it has no parameters of any	3257	Initialises and configures the fork watcher - it has no parameters of any
2917	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2918	believe me.	3259	really.
2919		3260
2920	=back	3261	=back
2921		3262
2922		3263
		3264	=head2 C<ev_cleanup> - even the best things end
		3265
		3266	Cleanup watchers are called just before the event loop is being destroyed
		3267	by a call to C<ev_loop_destroy>.
		3268
		3269	While there is no guarantee that the event loop gets destroyed, cleanup
		3270	watchers provide a convenient method to install cleanup hooks for your
		3271	program, worker threads and so on - you just to make sure to destroy the
		3272	loop when you want them to be invoked.
		3273
		3274	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3275	all other watchers, they do not keep a reference to the event loop (which
		3276	makes a lot of sense if you think about it). Like all other watchers, you
		3277	can call libev functions in the callback, except C<ev_cleanup_start>.
		3278
		3279	=head3 Watcher-Specific Functions and Data Members
		3280
		3281	=over 4
		3282
		3283	=item ev_cleanup_init (ev_cleanup *, callback)
		3284
		3285	Initialises and configures the cleanup watcher - it has no parameters of
		3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3287	pointless, I assure you.
		3288
		3289	=back
		3290
		3291	Example: Register an atexit handler to destroy the default loop, so any
		3292	cleanup functions are called.
		3293
		3294	static void
		3295	program_exits (void)
		3296	{
		3297	ev_loop_destroy (EV_DEFAULT_UC);
		3298	}
		3299
		3300	...
		3301	atexit (program_exits);
		3302
		3303
2923	=head2 C<ev_async> - how to wake up another event loop	3304	=head2 C<ev_async> - how to wake up an event loop
2924		3305
2925	In general, you cannot use an C<ev_loop> from multiple threads or other	3306	In general, you cannot use an C<ev_loop> from multiple threads or other
2926	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
2927	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
2928		3309
2929	Sometimes, however, you need to wake up another event loop you do not	3310	Sometimes, however, you need to wake up an event loop you do not control,
2930	control, for example because it belongs to another thread. This is what	3311	for example because it belongs to another thread. This is what C<ev_async>
2931	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3312	watchers do: as long as the C<ev_async> watcher is active, you can signal
2932	can signal it by calling C<ev_async_send>, which is thread- and signal	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
2933	safe.
2934		3314
2935	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
2936	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
2937	(i.e. the number of callback invocations may be less than the number of	3317	(i.e. the number of callback invocations may be less than the number of
2938	C<ev_async_sent> calls).	3318	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2939		3319	of "global async watchers" by using a watcher on an otherwise unused
2940	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2941	just the default loop.	3321	even without knowing which loop owns the signal.
2942		3322
2943	=head3 Queueing	3323	=head3 Queueing
2944		3324
2945	C<ev_async> does not support queueing of data in any way. The reason	3325	C<ev_async> does not support queueing of data in any way. The reason
2946	is that the author does not know of a simple (or any) algorithm for a	3326	is that the author does not know of a simple (or any) algorithm for a
2947	multiple-writer-single-reader queue that works in all cases and doesn't	3327	multiple-writer-single-reader queue that works in all cases and doesn't
2948	need elaborate support such as pthreads.	3328	need elaborate support such as pthreads or unportable memory access
		3329	semantics.
2949		3330
2950	That means that if you want to queue data, you have to provide your own	3331	That means that if you want to queue data, you have to provide your own
2951	queue. But at least I can tell you how to implement locking around your	3332	queue. But at least I can tell you how to implement locking around your
2952	queue:	3333	queue:
2953		3334
…		…
3037	trust me.	3418	trust me.
3038		3419
3039	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3040		3421
3041	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3042	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
3043	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3044	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3045	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3046		3429
3047	Note that, as with other watchers in libev, multiple events might get	3430	Note that, as with other watchers in libev, multiple events might get
3048	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
3049	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3432	this is that C<ev_async> watchers are level-triggered: they are set on
3050	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3051		3434
3052	This call incurs the overhead of a system call only once per event loop	3435	This call incurs the overhead of at most one extra system call per event
3053	iteration, so while the overhead might be noticeable, it doesn't apply to	3436	loop iteration, if the event loop is blocked, and no syscall at all if
3054	repeated calls to C<ev_async_send> for the same event loop.	3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
3055		3441
3056	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3057		3443
3058	Returns a non-zero value when C<ev_async_send> has been called on the	3444	Returns a non-zero value when C<ev_async_send> has been called on the
3059	watcher but the event has not yet been processed (or even noted) by the	3445	watcher but the event has not yet been processed (or even noted) by the
…		…
3092		3478
3093	If C<timeout> is less than 0, then no timeout watcher will be	3479	If C<timeout> is less than 0, then no timeout watcher will be
3094	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3480	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3095	repeat = 0) will be started. C<0> is a valid timeout.	3481	repeat = 0) will be started. C<0> is a valid timeout.
3096		3482
3097	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3483	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3098	passed an C<revents> set like normal event callbacks (a combination of	3484	passed an C<revents> set like normal event callbacks (a combination of
3099	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3485	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3100	value passed to C<ev_once>. Note that it is possible to receive I<both>	3486	value passed to C<ev_once>. Note that it is possible to receive I<both>
3101	a timeout and an io event at the same time - you probably should give io	3487	a timeout and an io event at the same time - you probably should give io
3102	events precedence.	3488	events precedence.
3103		3489
3104	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3490	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3105		3491
3106	static void stdin_ready (int revents, void *arg)	3492	static void stdin_ready (int revents, void *arg)
3107	{	3493	{
3108	if (revents & EV_READ)	3494	if (revents & EV_READ)
3109	/* stdin might have data for us, joy! */;	3495	/* stdin might have data for us, joy! */;
3110	else if (revents & EV_TIMEOUT)	3496	else if (revents & EV_TIMER)
3111	/* doh, nothing entered */;	3497	/* doh, nothing entered */;
3112	}	3498	}
3113		3499
3114	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3115		3501
3116	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3117
3118	Feeds the given event set into the event loop, as if the specified event
3119	had happened for the specified watcher (which must be a pointer to an
3120	initialised but not necessarily started event watcher).
3121
3122	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3123		3503
3124	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
3125	the given events it.	3505	the given events.
3126		3506
3127	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3128		3508
3129	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3130	loop!).	3510	which is async-safe.
3131		3511
3132	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
3133		3863
3134		3864
3135	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3136		3866
3137	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3138	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3139		3869
3140	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
3141		3876
3142	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3143		3878
3144	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3145	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3151	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3152	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
3153	is an ev_pri field.	3888	is an ev_pri field.
3154		3889
3155	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
3156	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3157		3892
3158	=item * Other members are not supported.	3893	=item * Other members are not supported.
3159		3894
3160	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3161	to use the libev header file and library.	3896	to use the libev header file and library.
3162		3897
3163	=back	3898	=back
3164		3899
3165	=head1 C++ SUPPORT	3900	=head1 C++ SUPPORT
		3901
		3902	=head2 C API
		3903
		3904	The normal C API should work fine when used from C++: both ev.h and the
		3905	libev sources can be compiled as C++. Therefore, code that uses the C API
		3906	will work fine.
		3907
		3908	Proper exception specifications might have to be added to callbacks passed
		3909	to libev: exceptions may be thrown only from watcher callbacks, all
		3910	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3911	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3912	()> specification. If you have code that needs to be compiled as both C
		3913	and C++ you can use the C<EV_THROW> macro for this:
		3914
		3915	static void
		3916	fatal_error (const char *msg) EV_THROW
		3917	{
		3918	perror (msg);
		3919	abort ();
		3920	}
		3921
		3922	...
		3923	ev_set_syserr_cb (fatal_error);
		3924
		3925	The only API functions that can currently throw exceptions are C<ev_run>,
		3926	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3927	because it runs cleanup watchers).
		3928
		3929	Throwing exceptions in watcher callbacks is only supported if libev itself
		3930	is compiled with a C++ compiler or your C and C++ environments allow
		3931	throwing exceptions through C libraries (most do).
		3932
		3933	=head2 C++ API
3166		3934
3167	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3935	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3168	you to use some convenience methods to start/stop watchers and also change	3936	you to use some convenience methods to start/stop watchers and also change
3169	the callback model to a model using method callbacks on objects.	3937	the callback model to a model using method callbacks on objects.
3170		3938
…		…
3180	Care has been taken to keep the overhead low. The only data member the C++	3948	Care has been taken to keep the overhead low. The only data member the C++
3181	classes add (compared to plain C-style watchers) is the event loop pointer	3949	classes add (compared to plain C-style watchers) is the event loop pointer
3182	that the watcher is associated with (or no additional members at all if	3950	that the watcher is associated with (or no additional members at all if
3183	you disable C<EV_MULTIPLICITY> when embedding libev).	3951	you disable C<EV_MULTIPLICITY> when embedding libev).
3184		3952
3185	Currently, functions, and static and non-static member functions can be	3953	Currently, functions, static and non-static member functions and classes
3186	used as callbacks. Other types should be easy to add as long as they only	3954	with C<operator ()> can be used as callbacks. Other types should be easy
3187	need one additional pointer for context. If you need support for other	3955	to add as long as they only need one additional pointer for context. If
3188	types of functors please contact the author (preferably after implementing	3956	you need support for other types of functors please contact the author
3189	it).	3957	(preferably after implementing it).
		3958
		3959	For all this to work, your C++ compiler either has to use the same calling
		3960	conventions as your C compiler (for static member functions), or you have
		3961	to embed libev and compile libev itself as C++.
3190		3962
3191	Here is a list of things available in the C<ev> namespace:	3963	Here is a list of things available in the C<ev> namespace:
3192		3964
3193	=over 4	3965	=over 4
3194		3966
…		…
3204	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3976	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3205		3977
3206	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3978	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3207	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3979	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3208	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3980	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3209	defines by many implementations.	3981	defined by many implementations.
3210		3982
3211	All of those classes have these methods:	3983	All of those classes have these methods:
3212		3984
3213	=over 4	3985	=over 4
3214		3986
3215	=item ev::TYPE::TYPE ()	3987	=item ev::TYPE::TYPE ()
3216		3988
3217	=item ev::TYPE::TYPE (struct ev_loop *)	3989	=item ev::TYPE::TYPE (loop)
3218		3990
3219	=item ev::TYPE::~TYPE	3991	=item ev::TYPE::~TYPE
3220		3992
3221	The constructor (optionally) takes an event loop to associate the watcher	3993	The constructor (optionally) takes an event loop to associate the watcher
3222	with. If it is omitted, it will use C<EV_DEFAULT>.	3994	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3255	myclass obj;	4027	myclass obj;
3256	ev::io iow;	4028	ev::io iow;
3257	iow.set <myclass, &myclass::io_cb> (&obj);	4029	iow.set <myclass, &myclass::io_cb> (&obj);
3258		4030
3259	=item w->set (object *)	4031	=item w->set (object *)
3260
3261	This is an B<experimental> feature that might go away in a future version.
3262		4032
3263	This is a variation of a method callback - leaving out the method to call	4033	This is a variation of a method callback - leaving out the method to call
3264	will default the method to C<operator ()>, which makes it possible to use	4034	will default the method to C<operator ()>, which makes it possible to use
3265	functor objects without having to manually specify the C<operator ()> all	4035	functor objects without having to manually specify the C<operator ()> all
3266	the time. Incidentally, you can then also leave out the template argument	4036	the time. Incidentally, you can then also leave out the template argument
…		…
3299	Example: Use a plain function as callback.	4069	Example: Use a plain function as callback.
3300		4070
3301	static void io_cb (ev::io &w, int revents) { }	4071	static void io_cb (ev::io &w, int revents) { }
3302	iow.set <io_cb> ();	4072	iow.set <io_cb> ();
3303		4073
3304	=item w->set (struct ev_loop *)	4074	=item w->set (loop)
3305		4075
3306	Associates a different C<struct ev_loop> with this watcher. You can only	4076	Associates a different C<struct ev_loop> with this watcher. You can only
3307	do this when the watcher is inactive (and not pending either).	4077	do this when the watcher is inactive (and not pending either).
3308		4078
3309	=item w->set ([arguments])	4079	=item w->set ([arguments])
3310		4080
3311	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4081	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3312	called at least once. Unlike the C counterpart, an active watcher gets	4082	method or a suitable start method must be called at least once. Unlike the
3313	automatically stopped and restarted when reconfiguring it with this	4083	C counterpart, an active watcher gets automatically stopped and restarted
3314	method.	4084	when reconfiguring it with this method.
3315		4085
3316	=item w->start ()	4086	=item w->start ()
3317		4087
3318	Starts the watcher. Note that there is no C<loop> argument, as the	4088	Starts the watcher. Note that there is no C<loop> argument, as the
3319	constructor already stores the event loop.	4089	constructor already stores the event loop.
3320		4090
		4091	=item w->start ([arguments])
		4092
		4093	Instead of calling C<set> and C<start> methods separately, it is often
		4094	convenient to wrap them in one call. Uses the same type of arguments as
		4095	the configure C<set> method of the watcher.
		4096
3321	=item w->stop ()	4097	=item w->stop ()
3322		4098
3323	Stops the watcher if it is active. Again, no C<loop> argument.	4099	Stops the watcher if it is active. Again, no C<loop> argument.
3324		4100
3325	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4101	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3337		4113
3338	=back	4114	=back
3339		4115
3340	=back	4116	=back
3341		4117
3342	Example: Define a class with an IO and idle watcher, start one of them in	4118	Example: Define a class with two I/O and idle watchers, start the I/O
3343	the constructor.	4119	watchers in the constructor.
3344		4120
3345	class myclass	4121	class myclass
3346	{	4122	{
3347	ev::io io ; void io_cb (ev::io &w, int revents);	4123	ev::io io ; void io_cb (ev::io &w, int revents);
		4124	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3348	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4125	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3349		4126
3350	myclass (int fd)	4127	myclass (int fd)
3351	{	4128	{
3352	io .set <myclass, &myclass::io_cb > (this);	4129	io .set <myclass, &myclass::io_cb > (this);
		4130	io2 .set <myclass, &myclass::io2_cb > (this);
3353	idle.set <myclass, &myclass::idle_cb> (this);	4131	idle.set <myclass, &myclass::idle_cb> (this);
3354		4132
3355	io.start (fd, ev::READ);	4133	io.set (fd, ev::WRITE); // configure the watcher
		4134	io.start (); // start it whenever convenient
		4135
		4136	io2.start (fd, ev::READ); // set + start in one call
3356	}	4137	}
3357	};	4138	};
3358		4139
3359		4140
3360	=head1 OTHER LANGUAGE BINDINGS	4141	=head1 OTHER LANGUAGE BINDINGS
…		…
3399	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4180	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3400		4181
3401	=item D	4182	=item D
3402		4183
3403	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4184	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3404	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4185	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3405		4186
3406	=item Ocaml	4187	=item Ocaml
3407		4188
3408	Erkki Seppala has written Ocaml bindings for libev, to be found at	4189	Erkki Seppala has written Ocaml bindings for libev, to be found at
3409	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4190	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4191
		4192	=item Lua
		4193
		4194	Brian Maher has written a partial interface to libev for lua (at the
		4195	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4196	L<http://github.com/brimworks/lua-ev>.
3410		4197
3411	=back	4198	=back
3412		4199
3413		4200
3414	=head1 MACRO MAGIC	4201	=head1 MACRO MAGIC
…		…
3428	loop argument"). The C<EV_A> form is used when this is the sole argument,	4215	loop argument"). The C<EV_A> form is used when this is the sole argument,
3429	C<EV_A_> is used when other arguments are following. Example:	4216	C<EV_A_> is used when other arguments are following. Example:
3430		4217
3431	ev_unref (EV_A);	4218	ev_unref (EV_A);
3432	ev_timer_add (EV_A_ watcher);	4219	ev_timer_add (EV_A_ watcher);
3433	ev_loop (EV_A_ 0);	4220	ev_run (EV_A_ 0);
3434		4221
3435	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4222	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3436	which is often provided by the following macro.	4223	which is often provided by the following macro.
3437		4224
3438	=item C<EV_P>, C<EV_P_>	4225	=item C<EV_P>, C<EV_P_>
…		…
3451	suitable for use with C<EV_A>.	4238	suitable for use with C<EV_A>.
3452		4239
3453	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4240	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3454		4241
3455	Similar to the other two macros, this gives you the value of the default	4242	Similar to the other two macros, this gives you the value of the default
3456	loop, if multiple loops are supported ("ev loop default").	4243	loop, if multiple loops are supported ("ev loop default"). The default loop
		4244	will be initialised if it isn't already initialised.
		4245
		4246	For non-multiplicity builds, these macros do nothing, so you always have
		4247	to initialise the loop somewhere.
3457		4248
3458	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4249	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3459		4250
3460	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4251	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3461	default loop has been initialised (C<UC> == unchecked). Their behaviour	4252	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3478	}	4269	}
3479		4270
3480	ev_check check;	4271	ev_check check;
3481	ev_check_init (&check, check_cb);	4272	ev_check_init (&check, check_cb);
3482	ev_check_start (EV_DEFAULT_ &check);	4273	ev_check_start (EV_DEFAULT_ &check);
3483	ev_loop (EV_DEFAULT_ 0);	4274	ev_run (EV_DEFAULT_ 0);
3484		4275
3485	=head1 EMBEDDING	4276	=head1 EMBEDDING
3486		4277
3487	Libev can (and often is) directly embedded into host	4278	Libev can (and often is) directly embedded into host
3488	applications. Examples of applications that embed it include the Deliantra	4279	applications. Examples of applications that embed it include the Deliantra
…		…
3568	libev.m4	4359	libev.m4
3569		4360
3570	=head2 PREPROCESSOR SYMBOLS/MACROS	4361	=head2 PREPROCESSOR SYMBOLS/MACROS
3571		4362
3572	Libev can be configured via a variety of preprocessor symbols you have to	4363	Libev can be configured via a variety of preprocessor symbols you have to
3573	define before including any of its files. The default in the absence of	4364	define before including (or compiling) any of its files. The default in
3574	autoconf is documented for every option.	4365	the absence of autoconf is documented for every option.
		4366
		4367	Symbols marked with "(h)" do not change the ABI, and can have different
		4368	values when compiling libev vs. including F<ev.h>, so it is permissible
		4369	to redefine them before including F<ev.h> without breaking compatibility
		4370	to a compiled library. All other symbols change the ABI, which means all
		4371	users of libev and the libev code itself must be compiled with compatible
		4372	settings.
3575		4373
3576	=over 4	4374	=over 4
3577		4375
		4376	=item EV_COMPAT3 (h)
		4377
		4378	Backwards compatibility is a major concern for libev. This is why this
		4379	release of libev comes with wrappers for the functions and symbols that
		4380	have been renamed between libev version 3 and 4.
		4381
		4382	You can disable these wrappers (to test compatibility with future
		4383	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4384	sources. This has the additional advantage that you can drop the C<struct>
		4385	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4386	typedef in that case.
		4387
		4388	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4389	and in some even more future version the compatibility code will be
		4390	removed completely.
		4391
3578	=item EV_STANDALONE	4392	=item EV_STANDALONE (h)
3579		4393
3580	Must always be C<1> if you do not use autoconf configuration, which	4394	Must always be C<1> if you do not use autoconf configuration, which
3581	keeps libev from including F<config.h>, and it also defines dummy	4395	keeps libev from including F<config.h>, and it also defines dummy
3582	implementations for some libevent functions (such as logging, which is not	4396	implementations for some libevent functions (such as logging, which is not
3583	supported). It will also not define any of the structs usually found in	4397	supported). It will also not define any of the structs usually found in
3584	F<event.h> that are not directly supported by the libev core alone.	4398	F<event.h> that are not directly supported by the libev core alone.
3585		4399
3586	In stanbdalone mode, libev will still try to automatically deduce the	4400	In standalone mode, libev will still try to automatically deduce the
3587	configuration, but has to be more conservative.	4401	configuration, but has to be more conservative.
		4402
		4403	=item EV_USE_FLOOR
		4404
		4405	If defined to be C<1>, libev will use the C<floor ()> function for its
		4406	periodic reschedule calculations, otherwise libev will fall back on a
		4407	portable (slower) implementation. If you enable this, you usually have to
		4408	link against libm or something equivalent. Enabling this when the C<floor>
		4409	function is not available will fail, so the safe default is to not enable
		4410	this.
3588		4411
3589	=item EV_USE_MONOTONIC	4412	=item EV_USE_MONOTONIC
3590		4413
3591	If defined to be C<1>, libev will try to detect the availability of the	4414	If defined to be C<1>, libev will try to detect the availability of the
3592	monotonic clock option at both compile time and runtime. Otherwise no	4415	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3656	be used is the winsock select). This means that it will call	4479	be used is the winsock select). This means that it will call
3657	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4480	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3658	it is assumed that all these functions actually work on fds, even	4481	it is assumed that all these functions actually work on fds, even
3659	on win32. Should not be defined on non-win32 platforms.	4482	on win32. Should not be defined on non-win32 platforms.
3660		4483
3661	=item EV_FD_TO_WIN32_HANDLE	4484	=item EV_FD_TO_WIN32_HANDLE(fd)
3662		4485
3663	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4486	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3664	file descriptors to socket handles. When not defining this symbol (the	4487	file descriptors to socket handles. When not defining this symbol (the
3665	default), then libev will call C<_get_osfhandle>, which is usually	4488	default), then libev will call C<_get_osfhandle>, which is usually
3666	correct. In some cases, programs use their own file descriptor management,	4489	correct. In some cases, programs use their own file descriptor management,
3667	in which case they can provide this function to map fds to socket handles.	4490	in which case they can provide this function to map fds to socket handles.
		4491
		4492	=item EV_WIN32_HANDLE_TO_FD(handle)
		4493
		4494	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4495	using the standard C<_open_osfhandle> function. For programs implementing
		4496	their own fd to handle mapping, overwriting this function makes it easier
		4497	to do so. This can be done by defining this macro to an appropriate value.
		4498
		4499	=item EV_WIN32_CLOSE_FD(fd)
		4500
		4501	If programs implement their own fd to handle mapping on win32, then this
		4502	macro can be used to override the C<close> function, useful to unregister
		4503	file descriptors again. Note that the replacement function has to close
		4504	the underlying OS handle.
3668		4505
3669	=item EV_USE_POLL	4506	=item EV_USE_POLL
3670		4507
3671	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4508	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3672	backend. Otherwise it will be enabled on non-win32 platforms. It	4509	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3708	If defined to be C<1>, libev will compile in support for the Linux inotify	4545	If defined to be C<1>, libev will compile in support for the Linux inotify
3709	interface to speed up C<ev_stat> watchers. Its actual availability will	4546	interface to speed up C<ev_stat> watchers. Its actual availability will
3710	be detected at runtime. If undefined, it will be enabled if the headers	4547	be detected at runtime. If undefined, it will be enabled if the headers
3711	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4548	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3712		4549
		4550	=item EV_NO_SMP
		4551
		4552	If defined to be C<1>, libev will assume that memory is always coherent
		4553	between threads, that is, threads can be used, but threads never run on
		4554	different cpus (or different cpu cores). This reduces dependencies
		4555	and makes libev faster.
		4556
		4557	=item EV_NO_THREADS
		4558
		4559	If defined to be C<1>, libev will assume that it will never be called
		4560	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4561	above. This reduces dependencies and makes libev faster.
		4562
3713	=item EV_ATOMIC_T	4563	=item EV_ATOMIC_T
3714		4564
3715	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4565	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3716	access is atomic with respect to other threads or signal contexts. No such	4566	access is atomic and serialised with respect to other threads or signal
3717	type is easily found in the C language, so you can provide your own type	4567	contexts. No such type is easily found in the C language, so you can
3718	that you know is safe for your purposes. It is used both for signal handler "locking"	4568	provide your own type that you know is safe for your purposes. It is used
3719	as well as for signal and thread safety in C<ev_async> watchers.	4569	both for signal handler "locking" as well as for signal and thread safety
		4570	in C<ev_async> watchers.
3720		4571
3721	In the absence of this define, libev will use C<sig_atomic_t volatile>	4572	In the absence of this define, libev will use C<sig_atomic_t volatile>
3722	(from F<signal.h>), which is usually good enough on most platforms.	4573	(from F<signal.h>), which is usually good enough on most platforms,
		4574	although strictly speaking using a type that also implies a memory fence
		4575	is required.
3723		4576
3724	=item EV_H	4577	=item EV_H (h)
3725		4578
3726	The name of the F<ev.h> header file used to include it. The default if	4579	The name of the F<ev.h> header file used to include it. The default if
3727	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4580	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3728	used to virtually rename the F<ev.h> header file in case of conflicts.	4581	used to virtually rename the F<ev.h> header file in case of conflicts.
3729		4582
3730	=item EV_CONFIG_H	4583	=item EV_CONFIG_H (h)
3731		4584
3732	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4585	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3733	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4586	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3734	C<EV_H>, above.	4587	C<EV_H>, above.
3735		4588
3736	=item EV_EVENT_H	4589	=item EV_EVENT_H (h)
3737		4590
3738	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4591	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3739	of how the F<event.h> header can be found, the default is C<"event.h">.	4592	of how the F<event.h> header can be found, the default is C<"event.h">.
3740		4593
3741	=item EV_PROTOTYPES	4594	=item EV_PROTOTYPES (h)
3742		4595
3743	If defined to be C<0>, then F<ev.h> will not define any function	4596	If defined to be C<0>, then F<ev.h> will not define any function
3744	prototypes, but still define all the structs and other symbols. This is	4597	prototypes, but still define all the structs and other symbols. This is
3745	occasionally useful if you want to provide your own wrapper functions	4598	occasionally useful if you want to provide your own wrapper functions
3746	around libev functions.	4599	around libev functions.
…		…
3751	will have the C<struct ev_loop *> as first argument, and you can create	4604	will have the C<struct ev_loop *> as first argument, and you can create
3752	additional independent event loops. Otherwise there will be no support	4605	additional independent event loops. Otherwise there will be no support
3753	for multiple event loops and there is no first event loop pointer	4606	for multiple event loops and there is no first event loop pointer
3754	argument. Instead, all functions act on the single default loop.	4607	argument. Instead, all functions act on the single default loop.
3755		4608
		4609	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4610	default loop when multiplicity is switched off - you always have to
		4611	initialise the loop manually in this case.
		4612
3756	=item EV_MINPRI	4613	=item EV_MINPRI
3757		4614
3758	=item EV_MAXPRI	4615	=item EV_MAXPRI
3759		4616
3760	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4617	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3768	fine.	4625	fine.
3769		4626
3770	If your embedding application does not need any priorities, defining these	4627	If your embedding application does not need any priorities, defining these
3771	both to C<0> will save some memory and CPU.	4628	both to C<0> will save some memory and CPU.
3772		4629
3773	=item EV_PERIODIC_ENABLE	4630	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4631	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4632	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3774		4633
3775	If undefined or defined to be C<1>, then periodic timers are supported. If	4634	If undefined or defined to be C<1> (and the platform supports it), then
3776	defined to be C<0>, then they are not. Disabling them saves a few kB of	4635	the respective watcher type is supported. If defined to be C<0>, then it
3777	code.	4636	is not. Disabling watcher types mainly saves code size.
3778		4637
3779	=item EV_IDLE_ENABLE	4638	=item EV_FEATURES
3780
3781	If undefined or defined to be C<1>, then idle watchers are supported. If
3782	defined to be C<0>, then they are not. Disabling them saves a few kB of
3783	code.
3784
3785	=item EV_EMBED_ENABLE
3786
3787	If undefined or defined to be C<1>, then embed watchers are supported. If
3788	defined to be C<0>, then they are not. Embed watchers rely on most other
3789	watcher types, which therefore must not be disabled.
3790
3791	=item EV_STAT_ENABLE
3792
3793	If undefined or defined to be C<1>, then stat watchers are supported. If
3794	defined to be C<0>, then they are not.
3795
3796	=item EV_FORK_ENABLE
3797
3798	If undefined or defined to be C<1>, then fork watchers are supported. If
3799	defined to be C<0>, then they are not.
3800
3801	=item EV_ASYNC_ENABLE
3802
3803	If undefined or defined to be C<1>, then async watchers are supported. If
3804	defined to be C<0>, then they are not.
3805
3806	=item EV_MINIMAL
3807		4639
3808	If you need to shave off some kilobytes of code at the expense of some	4640	If you need to shave off some kilobytes of code at the expense of some
3809	speed (but with the full API), define this symbol to C<1>. Currently this	4641	speed (but with the full API), you can define this symbol to request
3810	is used to override some inlining decisions, saves roughly 30% code size	4642	certain subsets of functionality. The default is to enable all features
3811	on amd64. It also selects a much smaller 2-heap for timer management over	4643	that can be enabled on the platform.
3812	the default 4-heap.
3813		4644
3814	You can save even more by disabling watcher types you do not need	4645	A typical way to use this symbol is to define it to C<0> (or to a bitset
3815	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4646	with some broad features you want) and then selectively re-enable
3816	(C<-DNDEBUG>) will usually reduce code size a lot.	4647	additional parts you want, for example if you want everything minimal,
		4648	but multiple event loop support, async and child watchers and the poll
		4649	backend, use this:
3817		4650
3818	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4651	#define EV_FEATURES 0
3819	provide a bare-bones event library. See C<ev.h> for details on what parts	4652	#define EV_MULTIPLICITY 1
3820	of the API are still available, and do not complain if this subset changes	4653	#define EV_USE_POLL 1
3821	over time.	4654	#define EV_CHILD_ENABLE 1
		4655	#define EV_ASYNC_ENABLE 1
		4656
		4657	The actual value is a bitset, it can be a combination of the following
		4658	values (by default, all of these are enabled):
		4659
		4660	=over 4
		4661
		4662	=item C<1> - faster/larger code
		4663
		4664	Use larger code to speed up some operations.
		4665
		4666	Currently this is used to override some inlining decisions (enlarging the
		4667	code size by roughly 30% on amd64).
		4668
		4669	When optimising for size, use of compiler flags such as C<-Os> with
		4670	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4671	assertions.
		4672
		4673	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4674	(e.g. gcc with C<-Os>).
		4675
		4676	=item C<2> - faster/larger data structures
		4677
		4678	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4679	hash table sizes and so on. This will usually further increase code size
		4680	and can additionally have an effect on the size of data structures at
		4681	runtime.
		4682
		4683	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4684	(e.g. gcc with C<-Os>).
		4685
		4686	=item C<4> - full API configuration
		4687
		4688	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4689	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4690
		4691	=item C<8> - full API
		4692
		4693	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4694	details on which parts of the API are still available without this
		4695	feature, and do not complain if this subset changes over time.
		4696
		4697	=item C<16> - enable all optional watcher types
		4698
		4699	Enables all optional watcher types. If you want to selectively enable
		4700	only some watcher types other than I/O and timers (e.g. prepare,
		4701	embed, async, child...) you can enable them manually by defining
		4702	C<EV_watchertype_ENABLE> to C<1> instead.
		4703
		4704	=item C<32> - enable all backends
		4705
		4706	This enables all backends - without this feature, you need to enable at
		4707	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4708
		4709	=item C<64> - enable OS-specific "helper" APIs
		4710
		4711	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4712	default.
		4713
		4714	=back
		4715
		4716	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4717	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4718	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4719	watchers, timers and monotonic clock support.
		4720
		4721	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4722	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4723	your program might be left out as well - a binary starting a timer and an
		4724	I/O watcher then might come out at only 5Kb.
		4725
		4726	=item EV_API_STATIC
		4727
		4728	If this symbol is defined (by default it is not), then all identifiers
		4729	will have static linkage. This means that libev will not export any
		4730	identifiers, and you cannot link against libev anymore. This can be useful
		4731	when you embed libev, only want to use libev functions in a single file,
		4732	and do not want its identifiers to be visible.
		4733
		4734	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4735	wants to use libev.
		4736
		4737	This option only works when libev is compiled with a C compiler, as C++
		4738	doesn't support the required declaration syntax.
		4739
		4740	=item EV_AVOID_STDIO
		4741
		4742	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4743	functions (printf, scanf, perror etc.). This will increase the code size
		4744	somewhat, but if your program doesn't otherwise depend on stdio and your
		4745	libc allows it, this avoids linking in the stdio library which is quite
		4746	big.
		4747
		4748	Note that error messages might become less precise when this option is
		4749	enabled.
3822		4750
3823	=item EV_NSIG	4751	=item EV_NSIG
3824		4752
3825	The highest supported signal number, +1 (or, the number of	4753	The highest supported signal number, +1 (or, the number of
3826	signals): Normally, libev tries to deduce the maximum number of signals	4754	signals): Normally, libev tries to deduce the maximum number of signals
3827	automatically, but sometimes this fails, in which case it can be	4755	automatically, but sometimes this fails, in which case it can be
3828	specified. Also, using a lower number than detected (C<32> should be	4756	specified. Also, using a lower number than detected (C<32> should be
3829	good for about any system in existance) can save some memory, as libev	4757	good for about any system in existence) can save some memory, as libev
3830	statically allocates some 12-24 bytes per signal number.	4758	statically allocates some 12-24 bytes per signal number.
3831		4759
3832	=item EV_PID_HASHSIZE	4760	=item EV_PID_HASHSIZE
3833		4761
3834	C<ev_child> watchers use a small hash table to distribute workload by	4762	C<ev_child> watchers use a small hash table to distribute workload by
3835	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4763	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3836	than enough. If you need to manage thousands of children you might want to	4764	usually more than enough. If you need to manage thousands of children you
3837	increase this value (I<must> be a power of two).	4765	might want to increase this value (I<must> be a power of two).
3838		4766
3839	=item EV_INOTIFY_HASHSIZE	4767	=item EV_INOTIFY_HASHSIZE
3840		4768
3841	C<ev_stat> watchers use a small hash table to distribute workload by	4769	C<ev_stat> watchers use a small hash table to distribute workload by
3842	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4770	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3843	usually more than enough. If you need to manage thousands of C<ev_stat>	4771	disabled), usually more than enough. If you need to manage thousands of
3844	watchers you might want to increase this value (I<must> be a power of	4772	C<ev_stat> watchers you might want to increase this value (I<must> be a
3845	two).	4773	power of two).
3846		4774
3847	=item EV_USE_4HEAP	4775	=item EV_USE_4HEAP
3848		4776
3849	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4777	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3850	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4778	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3851	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4779	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3852	faster performance with many (thousands) of watchers.	4780	faster performance with many (thousands) of watchers.
3853		4781
3854	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4782	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3855	(disabled).	4783	will be C<0>.
3856		4784
3857	=item EV_HEAP_CACHE_AT	4785	=item EV_HEAP_CACHE_AT
3858		4786
3859	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4787	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3860	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4788	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3861	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4789	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3862	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4790	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3863	but avoids random read accesses on heap changes. This improves performance	4791	but avoids random read accesses on heap changes. This improves performance
3864	noticeably with many (hundreds) of watchers.	4792	noticeably with many (hundreds) of watchers.
3865		4793
3866	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4794	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3867	(disabled).	4795	will be C<0>.
3868		4796
3869	=item EV_VERIFY	4797	=item EV_VERIFY
3870		4798
3871	Controls how much internal verification (see C<ev_loop_verify ()>) will	4799	Controls how much internal verification (see C<ev_verify ()>) will
3872	be done: If set to C<0>, no internal verification code will be compiled	4800	be done: If set to C<0>, no internal verification code will be compiled
3873	in. If set to C<1>, then verification code will be compiled in, but not	4801	in. If set to C<1>, then verification code will be compiled in, but not
3874	called. If set to C<2>, then the internal verification code will be	4802	called. If set to C<2>, then the internal verification code will be
3875	called once per loop, which can slow down libev. If set to C<3>, then the	4803	called once per loop, which can slow down libev. If set to C<3>, then the
3876	verification code will be called very frequently, which will slow down	4804	verification code will be called very frequently, which will slow down
3877	libev considerably.	4805	libev considerably.
3878		4806
3879	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4807	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3880	C<0>.	4808	will be C<0>.
3881		4809
3882	=item EV_COMMON	4810	=item EV_COMMON
3883		4811
3884	By default, all watchers have a C<void *data> member. By redefining	4812	By default, all watchers have a C<void *data> member. By redefining
3885	this macro to a something else you can include more and other types of	4813	this macro to something else you can include more and other types of
3886	members. You have to define it each time you include one of the files,	4814	members. You have to define it each time you include one of the files,
3887	though, and it must be identical each time.	4815	though, and it must be identical each time.
3888		4816
3889	For example, the perl EV module uses something like this:	4817	For example, the perl EV module uses something like this:
3890		4818
…		…
3943	file.	4871	file.
3944		4872
3945	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4873	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3946	that everybody includes and which overrides some configure choices:	4874	that everybody includes and which overrides some configure choices:
3947		4875
3948	#define EV_MINIMAL 1	4876	#define EV_FEATURES 8
3949	#define EV_USE_POLL 0	4877	#define EV_USE_SELECT 1
3950	#define EV_MULTIPLICITY 0
3951	#define EV_PERIODIC_ENABLE 0	4878	#define EV_PREPARE_ENABLE 1
		4879	#define EV_IDLE_ENABLE 1
3952	#define EV_STAT_ENABLE 0	4880	#define EV_SIGNAL_ENABLE 1
3953	#define EV_FORK_ENABLE 0	4881	#define EV_CHILD_ENABLE 1
		4882	#define EV_USE_STDEXCEPT 0
3954	#define EV_CONFIG_H <config.h>	4883	#define EV_CONFIG_H <config.h>
3955	#define EV_MINPRI 0
3956	#define EV_MAXPRI 0
3957		4884
3958	#include "ev++.h"	4885	#include "ev++.h"
3959		4886
3960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3961		4888
3962	#include "ev_cpp.h"	4889	#include "ev_cpp.h"
3963	#include "ev.c"	4890	#include "ev.c"
3964		4891
3965	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4892	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3966		4893
3967	=head2 THREADS AND COROUTINES	4894	=head2 THREADS AND COROUTINES
3968		4895
3969	=head3 THREADS	4896	=head3 THREADS
3970		4897
…		…
4021	default loop and triggering an C<ev_async> watcher from the default loop	4948	default loop and triggering an C<ev_async> watcher from the default loop
4022	watcher callback into the event loop interested in the signal.	4949	watcher callback into the event loop interested in the signal.
4023		4950
4024	=back	4951	=back
4025		4952
4026	=head4 THREAD LOCKING EXAMPLE	4953	See also L<THREAD LOCKING EXAMPLE>.
4027
4028	Here is a fictitious example of how to run an event loop in a different
4029	thread than where callbacks are being invoked and watchers are
4030	created/added/removed.
4031
4032	For a real-world example, see the C<EV::Loop::Async> perl module,
4033	which uses exactly this technique (which is suited for many high-level
4034	languages).
4035
4036	The example uses a pthread mutex to protect the loop data, a condition
4037	variable to wait for callback invocations, an async watcher to notify the
4038	event loop thread and an unspecified mechanism to wake up the main thread.
4039
4040	First, you need to associate some data with the event loop:
4041
4042	typedef struct {
4043	mutex_t lock; /* global loop lock */
4044	ev_async async_w;
4045	thread_t tid;
4046	cond_t invoke_cv;
4047	} userdata;
4048
4049	void prepare_loop (EV_P)
4050	{
4051	// for simplicity, we use a static userdata struct.
4052	static userdata u;
4053
4054	ev_async_init (&u->async_w, async_cb);
4055	ev_async_start (EV_A_ &u->async_w);
4056
4057	pthread_mutex_init (&u->lock, 0);
4058	pthread_cond_init (&u->invoke_cv, 0);
4059
4060	// now associate this with the loop
4061	ev_set_userdata (EV_A_ u);
4062	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4063	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4064
4065	// then create the thread running ev_loop
4066	pthread_create (&u->tid, 0, l_run, EV_A);
4067	}
4068
4069	The callback for the C<ev_async> watcher does nothing: the watcher is used
4070	solely to wake up the event loop so it takes notice of any new watchers
4071	that might have been added:
4072
4073	static void
4074	async_cb (EV_P_ ev_async *w, int revents)
4075	{
4076	// just used for the side effects
4077	}
4078
4079	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4080	protecting the loop data, respectively.
4081
4082	static void
4083	l_release (EV_P)
4084	{
4085	userdata *u = ev_userdata (EV_A);
4086	pthread_mutex_unlock (&u->lock);
4087	}
4088
4089	static void
4090	l_acquire (EV_P)
4091	{
4092	userdata *u = ev_userdata (EV_A);
4093	pthread_mutex_lock (&u->lock);
4094	}
4095
4096	The event loop thread first acquires the mutex, and then jumps straight
4097	into C<ev_loop>:
4098
4099	void *
4100	l_run (void *thr_arg)
4101	{
4102	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4103
4104	l_acquire (EV_A);
4105	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4106	ev_loop (EV_A_ 0);
4107	l_release (EV_A);
4108
4109	return 0;
4110	}
4111
4112	Instead of invoking all pending watchers, the C<l_invoke> callback will
4113	signal the main thread via some unspecified mechanism (signals? pipe
4114	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4115	have been called (in a while loop because a) spurious wakeups are possible
4116	and b) skipping inter-thread-communication when there are no pending
4117	watchers is very beneficial):
4118
4119	static void
4120	l_invoke (EV_P)
4121	{
4122	userdata *u = ev_userdata (EV_A);
4123
4124	while (ev_pending_count (EV_A))
4125	{
4126	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4127	pthread_cond_wait (&u->invoke_cv, &u->lock);
4128	}
4129	}
4130
4131	Now, whenever the main thread gets told to invoke pending watchers, it
4132	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4133	thread to continue:
4134
4135	static void
4136	real_invoke_pending (EV_P)
4137	{
4138	userdata *u = ev_userdata (EV_A);
4139
4140	pthread_mutex_lock (&u->lock);
4141	ev_invoke_pending (EV_A);
4142	pthread_cond_signal (&u->invoke_cv);
4143	pthread_mutex_unlock (&u->lock);
4144	}
4145
4146	Whenever you want to start/stop a watcher or do other modifications to an
4147	event loop, you will now have to lock:
4148
4149	ev_timer timeout_watcher;
4150	userdata *u = ev_userdata (EV_A);
4151
4152	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4153
4154	pthread_mutex_lock (&u->lock);
4155	ev_timer_start (EV_A_ &timeout_watcher);
4156	ev_async_send (EV_A_ &u->async_w);
4157	pthread_mutex_unlock (&u->lock);
4158
4159	Note that sending the C<ev_async> watcher is required because otherwise
4160	an event loop currently blocking in the kernel will have no knowledge
4161	about the newly added timer. By waking up the loop it will pick up any new
4162	watchers in the next event loop iteration.
4163		4954
4164	=head3 COROUTINES	4955	=head3 COROUTINES
4165		4956
4166	Libev is very accommodating to coroutines ("cooperative threads"):	4957	Libev is very accommodating to coroutines ("cooperative threads"):
4167	libev fully supports nesting calls to its functions from different	4958	libev fully supports nesting calls to its functions from different
4168	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4959	coroutines (e.g. you can call C<ev_run> on the same loop from two
4169	different coroutines, and switch freely between both coroutines running	4960	different coroutines, and switch freely between both coroutines running
4170	the loop, as long as you don't confuse yourself). The only exception is	4961	the loop, as long as you don't confuse yourself). The only exception is
4171	that you must not do this from C<ev_periodic> reschedule callbacks.	4962	that you must not do this from C<ev_periodic> reschedule callbacks.
4172		4963
4173	Care has been taken to ensure that libev does not keep local state inside	4964	Care has been taken to ensure that libev does not keep local state inside
4174	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4965	C<ev_run>, and other calls do not usually allow for coroutine switches as
4175	they do not call any callbacks.	4966	they do not call any callbacks.
4176		4967
4177	=head2 COMPILER WARNINGS	4968	=head2 COMPILER WARNINGS
4178		4969
4179	Depending on your compiler and compiler settings, you might get no or a	4970	Depending on your compiler and compiler settings, you might get no or a
…		…
4190	maintainable.	4981	maintainable.
4191		4982
4192	And of course, some compiler warnings are just plain stupid, or simply	4983	And of course, some compiler warnings are just plain stupid, or simply
4193	wrong (because they don't actually warn about the condition their message	4984	wrong (because they don't actually warn about the condition their message
4194	seems to warn about). For example, certain older gcc versions had some	4985	seems to warn about). For example, certain older gcc versions had some
4195	warnings that resulted an extreme number of false positives. These have	4986	warnings that resulted in an extreme number of false positives. These have
4196	been fixed, but some people still insist on making code warn-free with	4987	been fixed, but some people still insist on making code warn-free with
4197	such buggy versions.	4988	such buggy versions.
4198		4989
4199	While libev is written to generate as few warnings as possible,	4990	While libev is written to generate as few warnings as possible,
4200	"warn-free" code is not a goal, and it is recommended not to build libev	4991	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4236	I suggest using suppression lists.	5027	I suggest using suppression lists.
4237		5028
4238		5029
4239	=head1 PORTABILITY NOTES	5030	=head1 PORTABILITY NOTES
4240		5031
		5032	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5033
		5034	GNU/Linux is the only common platform that supports 64 bit file/large file
		5035	interfaces but I<disables> them by default.
		5036
		5037	That means that libev compiled in the default environment doesn't support
		5038	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5039
		5040	Unfortunately, many programs try to work around this GNU/Linux issue
		5041	by enabling the large file API, which makes them incompatible with the
		5042	standard libev compiled for their system.
		5043
		5044	Likewise, libev cannot enable the large file API itself as this would
		5045	suddenly make it incompatible to the default compile time environment,
		5046	i.e. all programs not using special compile switches.
		5047
		5048	=head2 OS/X AND DARWIN BUGS
		5049
		5050	The whole thing is a bug if you ask me - basically any system interface
		5051	you touch is broken, whether it is locales, poll, kqueue or even the
		5052	OpenGL drivers.
		5053
		5054	=head3 C<kqueue> is buggy
		5055
		5056	The kqueue syscall is broken in all known versions - most versions support
		5057	only sockets, many support pipes.
		5058
		5059	Libev tries to work around this by not using C<kqueue> by default on this
		5060	rotten platform, but of course you can still ask for it when creating a
		5061	loop - embedding a socket-only kqueue loop into a select-based one is
		5062	probably going to work well.
		5063
		5064	=head3 C<poll> is buggy
		5065
		5066	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5067	implementation by something calling C<kqueue> internally around the 10.5.6
		5068	release, so now C<kqueue> I<and> C<poll> are broken.
		5069
		5070	Libev tries to work around this by not using C<poll> by default on
		5071	this rotten platform, but of course you can still ask for it when creating
		5072	a loop.
		5073
		5074	=head3 C<select> is buggy
		5075
		5076	All that's left is C<select>, and of course Apple found a way to fuck this
		5077	one up as well: On OS/X, C<select> actively limits the number of file
		5078	descriptors you can pass in to 1024 - your program suddenly crashes when
		5079	you use more.
		5080
		5081	There is an undocumented "workaround" for this - defining
		5082	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5083	work on OS/X.
		5084
		5085	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5086
		5087	=head3 C<errno> reentrancy
		5088
		5089	The default compile environment on Solaris is unfortunately so
		5090	thread-unsafe that you can't even use components/libraries compiled
		5091	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5092	defined by default. A valid, if stupid, implementation choice.
		5093
		5094	If you want to use libev in threaded environments you have to make sure
		5095	it's compiled with C<_REENTRANT> defined.
		5096
		5097	=head3 Event port backend
		5098
		5099	The scalable event interface for Solaris is called "event
		5100	ports". Unfortunately, this mechanism is very buggy in all major
		5101	releases. If you run into high CPU usage, your program freezes or you get
		5102	a large number of spurious wakeups, make sure you have all the relevant
		5103	and latest kernel patches applied. No, I don't know which ones, but there
		5104	are multiple ones to apply, and afterwards, event ports actually work
		5105	great.
		5106
		5107	If you can't get it to work, you can try running the program by setting
		5108	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5109	C<select> backends.
		5110
		5111	=head2 AIX POLL BUG
		5112
		5113	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5114	this by trying to avoid the poll backend altogether (i.e. it's not even
		5115	compiled in), which normally isn't a big problem as C<select> works fine
		5116	with large bitsets on AIX, and AIX is dead anyway.
		5117
4241	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5118	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5119
		5120	=head3 General issues
4242		5121
4243	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5122	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4244	requires, and its I/O model is fundamentally incompatible with the POSIX	5123	requires, and its I/O model is fundamentally incompatible with the POSIX
4245	model. Libev still offers limited functionality on this platform in	5124	model. Libev still offers limited functionality on this platform in
4246	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5125	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4247	descriptors. This only applies when using Win32 natively, not when using	5126	descriptors. This only applies when using Win32 natively, not when using
4248	e.g. cygwin.	5127	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5128	as every compiler comes with a slightly differently broken/incompatible
		5129	environment.
4249		5130
4250	Lifting these limitations would basically require the full	5131	Lifting these limitations would basically require the full
4251	re-implementation of the I/O system. If you are into these kinds of	5132	re-implementation of the I/O system. If you are into this kind of thing,
4252	things, then note that glib does exactly that for you in a very portable	5133	then note that glib does exactly that for you in a very portable way (note
4253	way (note also that glib is the slowest event library known to man).	5134	also that glib is the slowest event library known to man).
4254		5135
4255	There is no supported compilation method available on windows except	5136	There is no supported compilation method available on windows except
4256	embedding it into other applications.	5137	embedding it into other applications.
4257		5138
4258	Sensible signal handling is officially unsupported by Microsoft - libev	5139	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4286	you do I<not> compile the F<ev.c> or any other embedded source files!):	5167	you do I<not> compile the F<ev.c> or any other embedded source files!):
4287		5168
4288	#include "evwrap.h"	5169	#include "evwrap.h"
4289	#include "ev.c"	5170	#include "ev.c"
4290		5171
4291	=over 4
4292
4293	=item The winsocket select function	5172	=head3 The winsocket C<select> function
4294		5173
4295	The winsocket C<select> function doesn't follow POSIX in that it	5174	The winsocket C<select> function doesn't follow POSIX in that it
4296	requires socket I<handles> and not socket I<file descriptors> (it is	5175	requires socket I<handles> and not socket I<file descriptors> (it is
4297	also extremely buggy). This makes select very inefficient, and also	5176	also extremely buggy). This makes select very inefficient, and also
4298	requires a mapping from file descriptors to socket handles (the Microsoft	5177	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4307	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5186	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4308		5187
4309	Note that winsockets handling of fd sets is O(n), so you can easily get a	5188	Note that winsockets handling of fd sets is O(n), so you can easily get a
4310	complexity in the O(n²) range when using win32.	5189	complexity in the O(n²) range when using win32.
4311		5190
4312	=item Limited number of file descriptors	5191	=head3 Limited number of file descriptors
4313		5192
4314	Windows has numerous arbitrary (and low) limits on things.	5193	Windows has numerous arbitrary (and low) limits on things.
4315		5194
4316	Early versions of winsocket's select only supported waiting for a maximum	5195	Early versions of winsocket's select only supported waiting for a maximum
4317	of C<64> handles (probably owning to the fact that all windows kernels	5196	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4332	runtime libraries. This might get you to about C<512> or C<2048> sockets	5211	runtime libraries. This might get you to about C<512> or C<2048> sockets
4333	(depending on windows version and/or the phase of the moon). To get more,	5212	(depending on windows version and/or the phase of the moon). To get more,
4334	you need to wrap all I/O functions and provide your own fd management, but	5213	you need to wrap all I/O functions and provide your own fd management, but
4335	the cost of calling select (O(n²)) will likely make this unworkable.	5214	the cost of calling select (O(n²)) will likely make this unworkable.
4336		5215
4337	=back
4338
4339	=head2 PORTABILITY REQUIREMENTS	5216	=head2 PORTABILITY REQUIREMENTS
4340		5217
4341	In addition to a working ISO-C implementation and of course the	5218	In addition to a working ISO-C implementation and of course the
4342	backend-specific APIs, libev relies on a few additional extensions:	5219	backend-specific APIs, libev relies on a few additional extensions:
4343		5220
…		…
4349	Libev assumes not only that all watcher pointers have the same internal	5226	Libev assumes not only that all watcher pointers have the same internal
4350	structure (guaranteed by POSIX but not by ISO C for example), but it also	5227	structure (guaranteed by POSIX but not by ISO C for example), but it also
4351	assumes that the same (machine) code can be used to call any watcher	5228	assumes that the same (machine) code can be used to call any watcher
4352	callback: The watcher callbacks have different type signatures, but libev	5229	callback: The watcher callbacks have different type signatures, but libev
4353	calls them using an C<ev_watcher *> internally.	5230	calls them using an C<ev_watcher *> internally.
		5231
		5232	=item pointer accesses must be thread-atomic
		5233
		5234	Accessing a pointer value must be atomic, it must both be readable and
		5235	writable in one piece - this is the case on all current architectures.
4354		5236
4355	=item C<sig_atomic_t volatile> must be thread-atomic as well	5237	=item C<sig_atomic_t volatile> must be thread-atomic as well
4356		5238
4357	The type C<sig_atomic_t volatile> (or whatever is defined as	5239	The type C<sig_atomic_t volatile> (or whatever is defined as
4358	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5240	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4381	watchers.	5263	watchers.
4382		5264
4383	=item C<double> must hold a time value in seconds with enough accuracy	5265	=item C<double> must hold a time value in seconds with enough accuracy
4384		5266
4385	The type C<double> is used to represent timestamps. It is required to	5267	The type C<double> is used to represent timestamps. It is required to
4386	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5268	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4387	enough for at least into the year 4000. This requirement is fulfilled by	5269	good enough for at least into the year 4000 with millisecond accuracy
		5270	(the design goal for libev). This requirement is overfulfilled by
4388	implementations implementing IEEE 754, which is basically all existing	5271	implementations using IEEE 754, which is basically all existing ones.
		5272
4389	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5273	With IEEE 754 doubles, you get microsecond accuracy until at least the
4390	2200.	5274	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5275	is either obsolete or somebody patched it to use C<long double> or
		5276	something like that, just kidding).
4391		5277
4392	=back	5278	=back
4393		5279
4394	If you know of other additional requirements drop me a note.	5280	If you know of other additional requirements drop me a note.
4395		5281
…		…
4457	=item Processing ev_async_send: O(number_of_async_watchers)	5343	=item Processing ev_async_send: O(number_of_async_watchers)
4458		5344
4459	=item Processing signals: O(max_signal_number)	5345	=item Processing signals: O(max_signal_number)
4460		5346
4461	Sending involves a system call I<iff> there were no other C<ev_async_send>	5347	Sending involves a system call I<iff> there were no other C<ev_async_send>
4462	calls in the current loop iteration. Checking for async and signal events	5348	calls in the current loop iteration and the loop is currently
		5349	blocked. Checking for async and signal events involves iterating over all
4463	involves iterating over all running async watchers or all signal numbers.	5350	running async watchers or all signal numbers.
4464		5351
4465	=back	5352	=back
4466		5353
4467		5354
		5355	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5356
		5357	The major version 4 introduced some incompatible changes to the API.
		5358
		5359	At the moment, the C<ev.h> header file provides compatibility definitions
		5360	for all changes, so most programs should still compile. The compatibility
		5361	layer might be removed in later versions of libev, so better update to the
		5362	new API early than late.
		5363
		5364	=over 4
		5365
		5366	=item C<EV_COMPAT3> backwards compatibility mechanism
		5367
		5368	The backward compatibility mechanism can be controlled by
		5369	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5370	section.
		5371
		5372	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5373
		5374	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5375
		5376	ev_loop_destroy (EV_DEFAULT_UC);
		5377	ev_loop_fork (EV_DEFAULT);
		5378
		5379	=item function/symbol renames
		5380
		5381	A number of functions and symbols have been renamed:
		5382
		5383	ev_loop => ev_run
		5384	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5385	EVLOOP_ONESHOT => EVRUN_ONCE
		5386
		5387	ev_unloop => ev_break
		5388	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5389	EVUNLOOP_ONE => EVBREAK_ONE
		5390	EVUNLOOP_ALL => EVBREAK_ALL
		5391
		5392	EV_TIMEOUT => EV_TIMER
		5393
		5394	ev_loop_count => ev_iteration
		5395	ev_loop_depth => ev_depth
		5396	ev_loop_verify => ev_verify
		5397
		5398	Most functions working on C<struct ev_loop> objects don't have an
		5399	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5400	associated constants have been renamed to not collide with the C<struct
		5401	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5402	as all other watcher types. Note that C<ev_loop_fork> is still called
		5403	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5404	typedef.
		5405
		5406	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5407
		5408	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5409	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5410	and work, but the library code will of course be larger.
		5411
		5412	=back
		5413
		5414
4468	=head1 GLOSSARY	5415	=head1 GLOSSARY
4469		5416
4470	=over 4	5417	=over 4
4471		5418
4472	=item active	5419	=item active
4473		5420
4474	A watcher is active as long as it has been started (has been attached to	5421	A watcher is active as long as it has been started and not yet stopped.
4475	an event loop) but not yet stopped (disassociated from the event loop).	5422	See L<WATCHER STATES> for details.
4476		5423
4477	=item application	5424	=item application
4478		5425
4479	In this document, an application is whatever is using libev.	5426	In this document, an application is whatever is using libev.
		5427
		5428	=item backend
		5429
		5430	The part of the code dealing with the operating system interfaces.
4480		5431
4481	=item callback	5432	=item callback
4482		5433
4483	The address of a function that is called when some event has been	5434	The address of a function that is called when some event has been
4484	detected. Callbacks are being passed the event loop, the watcher that	5435	detected. Callbacks are being passed the event loop, the watcher that
4485	received the event, and the actual event bitset.	5436	received the event, and the actual event bitset.
4486		5437
4487	=item callback invocation	5438	=item callback/watcher invocation
4488		5439
4489	The act of calling the callback associated with a watcher.	5440	The act of calling the callback associated with a watcher.
4490		5441
4491	=item event	5442	=item event
4492		5443
4493	A change of state of some external event, such as data now being available	5444	A change of state of some external event, such as data now being available
4494	for reading on a file descriptor, time having passed or simply not having	5445	for reading on a file descriptor, time having passed or simply not having
4495	any other events happening anymore.	5446	any other events happening anymore.
4496		5447
4497	In libev, events are represented as single bits (such as C<EV_READ> or	5448	In libev, events are represented as single bits (such as C<EV_READ> or
4498	C<EV_TIMEOUT>).	5449	C<EV_TIMER>).
4499		5450
4500	=item event library	5451	=item event library
4501		5452
4502	A software package implementing an event model and loop.	5453	A software package implementing an event model and loop.
4503		5454
…		…
4511	The model used to describe how an event loop handles and processes	5462	The model used to describe how an event loop handles and processes
4512	watchers and events.	5463	watchers and events.
4513		5464
4514	=item pending	5465	=item pending
4515		5466
4516	A watcher is pending as soon as the corresponding event has been detected,	5467	A watcher is pending as soon as the corresponding event has been
4517	and stops being pending as soon as the watcher will be invoked or its	5468	detected. See L<WATCHER STATES> for details.
4518	pending status is explicitly cleared by the application.
4519
4520	A watcher can be pending, but not active. Stopping a watcher also clears
4521	its pending status.
4522		5469
4523	=item real time	5470	=item real time
4524		5471
4525	The physical time that is observed. It is apparently strictly monotonic :)	5472	The physical time that is observed. It is apparently strictly monotonic :)
4526		5473
4527	=item wall-clock time	5474	=item wall-clock time
4528		5475
4529	The time and date as shown on clocks. Unlike real time, it can actually	5476	The time and date as shown on clocks. Unlike real time, it can actually
4530	be wrong and jump forwards and backwards, e.g. when the you adjust your	5477	be wrong and jump forwards and backwards, e.g. when you adjust your
4531	clock.	5478	clock.
4532		5479
4533	=item watcher	5480	=item watcher
4534		5481
4535	A data structure that describes interest in certain events. Watchers need	5482	A data structure that describes interest in certain events. Watchers need
4536	to be started (attached to an event loop) before they can receive events.	5483	to be started (attached to an event loop) before they can receive events.
4537		5484
4538	=item watcher invocation
4539
4540	The act of calling the callback associated with a watcher.
4541
4542	=back	5485	=back
4543		5486
4544	=head1 AUTHOR	5487	=head1 AUTHOR
4545		5488
4546	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5489	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5490	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4547		5491

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