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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
…		…
362	flag.	418	flag.
363		419
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	421	environment variable.
366		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		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.
		457
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		459
369	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
370	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,
371	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
395	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
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		488
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
400	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
401	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
402	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
403	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
404		498
405	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
408	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
409	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
410	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
411	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	508	and is of course hard to detect.
413		509
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
415	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
416	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
417	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
418	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
420	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...
421		526
422	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
423	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
424	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
425	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
…		…
462		567
463	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
464	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
465	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
466	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
467	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
468	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
469	cases	574	drops fds silently in similarly hard-to-detect cases
470		575
471	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
472		577
473	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
474	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
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		597
493	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,
494	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)).
495		600
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	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
501	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
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	604	might perform better.
504		605
505	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	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
508	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.
509		620
510	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
511	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
512		623
513	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
514		625
515	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
516	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
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		629
519	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).
520		639
521	=back	640	=back
522		641
523	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
526		645	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		646
555	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.
556		648
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	650	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
560		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
561	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
562		659
563	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
564	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
565	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
566	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
567	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
568	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
…		…
570		667
571	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
572	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
573	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
574		671
575	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
576	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.
577	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>
578	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
579		680
580	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
581		682
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	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
588	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
589	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
590	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
591	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
592	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.
593		693
594	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
595	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
596	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).
597		700
598	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
599	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		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	...
602	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		715
611	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
612		717
613	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
614	otherwise.	719	otherwise.
615		720
616	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
617		722
618	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
619	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>
620	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
621		726
622	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
623	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
624	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.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		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.
625		745
626	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
627		747
628	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
629	use.	749	use.
…		…
638		758
639	=item ev_now_update (loop)	759	=item ev_now_update (loop)
640		760
641	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
642	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
643	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
644		764
645	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
646	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
647	the current time is a good idea.	767	the current time is a good idea.
648		768
…		…
650		770
651	=item ev_suspend (loop)	771	=item ev_suspend (loop)
652		772
653	=item ev_resume (loop)	773	=item ev_resume (loop)
654		774
655	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
656	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.
657		777
658	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
659	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
660	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
661	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>
…		…
663	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
664		784
665	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
666	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
667	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
668	occured while suspended).	788	occurred while suspended).
669		789
670	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
671	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>
672	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
673		793
674	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
675	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
676		796
677	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
678		798
679	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
680	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
681	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>.
682		804
683	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
684	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.
685		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
686	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
687	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
688	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
689	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
690	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
691	beauty.	818	beauty.
692		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
693	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
694	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
695	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
696	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.
697		830
698	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
699	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
700	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
701	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
702	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
703	iteration of the loop.	836	iteration of the loop.
704		837
705	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
706	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
707	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
708	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
709		842
710	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):
711		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
712	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
713	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
714	- 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.
715	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
716	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
717	as to not disturb the other process.	856	as to not disturb the other process.
718	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
719	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
720	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
721	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
722	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
723	- 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.
724	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
725	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
726	- 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.
727	- Queue all expired timers.	867	- Queue all expired timers.
728	- Queue all expired periodics.	868	- Queue all expired periodics.
729	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
730	- Queue all check watchers.	870	- Queue all check watchers.
731	- 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).
732	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
733	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
734	- 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
735	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
736	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.
737		881
738	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
739	anymore.	883	anymore.
740		884
741	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
742	... 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..)
743	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
744	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
745		889
746	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
747		891
748	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
749	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
750	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
751	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.
752		896
753	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>.
754		898
755	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.
756		901
757	=item ev_ref (loop)	902	=item ev_ref (loop)
758		903
759	=item ev_unref (loop)	904	=item ev_unref (loop)
760		905
761	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
762	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
763	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.
764		909
765	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
766	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>
767	stopping it.	913	before stopping it.
768		914
769	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
770	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
771	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
772	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
773	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
774	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
775	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
776	(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>
777	in the callback).	923	in the callback).
778		924
779	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>
780	running when nothing else is active.	926	running when nothing else is active.
781		927
782	ev_signal exitsig;	928	ev_signal exitsig;
783	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
784	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
785	evf_unref (loop);	931	ev_unref (loop);
786		932
787	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
788		934
789	ev_ref (loop);	935	ev_ref (loop);
790	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
810	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.
811		957
812	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
813	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,
814	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
815	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
816	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
817	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
818	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
819		966
820	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
821	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
822	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
823	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
…		…
829	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>,
830	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
831	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
832	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
833	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,
834	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
835		982
836	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
837	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
838	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
839	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
…		…
844	more often than 100 times per second:	991	more often than 100 times per second:
845		992
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	993	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		995
		996	=item ev_invoke_pending (loop)
		997
		998	This call will simply invoke all pending watchers while resetting their
		999	pending state. Normally, C<ev_run> does this automatically when required,
		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).
		1005
		1006	=item int ev_pending_count (loop)
		1007
		1008	Returns the number of pending watchers - zero indicates that no watchers
		1009	are pending.
		1010
		1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1012
		1013	This overrides the invoke pending functionality of the loop: Instead of
		1014	invoking all pending watchers when there are any, C<ev_run> will call
		1015	this callback instead. This is useful, for example, when you want to
		1016	invoke the actual watchers inside another context (another thread etc.).
		1017
		1018	If you want to reset the callback, use C<ev_invoke_pending> as new
		1019	callback.
		1020
		1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1022
		1023	Sometimes you want to share the same loop between multiple threads. This
		1024	can be done relatively simply by putting mutex_lock/unlock calls around
		1025	each call to a libev function.
		1026
		1027	However, C<ev_run> can run an indefinite time, so it is not feasible
		1028	to wait for it to return. One way around this is to wake up the event
		1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1030	I<release> and I<acquire> callbacks on the loop.
		1031
		1032	When set, then C<release> will be called just before the thread is
		1033	suspended waiting for new events, and C<acquire> is called just
		1034	afterwards.
		1035
		1036	Ideally, C<release> will just call your mutex_unlock function, and
		1037	C<acquire> will just call the mutex_lock function again.
		1038
		1039	While event loop modifications are allowed between invocations of
		1040	C<release> and C<acquire> (that's their only purpose after all), no
		1041	modifications done will affect the event loop, i.e. adding watchers will
		1042	have no effect on the set of file descriptors being watched, or the time
		1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1044	to take note of any changes you made.
		1045
		1046	In theory, threads executing C<ev_run> will be async-cancel safe between
		1047	invocations of C<release> and C<acquire>.
		1048
		1049	See also the locking example in the C<THREADS> section later in this
		1050	document.
		1051
		1052	=item ev_set_userdata (loop, void *data)
		1053
		1054	=item void *ev_userdata (loop)
		1055
		1056	Set and retrieve a single C<void *> associated with a loop. When
		1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1058	C<0>.
		1059
		1060	These two functions can be used to associate arbitrary data with a loop,
		1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1062	C<acquire> callbacks described above, but of course can be (ab-)used for
		1063	any other purpose as well.
		1064
849	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
850		1066
851	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
852	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
853	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
854	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
…		…
865		1081
866	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
867	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
868	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
869		1085
870	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
871	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
872	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:
873		1090
874	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)
875	{	1092	{
876	ev_io_stop (w);	1093	ev_io_stop (w);
877	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
878	}	1095	}
879		1096
880	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
881		1098
882	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
883		1100
884	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
885	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
886	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
887		1104
888	ev_loop (loop, 0);	1105	ev_run (loop, 0);
889		1106
890	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
891	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
892	stack).	1109	stack).
893		1110
894	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>
895	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).
896		1113
897	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
898	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
899	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
900	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
901	is readable and/or writable).	1118	and/or writable).
902		1119
903	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 *, ...) >>
904	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
905	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<<
906	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
929	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
930		1147
931	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
932	writable.	1149	writable.
933		1150
934	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
935		1152
936	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
937		1154
938	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
939		1156
…		…
957		1174
958	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
959		1176
960	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
961		1178
962	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
963	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
964	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
965	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
966	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
967	(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
968	C<ev_loop> from blocking).	1185	C<ev_run> from blocking).
969		1186
970	=item C<EV_EMBED>	1187	=item C<EV_EMBED>
971		1188
972	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.
973		1190
974	=item C<EV_FORK>	1191	=item C<EV_FORK>
975		1192
976	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
977	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>).
978		1199
979	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
980		1201
981	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>).
982		1203
…		…
1029		1250
1030	ev_io w;	1251	ev_io w;
1031	ev_init (&w, my_cb);	1252	ev_init (&w, my_cb);
1032	ev_io_set (&w, STDIN_FILENO, EV_READ);	1253	ev_io_set (&w, STDIN_FILENO, EV_READ);
1033		1254
1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1255	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1035		1256
1036	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
1037	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
1038	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
1039	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
…		…
1052		1273
1053	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.
1054		1275
1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1276	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1056		1277
1057	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1278	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1058		1279
1059	Starts (activates) the given watcher. Only active watchers will receive	1280	Starts (activates) the given watcher. Only active watchers will receive
1060	events. If the watcher is already active nothing will happen.	1281	events. If the watcher is already active nothing will happen.
1061		1282
1062	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
1063	whole section.	1284	whole section.
1064		1285
1065	ev_io_start (EV_DEFAULT_UC, &w);	1286	ev_io_start (EV_DEFAULT_UC, &w);
1066		1287
1067	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1288	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1068		1289
1069	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
1070	the watcher was active or not).	1291	the watcher was active or not).
1071		1292
1072	It is possible that stopped watchers are pending - for example,	1293	It is possible that stopped watchers are pending - for example,
…		…
1097	=item ev_cb_set (ev_TYPE *watcher, callback)	1318	=item ev_cb_set (ev_TYPE *watcher, callback)
1098		1319
1099	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
1100	(modulo threads).	1321	(modulo threads).
1101		1322
1102	=item ev_set_priority (ev_TYPE *watcher, priority)	1323	=item ev_set_priority (ev_TYPE *watcher, int priority)
1103		1324
1104	=item int ev_priority (ev_TYPE *watcher)	1325	=item int ev_priority (ev_TYPE *watcher)
1105		1326
1106	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
1107	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>
…		…
1139	watcher isn't pending it does nothing and returns C<0>.	1360	watcher isn't pending it does nothing and returns C<0>.
1140		1361
1141	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
1142	callback to be invoked, which can be accomplished with this function.	1363	callback to be invoked, which can be accomplished with this function.
1143		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
1144	=back	1379	=back
1145		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
1146		1383
1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1384	=head2 WATCHER STATES
1148		1385
1149	Each watcher has, by default, a member C<void *data> that you can change	1386	There are various watcher states mentioned throughout this manual -
1150	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
1151	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
1152	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".
1153	member, you can also "subclass" the watcher type and provide your own
1154	data:
1155		1390
1156	struct my_io	1391	=over 4
1157	{
1158	ev_io io;
1159	int otherfd;
1160	void *somedata;
1161	struct whatever *mostinteresting;
1162	};
1163		1392
1164	...	1393	=item initialiased
1165	struct my_io w;
1166	ev_io_init (&w.io, my_cb, fd, EV_READ);
1167		1394
1168	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
1169	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.
1170		1398
1171	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
1172	{	1400	use in an event loop. It can be moved around, freed, reused etc. at
1173	struct my_io *w = (struct my_io *)w_;	1401	will - as long as you either keep the memory contents intact, or call
1174	...	1402	C<ev_TYPE_init> again.
1175	}
1176		1403
1177	More interesting and less C-conformant ways of casting your callback type	1404	=item started/running/active
1178	instead have been omitted.
1179		1405
1180	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
1181	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.
1182		1411
1183	struct my_biggy	1412	=item pending
1184	{
1185	int some_data;
1186	ev_timer t1;
1187	ev_timer t2;
1188	}
1189		1413
1190	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
1191	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
1192	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
1193	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
1194	programmers):	1418	callback.
1195		1419
1196	#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.
1197		1426
1198	static void	1427	It is also possible to feed an event on a watcher that is not active (e.g.
1199	t1_cb (EV_P_ ev_timer *w, int revents)	1428	via C<ev_feed_event>), in which case it becomes pending without being
1200	{	1429	active.
1201	struct my_biggy big = (struct my_biggy *)
1202	(((char *)w) - offsetof (struct my_biggy, t1));
1203	}
1204		1430
1205	static void	1431	=item stopped
1206	t2_cb (EV_P_ ev_timer *w, int revents)	1432
1207	{	1433	A watcher can be stopped implicitly by libev (in which case it might still
1208	struct my_biggy big = (struct my_biggy *)	1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1209	(((char *)w) - offsetof (struct my_biggy, t2));	1435	latter will clear any pending state the watcher might be in, regardless
1210	}	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
1211		1445
1212	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1213		1447
1214	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1215	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1258		1492
1259	For example, to emulate how many other event libraries handle priorities,	1493	For example, to emulate how many other event libraries handle priorities,
1260	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
1261	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
1262	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
1263	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
1264	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
1265	workable.	1499	workable.
1266		1500
1267	Usually, however, the lock-out model implemented that way will perform	1501	Usually, however, the lock-out model implemented that way will perform
1268	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,
…		…
1282	{	1516	{
1283	// stop the I/O watcher, we received the event, but	1517	// stop the I/O watcher, we received the event, but
1284	// are not yet ready to handle it.	1518	// are not yet ready to handle it.
1285	ev_io_stop (EV_A_ w);	1519	ev_io_stop (EV_A_ w);
1286		1520
1287	// start the idle watcher to ahndle the actual event.	1521	// start the idle watcher to handle the actual event.
1288	// it will not be executed as long as other watchers	1522	// it will not be executed as long as other watchers
1289	// with the default priority are receiving events.	1523	// with the default priority are receiving events.
1290	ev_idle_start (EV_A_ &idle);	1524	ev_idle_start (EV_A_ &idle);
1291	}	1525	}
1292		1526
…		…
1342	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
1343	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
1344	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
1345	required if you know what you are doing).	1579	required if you know what you are doing).
1346		1580
1347	If you cannot use non-blocking mode, then force the use of a
1348	known-to-be-good backend (at the time of this writing, this includes only
1349	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1350	descriptors for which non-blocking operation makes no sense (such as
1351	files) - libev doesn't guarentee any specific behaviour in that case.
1352
1353	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
1354	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1355	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
1356	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
1357	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
1358	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
1359	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1360	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1361		1588
1362	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
1363	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
1364	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
1365	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
1366	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
1367	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
1368	indefinitely.	1595	indefinitely.
1369		1596
1370	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1371		1598
…		…
1399		1626
1400	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1401	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1402	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1403		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
1404	=head3 The special problem of fork	1664	=head3 The special problem of fork
1405		1665
1406	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
1407	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
1408	it in the child.	1668	it in the child if you want to continue to use it in the child.
1409		1669
1410	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
1411	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
1412	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1413	C<EVBACKEND_POLL>.
1414		1673
1415	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1416		1675
1417	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>:
1418	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
…		…
1421		1680
1422	So when you encounter spurious, unexplained daemon exits, make sure you	1681	So when you encounter spurious, unexplained daemon exits, make sure you
1423	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
1424	somewhere, as that would have given you a big clue).	1683	somewhere, as that would have given you a big clue).
1425		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.
1426		1723
1427	=head3 Watcher-Specific Functions	1724	=head3 Watcher-Specific Functions
1428		1725
1429	=over 4	1726	=over 4
1430		1727
…		…
1462	...	1759	...
1463	struct ev_loop *loop = ev_default_init (0);	1760	struct ev_loop *loop = ev_default_init (0);
1464	ev_io stdin_readable;	1761	ev_io stdin_readable;
1465	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);
1466	ev_io_start (loop, &stdin_readable);	1763	ev_io_start (loop, &stdin_readable);
1467	ev_loop (loop, 0);	1764	ev_run (loop, 0);
1468		1765
1469		1766
1470	=head2 C<ev_timer> - relative and optionally repeating timeouts	1767	=head2 C<ev_timer> - relative and optionally repeating timeouts
1471		1768
1472	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
…		…
1478	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1479	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1480		1777
1481	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
1482	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
1483	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
1484	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
1485	before ones with later time-out values (but this is no longer true when a	1783	ones of the same priority with later time-out values (but this is no
1486	callback calls C<ev_loop> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1487		1785
1488	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1489		1787
1490	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
1491	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,
…		…
1566		1864
1567	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,
1568	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
1569	within the callback:	1867	within the callback:
1570		1868
		1869	ev_tstamp timeout = 60.;
1571	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1572		1872
1573	static void	1873	static void
1574	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1575	{	1875	{
1576	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1577	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1578		1878
1579	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1580	if (timeout < now)	1880	if (after < 0.)
1581	{	1881	{
1582	// timeout occured, take action	1882	// timeout occurred, take action
1583	}	1883	}
1584	else	1884	else
1585	{	1885	{
1586	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1587	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1588	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1589	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1590	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1591	}	1892	}
1592	}	1893	}
1593		1894
1594	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1595	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,
1596	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
1597	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1598	re-schedule the timer to fire at that future time, to see if maybe we have
1599	a timeout then.
1600		1899
1601	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
1602	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 cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1603		1909
1604	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1605	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
1606	libev to change the timeout.	1912	libev to change the timeout.
1607		1913
1608	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1609	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
1610	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:
1611		1918
		1919	last_activity = ev_now (EV_A);
1612	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1613	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1614	callback (loop, timer, EV_TIMEOUT);
1615		1922
1616	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1617	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1618		1925
		1926	if (activity detected)
1619	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 agaion 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);
1620		1936
1621	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
1622	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1623
1624	Changing the timeout is trivial as well (if it isn't hard-coded in the
1625	callback :) - just change the timeout and invoke the callback, which will
1626	fix things for you.
1627		1939
1628	=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.
1629		1941
1630	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1631	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
…		…
1658	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
1659	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1660	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
1661	overkill :)	1973	overkill :)
1662		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
1663	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1664		2013
1665	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1666	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
1667	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
1668	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
1669	lots of events in one iteration.	2018	lots of events in one iteration.
1670		2019
1671	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
1672	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
…		…
1678		2027
1679	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
1680	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
1681	()>.	2030	()>.
1682		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.
		2064
		2065	=head3 The special problems of suspended animation
		2066
		2067	When you leave the server world it is quite customary to hit machines that
		2068	can suspend/hibernate - what happens to the clocks during such a suspend?
		2069
		2070	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2071	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2072	to run until the system is suspended, but they will not advance while the
		2073	system is suspended. That means, on resume, it will be as if the program
		2074	was frozen for a few seconds, but the suspend time will not be counted
		2075	towards C<ev_timer> when a monotonic clock source is used. The real time
		2076	clock advanced as expected, but if it is used as sole clocksource, then a
		2077	long suspend would be detected as a time jump by libev, and timers would
		2078	be adjusted accordingly.
		2079
		2080	I would not be surprised to see different behaviour in different between
		2081	operating systems, OS versions or even different hardware.
		2082
		2083	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2084	time jump in the monotonic clocks and the realtime clock. If the program
		2085	is suspended for a very long time, and monotonic clock sources are in use,
		2086	then you can expect C<ev_timer>s to expire as the full suspension time
		2087	will be counted towards the timers. When no monotonic clock source is in
		2088	use, then libev will again assume a timejump and adjust accordingly.
		2089
		2090	It might be beneficial for this latter case to call C<ev_suspend>
		2091	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2092	deterministic behaviour in this case (you can do nothing against
		2093	C<SIGSTOP>).
		2094
1683	=head3 Watcher-Specific Functions and Data Members	2095	=head3 Watcher-Specific Functions and Data Members
1684		2096
1685	=over 4	2097	=over 4
1686		2098
1687	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2099	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1700	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
1701	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.
1702		2114
1703	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1704		2116
1705	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
1706	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>.
1707		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
1708	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1709		2127
1710	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).
1711		2130
1712	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
1713	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1714		2135
1715	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
1716	usage example.	2137	usage example.
		2138
		2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2140
		2141	Returns the remaining time until a timer fires. If the timer is active,
		2142	then this time is relative to the current event loop time, otherwise it's
		2143	the timeout value currently configured.
		2144
		2145	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2146	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2147	will return C<4>. When the timer expires and is restarted, it will return
		2148	roughly C<7> (likely slightly less as callback invocation takes some time,
		2149	too), and so on.
1717		2150
1718	=item ev_tstamp repeat [read-write]	2151	=item ev_tstamp repeat [read-write]
1719		2152
1720	The current C<repeat> value. Will be used each time the watcher times out	2153	The current C<repeat> value. Will be used each time the watcher times out
1721	or C<ev_timer_again> is called, and determines the next timeout (if any),	2154	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1747	}	2180	}
1748		2181
1749	ev_timer mytimer;	2182	ev_timer mytimer;
1750	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 */
1751	ev_timer_again (&mytimer); /* start timer */	2184	ev_timer_again (&mytimer); /* start timer */
1752	ev_loop (loop, 0);	2185	ev_run (loop, 0);
1753		2186
1754	// 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":
1755	// reset the timeout to start ticking again at 10 seconds	2188	// reset the timeout to start ticking again at 10 seconds
1756	ev_timer_again (&mytimer);	2189	ev_timer_again (&mytimer);
1757		2190
…		…
1783		2216
1784	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
1785	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
1786	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
1787	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
1788	(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).
1789		2222
1790	=head3 Watcher-Specific Functions and Data Members	2223	=head3 Watcher-Specific Functions and Data Members
1791		2224
1792	=over 4	2225	=over 4
1793		2226
…		…
1828		2261
1829	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
1830	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
1831	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.
1832		2265
1833	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
1834	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
1835	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.
1836		2272
1837	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
1838	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
1839	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
1840	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).
…		…
1921	Example: Call a callback every hour, or, more precisely, whenever the	2357	Example: Call a callback every hour, or, more precisely, whenever the
1922	system time is divisible by 3600. The callback invocation times have	2358	system time is divisible by 3600. The callback invocation times have
1923	potentially a lot of jitter, but good long-term stability.	2359	potentially a lot of jitter, but good long-term stability.
1924		2360
1925	static void	2361	static void
1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2362	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1927	{	2363	{
1928	... 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)
1929	}	2365	}
1930		2366
1931	ev_periodic hourly_tick;	2367	ev_periodic hourly_tick;
…		…
1954		2390
1955	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
1956		2392
1957	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
1958	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
1959	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
1960	normal event processing, like any other event.	2396	normal event processing, like any other event.
1961		2397
1962	If you want signals asynchronously, just use C<sigaction> as you would	2398	If you want signals to be delivered truly asynchronously, just use
1963	do without libev and forget about sharing the signal. You can even use	2399	C<sigaction> as you would do without libev and forget about sharing
1964	C<ev_async> from a signal handler to synchronously wake up an event loop.	2400	the signal. You can even use C<ev_async> from a signal handler to
		2401	synchronously wake up an event loop.
1965		2402
1966	You can configure as many watchers as you like per signal. Only when the	2403	You can configure as many watchers as you like for the same signal, but
		2404	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2405	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2406	C<SIGINT> in both the default loop and another loop at the same time. At
		2407	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2408
1967	first watcher gets started will libev actually register a signal handler	2409	When the first watcher gets started will libev actually register something
1968	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
1969	you don't register any with libev for the same signal). Similarly, when	2411	you don't register any with libev for the same signal).
1970	the last signal watcher for a signal is stopped, libev will reset the
1971	signal handler to SIG_DFL (regardless of what it was set to before).
1972		2412
1973	If possible and supported, libev will install its handlers with	2413	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2414	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2415	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2416	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2417	and unblock them in an C<ev_prepare> watcher.
		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>.
1978		2462
1979	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
1980		2464
1981	=over 4	2465	=over 4
1982		2466
…		…
1998	Example: Try to exit cleanly on SIGINT.	2482	Example: Try to exit cleanly on SIGINT.
1999		2483
2000	static void	2484	static void
2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2485	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2002	{	2486	{
2003	ev_unloop (loop, EVUNLOOP_ALL);	2487	ev_break (loop, EVBREAK_ALL);
2004	}	2488	}
2005		2489
2006	ev_signal signal_watcher;	2490	ev_signal signal_watcher;
2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2491	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2008	ev_signal_start (loop, &signal_watcher);	2492	ev_signal_start (loop, &signal_watcher);
…		…
2020	in the next callback invocation is not.	2504	in the next callback invocation is not.
2021		2505
2022	Only the default event loop is capable of handling signals, and therefore	2506	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2507	you can only register child watchers in the default event loop.
2024		2508
		2509	Due to some design glitches inside libev, child watchers will always be
		2510	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2511	libev)
		2512
2025	=head3 Process Interaction	2513	=head3 Process Interaction
2026		2514
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2515	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2516	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2517	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2518	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2519	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2520	children, even ones not watched.
2033		2521
2034	=head3 Overriding the Built-In Processing	2522	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2532	=head3 Stopping the Child Watcher
2045		2533
2046	Currently, the child watcher never gets stopped, even when the	2534	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2535	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2536	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2537	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2538	problem).
2050		2539
2051	=head3 Watcher-Specific Functions and Data Members	2540	=head3 Watcher-Specific Functions and Data Members
2052		2541
2053	=over 4	2542	=over 4
2054		2543
…		…
2389		2878
2390	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:
2391	prepare watchers get invoked before the process blocks and check watchers	2880	prepare watchers get invoked before the process blocks and check watchers
2392	afterwards.	2881	afterwards.
2393		2882
2394	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
2395	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>
2396	watchers. Other loops than the current one are fine, however. The	2885	watchers. Other loops than the current one are fine, however. The
2397	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
2398	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,
2399	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
…		…
2567		3056
2568	if (timeout >= 0)	3057	if (timeout >= 0)
2569	// create/start timer	3058	// create/start timer
2570		3059
2571	// poll	3060	// poll
2572	ev_loop (EV_A_ 0);	3061	ev_run (EV_A_ 0);
2573		3062
2574	// stop timer again	3063	// stop timer again
2575	if (timeout >= 0)	3064	if (timeout >= 0)
2576	ev_timer_stop (EV_A_ &to);	3065	ev_timer_stop (EV_A_ &to);
2577		3066
…		…
2655	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).
2656		3145
2657	=item ev_embed_sweep (loop, ev_embed *)	3146	=item ev_embed_sweep (loop, ev_embed *)
2658		3147
2659	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
2660	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
2661	appropriate way for embedded loops.	3150	appropriate way for embedded loops.
2662		3151
2663	=item struct ev_loop *other [read-only]	3152	=item struct ev_loop *other [read-only]
2664		3153
2665	The embedded event loop.	3154	The embedded event loop.
…		…
2725	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
2726	handlers will be invoked, too, of course.	3215	handlers will be invoked, too, of course.
2727		3216
2728	=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?
2729		3218
2730	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
2731	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
2732	sequence should be handled by libev without any problems.	3221	sequence should be handled by libev without any problems.
2733		3222
2734	This changes when the application actually wants to do event handling	3223	This changes when the application actually wants to do event handling
2735	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
…		…
2751	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
2752	signal watchers).	3241	signal watchers).
2753		3242
2754	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
2755	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
2756	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3245	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2757	the default loop will "orphan" (not stop) all registered watchers, so you	3246	Destroying the default loop will "orphan" (not stop) all registered
2758	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
2759	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.
2760		3250
2761	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
2762		3252
2763	=over 4	3253	=over 4
2764		3254
2765	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
2766		3256
2767	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
2768	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,
2769	believe me.	3259	really.
2770		3260
2771	=back	3261	=back
2772		3262
2773		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
2774	=head2 C<ev_async> - how to wake up another event loop	3304	=head2 C<ev_async> - how to wake up an event loop
2775		3305
2776	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
2777	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
2778	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
2779		3309
2780	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,
2781	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>
2782	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
2783	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.
2784	safe.
2785		3314
2786	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,
2787	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
2788	(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
2789	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2790		3319	of "global async watchers" by using a watcher on an otherwise unused
2791	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,
2792	just the default loop.	3321	even without knowing which loop owns the signal.
2793		3322
2794	=head3 Queueing	3323	=head3 Queueing
2795		3324
2796	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
2797	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
2798	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
2799	need elaborate support such as pthreads.	3328	need elaborate support such as pthreads or unportable memory access
		3329	semantics.
2800		3330
2801	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
2802	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
2803	queue:	3333	queue:
2804		3334
…		…
2888	trust me.	3418	trust me.
2889		3419
2890	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
2891		3421
2892	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
2893	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
2894	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,
2895	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
2896	section below on what exactly this means).	3428	embedding section below on what exactly this means).
2897		3429
2898	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
2899	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
2900	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
2901	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
2902		3434
2903	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
2904	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
2905	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.
2906		3441
2907	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
2908		3443
2909	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
2910	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
…		…
2943		3478
2944	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
2945	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
2946	repeat = 0) will be started. C<0> is a valid timeout.	3481	repeat = 0) will be started. C<0> is a valid timeout.
2947		3482
2948	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
2949	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
2950	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>
2951	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>
2952	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
2953	events precedence.	3488	events precedence.
2954		3489
2955	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.
2956		3491
2957	static void stdin_ready (int revents, void *arg)	3492	static void stdin_ready (int revents, void *arg)
2958	{	3493	{
2959	if (revents & EV_READ)	3494	if (revents & EV_READ)
2960	/* stdin might have data for us, joy! */;	3495	/* stdin might have data for us, joy! */;
2961	else if (revents & EV_TIMEOUT)	3496	else if (revents & EV_TIMER)
2962	/* doh, nothing entered */;	3497	/* doh, nothing entered */;
2963	}	3498	}
2964		3499
2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2966		3501
2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2968
2969	Feeds the given event set into the event loop, as if the specified event
2970	had happened for the specified watcher (which must be a pointer to an
2971	initialised but not necessarily started event watcher).
2972
2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
2974		3503
2975	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
2976	the given events it.	3505	the given events.
2977		3506
2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
2979		3508
2980	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>,
2981	loop!).	3510	which is async-safe.
2982		3511
2983	=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.
2984		3863
2985		3864
2986	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
2987		3866
2988	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
2989	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
2990		3869
2991	=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.
2992		3876
2993	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
2994		3878
2995	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
2996	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3002	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3003	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
3004	is an ev_pri field.	3888	is an ev_pri field.
3005		3889
3006	=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
3007	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3008		3892
3009	=item * Other members are not supported.	3893	=item * Other members are not supported.
3010		3894
3011	=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
3012	to use the libev header file and library.	3896	to use the libev header file and library.
3013		3897
3014	=back	3898	=back
3015		3899
3016	=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_inoke> and C<ev_invoke_pending>.
		3927
		3928	Throwing exceptions in watcher callbacks is only supported if libev itself
		3929	is compiled with a C++ compiler or your C and C++ environments allow
		3930	throwing exceptions through C libraries (most do).
		3931
		3932	=head2 C++ API
3017		3933
3018	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3934	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3019	you to use some convenience methods to start/stop watchers and also change	3935	you to use some convenience methods to start/stop watchers and also change
3020	the callback model to a model using method callbacks on objects.	3936	the callback model to a model using method callbacks on objects.
3021		3937
…		…
3031	Care has been taken to keep the overhead low. The only data member the C++	3947	Care has been taken to keep the overhead low. The only data member the C++
3032	classes add (compared to plain C-style watchers) is the event loop pointer	3948	classes add (compared to plain C-style watchers) is the event loop pointer
3033	that the watcher is associated with (or no additional members at all if	3949	that the watcher is associated with (or no additional members at all if
3034	you disable C<EV_MULTIPLICITY> when embedding libev).	3950	you disable C<EV_MULTIPLICITY> when embedding libev).
3035		3951
3036	Currently, functions, and static and non-static member functions can be	3952	Currently, functions, static and non-static member functions and classes
3037	used as callbacks. Other types should be easy to add as long as they only	3953	with C<operator ()> can be used as callbacks. Other types should be easy
3038	need one additional pointer for context. If you need support for other	3954	to add as long as they only need one additional pointer for context. If
3039	types of functors please contact the author (preferably after implementing	3955	you need support for other types of functors please contact the author
3040	it).	3956	(preferably after implementing it).
		3957
		3958	For all this to work, your C++ compiler either has to use the same calling
		3959	conventions as your C compiler (for static member functions), or you have
		3960	to embed libev and compile libev itself as C++.
3041		3961
3042	Here is a list of things available in the C<ev> namespace:	3962	Here is a list of things available in the C<ev> namespace:
3043		3963
3044	=over 4	3964	=over 4
3045		3965
…		…
3055	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3975	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3056		3976
3057	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3977	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3058	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3978	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3059	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3979	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3060	defines by many implementations.	3980	defined by many implementations.
3061		3981
3062	All of those classes have these methods:	3982	All of those classes have these methods:
3063		3983
3064	=over 4	3984	=over 4
3065		3985
3066	=item ev::TYPE::TYPE ()	3986	=item ev::TYPE::TYPE ()
3067		3987
3068	=item ev::TYPE::TYPE (struct ev_loop *)	3988	=item ev::TYPE::TYPE (loop)
3069		3989
3070	=item ev::TYPE::~TYPE	3990	=item ev::TYPE::~TYPE
3071		3991
3072	The constructor (optionally) takes an event loop to associate the watcher	3992	The constructor (optionally) takes an event loop to associate the watcher
3073	with. If it is omitted, it will use C<EV_DEFAULT>.	3993	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3106	myclass obj;	4026	myclass obj;
3107	ev::io iow;	4027	ev::io iow;
3108	iow.set <myclass, &myclass::io_cb> (&obj);	4028	iow.set <myclass, &myclass::io_cb> (&obj);
3109		4029
3110	=item w->set (object *)	4030	=item w->set (object *)
3111
3112	This is an B<experimental> feature that might go away in a future version.
3113		4031
3114	This is a variation of a method callback - leaving out the method to call	4032	This is a variation of a method callback - leaving out the method to call
3115	will default the method to C<operator ()>, which makes it possible to use	4033	will default the method to C<operator ()>, which makes it possible to use
3116	functor objects without having to manually specify the C<operator ()> all	4034	functor objects without having to manually specify the C<operator ()> all
3117	the time. Incidentally, you can then also leave out the template argument	4035	the time. Incidentally, you can then also leave out the template argument
…		…
3150	Example: Use a plain function as callback.	4068	Example: Use a plain function as callback.
3151		4069
3152	static void io_cb (ev::io &w, int revents) { }	4070	static void io_cb (ev::io &w, int revents) { }
3153	iow.set <io_cb> ();	4071	iow.set <io_cb> ();
3154		4072
3155	=item w->set (struct ev_loop *)	4073	=item w->set (loop)
3156		4074
3157	Associates a different C<struct ev_loop> with this watcher. You can only	4075	Associates a different C<struct ev_loop> with this watcher. You can only
3158	do this when the watcher is inactive (and not pending either).	4076	do this when the watcher is inactive (and not pending either).
3159		4077
3160	=item w->set ([arguments])	4078	=item w->set ([arguments])
3161		4079
3162	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4080	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3163	called at least once. Unlike the C counterpart, an active watcher gets	4081	method or a suitable start method must be called at least once. Unlike the
3164	automatically stopped and restarted when reconfiguring it with this	4082	C counterpart, an active watcher gets automatically stopped and restarted
3165	method.	4083	when reconfiguring it with this method.
3166		4084
3167	=item w->start ()	4085	=item w->start ()
3168		4086
3169	Starts the watcher. Note that there is no C<loop> argument, as the	4087	Starts the watcher. Note that there is no C<loop> argument, as the
3170	constructor already stores the event loop.	4088	constructor already stores the event loop.
3171		4089
		4090	=item w->start ([arguments])
		4091
		4092	Instead of calling C<set> and C<start> methods separately, it is often
		4093	convenient to wrap them in one call. Uses the same type of arguments as
		4094	the configure C<set> method of the watcher.
		4095
3172	=item w->stop ()	4096	=item w->stop ()
3173		4097
3174	Stops the watcher if it is active. Again, no C<loop> argument.	4098	Stops the watcher if it is active. Again, no C<loop> argument.
3175		4099
3176	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4100	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3188		4112
3189	=back	4113	=back
3190		4114
3191	=back	4115	=back
3192		4116
3193	Example: Define a class with an IO and idle watcher, start one of them in	4117	Example: Define a class with two I/O and idle watchers, start the I/O
3194	the constructor.	4118	watchers in the constructor.
3195		4119
3196	class myclass	4120	class myclass
3197	{	4121	{
3198	ev::io io ; void io_cb (ev::io &w, int revents);	4122	ev::io io ; void io_cb (ev::io &w, int revents);
		4123	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4124	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3200		4125
3201	myclass (int fd)	4126	myclass (int fd)
3202	{	4127	{
3203	io .set <myclass, &myclass::io_cb > (this);	4128	io .set <myclass, &myclass::io_cb > (this);
		4129	io2 .set <myclass, &myclass::io2_cb > (this);
3204	idle.set <myclass, &myclass::idle_cb> (this);	4130	idle.set <myclass, &myclass::idle_cb> (this);
3205		4131
3206	io.start (fd, ev::READ);	4132	io.set (fd, ev::WRITE); // configure the watcher
		4133	io.start (); // start it whenever convenient
		4134
		4135	io2.start (fd, ev::READ); // set + start in one call
3207	}	4136	}
3208	};	4137	};
3209		4138
3210		4139
3211	=head1 OTHER LANGUAGE BINDINGS	4140	=head1 OTHER LANGUAGE BINDINGS
…		…
3250	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4179	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3251		4180
3252	=item D	4181	=item D
3253		4182
3254	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4183	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3255	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4184	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3256		4185
3257	=item Ocaml	4186	=item Ocaml
3258		4187
3259	Erkki Seppala has written Ocaml bindings for libev, to be found at	4188	Erkki Seppala has written Ocaml bindings for libev, to be found at
3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4189	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4190
		4191	=item Lua
		4192
		4193	Brian Maher has written a partial interface to libev for lua (at the
		4194	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4195	L<http://github.com/brimworks/lua-ev>.
3261		4196
3262	=back	4197	=back
3263		4198
3264		4199
3265	=head1 MACRO MAGIC	4200	=head1 MACRO MAGIC
…		…
3279	loop argument"). The C<EV_A> form is used when this is the sole argument,	4214	loop argument"). The C<EV_A> form is used when this is the sole argument,
3280	C<EV_A_> is used when other arguments are following. Example:	4215	C<EV_A_> is used when other arguments are following. Example:
3281		4216
3282	ev_unref (EV_A);	4217	ev_unref (EV_A);
3283	ev_timer_add (EV_A_ watcher);	4218	ev_timer_add (EV_A_ watcher);
3284	ev_loop (EV_A_ 0);	4219	ev_run (EV_A_ 0);
3285		4220
3286	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4221	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3287	which is often provided by the following macro.	4222	which is often provided by the following macro.
3288		4223
3289	=item C<EV_P>, C<EV_P_>	4224	=item C<EV_P>, C<EV_P_>
…		…
3302	suitable for use with C<EV_A>.	4237	suitable for use with C<EV_A>.
3303		4238
3304	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4239	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3305		4240
3306	Similar to the other two macros, this gives you the value of the default	4241	Similar to the other two macros, this gives you the value of the default
3307	loop, if multiple loops are supported ("ev loop default").	4242	loop, if multiple loops are supported ("ev loop default"). The default loop
		4243	will be initialised if it isn't already initialised.
		4244
		4245	For non-multiplicity builds, these macros do nothing, so you always have
		4246	to initialise the loop somewhere.
3308		4247
3309	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4248	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3310		4249
3311	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4250	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3312	default loop has been initialised (C<UC> == unchecked). Their behaviour	4251	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3329	}	4268	}
3330		4269
3331	ev_check check;	4270	ev_check check;
3332	ev_check_init (&check, check_cb);	4271	ev_check_init (&check, check_cb);
3333	ev_check_start (EV_DEFAULT_ &check);	4272	ev_check_start (EV_DEFAULT_ &check);
3334	ev_loop (EV_DEFAULT_ 0);	4273	ev_run (EV_DEFAULT_ 0);
3335		4274
3336	=head1 EMBEDDING	4275	=head1 EMBEDDING
3337		4276
3338	Libev can (and often is) directly embedded into host	4277	Libev can (and often is) directly embedded into host
3339	applications. Examples of applications that embed it include the Deliantra	4278	applications. Examples of applications that embed it include the Deliantra
…		…
3419	libev.m4	4358	libev.m4
3420		4359
3421	=head2 PREPROCESSOR SYMBOLS/MACROS	4360	=head2 PREPROCESSOR SYMBOLS/MACROS
3422		4361
3423	Libev can be configured via a variety of preprocessor symbols you have to	4362	Libev can be configured via a variety of preprocessor symbols you have to
3424	define before including any of its files. The default in the absence of	4363	define before including (or compiling) any of its files. The default in
3425	autoconf is documented for every option.	4364	the absence of autoconf is documented for every option.
		4365
		4366	Symbols marked with "(h)" do not change the ABI, and can have different
		4367	values when compiling libev vs. including F<ev.h>, so it is permissible
		4368	to redefine them before including F<ev.h> without breaking compatibility
		4369	to a compiled library. All other symbols change the ABI, which means all
		4370	users of libev and the libev code itself must be compiled with compatible
		4371	settings.
3426		4372
3427	=over 4	4373	=over 4
3428		4374
		4375	=item EV_COMPAT3 (h)
		4376
		4377	Backwards compatibility is a major concern for libev. This is why this
		4378	release of libev comes with wrappers for the functions and symbols that
		4379	have been renamed between libev version 3 and 4.
		4380
		4381	You can disable these wrappers (to test compatibility with future
		4382	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4383	sources. This has the additional advantage that you can drop the C<struct>
		4384	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4385	typedef in that case.
		4386
		4387	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4388	and in some even more future version the compatibility code will be
		4389	removed completely.
		4390
3429	=item EV_STANDALONE	4391	=item EV_STANDALONE (h)
3430		4392
3431	Must always be C<1> if you do not use autoconf configuration, which	4393	Must always be C<1> if you do not use autoconf configuration, which
3432	keeps libev from including F<config.h>, and it also defines dummy	4394	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	4395	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	4396	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	4397	F<event.h> that are not directly supported by the libev core alone.
3436		4398
3437	In stanbdalone mode, libev will still try to automatically deduce the	4399	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	4400	configuration, but has to be more conservative.
		4401
		4402	=item EV_USE_FLOOR
		4403
		4404	If defined to be C<1>, libev will use the C<floor ()> function for its
		4405	periodic reschedule calculations, otherwise libev will fall back on a
		4406	portable (slower) implementation. If you enable this, you usually have to
		4407	link against libm or something equivalent. Enabling this when the C<floor>
		4408	function is not available will fail, so the safe default is to not enable
		4409	this.
3439		4410
3440	=item EV_USE_MONOTONIC	4411	=item EV_USE_MONOTONIC
3441		4412
3442	If defined to be C<1>, libev will try to detect the availability of the	4413	If defined to be C<1>, libev will try to detect the availability of the
3443	monotonic clock option at both compile time and runtime. Otherwise no	4414	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3507	be used is the winsock select). This means that it will call	4478	be used is the winsock select). This means that it will call
3508	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4479	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3509	it is assumed that all these functions actually work on fds, even	4480	it is assumed that all these functions actually work on fds, even
3510	on win32. Should not be defined on non-win32 platforms.	4481	on win32. Should not be defined on non-win32 platforms.
3511		4482
3512	=item EV_FD_TO_WIN32_HANDLE	4483	=item EV_FD_TO_WIN32_HANDLE(fd)
3513		4484
3514	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4485	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3515	file descriptors to socket handles. When not defining this symbol (the	4486	file descriptors to socket handles. When not defining this symbol (the
3516	default), then libev will call C<_get_osfhandle>, which is usually	4487	default), then libev will call C<_get_osfhandle>, which is usually
3517	correct. In some cases, programs use their own file descriptor management,	4488	correct. In some cases, programs use their own file descriptor management,
3518	in which case they can provide this function to map fds to socket handles.	4489	in which case they can provide this function to map fds to socket handles.
		4490
		4491	=item EV_WIN32_HANDLE_TO_FD(handle)
		4492
		4493	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4494	using the standard C<_open_osfhandle> function. For programs implementing
		4495	their own fd to handle mapping, overwriting this function makes it easier
		4496	to do so. This can be done by defining this macro to an appropriate value.
		4497
		4498	=item EV_WIN32_CLOSE_FD(fd)
		4499
		4500	If programs implement their own fd to handle mapping on win32, then this
		4501	macro can be used to override the C<close> function, useful to unregister
		4502	file descriptors again. Note that the replacement function has to close
		4503	the underlying OS handle.
3519		4504
3520	=item EV_USE_POLL	4505	=item EV_USE_POLL
3521		4506
3522	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4507	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3523	backend. Otherwise it will be enabled on non-win32 platforms. It	4508	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3559	If defined to be C<1>, libev will compile in support for the Linux inotify	4544	If defined to be C<1>, libev will compile in support for the Linux inotify
3560	interface to speed up C<ev_stat> watchers. Its actual availability will	4545	interface to speed up C<ev_stat> watchers. Its actual availability will
3561	be detected at runtime. If undefined, it will be enabled if the headers	4546	be detected at runtime. If undefined, it will be enabled if the headers
3562	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4547	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3563		4548
		4549	=item EV_NO_SMP
		4550
		4551	If defined to be C<1>, libev will assume that memory is always coherent
		4552	between threads, that is, threads can be used, but threads never run on
		4553	different cpus (or different cpu cores). This reduces dependencies
		4554	and makes libev faster.
		4555
		4556	=item EV_NO_THREADS
		4557
		4558	If defined to be C<1>, libev will assume that it will never be called
		4559	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4560	above. This reduces dependencies and makes libev faster.
		4561
3564	=item EV_ATOMIC_T	4562	=item EV_ATOMIC_T
3565		4563
3566	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4564	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3567	access is atomic with respect to other threads or signal contexts. No such	4565	access is atomic and serialised with respect to other threads or signal
3568	type is easily found in the C language, so you can provide your own type	4566	contexts. No such type is easily found in the C language, so you can
3569	that you know is safe for your purposes. It is used both for signal handler "locking"	4567	provide your own type that you know is safe for your purposes. It is used
3570	as well as for signal and thread safety in C<ev_async> watchers.	4568	both for signal handler "locking" as well as for signal and thread safety
		4569	in C<ev_async> watchers.
3571		4570
3572	In the absence of this define, libev will use C<sig_atomic_t volatile>	4571	In the absence of this define, libev will use C<sig_atomic_t volatile>
3573	(from F<signal.h>), which is usually good enough on most platforms.	4572	(from F<signal.h>), which is usually good enough on most platforms,
		4573	although strictly speaking using a type that also implies a memory fence
		4574	is required.
3574		4575
3575	=item EV_H	4576	=item EV_H (h)
3576		4577
3577	The name of the F<ev.h> header file used to include it. The default if	4578	The name of the F<ev.h> header file used to include it. The default if
3578	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4579	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3579	used to virtually rename the F<ev.h> header file in case of conflicts.	4580	used to virtually rename the F<ev.h> header file in case of conflicts.
3580		4581
3581	=item EV_CONFIG_H	4582	=item EV_CONFIG_H (h)
3582		4583
3583	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4584	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3584	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4585	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3585	C<EV_H>, above.	4586	C<EV_H>, above.
3586		4587
3587	=item EV_EVENT_H	4588	=item EV_EVENT_H (h)
3588		4589
3589	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4590	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3590	of how the F<event.h> header can be found, the default is C<"event.h">.	4591	of how the F<event.h> header can be found, the default is C<"event.h">.
3591		4592
3592	=item EV_PROTOTYPES	4593	=item EV_PROTOTYPES (h)
3593		4594
3594	If defined to be C<0>, then F<ev.h> will not define any function	4595	If defined to be C<0>, then F<ev.h> will not define any function
3595	prototypes, but still define all the structs and other symbols. This is	4596	prototypes, but still define all the structs and other symbols. This is
3596	occasionally useful if you want to provide your own wrapper functions	4597	occasionally useful if you want to provide your own wrapper functions
3597	around libev functions.	4598	around libev functions.
…		…
3602	will have the C<struct ev_loop *> as first argument, and you can create	4603	will have the C<struct ev_loop *> as first argument, and you can create
3603	additional independent event loops. Otherwise there will be no support	4604	additional independent event loops. Otherwise there will be no support
3604	for multiple event loops and there is no first event loop pointer	4605	for multiple event loops and there is no first event loop pointer
3605	argument. Instead, all functions act on the single default loop.	4606	argument. Instead, all functions act on the single default loop.
3606		4607
		4608	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4609	default loop when multiplicity is switched off - you always have to
		4610	initialise the loop manually in this case.
		4611
3607	=item EV_MINPRI	4612	=item EV_MINPRI
3608		4613
3609	=item EV_MAXPRI	4614	=item EV_MAXPRI
3610		4615
3611	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4616	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3619	fine.	4624	fine.
3620		4625
3621	If your embedding application does not need any priorities, defining these	4626	If your embedding application does not need any priorities, defining these
3622	both to C<0> will save some memory and CPU.	4627	both to C<0> will save some memory and CPU.
3623		4628
3624	=item EV_PERIODIC_ENABLE	4629	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4630	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4631	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3625		4632
3626	If undefined or defined to be C<1>, then periodic timers are supported. If	4633	If undefined or defined to be C<1> (and the platform supports it), then
3627	defined to be C<0>, then they are not. Disabling them saves a few kB of	4634	the respective watcher type is supported. If defined to be C<0>, then it
3628	code.	4635	is not. Disabling watcher types mainly saves code size.
3629		4636
3630	=item EV_IDLE_ENABLE	4637	=item EV_FEATURES
3631
3632	If undefined or defined to be C<1>, then idle watchers are supported. If
3633	defined to be C<0>, then they are not. Disabling them saves a few kB of
3634	code.
3635
3636	=item EV_EMBED_ENABLE
3637
3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3639	defined to be C<0>, then they are not. Embed watchers rely on most other
3640	watcher types, which therefore must not be disabled.
3641
3642	=item EV_STAT_ENABLE
3643
3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3645	defined to be C<0>, then they are not.
3646
3647	=item EV_FORK_ENABLE
3648
3649	If undefined or defined to be C<1>, then fork watchers are supported. If
3650	defined to be C<0>, then they are not.
3651
3652	=item EV_ASYNC_ENABLE
3653
3654	If undefined or defined to be C<1>, then async watchers are supported. If
3655	defined to be C<0>, then they are not.
3656
3657	=item EV_MINIMAL
3658		4638
3659	If you need to shave off some kilobytes of code at the expense of some	4639	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	4640	speed (but with the full API), you can define this symbol to request
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4641	certain subsets of functionality. The default is to enable all features
3662	much smaller 2-heap for timer management over the default 4-heap.	4642	that can be enabled on the platform.
		4643
		4644	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4645	with some broad features you want) and then selectively re-enable
		4646	additional parts you want, for example if you want everything minimal,
		4647	but multiple event loop support, async and child watchers and the poll
		4648	backend, use this:
		4649
		4650	#define EV_FEATURES 0
		4651	#define EV_MULTIPLICITY 1
		4652	#define EV_USE_POLL 1
		4653	#define EV_CHILD_ENABLE 1
		4654	#define EV_ASYNC_ENABLE 1
		4655
		4656	The actual value is a bitset, it can be a combination of the following
		4657	values (by default, all of these are enabled):
		4658
		4659	=over 4
		4660
		4661	=item C<1> - faster/larger code
		4662
		4663	Use larger code to speed up some operations.
		4664
		4665	Currently this is used to override some inlining decisions (enlarging the
		4666	code size by roughly 30% on amd64).
		4667
		4668	When optimising for size, use of compiler flags such as C<-Os> with
		4669	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4670	assertions.
		4671
		4672	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4673	(e.g. gcc with C<-Os>).
		4674
		4675	=item C<2> - faster/larger data structures
		4676
		4677	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4678	hash table sizes and so on. This will usually further increase code size
		4679	and can additionally have an effect on the size of data structures at
		4680	runtime.
		4681
		4682	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4683	(e.g. gcc with C<-Os>).
		4684
		4685	=item C<4> - full API configuration
		4686
		4687	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4688	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4689
		4690	=item C<8> - full API
		4691
		4692	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4693	details on which parts of the API are still available without this
		4694	feature, and do not complain if this subset changes over time.
		4695
		4696	=item C<16> - enable all optional watcher types
		4697
		4698	Enables all optional watcher types. If you want to selectively enable
		4699	only some watcher types other than I/O and timers (e.g. prepare,
		4700	embed, async, child...) you can enable them manually by defining
		4701	C<EV_watchertype_ENABLE> to C<1> instead.
		4702
		4703	=item C<32> - enable all backends
		4704
		4705	This enables all backends - without this feature, you need to enable at
		4706	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4707
		4708	=item C<64> - enable OS-specific "helper" APIs
		4709
		4710	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4711	default.
		4712
		4713	=back
		4714
		4715	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4716	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4717	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4718	watchers, timers and monotonic clock support.
		4719
		4720	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4721	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4722	your program might be left out as well - a binary starting a timer and an
		4723	I/O watcher then might come out at only 5Kb.
		4724
		4725	=item EV_API_STATIC
		4726
		4727	If this symbol is defined (by default it is not), then all identifiers
		4728	will have static linkage. This means that libev will not export any
		4729	identifiers, and you cannot link against libev anymore. This can be useful
		4730	when you embed libev, only want to use libev functions in a single file,
		4731	and do not want its identifiers to be visible.
		4732
		4733	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4734	wants to use libev.
		4735
		4736	This option only works when libev is compiled with a C compiler, as C++
		4737	doesn't support the required declaration syntax.
		4738
		4739	=item EV_AVOID_STDIO
		4740
		4741	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4742	functions (printf, scanf, perror etc.). This will increase the code size
		4743	somewhat, but if your program doesn't otherwise depend on stdio and your
		4744	libc allows it, this avoids linking in the stdio library which is quite
		4745	big.
		4746
		4747	Note that error messages might become less precise when this option is
		4748	enabled.
		4749
		4750	=item EV_NSIG
		4751
		4752	The highest supported signal number, +1 (or, the number of
		4753	signals): Normally, libev tries to deduce the maximum number of signals
		4754	automatically, but sometimes this fails, in which case it can be
		4755	specified. Also, using a lower number than detected (C<32> should be
		4756	good for about any system in existence) can save some memory, as libev
		4757	statically allocates some 12-24 bytes per signal number.
3663		4758
3664	=item EV_PID_HASHSIZE	4759	=item EV_PID_HASHSIZE
3665		4760
3666	C<ev_child> watchers use a small hash table to distribute workload by	4761	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4762	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3668	than enough. If you need to manage thousands of children you might want to	4763	usually more than enough. If you need to manage thousands of children you
3669	increase this value (I<must> be a power of two).	4764	might want to increase this value (I<must> be a power of two).
3670		4765
3671	=item EV_INOTIFY_HASHSIZE	4766	=item EV_INOTIFY_HASHSIZE
3672		4767
3673	C<ev_stat> watchers use a small hash table to distribute workload by	4768	C<ev_stat> watchers use a small hash table to distribute workload by
3674	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4769	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3675	usually more than enough. If you need to manage thousands of C<ev_stat>	4770	disabled), usually more than enough. If you need to manage thousands of
3676	watchers you might want to increase this value (I<must> be a power of	4771	C<ev_stat> watchers you might want to increase this value (I<must> be a
3677	two).	4772	power of two).
3678		4773
3679	=item EV_USE_4HEAP	4774	=item EV_USE_4HEAP
3680		4775
3681	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4776	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3682	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4777	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3683	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4778	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3684	faster performance with many (thousands) of watchers.	4779	faster performance with many (thousands) of watchers.
3685		4780
3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4781	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3687	(disabled).	4782	will be C<0>.
3688		4783
3689	=item EV_HEAP_CACHE_AT	4784	=item EV_HEAP_CACHE_AT
3690		4785
3691	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4786	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3692	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4787	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3693	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4788	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3694	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4789	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3695	but avoids random read accesses on heap changes. This improves performance	4790	but avoids random read accesses on heap changes. This improves performance
3696	noticeably with many (hundreds) of watchers.	4791	noticeably with many (hundreds) of watchers.
3697		4792
3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4793	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3699	(disabled).	4794	will be C<0>.
3700		4795
3701	=item EV_VERIFY	4796	=item EV_VERIFY
3702		4797
3703	Controls how much internal verification (see C<ev_loop_verify ()>) will	4798	Controls how much internal verification (see C<ev_verify ()>) will
3704	be done: If set to C<0>, no internal verification code will be compiled	4799	be done: If set to C<0>, no internal verification code will be compiled
3705	in. If set to C<1>, then verification code will be compiled in, but not	4800	in. If set to C<1>, then verification code will be compiled in, but not
3706	called. If set to C<2>, then the internal verification code will be	4801	called. If set to C<2>, then the internal verification code will be
3707	called once per loop, which can slow down libev. If set to C<3>, then the	4802	called once per loop, which can slow down libev. If set to C<3>, then the
3708	verification code will be called very frequently, which will slow down	4803	verification code will be called very frequently, which will slow down
3709	libev considerably.	4804	libev considerably.
3710		4805
3711	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4806	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3712	C<0>.	4807	will be C<0>.
3713		4808
3714	=item EV_COMMON	4809	=item EV_COMMON
3715		4810
3716	By default, all watchers have a C<void *data> member. By redefining	4811	By default, all watchers have a C<void *data> member. By redefining
3717	this macro to a something else you can include more and other types of	4812	this macro to something else you can include more and other types of
3718	members. You have to define it each time you include one of the files,	4813	members. You have to define it each time you include one of the files,
3719	though, and it must be identical each time.	4814	though, and it must be identical each time.
3720		4815
3721	For example, the perl EV module uses something like this:	4816	For example, the perl EV module uses something like this:
3722		4817
…		…
3775	file.	4870	file.
3776		4871
3777	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4872	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3778	that everybody includes and which overrides some configure choices:	4873	that everybody includes and which overrides some configure choices:
3779		4874
3780	#define EV_MINIMAL 1	4875	#define EV_FEATURES 8
3781	#define EV_USE_POLL 0	4876	#define EV_USE_SELECT 1
3782	#define EV_MULTIPLICITY 0
3783	#define EV_PERIODIC_ENABLE 0	4877	#define EV_PREPARE_ENABLE 1
		4878	#define EV_IDLE_ENABLE 1
3784	#define EV_STAT_ENABLE 0	4879	#define EV_SIGNAL_ENABLE 1
3785	#define EV_FORK_ENABLE 0	4880	#define EV_CHILD_ENABLE 1
		4881	#define EV_USE_STDEXCEPT 0
3786	#define EV_CONFIG_H <config.h>	4882	#define EV_CONFIG_H <config.h>
3787	#define EV_MINPRI 0
3788	#define EV_MAXPRI 0
3789		4883
3790	#include "ev++.h"	4884	#include "ev++.h"
3791		4885
3792	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4886	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3793		4887
3794	#include "ev_cpp.h"	4888	#include "ev_cpp.h"
3795	#include "ev.c"	4889	#include "ev.c"
3796		4890
3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4891	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3798		4892
3799	=head2 THREADS AND COROUTINES	4893	=head2 THREADS AND COROUTINES
3800		4894
3801	=head3 THREADS	4895	=head3 THREADS
3802		4896
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4947	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4948	watcher callback into the event loop interested in the signal.
3855		4949
3856	=back	4950	=back
3857		4951
		4952	See also L<THREAD LOCKING EXAMPLE>.
		4953
3858	=head3 COROUTINES	4954	=head3 COROUTINES
3859		4955
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4956	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4957	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4958	coroutines (e.g. you can call C<ev_run> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4959	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4960	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4961	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4962
3867	Care has been taken to ensure that libev does not keep local state inside	4963	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4964	C<ev_run>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4965	they do not call any callbacks.
3870		4966
3871	=head2 COMPILER WARNINGS	4967	=head2 COMPILER WARNINGS
3872		4968
3873	Depending on your compiler and compiler settings, you might get no or a	4969	Depending on your compiler and compiler settings, you might get no or a
…		…
3884	maintainable.	4980	maintainable.
3885		4981
3886	And of course, some compiler warnings are just plain stupid, or simply	4982	And of course, some compiler warnings are just plain stupid, or simply
3887	wrong (because they don't actually warn about the condition their message	4983	wrong (because they don't actually warn about the condition their message
3888	seems to warn about). For example, certain older gcc versions had some	4984	seems to warn about). For example, certain older gcc versions had some
3889	warnings that resulted an extreme number of false positives. These have	4985	warnings that resulted in an extreme number of false positives. These have
3890	been fixed, but some people still insist on making code warn-free with	4986	been fixed, but some people still insist on making code warn-free with
3891	such buggy versions.	4987	such buggy versions.
3892		4988
3893	While libev is written to generate as few warnings as possible,	4989	While libev is written to generate as few warnings as possible,
3894	"warn-free" code is not a goal, and it is recommended not to build libev	4990	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3930	I suggest using suppression lists.	5026	I suggest using suppression lists.
3931		5027
3932		5028
3933	=head1 PORTABILITY NOTES	5029	=head1 PORTABILITY NOTES
3934		5030
		5031	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5032
		5033	GNU/Linux is the only common platform that supports 64 bit file/large file
		5034	interfaces but I<disables> them by default.
		5035
		5036	That means that libev compiled in the default environment doesn't support
		5037	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5038
		5039	Unfortunately, many programs try to work around this GNU/Linux issue
		5040	by enabling the large file API, which makes them incompatible with the
		5041	standard libev compiled for their system.
		5042
		5043	Likewise, libev cannot enable the large file API itself as this would
		5044	suddenly make it incompatible to the default compile time environment,
		5045	i.e. all programs not using special compile switches.
		5046
		5047	=head2 OS/X AND DARWIN BUGS
		5048
		5049	The whole thing is a bug if you ask me - basically any system interface
		5050	you touch is broken, whether it is locales, poll, kqueue or even the
		5051	OpenGL drivers.
		5052
		5053	=head3 C<kqueue> is buggy
		5054
		5055	The kqueue syscall is broken in all known versions - most versions support
		5056	only sockets, many support pipes.
		5057
		5058	Libev tries to work around this by not using C<kqueue> by default on this
		5059	rotten platform, but of course you can still ask for it when creating a
		5060	loop - embedding a socket-only kqueue loop into a select-based one is
		5061	probably going to work well.
		5062
		5063	=head3 C<poll> is buggy
		5064
		5065	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5066	implementation by something calling C<kqueue> internally around the 10.5.6
		5067	release, so now C<kqueue> I<and> C<poll> are broken.
		5068
		5069	Libev tries to work around this by not using C<poll> by default on
		5070	this rotten platform, but of course you can still ask for it when creating
		5071	a loop.
		5072
		5073	=head3 C<select> is buggy
		5074
		5075	All that's left is C<select>, and of course Apple found a way to fuck this
		5076	one up as well: On OS/X, C<select> actively limits the number of file
		5077	descriptors you can pass in to 1024 - your program suddenly crashes when
		5078	you use more.
		5079
		5080	There is an undocumented "workaround" for this - defining
		5081	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5082	work on OS/X.
		5083
		5084	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5085
		5086	=head3 C<errno> reentrancy
		5087
		5088	The default compile environment on Solaris is unfortunately so
		5089	thread-unsafe that you can't even use components/libraries compiled
		5090	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5091	defined by default. A valid, if stupid, implementation choice.
		5092
		5093	If you want to use libev in threaded environments you have to make sure
		5094	it's compiled with C<_REENTRANT> defined.
		5095
		5096	=head3 Event port backend
		5097
		5098	The scalable event interface for Solaris is called "event
		5099	ports". Unfortunately, this mechanism is very buggy in all major
		5100	releases. If you run into high CPU usage, your program freezes or you get
		5101	a large number of spurious wakeups, make sure you have all the relevant
		5102	and latest kernel patches applied. No, I don't know which ones, but there
		5103	are multiple ones to apply, and afterwards, event ports actually work
		5104	great.
		5105
		5106	If you can't get it to work, you can try running the program by setting
		5107	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5108	C<select> backends.
		5109
		5110	=head2 AIX POLL BUG
		5111
		5112	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5113	this by trying to avoid the poll backend altogether (i.e. it's not even
		5114	compiled in), which normally isn't a big problem as C<select> works fine
		5115	with large bitsets on AIX, and AIX is dead anyway.
		5116
3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5117	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5118
		5119	=head3 General issues
3936		5120
3937	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5121	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3938	requires, and its I/O model is fundamentally incompatible with the POSIX	5122	requires, and its I/O model is fundamentally incompatible with the POSIX
3939	model. Libev still offers limited functionality on this platform in	5123	model. Libev still offers limited functionality on this platform in
3940	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5124	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3941	descriptors. This only applies when using Win32 natively, not when using	5125	descriptors. This only applies when using Win32 natively, not when using
3942	e.g. cygwin.	5126	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5127	as every compiler comes with a slightly differently broken/incompatible
		5128	environment.
3943		5129
3944	Lifting these limitations would basically require the full	5130	Lifting these limitations would basically require the full
3945	re-implementation of the I/O system. If you are into these kinds of	5131	re-implementation of the I/O system. If you are into this kind of thing,
3946	things, then note that glib does exactly that for you in a very portable	5132	then note that glib does exactly that for you in a very portable way (note
3947	way (note also that glib is the slowest event library known to man).	5133	also that glib is the slowest event library known to man).
3948		5134
3949	There is no supported compilation method available on windows except	5135	There is no supported compilation method available on windows except
3950	embedding it into other applications.	5136	embedding it into other applications.
3951		5137
3952	Sensible signal handling is officially unsupported by Microsoft - libev	5138	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3980	you do I<not> compile the F<ev.c> or any other embedded source files!):	5166	you do I<not> compile the F<ev.c> or any other embedded source files!):
3981		5167
3982	#include "evwrap.h"	5168	#include "evwrap.h"
3983	#include "ev.c"	5169	#include "ev.c"
3984		5170
3985	=over 4
3986
3987	=item The winsocket select function	5171	=head3 The winsocket C<select> function
3988		5172
3989	The winsocket C<select> function doesn't follow POSIX in that it	5173	The winsocket C<select> function doesn't follow POSIX in that it
3990	requires socket I<handles> and not socket I<file descriptors> (it is	5174	requires socket I<handles> and not socket I<file descriptors> (it is
3991	also extremely buggy). This makes select very inefficient, and also	5175	also extremely buggy). This makes select very inefficient, and also
3992	requires a mapping from file descriptors to socket handles (the Microsoft	5176	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4001	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5185	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4002		5186
4003	Note that winsockets handling of fd sets is O(n), so you can easily get a	5187	Note that winsockets handling of fd sets is O(n), so you can easily get a
4004	complexity in the O(n²) range when using win32.	5188	complexity in the O(n²) range when using win32.
4005		5189
4006	=item Limited number of file descriptors	5190	=head3 Limited number of file descriptors
4007		5191
4008	Windows has numerous arbitrary (and low) limits on things.	5192	Windows has numerous arbitrary (and low) limits on things.
4009		5193
4010	Early versions of winsocket's select only supported waiting for a maximum	5194	Early versions of winsocket's select only supported waiting for a maximum
4011	of C<64> handles (probably owning to the fact that all windows kernels	5195	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4026	runtime libraries. This might get you to about C<512> or C<2048> sockets	5210	runtime libraries. This might get you to about C<512> or C<2048> sockets
4027	(depending on windows version and/or the phase of the moon). To get more,	5211	(depending on windows version and/or the phase of the moon). To get more,
4028	you need to wrap all I/O functions and provide your own fd management, but	5212	you need to wrap all I/O functions and provide your own fd management, but
4029	the cost of calling select (O(n²)) will likely make this unworkable.	5213	the cost of calling select (O(n²)) will likely make this unworkable.
4030		5214
4031	=back
4032
4033	=head2 PORTABILITY REQUIREMENTS	5215	=head2 PORTABILITY REQUIREMENTS
4034		5216
4035	In addition to a working ISO-C implementation and of course the	5217	In addition to a working ISO-C implementation and of course the
4036	backend-specific APIs, libev relies on a few additional extensions:	5218	backend-specific APIs, libev relies on a few additional extensions:
4037		5219
…		…
4043	Libev assumes not only that all watcher pointers have the same internal	5225	Libev assumes not only that all watcher pointers have the same internal
4044	structure (guaranteed by POSIX but not by ISO C for example), but it also	5226	structure (guaranteed by POSIX but not by ISO C for example), but it also
4045	assumes that the same (machine) code can be used to call any watcher	5227	assumes that the same (machine) code can be used to call any watcher
4046	callback: The watcher callbacks have different type signatures, but libev	5228	callback: The watcher callbacks have different type signatures, but libev
4047	calls them using an C<ev_watcher *> internally.	5229	calls them using an C<ev_watcher *> internally.
		5230
		5231	=item pointer accesses must be thread-atomic
		5232
		5233	Accessing a pointer value must be atomic, it must both be readable and
		5234	writable in one piece - this is the case on all current architectures.
4048		5235
4049	=item C<sig_atomic_t volatile> must be thread-atomic as well	5236	=item C<sig_atomic_t volatile> must be thread-atomic as well
4050		5237
4051	The type C<sig_atomic_t volatile> (or whatever is defined as	5238	The type C<sig_atomic_t volatile> (or whatever is defined as
4052	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5239	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4075	watchers.	5262	watchers.
4076		5263
4077	=item C<double> must hold a time value in seconds with enough accuracy	5264	=item C<double> must hold a time value in seconds with enough accuracy
4078		5265
4079	The type C<double> is used to represent timestamps. It is required to	5266	The type C<double> is used to represent timestamps. It is required to
4080	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5267	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4081	enough for at least into the year 4000. This requirement is fulfilled by	5268	good enough for at least into the year 4000 with millisecond accuracy
		5269	(the design goal for libev). This requirement is overfulfilled by
4082	implementations implementing IEEE 754, which is basically all existing	5270	implementations using IEEE 754, which is basically all existing ones.
		5271
4083	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5272	With IEEE 754 doubles, you get microsecond accuracy until at least the
4084	2200.	5273	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5274	is either obsolete or somebody patched it to use C<long double> or
		5275	something like that, just kidding).
4085		5276
4086	=back	5277	=back
4087		5278
4088	If you know of other additional requirements drop me a note.	5279	If you know of other additional requirements drop me a note.
4089		5280
…		…
4151	=item Processing ev_async_send: O(number_of_async_watchers)	5342	=item Processing ev_async_send: O(number_of_async_watchers)
4152		5343
4153	=item Processing signals: O(max_signal_number)	5344	=item Processing signals: O(max_signal_number)
4154		5345
4155	Sending involves a system call I<iff> there were no other C<ev_async_send>	5346	Sending involves a system call I<iff> there were no other C<ev_async_send>
4156	calls in the current loop iteration. Checking for async and signal events	5347	calls in the current loop iteration and the loop is currently
		5348	blocked. Checking for async and signal events involves iterating over all
4157	involves iterating over all running async watchers or all signal numbers.	5349	running async watchers or all signal numbers.
4158		5350
4159	=back	5351	=back
4160		5352
4161		5353
		5354	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5355
		5356	The major version 4 introduced some incompatible changes to the API.
		5357
		5358	At the moment, the C<ev.h> header file provides compatibility definitions
		5359	for all changes, so most programs should still compile. The compatibility
		5360	layer might be removed in later versions of libev, so better update to the
		5361	new API early than late.
		5362
		5363	=over 4
		5364
		5365	=item C<EV_COMPAT3> backwards compatibility mechanism
		5366
		5367	The backward compatibility mechanism can be controlled by
		5368	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5369	section.
		5370
		5371	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5372
		5373	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5374
		5375	ev_loop_destroy (EV_DEFAULT_UC);
		5376	ev_loop_fork (EV_DEFAULT);
		5377
		5378	=item function/symbol renames
		5379
		5380	A number of functions and symbols have been renamed:
		5381
		5382	ev_loop => ev_run
		5383	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5384	EVLOOP_ONESHOT => EVRUN_ONCE
		5385
		5386	ev_unloop => ev_break
		5387	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5388	EVUNLOOP_ONE => EVBREAK_ONE
		5389	EVUNLOOP_ALL => EVBREAK_ALL
		5390
		5391	EV_TIMEOUT => EV_TIMER
		5392
		5393	ev_loop_count => ev_iteration
		5394	ev_loop_depth => ev_depth
		5395	ev_loop_verify => ev_verify
		5396
		5397	Most functions working on C<struct ev_loop> objects don't have an
		5398	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5399	associated constants have been renamed to not collide with the C<struct
		5400	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5401	as all other watcher types. Note that C<ev_loop_fork> is still called
		5402	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5403	typedef.
		5404
		5405	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5406
		5407	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5408	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5409	and work, but the library code will of course be larger.
		5410
		5411	=back
		5412
		5413
4162	=head1 GLOSSARY	5414	=head1 GLOSSARY
4163		5415
4164	=over 4	5416	=over 4
4165		5417
4166	=item active	5418	=item active
4167		5419
4168	A watcher is active as long as it has been started (has been attached to	5420	A watcher is active as long as it has been started and not yet stopped.
4169	an event loop) but not yet stopped (disassociated from the event loop).	5421	See L<WATCHER STATES> for details.
4170		5422
4171	=item application	5423	=item application
4172		5424
4173	In this document, an application is whatever is using libev.	5425	In this document, an application is whatever is using libev.
		5426
		5427	=item backend
		5428
		5429	The part of the code dealing with the operating system interfaces.
4174		5430
4175	=item callback	5431	=item callback
4176		5432
4177	The address of a function that is called when some event has been	5433	The address of a function that is called when some event has been
4178	detected. Callbacks are being passed the event loop, the watcher that	5434	detected. Callbacks are being passed the event loop, the watcher that
4179	received the event, and the actual event bitset.	5435	received the event, and the actual event bitset.
4180		5436
4181	=item callback invocation	5437	=item callback/watcher invocation
4182		5438
4183	The act of calling the callback associated with a watcher.	5439	The act of calling the callback associated with a watcher.
4184		5440
4185	=item event	5441	=item event
4186		5442
4187	A change of state of some external event, such as data now being available	5443	A change of state of some external event, such as data now being available
4188	for reading on a file descriptor, time having passed or simply not having	5444	for reading on a file descriptor, time having passed or simply not having
4189	any other events happening anymore.	5445	any other events happening anymore.
4190		5446
4191	In libev, events are represented as single bits (such as C<EV_READ> or	5447	In libev, events are represented as single bits (such as C<EV_READ> or
4192	C<EV_TIMEOUT>).	5448	C<EV_TIMER>).
4193		5449
4194	=item event library	5450	=item event library
4195		5451
4196	A software package implementing an event model and loop.	5452	A software package implementing an event model and loop.
4197		5453
…		…
4205	The model used to describe how an event loop handles and processes	5461	The model used to describe how an event loop handles and processes
4206	watchers and events.	5462	watchers and events.
4207		5463
4208	=item pending	5464	=item pending
4209		5465
4210	A watcher is pending as soon as the corresponding event has been detected,	5466	A watcher is pending as soon as the corresponding event has been
4211	and stops being pending as soon as the watcher will be invoked or its	5467	detected. See L<WATCHER STATES> for details.
4212	pending status is explicitly cleared by the application.
4213
4214	A watcher can be pending, but not active. Stopping a watcher also clears
4215	its pending status.
4216		5468
4217	=item real time	5469	=item real time
4218		5470
4219	The physical time that is observed. It is apparently strictly monotonic :)	5471	The physical time that is observed. It is apparently strictly monotonic :)
4220		5472
4221	=item wall-clock time	5473	=item wall-clock time
4222		5474
4223	The time and date as shown on clocks. Unlike real time, it can actually	5475	The time and date as shown on clocks. Unlike real time, it can actually
4224	be wrong and jump forwards and backwards, e.g. when the you adjust your	5476	be wrong and jump forwards and backwards, e.g. when you adjust your
4225	clock.	5477	clock.
4226		5478
4227	=item watcher	5479	=item watcher
4228		5480
4229	A data structure that describes interest in certain events. Watchers need	5481	A data structure that describes interest in certain events. Watchers need
4230	to be started (attached to an event loop) before they can receive events.	5482	to be started (attached to an event loop) before they can receive events.
4231		5483
4232	=item watcher invocation
4233
4234	The act of calling the callback associated with a watcher.
4235
4236	=back	5484	=back
4237		5485
4238	=head1 AUTHOR	5486	=head1 AUTHOR
4239		5487
4240	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5488	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5489	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4241		5490

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