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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.
625		731
626	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
627		733
628	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
630		736
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	739	in which case it is higher.
634		740
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
637		745
638	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
639		747
640	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
641	use.	749	use.
…		…
650		758
651	=item ev_now_update (loop)	759	=item ev_now_update (loop)
652		760
653	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
654	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
655	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
656		764
657	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
658	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
659	the current time is a good idea.	767	the current time is a good idea.
660		768
661	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
662		770
663	=item ev_suspend (loop)	771	=item ev_suspend (loop)
664		772
665	=item ev_resume (loop)	773	=item ev_resume (loop)
666		774
667	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
668	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.
669		777
670	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
671	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
672	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
673	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>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
676		784
677	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
678	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
679	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
680	occured while suspended).	788	occurred while suspended).
681		789
682	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
683	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>
684	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
685		793
686	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
687	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
688		796
689	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
690		798
691	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
692	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
693	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>.
694		804
695	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
696	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.
697		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
698	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
699	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
700	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
701	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
702	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
703	beauty.	818	beauty.
704		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
705	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
706	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
707	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
708	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.
709		830
710	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
711	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
712	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
713	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
714	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
715	iteration of the loop.	836	iteration of the loop.
716		837
717	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
718	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
719	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
720	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
721		842
722	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):
723		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- 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.
727	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	856	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
735	- 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.
736	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
738	- 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.
739	- Queue all expired timers.	867	- Queue all expired timers.
740	- Queue all expired periodics.	868	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	870	- Queue all check watchers.
743	- 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).
744	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
745	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
746	- 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
747	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
748	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.
749		881
750	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
751	anymore.	883	anymore.
752		884
753	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
754	... 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..)
755	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
757		889
758	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
759		891
760	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
761	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
762	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
763	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.
764		896
765	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>.
766		898
767	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.
768		901
769	=item ev_ref (loop)	902	=item ev_ref (loop)
770		903
771	=item ev_unref (loop)	904	=item ev_unref (loop)
772		905
773	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
774	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
775	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.
776		909
777	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
778	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>
779	stopping it.	913	before stopping it.
780		914
781	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
782	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
783	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
784	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
785	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
786	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
787	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
788	(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>
789	in the callback).	923	in the callback).
790		924
791	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>
792	running when nothing else is active.	926	running when nothing else is active.
793		927
794	ev_signal exitsig;	928	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	931	ev_unref (loop);
798		932
799	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
800		934
801	ev_ref (loop);	935	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
822	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.
823		957
824	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
825	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,
826	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
827	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
828	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
829	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
830	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
831		966
832	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
833	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
834	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
835	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
…		…
841	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>,
842	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
843	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
844	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
845	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,
846	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
847		982
848	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
850	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
851	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
…		…
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		995
861	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
862		997
863	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1005
		1006	=item int ev_pending_count (loop)
		1007
		1008	Returns the number of pending watchers - zero indicates that no watchers
		1009	are pending.
866		1010
867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868		1012
869	This overrides the invoke pending functionality of the loop: Instead of	1013	This overrides the invoke pending functionality of the loop: Instead of
870	invoking all pending watchers when there are any, C<ev_loop> will call	1014	invoking all pending watchers when there are any, C<ev_run> will call
871	this callback instead. This is useful, for example, when you want to	1015	this callback instead. This is useful, for example, when you want to
872	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
873		1017
874	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
875	callback.	1019	callback.
876		1020
877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
878		1022
879	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
880	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
881	each call to a libev function.	1025	each call to a libev function.
882		1026
883	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
884	wait for it to return. One way around this is to wake up the loop via	1028	to wait for it to return. One way around this is to wake up the event
885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
886	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
887		1031
888	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
889	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
890	afterwards.	1034	afterwards.
891		1035
892	Ideally, C<release> will just call your mutex_unlock function, and	1036	Ideally, C<release> will just call your mutex_unlock function, and
893	C<acquire> will just call the mutex_lock function again.	1037	C<acquire> will just call the mutex_lock function again.
894		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
895	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
896		1053
897	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
898		1055
899	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
901	C<0.>	1058	C<0>.
902		1059
903	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
904	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
905	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
906	any other purpose as well.	1063	any other purpose as well.
907		1064
908	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
909		1066
910	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
911	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
912	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
913	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
…		…
924		1081
925	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
926	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
927	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
928		1085
929	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
930	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
931	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:
932		1090
933	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)
934	{	1092	{
935	ev_io_stop (w);	1093	ev_io_stop (w);
936	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
937	}	1095	}
938		1096
939	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
940		1098
941	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
942		1100
943	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
945	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
946		1104
947	ev_loop (loop, 0);	1105	ev_run (loop, 0);
948		1106
949	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
950	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
951	stack).	1109	stack).
952		1110
953	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>
954	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).
955		1113
956	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
957	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
958	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
959	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
960	is readable and/or writable).	1118	and/or writable).
961		1119
962	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 *, ...) >>
963	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
964	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<<
965	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
988	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
989		1147
990	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
991	writable.	1149	writable.
992		1150
993	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
994		1152
995	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
996		1154
997	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
998		1156
…		…
1016		1174
1017	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1018		1176
1019	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1020		1178
1021	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 to
1022	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1023	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1024	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1025	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1026	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1027	C<ev_loop> from blocking).	1190	blocking).
1028		1191
1029	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1030		1193
1031	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1032		1195
1033	=item C<EV_FORK>	1196	=item C<EV_FORK>
1034		1197
1035	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1036	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1037		1204
1038	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1039		1206
1040	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1041		1208
…		…
1088		1255
1089	ev_io w;	1256	ev_io w;
1090	ev_init (&w, my_cb);	1257	ev_init (&w, my_cb);
1091	ev_io_set (&w, STDIN_FILENO, EV_READ);	1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
1092		1259
1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1094		1261
1095	This macro initialises the type-specific parts of a watcher. You need to	1262	This macro initialises the type-specific parts of a watcher. You need to
1096	call C<ev_init> at least once before you call this macro, but you can	1263	call C<ev_init> at least once before you call this macro, but you can
1097	call C<ev_TYPE_set> any number of times. You must not, however, call this	1264	call C<ev_TYPE_set> any number of times. You must not, however, call this
1098	macro on a watcher that is active (it can be pending, however, which is a	1265	macro on a watcher that is active (it can be pending, however, which is a
…		…
1111		1278
1112	Example: Initialise and set an C<ev_io> watcher in one step.	1279	Example: Initialise and set an C<ev_io> watcher in one step.
1113		1280
1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1115		1282
1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1117		1284
1118	Starts (activates) the given watcher. Only active watchers will receive	1285	Starts (activates) the given watcher. Only active watchers will receive
1119	events. If the watcher is already active nothing will happen.	1286	events. If the watcher is already active nothing will happen.
1120		1287
1121	Example: Start the C<ev_io> watcher that is being abused as example in this	1288	Example: Start the C<ev_io> watcher that is being abused as example in this
1122	whole section.	1289	whole section.
1123		1290
1124	ev_io_start (EV_DEFAULT_UC, &w);	1291	ev_io_start (EV_DEFAULT_UC, &w);
1125		1292
1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1127		1294
1128	Stops the given watcher if active, and clears the pending status (whether	1295	Stops the given watcher if active, and clears the pending status (whether
1129	the watcher was active or not).	1296	the watcher was active or not).
1130		1297
1131	It is possible that stopped watchers are pending - for example,	1298	It is possible that stopped watchers are pending - for example,
…		…
1151		1318
1152	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1153		1320
1154	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1155		1322
1156	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1157		1324
1158	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1159	(modulo threads).	1326	(modulo threads).
1160		1327
1161	=item ev_set_priority (ev_TYPE *watcher, priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
1162		1329
1163	=item int ev_priority (ev_TYPE *watcher)	1330	=item int ev_priority (ev_TYPE *watcher)
1164		1331
1165	Set and query the priority of the watcher. The priority is a small	1332	Set and query the priority of the watcher. The priority is a small
1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1179	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
1180		1347
1181	The default priority used by watchers when no priority has been set is	1348	The default priority used by watchers when no priority has been set is
1182	always C<0>, which is supposed to not be too high and not be too low :).	1349	always C<0>, which is supposed to not be too high and not be too low :).
1183		1350
1184	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1185	priorities.	1352	priorities.
1186		1353
1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1188		1355
1189	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1198	watcher isn't pending it does nothing and returns C<0>.	1365	watcher isn't pending it does nothing and returns C<0>.
1199		1366
1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1367	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1201	callback to be invoked, which can be accomplished with this function.	1368	callback to be invoked, which can be accomplished with this function.
1202		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
1203	=back	1384	=back
1204		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1205		1388
1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1207		1390
1208	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1209	and read at any time: libev will completely ignore it. This can be used	1392	active, pending and so on. In this section these states and the rules to
1210	to associate arbitrary data with your watcher. If you need more data and	1393	transition between them will be described in more detail - and while these
1211	don't want to allocate memory and store a pointer to it in that data	1394	rules might look complicated, they usually do "the right thing".
1212	member, you can also "subclass" the watcher type and provide your own
1213	data:
1214		1395
1215	struct my_io	1396	=over 4
1216	{
1217	ev_io io;
1218	int otherfd;
1219	void *somedata;
1220	struct whatever *mostinteresting;
1221	};
1222		1397
1223	...	1398	=item initialiased
1224	struct my_io w;
1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1226		1399
1227	And since your callback will be called with a pointer to the watcher, you	1400	Before a watcher can be registered with the event loop it has to be
1228	can cast it back to your own type:	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1229		1403
1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1404	In this state it is simply some block of memory that is suitable for
1231	{	1405	use in an event loop. It can be moved around, freed, reused etc. at
1232	struct my_io *w = (struct my_io *)w_;	1406	will - as long as you either keep the memory contents intact, or call
1233	...	1407	C<ev_TYPE_init> again.
1234	}
1235		1408
1236	More interesting and less C-conformant ways of casting your callback type	1409	=item started/running/active
1237	instead have been omitted.
1238		1410
1239	Another common scenario is to use some data structure with multiple	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1240	embedded watchers:	1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
1241		1416
1242	struct my_biggy	1417	=item pending
1243	{
1244	int some_data;
1245	ev_timer t1;
1246	ev_timer t2;
1247	}
1248		1418
1249	In this case getting the pointer to C<my_biggy> is a bit more	1419	If a watcher is active and libev determines that an event it is interested
1250	complicated: Either you store the address of your C<my_biggy> struct	1420	in has occurred (such as a timer expiring), it will become pending. It will
1251	in the C<data> member of the watcher (for woozies), or you need to use	1421	stay in this pending state until either it is stopped or its callback is
1252	some pointer arithmetic using C<offsetof> inside your watchers (for real	1422	about to be invoked, so it is not normally pending inside the watcher
1253	programmers):	1423	callback.
1254		1424
1255	#include <stddef.h>	1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
1256		1431
1257	static void	1432	It is also possible to feed an event on a watcher that is not active (e.g.
1258	t1_cb (EV_P_ ev_timer *w, int revents)	1433	via C<ev_feed_event>), in which case it becomes pending without being
1259	{	1434	active.
1260	struct my_biggy big = (struct my_biggy *)
1261	(((char *)w) - offsetof (struct my_biggy, t1));
1262	}
1263		1435
1264	static void	1436	=item stopped
1265	t2_cb (EV_P_ ev_timer *w, int revents)	1437
1266	{	1438	A watcher can be stopped implicitly by libev (in which case it might still
1267	struct my_biggy big = (struct my_biggy *)	1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1268	(((char *)w) - offsetof (struct my_biggy, t2));	1440	latter will clear any pending state the watcher might be in, regardless
1269	}	1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
1270		1450
1271	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1272		1452
1273	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1274	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1317		1497
1318	For example, to emulate how many other event libraries handle priorities,	1498	For example, to emulate how many other event libraries handle priorities,
1319	you can associate an C<ev_idle> watcher to each such watcher, and in	1499	you can associate an C<ev_idle> watcher to each such watcher, and in
1320	the normal watcher callback, you just start the idle watcher. The real	1500	the normal watcher callback, you just start the idle watcher. The real
1321	processing is done in the idle watcher callback. This causes libev to	1501	processing is done in the idle watcher callback. This causes libev to
1322	continously poll and process kernel event data for the watcher, but when	1502	continuously poll and process kernel event data for the watcher, but when
1323	the lock-out case is known to be rare (which in turn is rare :), this is	1503	the lock-out case is known to be rare (which in turn is rare :), this is
1324	workable.	1504	workable.
1325		1505
1326	Usually, however, the lock-out model implemented that way will perform	1506	Usually, however, the lock-out model implemented that way will perform
1327	miserably under the type of load it was designed to handle. In that case,	1507	miserably under the type of load it was designed to handle. In that case,
…		…
1341	{	1521	{
1342	// stop the I/O watcher, we received the event, but	1522	// stop the I/O watcher, we received the event, but
1343	// are not yet ready to handle it.	1523	// are not yet ready to handle it.
1344	ev_io_stop (EV_A_ w);	1524	ev_io_stop (EV_A_ w);
1345		1525
1346	// start the idle watcher to ahndle the actual event.	1526	// start the idle watcher to handle the actual event.
1347	// it will not be executed as long as other watchers	1527	// it will not be executed as long as other watchers
1348	// with the default priority are receiving events.	1528	// with the default priority are receiving events.
1349	ev_idle_start (EV_A_ &idle);	1529	ev_idle_start (EV_A_ &idle);
1350	}	1530	}
1351		1531
…		…
1401	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1402	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1403	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1404	required if you know what you are doing).	1584	required if you know what you are doing).
1405		1585
1406	If you cannot use non-blocking mode, then force the use of a
1407	known-to-be-good backend (at the time of this writing, this includes only
1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1409	descriptors for which non-blocking operation makes no sense (such as
1410	files) - libev doesn't guarentee any specific behaviour in that case.
1411
1412	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1413	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1415	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1416	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1417	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1418	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1420		1593
1421	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1422	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1423	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1424	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1425	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1426	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1427	indefinitely.	1600	indefinitely.
1428		1601
1429	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1430		1603
…		…
1458		1631
1459	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1460	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1461	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1462		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1463	=head3 The special problem of fork	1669	=head3 The special problem of fork
1464		1670
1465	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1466	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1467	it in the child.	1673	it in the child if you want to continue to use it in the child.
1468		1674
1469	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1470	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1472	C<EVBACKEND_POLL>.
1473		1678
1474	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1475		1680
1476	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1477	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1480		1685
1481	So when you encounter spurious, unexplained daemon exits, make sure you	1686	So when you encounter spurious, unexplained daemon exits, make sure you
1482	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1687	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1483	somewhere, as that would have given you a big clue).	1688	somewhere, as that would have given you a big clue).
1484		1689
		1690	=head3 The special problem of accept()ing when you can't
		1691
		1692	Many implementations of the POSIX C<accept> function (for example,
		1693	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1694	connection from the pending queue in all error cases.
		1695
		1696	For example, larger servers often run out of file descriptors (because
		1697	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1698	rejecting the connection, leading to libev signalling readiness on
		1699	the next iteration again (the connection still exists after all), and
		1700	typically causing the program to loop at 100% CPU usage.
		1701
		1702	Unfortunately, the set of errors that cause this issue differs between
		1703	operating systems, there is usually little the app can do to remedy the
		1704	situation, and no known thread-safe method of removing the connection to
		1705	cope with overload is known (to me).
		1706
		1707	One of the easiest ways to handle this situation is to just ignore it
		1708	- when the program encounters an overload, it will just loop until the
		1709	situation is over. While this is a form of busy waiting, no OS offers an
		1710	event-based way to handle this situation, so it's the best one can do.
		1711
		1712	A better way to handle the situation is to log any errors other than
		1713	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1714	messages, and continue as usual, which at least gives the user an idea of
		1715	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1716	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1717	usage.
		1718
		1719	If your program is single-threaded, then you could also keep a dummy file
		1720	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1721	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1722	close that fd, and create a new dummy fd. This will gracefully refuse
		1723	clients under typical overload conditions.
		1724
		1725	The last way to handle it is to simply log the error and C<exit>, as
		1726	is often done with C<malloc> failures, but this results in an easy
		1727	opportunity for a DoS attack.
1485		1728
1486	=head3 Watcher-Specific Functions	1729	=head3 Watcher-Specific Functions
1487		1730
1488	=over 4	1731	=over 4
1489		1732
…		…
1521	...	1764	...
1522	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1523	ev_io stdin_readable;	1766	ev_io stdin_readable;
1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1767	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1525	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1526	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1527		1770
1528		1771
1529	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1530		1773
1531	Timer watchers are simple relative timers that generate an event after a	1774	Timer watchers are simple relative timers that generate an event after a
…		…
1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1538	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1539		1782
1540	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1541	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1542	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1543	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1544	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1545	no longer true when a callback calls C<ev_loop> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1546		1790
1547	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1548		1792
1549	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1550	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1625		1869
1626	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1627	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1628	within the callback:	1872	within the callback:
1629		1873
		1874	ev_tstamp timeout = 60.;
1630	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1631		1877
1632	static void	1878	static void
1633	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1634	{	1880	{
1635	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1636	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1637		1883
1638	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1639	if (timeout < now)	1885	if (after < 0.)
1640	{	1886	{
1641	// timeout occured, take action	1887	// timeout occurred, take action
1642	}	1888	}
1643	else	1889	else
1644	{	1890	{
1645	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1646	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1647	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1648	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1649	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1650	}	1897	}
1651	}	1898	}
1652		1899
1653	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1654	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1655	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1656	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1657	re-schedule the timer to fire at that future time, to see if maybe we have
1658	a timeout then.
1659		1904
1660	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1661	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1662		1914
1663	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1664	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1665	libev to change the timeout.	1917	libev to change the timeout.
1666		1918
1667	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1668	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1669	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1670		1923
		1924	last_activity = ev_now (EV_A);
1671	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1672	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1673	callback (loop, timer, EV_TIMEOUT);
1674		1927
1675	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1676	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1677		1930
		1931	if (activity detected)
1678	last_actiivty = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1679		1941
1680	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1681	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1682
1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
1684	callback :) - just change the timeout and invoke the callback, which will
1685	fix things for you.
1686		1944
1687	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1688		1946
1689	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1690	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1718	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1719	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1720	overkill :)	1978	overkill :)
1721		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1722	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1723		2018
1724	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1725	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1726	time only before and after C<ev_loop> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1728	lots of events in one iteration.	2023	lots of events in one iteration.
1729		2024
1730	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
1731	time. This is usually the right thing as this timestamp refers to the time	2026	time. This is usually the right thing as this timestamp refers to the time
…		…
1737		2032
1738	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1740	()>.	2035	()>.
1741		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
		2069
		2070	=head3 The special problems of suspended animation
		2071
		2072	When you leave the server world it is quite customary to hit machines that
		2073	can suspend/hibernate - what happens to the clocks during such a suspend?
		2074
		2075	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2076	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2077	to run until the system is suspended, but they will not advance while the
		2078	system is suspended. That means, on resume, it will be as if the program
		2079	was frozen for a few seconds, but the suspend time will not be counted
		2080	towards C<ev_timer> when a monotonic clock source is used. The real time
		2081	clock advanced as expected, but if it is used as sole clocksource, then a
		2082	long suspend would be detected as a time jump by libev, and timers would
		2083	be adjusted accordingly.
		2084
		2085	I would not be surprised to see different behaviour in different between
		2086	operating systems, OS versions or even different hardware.
		2087
		2088	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2089	time jump in the monotonic clocks and the realtime clock. If the program
		2090	is suspended for a very long time, and monotonic clock sources are in use,
		2091	then you can expect C<ev_timer>s to expire as the full suspension time
		2092	will be counted towards the timers. When no monotonic clock source is in
		2093	use, then libev will again assume a timejump and adjust accordingly.
		2094
		2095	It might be beneficial for this latter case to call C<ev_suspend>
		2096	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2097	deterministic behaviour in this case (you can do nothing against
		2098	C<SIGSTOP>).
		2099
1742	=head3 Watcher-Specific Functions and Data Members	2100	=head3 Watcher-Specific Functions and Data Members
1743		2101
1744	=over 4	2102	=over 4
1745		2103
1746	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2104	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1759	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1760	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1761		2119
1762	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1763		2121
1764	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1765	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1766		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1767	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1768		2132
1769	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1770		2135
1771	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1772	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1773		2138
		2139	=back
		2140
1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1775	usage example.	2142	usage example.
		2143
		2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2145
		2146	Returns the remaining time until a timer fires. If the timer is active,
		2147	then this time is relative to the current event loop time, otherwise it's
		2148	the timeout value currently configured.
		2149
		2150	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2151	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2152	will return C<4>. When the timer expires and is restarted, it will return
		2153	roughly C<7> (likely slightly less as callback invocation takes some time,
		2154	too), and so on.
1776		2155
1777	=item ev_tstamp repeat [read-write]	2156	=item ev_tstamp repeat [read-write]
1778		2157
1779	The current C<repeat> value. Will be used each time the watcher times out	2158	The current C<repeat> value. Will be used each time the watcher times out
1780	or C<ev_timer_again> is called, and determines the next timeout (if any),	2159	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1806	}	2185	}
1807		2186
1808	ev_timer mytimer;	2187	ev_timer mytimer;
1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2188	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1810	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1811	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1812		2191
1813	// and in some piece of code that gets executed on any "activity":	2192	// and in some piece of code that gets executed on any "activity":
1814	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1815	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1816		2195
…		…
1842		2221
1843	As with timers, the callback is guaranteed to be invoked only when the	2222	As with timers, the callback is guaranteed to be invoked only when the
1844	point in time where it is supposed to trigger has passed. If multiple	2223	point in time where it is supposed to trigger has passed. If multiple
1845	timers become ready during the same loop iteration then the ones with	2224	timers become ready during the same loop iteration then the ones with
1846	earlier time-out values are invoked before ones with later time-out values	2225	earlier time-out values are invoked before ones with later time-out values
1847	(but this is no longer true when a callback calls C<ev_loop> recursively).	2226	(but this is no longer true when a callback calls C<ev_run> recursively).
1848		2227
1849	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1850		2229
1851	=over 4	2230	=over 4
1852		2231
…		…
1887		2266
1888	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
1889	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
1890	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
1891		2270
1892	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
1893	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
1894	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
1895		2277
1896	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
1897	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
1898	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
1899	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
1980	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
1981	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
1982	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
1983		2365
1984	static void	2366	static void
1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1986	{	2368	{
1987	... its now a full hour (UTC, or TAI or whatever your clock follows)	2369	... its now a full hour (UTC, or TAI or whatever your clock follows)
1988	}	2370	}
1989		2371
1990	ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
…		…
2013		2395
2014	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2015		2397
2016	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
2017	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
2018	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
2019	normal event processing, like any other event.	2401	normal event processing, like any other event.
2020		2402
2021	If you want signals asynchronously, just use C<sigaction> as you would	2403	If you want signals to be delivered truly asynchronously, just use
2022	do without libev and forget about sharing the signal. You can even use	2404	C<sigaction> as you would do without libev and forget about sharing
2023	C<ev_async> from a signal handler to synchronously wake up an event loop.	2405	the signal. You can even use C<ev_async> from a signal handler to
		2406	synchronously wake up an event loop.
2024		2407
2025	You can configure as many watchers as you like per signal. Only when the	2408	You can configure as many watchers as you like for the same signal, but
		2409	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2410	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2411	C<SIGINT> in both the default loop and another loop at the same time. At
		2412	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2413
2026	first watcher gets started will libev actually register a signal handler	2414	When the first watcher gets started will libev actually register something
2027	with the kernel (thus it coexists with your own signal handlers as long as	2415	with the kernel (thus it coexists with your own signal handlers as long as
2028	you don't register any with libev for the same signal). Similarly, when	2416	you don't register any with libev for the same signal).
2029	the last signal watcher for a signal is stopped, libev will reset the
2030	signal handler to SIG_DFL (regardless of what it was set to before).
2031		2417
2032	If possible and supported, libev will install its handlers with	2418	If possible and supported, libev will install its handlers with
2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2419	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2034	interrupted. If you have a problem with system calls getting interrupted by	2420	not be unduly interrupted. If you have a problem with system calls getting
2035	signals you can block all signals in an C<ev_check> watcher and unblock	2421	interrupted by signals you can block all signals in an C<ev_check> watcher
2036	them in an C<ev_prepare> watcher.	2422	and unblock them in an C<ev_prepare> watcher.
		2423
		2424	=head3 The special problem of inheritance over fork/execve/pthread_create
		2425
		2426	Both the signal mask (C<sigprocmask>) and the signal disposition
		2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2428	stopping it again), that is, libev might or might not block the signal,
		2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
		2431
		2432	While this does not matter for the signal disposition (libev never
		2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2434	C<execve>), this matters for the signal mask: many programs do not expect
		2435	certain signals to be blocked.
		2436
		2437	This means that before calling C<exec> (from the child) you should reset
		2438	the signal mask to whatever "default" you expect (all clear is a good
		2439	choice usually).
		2440
		2441	The simplest way to ensure that the signal mask is reset in the child is
		2442	to install a fork handler with C<pthread_atfork> that resets it. That will
		2443	catch fork calls done by libraries (such as the libc) as well.
		2444
		2445	In current versions of libev, the signal will not be blocked indefinitely
		2446	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2447	the window of opportunity for problems, it will not go away, as libev
		2448	I<has> to modify the signal mask, at least temporarily.
		2449
		2450	So I can't stress this enough: I<If you do not reset your signal mask when
		2451	you expect it to be empty, you have a race condition in your code>. This
		2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
2037		2467
2038	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2039		2469
2040	=over 4	2470	=over 4
2041		2471
…		…
2057	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
2058		2488
2059	static void	2489	static void
2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2061	{	2491	{
2062	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
2063	}	2493	}
2064		2494
2065	ev_signal signal_watcher;	2495	ev_signal signal_watcher;
2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2067	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
…		…
2086	libev)	2516	libev)
2087		2517
2088	=head3 Process Interaction	2518	=head3 Process Interaction
2089		2519
2090	Libev grabs C<SIGCHLD> as soon as the default event loop is	2520	Libev grabs C<SIGCHLD> as soon as the default event loop is
2091	initialised. This is necessary to guarantee proper behaviour even if	2521	initialised. This is necessary to guarantee proper behaviour even if the
2092	the first child watcher is started after the child exits. The occurrence	2522	first child watcher is started after the child exits. The occurrence
2093	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2523	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2094	synchronously as part of the event loop processing. Libev always reaps all	2524	synchronously as part of the event loop processing. Libev always reaps all
2095	children, even ones not watched.	2525	children, even ones not watched.
2096		2526
2097	=head3 Overriding the Built-In Processing	2527	=head3 Overriding the Built-In Processing
…		…
2107	=head3 Stopping the Child Watcher	2537	=head3 Stopping the Child Watcher
2108		2538
2109	Currently, the child watcher never gets stopped, even when the	2539	Currently, the child watcher never gets stopped, even when the
2110	child terminates, so normally one needs to stop the watcher in the	2540	child terminates, so normally one needs to stop the watcher in the
2111	callback. Future versions of libev might stop the watcher automatically	2541	callback. Future versions of libev might stop the watcher automatically
2112	when a child exit is detected.	2542	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2543	problem).
2113		2544
2114	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
2115		2546
2116	=over 4	2547	=over 4
2117		2548
…		…
2416	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2417	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2418	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2419	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2420		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2864	example.
		2865
2421	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2422		2867
2423	=over 4	2868	=over 4
2424		2869
2425	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2436	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2437		2882
2438	static void	2883	static void
2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2440	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2441	free (w);	2890	free (w);
		2891
2442	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2443	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2444	}	2894	}
2445		2895
2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2448	ev_idle_start (loop, idle_watcher);	2898	ev_idle_start (loop, idle_watcher);
2449		2899
2450		2900
2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2452		2902
2453	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2454	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2455	afterwards.	2905	afterwards.
2456		2906
2457	You I<must not> call C<ev_loop> or similar functions that enter	2907	You I<must not> call C<ev_run> or similar functions that enter
2458	the current event loop from either C<ev_prepare> or C<ev_check>	2908	the current event loop from either C<ev_prepare> or C<ev_check>
2459	watchers. Other loops than the current one are fine, however. The	2909	watchers. Other loops than the current one are fine, however. The
2460	rationale behind this is that you do not need to check for recursion in	2910	rationale behind this is that you do not need to check for recursion in
2461	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2911	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2462	C<ev_check> so if you have one watcher of each kind they will always be	2912	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2486	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2487	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2488	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2489	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2490		2940
2491	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2492	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2493	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2494		2945
2495	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2496	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2497	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2498	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2499	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2500	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2501	others).	2952	others).
		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2502		2973
2503	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2504		2975
2505	=over 4	2976	=over 4
2506		2977
…		…
2630		3101
2631	if (timeout >= 0)	3102	if (timeout >= 0)
2632	// create/start timer	3103	// create/start timer
2633		3104
2634	// poll	3105	// poll
2635	ev_loop (EV_A_ 0);	3106	ev_run (EV_A_ 0);
2636		3107
2637	// stop timer again	3108	// stop timer again
2638	if (timeout >= 0)	3109	if (timeout >= 0)
2639	ev_timer_stop (EV_A_ &to);	3110	ev_timer_stop (EV_A_ &to);
2640		3111
…		…
2718	if you do not want that, you need to temporarily stop the embed watcher).	3189	if you do not want that, you need to temporarily stop the embed watcher).
2719		3190
2720	=item ev_embed_sweep (loop, ev_embed *)	3191	=item ev_embed_sweep (loop, ev_embed *)
2721		3192
2722	Make a single, non-blocking sweep over the embedded loop. This works	3193	Make a single, non-blocking sweep over the embedded loop. This works
2723	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3194	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2724	appropriate way for embedded loops.	3195	appropriate way for embedded loops.
2725		3196
2726	=item struct ev_loop *other [read-only]	3197	=item struct ev_loop *other [read-only]
2727		3198
2728	The embedded event loop.	3199	The embedded event loop.
…		…
2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2789	handlers will be invoked, too, of course.	3260	handlers will be invoked, too, of course.
2790		3261
2791	=head3 The special problem of life after fork - how is it possible?	3262	=head3 The special problem of life after fork - how is it possible?
2792		3263
2793	Most uses of C<fork()> consist of forking, then some simple calls to ste	3264	Most uses of C<fork()> consist of forking, then some simple calls to set
2794	up/change the process environment, followed by a call to C<exec()>. This	3265	up/change the process environment, followed by a call to C<exec()>. This
2795	sequence should be handled by libev without any problems.	3266	sequence should be handled by libev without any problems.
2796		3267
2797	This changes when the application actually wants to do event handling	3268	This changes when the application actually wants to do event handling
2798	in the child, or both parent in child, in effect "continuing" after the	3269	in the child, or both parent in child, in effect "continuing" after the
…		…
2814	disadvantage of having to use multiple event loops (which do not support	3285	disadvantage of having to use multiple event loops (which do not support
2815	signal watchers).	3286	signal watchers).
2816		3287
2817	When this is not possible, or you want to use the default loop for	3288	When this is not possible, or you want to use the default loop for
2818	other reasons, then in the process that wants to start "fresh", call	3289	other reasons, then in the process that wants to start "fresh", call
2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3290	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2820	the default loop will "orphan" (not stop) all registered watchers, so you	3291	Destroying the default loop will "orphan" (not stop) all registered
2821	have to be careful not to execute code that modifies those watchers. Note	3292	watchers, so you have to be careful not to execute code that modifies
2822	also that in that case, you have to re-register any signal watchers.	3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
2823		3295
2824	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
2825		3297
2826	=over 4	3298	=over 4
2827		3299
2828	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
2829		3301
2830	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
2831	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2832	believe me.	3304	really.
2833		3305
2834	=back	3306	=back
2835		3307
2836		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
2837	=head2 C<ev_async> - how to wake up another event loop	3349	=head2 C<ev_async> - how to wake up an event loop
2838		3350
2839	In general, you cannot use an C<ev_loop> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
2840	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
2841	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
2842		3354
2843	Sometimes, however, you need to wake up another event loop you do not	3355	Sometimes, however, you need to wake up an event loop you do not control,
2844	control, for example because it belongs to another thread. This is what	3356	for example because it belongs to another thread. This is what C<ev_async>
2845	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3357	watchers do: as long as the C<ev_async> watcher is active, you can signal
2846	can signal it by calling C<ev_async_send>, which is thread- and signal	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
2847	safe.
2848		3359
2849	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
2850	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
2851	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
2852	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2853		3364	of "global async watchers" by using a watcher on an otherwise unused
2854	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2855	just the default loop.	3366	even without knowing which loop owns the signal.
2856		3367
2857	=head3 Queueing	3368	=head3 Queueing
2858		3369
2859	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
2860	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
2861	multiple-writer-single-reader queue that works in all cases and doesn't	3372	multiple-writer-single-reader queue that works in all cases and doesn't
2862	need elaborate support such as pthreads.	3373	need elaborate support such as pthreads or unportable memory access
		3374	semantics.
2863		3375
2864	That means that if you want to queue data, you have to provide your own	3376	That means that if you want to queue data, you have to provide your own
2865	queue. But at least I can tell you how to implement locking around your	3377	queue. But at least I can tell you how to implement locking around your
2866	queue:	3378	queue:
2867		3379
…		…
2951	trust me.	3463	trust me.
2952		3464
2953	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
2954		3466
2955	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2956	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
2957	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2959	section below on what exactly this means).	3473	embedding section below on what exactly this means).
2960		3474
2961	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
2962	compressed into a single callback invocation (another way to look at this	3476	compressed into a single callback invocation (another way to look at
2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
2964	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
2965		3479
2966	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
2967	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
2968	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
2969		3486
2970	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
2971		3488
2972	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
2973	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3006		3523
3007	If C<timeout> is less than 0, then no timeout watcher will be	3524	If C<timeout> is less than 0, then no timeout watcher will be
3008	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3525	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3009	repeat = 0) will be started. C<0> is a valid timeout.	3526	repeat = 0) will be started. C<0> is a valid timeout.
3010		3527
3011	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3528	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3012	passed an C<revents> set like normal event callbacks (a combination of	3529	passed an C<revents> set like normal event callbacks (a combination of
3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3530	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3014	value passed to C<ev_once>. Note that it is possible to receive I<both>	3531	value passed to C<ev_once>. Note that it is possible to receive I<both>
3015	a timeout and an io event at the same time - you probably should give io	3532	a timeout and an io event at the same time - you probably should give io
3016	events precedence.	3533	events precedence.
3017		3534
3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3535	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3019		3536
3020	static void stdin_ready (int revents, void *arg)	3537	static void stdin_ready (int revents, void *arg)
3021	{	3538	{
3022	if (revents & EV_READ)	3539	if (revents & EV_READ)
3023	/* stdin might have data for us, joy! */;	3540	/* stdin might have data for us, joy! */;
3024	else if (revents & EV_TIMEOUT)	3541	else if (revents & EV_TIMER)
3025	/* doh, nothing entered */;	3542	/* doh, nothing entered */;
3026	}	3543	}
3027		3544
3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3029		3546
3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3031
3032	Feeds the given event set into the event loop, as if the specified event
3033	had happened for the specified watcher (which must be a pointer to an
3034	initialised but not necessarily started event watcher).
3035
3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3037		3548
3038	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3039	the given events it.	3550	the given events.
3040		3551
3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3042		3553
3043	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3044	loop!).	3555	which is async-safe.
3045		3556
3046	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, C<ev_break> will not work alone.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3047		3908
3048		3909
3049	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3050		3911
3051	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3052	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3053		3914
3054	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3055		3921
3056	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3057		3923
3058	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3059	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3065	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3066	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3067	is an ev_pri field.	3933	is an ev_pri field.
3068		3934
3069	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3070	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3071		3937
3072	=item * Other members are not supported.	3938	=item * Other members are not supported.
3073		3939
3074	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3075	to use the libev header file and library.	3941	to use the libev header file and library.
3076		3942
3077	=back	3943	=back
3078		3944
3079	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3080		3979
3081	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3082	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3083	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3084		3983
…		…
3094	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
3095	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
3096	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
3097	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3098		3997
3099	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
3100	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
3101	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
3102	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
3103	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3104		4007
3105	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3106		4009
3107	=over 4	4010	=over 4
3108		4011
…		…
3118	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3119		4022
3120	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3121	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3122	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3123	defines by many implementations.	4026	defined by many implementations.
3124		4027
3125	All of those classes have these methods:	4028	All of those classes have these methods:
3126		4029
3127	=over 4	4030	=over 4
3128		4031
3129	=item ev::TYPE::TYPE ()	4032	=item ev::TYPE::TYPE ()
3130		4033
3131	=item ev::TYPE::TYPE (struct ev_loop *)	4034	=item ev::TYPE::TYPE (loop)
3132		4035
3133	=item ev::TYPE::~TYPE	4036	=item ev::TYPE::~TYPE
3134		4037
3135	The constructor (optionally) takes an event loop to associate the watcher	4038	The constructor (optionally) takes an event loop to associate the watcher
3136	with. If it is omitted, it will use C<EV_DEFAULT>.	4039	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3169	myclass obj;	4072	myclass obj;
3170	ev::io iow;	4073	ev::io iow;
3171	iow.set <myclass, &myclass::io_cb> (&obj);	4074	iow.set <myclass, &myclass::io_cb> (&obj);
3172		4075
3173	=item w->set (object *)	4076	=item w->set (object *)
3174
3175	This is an B<experimental> feature that might go away in a future version.
3176		4077
3177	This is a variation of a method callback - leaving out the method to call	4078	This is a variation of a method callback - leaving out the method to call
3178	will default the method to C<operator ()>, which makes it possible to use	4079	will default the method to C<operator ()>, which makes it possible to use
3179	functor objects without having to manually specify the C<operator ()> all	4080	functor objects without having to manually specify the C<operator ()> all
3180	the time. Incidentally, you can then also leave out the template argument	4081	the time. Incidentally, you can then also leave out the template argument
…		…
3213	Example: Use a plain function as callback.	4114	Example: Use a plain function as callback.
3214		4115
3215	static void io_cb (ev::io &w, int revents) { }	4116	static void io_cb (ev::io &w, int revents) { }
3216	iow.set <io_cb> ();	4117	iow.set <io_cb> ();
3217		4118
3218	=item w->set (struct ev_loop *)	4119	=item w->set (loop)
3219		4120
3220	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
3221	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
3222		4123
3223	=item w->set ([arguments])	4124	=item w->set ([arguments])
3224		4125
3225	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4126	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4127	with the same arguments. Either this method or a suitable start method
3226	called at least once. Unlike the C counterpart, an active watcher gets	4128	must be called at least once. Unlike the C counterpart, an active watcher
3227	automatically stopped and restarted when reconfiguring it with this	4129	gets automatically stopped and restarted when reconfiguring it with this
3228	method.	4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3229		4134
3230	=item w->start ()	4135	=item w->start ()
3231		4136
3232	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3233	constructor already stores the event loop.	4138	constructor already stores the event loop.
3234		4139
		4140	=item w->start ([arguments])
		4141
		4142	Instead of calling C<set> and C<start> methods separately, it is often
		4143	convenient to wrap them in one call. Uses the same type of arguments as
		4144	the configure C<set> method of the watcher.
		4145
3235	=item w->stop ()	4146	=item w->stop ()
3236		4147
3237	Stops the watcher if it is active. Again, no C<loop> argument.	4148	Stops the watcher if it is active. Again, no C<loop> argument.
3238		4149
3239	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4150	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3251		4162
3252	=back	4163	=back
3253		4164
3254	=back	4165	=back
3255		4166
3256	Example: Define a class with an IO and idle watcher, start one of them in	4167	Example: Define a class with two I/O and idle watchers, start the I/O
3257	the constructor.	4168	watchers in the constructor.
3258		4169
3259	class myclass	4170	class myclass
3260	{	4171	{
3261	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
		4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3263		4175
3264	myclass (int fd)	4176	myclass (int fd)
3265	{	4177	{
3266	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
		4179	io2 .set <myclass, &myclass::io2_cb > (this);
3267	idle.set <myclass, &myclass::idle_cb> (this);	4180	idle.set <myclass, &myclass::idle_cb> (this);
3268		4181
3269	io.start (fd, ev::READ);	4182	io.set (fd, ev::WRITE); // configure the watcher
		4183	io.start (); // start it whenever convenient
		4184
		4185	io2.start (fd, ev::READ); // set + start in one call
3270	}	4186	}
3271	};	4187	};
3272		4188
3273		4189
3274	=head1 OTHER LANGUAGE BINDINGS	4190	=head1 OTHER LANGUAGE BINDINGS
…		…
3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3314		4230
3315	=item D	4231	=item D
3316		4232
3317	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3319		4235
3320	=item Ocaml	4236	=item Ocaml
3321		4237
3322	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4240
		4241	=item Lua
		4242
		4243	Brian Maher has written a partial interface to libev for lua (at the
		4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4245	L<http://github.com/brimworks/lua-ev>.
		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
3324		4254
3325	=back	4255	=back
3326		4256
3327		4257
3328	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
…		…
3342	loop argument"). The C<EV_A> form is used when this is the sole argument,	4272	loop argument"). The C<EV_A> form is used when this is the sole argument,
3343	C<EV_A_> is used when other arguments are following. Example:	4273	C<EV_A_> is used when other arguments are following. Example:
3344		4274
3345	ev_unref (EV_A);	4275	ev_unref (EV_A);
3346	ev_timer_add (EV_A_ watcher);	4276	ev_timer_add (EV_A_ watcher);
3347	ev_loop (EV_A_ 0);	4277	ev_run (EV_A_ 0);
3348		4278
3349	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4279	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3350	which is often provided by the following macro.	4280	which is often provided by the following macro.
3351		4281
3352	=item C<EV_P>, C<EV_P_>	4282	=item C<EV_P>, C<EV_P_>
…		…
3365	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3366		4296
3367	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3368		4298
3369	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3370	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3371		4305
3372	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3373		4307
3374	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3375	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3392	}	4326	}
3393		4327
3394	ev_check check;	4328	ev_check check;
3395	ev_check_init (&check, check_cb);	4329	ev_check_init (&check, check_cb);
3396	ev_check_start (EV_DEFAULT_ &check);	4330	ev_check_start (EV_DEFAULT_ &check);
3397	ev_loop (EV_DEFAULT_ 0);	4331	ev_run (EV_DEFAULT_ 0);
3398		4332
3399	=head1 EMBEDDING	4333	=head1 EMBEDDING
3400		4334
3401	Libev can (and often is) directly embedded into host	4335	Libev can (and often is) directly embedded into host
3402	applications. Examples of applications that embed it include the Deliantra	4336	applications. Examples of applications that embed it include the Deliantra
…		…
3482	libev.m4	4416	libev.m4
3483		4417
3484	=head2 PREPROCESSOR SYMBOLS/MACROS	4418	=head2 PREPROCESSOR SYMBOLS/MACROS
3485		4419
3486	Libev can be configured via a variety of preprocessor symbols you have to	4420	Libev can be configured via a variety of preprocessor symbols you have to
3487	define before including any of its files. The default in the absence of	4421	define before including (or compiling) any of its files. The default in
3488	autoconf is documented for every option.	4422	the absence of autoconf is documented for every option.
		4423
		4424	Symbols marked with "(h)" do not change the ABI, and can have different
		4425	values when compiling libev vs. including F<ev.h>, so it is permissible
		4426	to redefine them before including F<ev.h> without breaking compatibility
		4427	to a compiled library. All other symbols change the ABI, which means all
		4428	users of libev and the libev code itself must be compiled with compatible
		4429	settings.
3489		4430
3490	=over 4	4431	=over 4
3491		4432
		4433	=item EV_COMPAT3 (h)
		4434
		4435	Backwards compatibility is a major concern for libev. This is why this
		4436	release of libev comes with wrappers for the functions and symbols that
		4437	have been renamed between libev version 3 and 4.
		4438
		4439	You can disable these wrappers (to test compatibility with future
		4440	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4441	sources. This has the additional advantage that you can drop the C<struct>
		4442	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4443	typedef in that case.
		4444
		4445	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4446	and in some even more future version the compatibility code will be
		4447	removed completely.
		4448
3492	=item EV_STANDALONE	4449	=item EV_STANDALONE (h)
3493		4450
3494	Must always be C<1> if you do not use autoconf configuration, which	4451	Must always be C<1> if you do not use autoconf configuration, which
3495	keeps libev from including F<config.h>, and it also defines dummy	4452	keeps libev from including F<config.h>, and it also defines dummy
3496	implementations for some libevent functions (such as logging, which is not	4453	implementations for some libevent functions (such as logging, which is not
3497	supported). It will also not define any of the structs usually found in	4454	supported). It will also not define any of the structs usually found in
3498	F<event.h> that are not directly supported by the libev core alone.	4455	F<event.h> that are not directly supported by the libev core alone.
3499		4456
3500	In stanbdalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3501	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3502		4468
3503	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3504		4470
3505	If defined to be C<1>, libev will try to detect the availability of the	4471	If defined to be C<1>, libev will try to detect the availability of the
3506	monotonic clock option at both compile time and runtime. Otherwise no	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3570	be used is the winsock select). This means that it will call	4536	be used is the winsock select). This means that it will call
3571	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4537	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3572	it is assumed that all these functions actually work on fds, even	4538	it is assumed that all these functions actually work on fds, even
3573	on win32. Should not be defined on non-win32 platforms.	4539	on win32. Should not be defined on non-win32 platforms.
3574		4540
3575	=item EV_FD_TO_WIN32_HANDLE	4541	=item EV_FD_TO_WIN32_HANDLE(fd)
3576		4542
3577	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4543	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3578	file descriptors to socket handles. When not defining this symbol (the	4544	file descriptors to socket handles. When not defining this symbol (the
3579	default), then libev will call C<_get_osfhandle>, which is usually	4545	default), then libev will call C<_get_osfhandle>, which is usually
3580	correct. In some cases, programs use their own file descriptor management,	4546	correct. In some cases, programs use their own file descriptor management,
3581	in which case they can provide this function to map fds to socket handles.	4547	in which case they can provide this function to map fds to socket handles.
		4548
		4549	=item EV_WIN32_HANDLE_TO_FD(handle)
		4550
		4551	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4552	using the standard C<_open_osfhandle> function. For programs implementing
		4553	their own fd to handle mapping, overwriting this function makes it easier
		4554	to do so. This can be done by defining this macro to an appropriate value.
		4555
		4556	=item EV_WIN32_CLOSE_FD(fd)
		4557
		4558	If programs implement their own fd to handle mapping on win32, then this
		4559	macro can be used to override the C<close> function, useful to unregister
		4560	file descriptors again. Note that the replacement function has to close
		4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3582		4569
3583	=item EV_USE_POLL	4570	=item EV_USE_POLL
3584		4571
3585	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3586	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3622	If defined to be C<1>, libev will compile in support for the Linux inotify	4609	If defined to be C<1>, libev will compile in support for the Linux inotify
3623	interface to speed up C<ev_stat> watchers. Its actual availability will	4610	interface to speed up C<ev_stat> watchers. Its actual availability will
3624	be detected at runtime. If undefined, it will be enabled if the headers	4611	be detected at runtime. If undefined, it will be enabled if the headers
3625	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3626		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called
		4624	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4625	above. This reduces dependencies and makes libev faster.
		4626
3627	=item EV_ATOMIC_T	4627	=item EV_ATOMIC_T
3628		4628
3629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3630	access is atomic with respect to other threads or signal contexts. No such	4630	access is atomic and serialised with respect to other threads or signal
3631	type is easily found in the C language, so you can provide your own type	4631	contexts. No such type is easily found in the C language, so you can
3632	that you know is safe for your purposes. It is used both for signal handler "locking"	4632	provide your own type that you know is safe for your purposes. It is used
3633	as well as for signal and thread safety in C<ev_async> watchers.	4633	both for signal handler "locking" as well as for signal and thread safety
		4634	in C<ev_async> watchers.
3634		4635
3635	In the absence of this define, libev will use C<sig_atomic_t volatile>	4636	In the absence of this define, libev will use C<sig_atomic_t volatile>
3636	(from F<signal.h>), which is usually good enough on most platforms.	4637	(from F<signal.h>), which is usually good enough on most platforms,
		4638	although strictly speaking using a type that also implies a memory fence
		4639	is required.
3637		4640
3638	=item EV_H	4641	=item EV_H (h)
3639		4642
3640	The name of the F<ev.h> header file used to include it. The default if	4643	The name of the F<ev.h> header file used to include it. The default if
3641	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4644	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3642	used to virtually rename the F<ev.h> header file in case of conflicts.	4645	used to virtually rename the F<ev.h> header file in case of conflicts.
3643		4646
3644	=item EV_CONFIG_H	4647	=item EV_CONFIG_H (h)
3645		4648
3646	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4649	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3647	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4650	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3648	C<EV_H>, above.	4651	C<EV_H>, above.
3649		4652
3650	=item EV_EVENT_H	4653	=item EV_EVENT_H (h)
3651		4654
3652	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4655	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3653	of how the F<event.h> header can be found, the default is C<"event.h">.	4656	of how the F<event.h> header can be found, the default is C<"event.h">.
3654		4657
3655	=item EV_PROTOTYPES	4658	=item EV_PROTOTYPES (h)
3656		4659
3657	If defined to be C<0>, then F<ev.h> will not define any function	4660	If defined to be C<0>, then F<ev.h> will not define any function
3658	prototypes, but still define all the structs and other symbols. This is	4661	prototypes, but still define all the structs and other symbols. This is
3659	occasionally useful if you want to provide your own wrapper functions	4662	occasionally useful if you want to provide your own wrapper functions
3660	around libev functions.	4663	around libev functions.
…		…
3665	will have the C<struct ev_loop *> as first argument, and you can create	4668	will have the C<struct ev_loop *> as first argument, and you can create
3666	additional independent event loops. Otherwise there will be no support	4669	additional independent event loops. Otherwise there will be no support
3667	for multiple event loops and there is no first event loop pointer	4670	for multiple event loops and there is no first event loop pointer
3668	argument. Instead, all functions act on the single default loop.	4671	argument. Instead, all functions act on the single default loop.
3669		4672
		4673	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4674	default loop when multiplicity is switched off - you always have to
		4675	initialise the loop manually in this case.
		4676
3670	=item EV_MINPRI	4677	=item EV_MINPRI
3671		4678
3672	=item EV_MAXPRI	4679	=item EV_MAXPRI
3673		4680
3674	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4681	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3682	fine.	4689	fine.
3683		4690
3684	If your embedding application does not need any priorities, defining these	4691	If your embedding application does not need any priorities, defining these
3685	both to C<0> will save some memory and CPU.	4692	both to C<0> will save some memory and CPU.
3686		4693
3687	=item EV_PERIODIC_ENABLE	4694	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4695	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4696	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3688		4697
3689	If undefined or defined to be C<1>, then periodic timers are supported. If	4698	If undefined or defined to be C<1> (and the platform supports it), then
3690	defined to be C<0>, then they are not. Disabling them saves a few kB of	4699	the respective watcher type is supported. If defined to be C<0>, then it
3691	code.	4700	is not. Disabling watcher types mainly saves code size.
3692		4701
3693	=item EV_IDLE_ENABLE	4702	=item EV_FEATURES
3694
3695	If undefined or defined to be C<1>, then idle watchers are supported. If
3696	defined to be C<0>, then they are not. Disabling them saves a few kB of
3697	code.
3698
3699	=item EV_EMBED_ENABLE
3700
3701	If undefined or defined to be C<1>, then embed watchers are supported. If
3702	defined to be C<0>, then they are not. Embed watchers rely on most other
3703	watcher types, which therefore must not be disabled.
3704
3705	=item EV_STAT_ENABLE
3706
3707	If undefined or defined to be C<1>, then stat watchers are supported. If
3708	defined to be C<0>, then they are not.
3709
3710	=item EV_FORK_ENABLE
3711
3712	If undefined or defined to be C<1>, then fork watchers are supported. If
3713	defined to be C<0>, then they are not.
3714
3715	=item EV_ASYNC_ENABLE
3716
3717	If undefined or defined to be C<1>, then async watchers are supported. If
3718	defined to be C<0>, then they are not.
3719
3720	=item EV_MINIMAL
3721		4703
3722	If you need to shave off some kilobytes of code at the expense of some	4704	If you need to shave off some kilobytes of code at the expense of some
3723	speed (but with the full API), define this symbol to C<1>. Currently this	4705	speed (but with the full API), you can define this symbol to request
3724	is used to override some inlining decisions, saves roughly 30% code size	4706	certain subsets of functionality. The default is to enable all features
3725	on amd64. It also selects a much smaller 2-heap for timer management over	4707	that can be enabled on the platform.
3726	the default 4-heap.
3727		4708
3728	You can save even more by disabling watcher types you do not need	4709	A typical way to use this symbol is to define it to C<0> (or to a bitset
3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4710	with some broad features you want) and then selectively re-enable
3730	(C<-DNDEBUG>) will usually reduce code size a lot.	4711	additional parts you want, for example if you want everything minimal,
		4712	but multiple event loop support, async and child watchers and the poll
		4713	backend, use this:
3731		4714
3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4715	#define EV_FEATURES 0
3733	provide a bare-bones event library. See C<ev.h> for details on what parts	4716	#define EV_MULTIPLICITY 1
3734	of the API are still available, and do not complain if this subset changes	4717	#define EV_USE_POLL 1
3735	over time.	4718	#define EV_CHILD_ENABLE 1
		4719	#define EV_ASYNC_ENABLE 1
		4720
		4721	The actual value is a bitset, it can be a combination of the following
		4722	values (by default, all of these are enabled):
		4723
		4724	=over 4
		4725
		4726	=item C<1> - faster/larger code
		4727
		4728	Use larger code to speed up some operations.
		4729
		4730	Currently this is used to override some inlining decisions (enlarging the
		4731	code size by roughly 30% on amd64).
		4732
		4733	When optimising for size, use of compiler flags such as C<-Os> with
		4734	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4735	assertions.
		4736
		4737	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4738	(e.g. gcc with C<-Os>).
		4739
		4740	=item C<2> - faster/larger data structures
		4741
		4742	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4743	hash table sizes and so on. This will usually further increase code size
		4744	and can additionally have an effect on the size of data structures at
		4745	runtime.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
		4749
		4750	=item C<4> - full API configuration
		4751
		4752	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4753	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4754
		4755	=item C<8> - full API
		4756
		4757	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4758	details on which parts of the API are still available without this
		4759	feature, and do not complain if this subset changes over time.
		4760
		4761	=item C<16> - enable all optional watcher types
		4762
		4763	Enables all optional watcher types. If you want to selectively enable
		4764	only some watcher types other than I/O and timers (e.g. prepare,
		4765	embed, async, child...) you can enable them manually by defining
		4766	C<EV_watchertype_ENABLE> to C<1> instead.
		4767
		4768	=item C<32> - enable all backends
		4769
		4770	This enables all backends - without this feature, you need to enable at
		4771	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4772
		4773	=item C<64> - enable OS-specific "helper" APIs
		4774
		4775	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4776	default.
		4777
		4778	=back
		4779
		4780	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4781	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4782	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4783	watchers, timers and monotonic clock support.
		4784
		4785	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4786	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4787	your program might be left out as well - a binary starting a timer and an
		4788	I/O watcher then might come out at only 5Kb.
		4789
		4790	=item EV_API_STATIC
		4791
		4792	If this symbol is defined (by default it is not), then all identifiers
		4793	will have static linkage. This means that libev will not export any
		4794	identifiers, and you cannot link against libev anymore. This can be useful
		4795	when you embed libev, only want to use libev functions in a single file,
		4796	and do not want its identifiers to be visible.
		4797
		4798	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4799	wants to use libev.
		4800
		4801	This option only works when libev is compiled with a C compiler, as C++
		4802	doesn't support the required declaration syntax.
		4803
		4804	=item EV_AVOID_STDIO
		4805
		4806	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4807	functions (printf, scanf, perror etc.). This will increase the code size
		4808	somewhat, but if your program doesn't otherwise depend on stdio and your
		4809	libc allows it, this avoids linking in the stdio library which is quite
		4810	big.
		4811
		4812	Note that error messages might become less precise when this option is
		4813	enabled.
		4814
		4815	=item EV_NSIG
		4816
		4817	The highest supported signal number, +1 (or, the number of
		4818	signals): Normally, libev tries to deduce the maximum number of signals
		4819	automatically, but sometimes this fails, in which case it can be
		4820	specified. Also, using a lower number than detected (C<32> should be
		4821	good for about any system in existence) can save some memory, as libev
		4822	statically allocates some 12-24 bytes per signal number.
3736		4823
3737	=item EV_PID_HASHSIZE	4824	=item EV_PID_HASHSIZE
3738		4825
3739	C<ev_child> watchers use a small hash table to distribute workload by	4826	C<ev_child> watchers use a small hash table to distribute workload by
3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4827	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3741	than enough. If you need to manage thousands of children you might want to	4828	usually more than enough. If you need to manage thousands of children you
3742	increase this value (I<must> be a power of two).	4829	might want to increase this value (I<must> be a power of two).
3743		4830
3744	=item EV_INOTIFY_HASHSIZE	4831	=item EV_INOTIFY_HASHSIZE
3745		4832
3746	C<ev_stat> watchers use a small hash table to distribute workload by	4833	C<ev_stat> watchers use a small hash table to distribute workload by
3747	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4834	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3748	usually more than enough. If you need to manage thousands of C<ev_stat>	4835	disabled), usually more than enough. If you need to manage thousands of
3749	watchers you might want to increase this value (I<must> be a power of	4836	C<ev_stat> watchers you might want to increase this value (I<must> be a
3750	two).	4837	power of two).
3751		4838
3752	=item EV_USE_4HEAP	4839	=item EV_USE_4HEAP
3753		4840
3754	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4841	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3755	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4842	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4843	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3757	faster performance with many (thousands) of watchers.	4844	faster performance with many (thousands) of watchers.
3758		4845
3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4846	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3760	(disabled).	4847	will be C<0>.
3761		4848
3762	=item EV_HEAP_CACHE_AT	4849	=item EV_HEAP_CACHE_AT
3763		4850
3764	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4851	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3765	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4852	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3766	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4853	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3767	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4854	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3768	but avoids random read accesses on heap changes. This improves performance	4855	but avoids random read accesses on heap changes. This improves performance
3769	noticeably with many (hundreds) of watchers.	4856	noticeably with many (hundreds) of watchers.
3770		4857
3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4858	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3772	(disabled).	4859	will be C<0>.
3773		4860
3774	=item EV_VERIFY	4861	=item EV_VERIFY
3775		4862
3776	Controls how much internal verification (see C<ev_loop_verify ()>) will	4863	Controls how much internal verification (see C<ev_verify ()>) will
3777	be done: If set to C<0>, no internal verification code will be compiled	4864	be done: If set to C<0>, no internal verification code will be compiled
3778	in. If set to C<1>, then verification code will be compiled in, but not	4865	in. If set to C<1>, then verification code will be compiled in, but not
3779	called. If set to C<2>, then the internal verification code will be	4866	called. If set to C<2>, then the internal verification code will be
3780	called once per loop, which can slow down libev. If set to C<3>, then the	4867	called once per loop, which can slow down libev. If set to C<3>, then the
3781	verification code will be called very frequently, which will slow down	4868	verification code will be called very frequently, which will slow down
3782	libev considerably.	4869	libev considerably.
3783		4870
3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4871	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3785	C<0>.	4872	will be C<0>.
3786		4873
3787	=item EV_COMMON	4874	=item EV_COMMON
3788		4875
3789	By default, all watchers have a C<void *data> member. By redefining	4876	By default, all watchers have a C<void *data> member. By redefining
3790	this macro to a something else you can include more and other types of	4877	this macro to something else you can include more and other types of
3791	members. You have to define it each time you include one of the files,	4878	members. You have to define it each time you include one of the files,
3792	though, and it must be identical each time.	4879	though, and it must be identical each time.
3793		4880
3794	For example, the perl EV module uses something like this:	4881	For example, the perl EV module uses something like this:
3795		4882
…		…
3848	file.	4935	file.
3849		4936
3850	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4937	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3851	that everybody includes and which overrides some configure choices:	4938	that everybody includes and which overrides some configure choices:
3852		4939
3853	#define EV_MINIMAL 1	4940	#define EV_FEATURES 8
3854	#define EV_USE_POLL 0	4941	#define EV_USE_SELECT 1
3855	#define EV_MULTIPLICITY 0
3856	#define EV_PERIODIC_ENABLE 0	4942	#define EV_PREPARE_ENABLE 1
		4943	#define EV_IDLE_ENABLE 1
3857	#define EV_STAT_ENABLE 0	4944	#define EV_SIGNAL_ENABLE 1
3858	#define EV_FORK_ENABLE 0	4945	#define EV_CHILD_ENABLE 1
		4946	#define EV_USE_STDEXCEPT 0
3859	#define EV_CONFIG_H <config.h>	4947	#define EV_CONFIG_H <config.h>
3860	#define EV_MINPRI 0
3861	#define EV_MAXPRI 0
3862		4948
3863	#include "ev++.h"	4949	#include "ev++.h"
3864		4950
3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4951	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3866		4952
3867	#include "ev_cpp.h"	4953	#include "ev_cpp.h"
3868	#include "ev.c"	4954	#include "ev.c"
3869		4955
3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4956	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3871		4957
3872	=head2 THREADS AND COROUTINES	4958	=head2 THREADS AND COROUTINES
3873		4959
3874	=head3 THREADS	4960	=head3 THREADS
3875		4961
…		…
3926	default loop and triggering an C<ev_async> watcher from the default loop	5012	default loop and triggering an C<ev_async> watcher from the default loop
3927	watcher callback into the event loop interested in the signal.	5013	watcher callback into the event loop interested in the signal.
3928		5014
3929	=back	5015	=back
3930		5016
3931	=head4 THREAD LOCKING EXAMPLE	5017	See also L</THREAD LOCKING EXAMPLE>.
3932		5018
3933	=head3 COROUTINES	5019	=head3 COROUTINES
3934		5020
3935	Libev is very accommodating to coroutines ("cooperative threads"):	5021	Libev is very accommodating to coroutines ("cooperative threads"):
3936	libev fully supports nesting calls to its functions from different	5022	libev fully supports nesting calls to its functions from different
3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5023	coroutines (e.g. you can call C<ev_run> on the same loop from two
3938	different coroutines, and switch freely between both coroutines running the	5024	different coroutines, and switch freely between both coroutines running
3939	loop, as long as you don't confuse yourself). The only exception is that	5025	the loop, as long as you don't confuse yourself). The only exception is
3940	you must not do this from C<ev_periodic> reschedule callbacks.	5026	that you must not do this from C<ev_periodic> reschedule callbacks.
3941		5027
3942	Care has been taken to ensure that libev does not keep local state inside	5028	Care has been taken to ensure that libev does not keep local state inside
3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5029	C<ev_run>, and other calls do not usually allow for coroutine switches as
3944	they do not call any callbacks.	5030	they do not call any callbacks.
3945		5031
3946	=head2 COMPILER WARNINGS	5032	=head2 COMPILER WARNINGS
3947		5033
3948	Depending on your compiler and compiler settings, you might get no or a	5034	Depending on your compiler and compiler settings, you might get no or a
…		…
3959	maintainable.	5045	maintainable.
3960		5046
3961	And of course, some compiler warnings are just plain stupid, or simply	5047	And of course, some compiler warnings are just plain stupid, or simply
3962	wrong (because they don't actually warn about the condition their message	5048	wrong (because they don't actually warn about the condition their message
3963	seems to warn about). For example, certain older gcc versions had some	5049	seems to warn about). For example, certain older gcc versions had some
3964	warnings that resulted an extreme number of false positives. These have	5050	warnings that resulted in an extreme number of false positives. These have
3965	been fixed, but some people still insist on making code warn-free with	5051	been fixed, but some people still insist on making code warn-free with
3966	such buggy versions.	5052	such buggy versions.
3967		5053
3968	While libev is written to generate as few warnings as possible,	5054	While libev is written to generate as few warnings as possible,
3969	"warn-free" code is not a goal, and it is recommended not to build libev	5055	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4005	I suggest using suppression lists.	5091	I suggest using suppression lists.
4006		5092
4007		5093
4008	=head1 PORTABILITY NOTES	5094	=head1 PORTABILITY NOTES
4009		5095
		5096	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5097
		5098	GNU/Linux is the only common platform that supports 64 bit file/large file
		5099	interfaces but I<disables> them by default.
		5100
		5101	That means that libev compiled in the default environment doesn't support
		5102	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5103
		5104	Unfortunately, many programs try to work around this GNU/Linux issue
		5105	by enabling the large file API, which makes them incompatible with the
		5106	standard libev compiled for their system.
		5107
		5108	Likewise, libev cannot enable the large file API itself as this would
		5109	suddenly make it incompatible to the default compile time environment,
		5110	i.e. all programs not using special compile switches.
		5111
		5112	=head2 OS/X AND DARWIN BUGS
		5113
		5114	The whole thing is a bug if you ask me - basically any system interface
		5115	you touch is broken, whether it is locales, poll, kqueue or even the
		5116	OpenGL drivers.
		5117
		5118	=head3 C<kqueue> is buggy
		5119
		5120	The kqueue syscall is broken in all known versions - most versions support
		5121	only sockets, many support pipes.
		5122
		5123	Libev tries to work around this by not using C<kqueue> by default on this
		5124	rotten platform, but of course you can still ask for it when creating a
		5125	loop - embedding a socket-only kqueue loop into a select-based one is
		5126	probably going to work well.
		5127
		5128	=head3 C<poll> is buggy
		5129
		5130	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5131	implementation by something calling C<kqueue> internally around the 10.5.6
		5132	release, so now C<kqueue> I<and> C<poll> are broken.
		5133
		5134	Libev tries to work around this by not using C<poll> by default on
		5135	this rotten platform, but of course you can still ask for it when creating
		5136	a loop.
		5137
		5138	=head3 C<select> is buggy
		5139
		5140	All that's left is C<select>, and of course Apple found a way to fuck this
		5141	one up as well: On OS/X, C<select> actively limits the number of file
		5142	descriptors you can pass in to 1024 - your program suddenly crashes when
		5143	you use more.
		5144
		5145	There is an undocumented "workaround" for this - defining
		5146	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5147	work on OS/X.
		5148
		5149	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5150
		5151	=head3 C<errno> reentrancy
		5152
		5153	The default compile environment on Solaris is unfortunately so
		5154	thread-unsafe that you can't even use components/libraries compiled
		5155	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5156	defined by default. A valid, if stupid, implementation choice.
		5157
		5158	If you want to use libev in threaded environments you have to make sure
		5159	it's compiled with C<_REENTRANT> defined.
		5160
		5161	=head3 Event port backend
		5162
		5163	The scalable event interface for Solaris is called "event
		5164	ports". Unfortunately, this mechanism is very buggy in all major
		5165	releases. If you run into high CPU usage, your program freezes or you get
		5166	a large number of spurious wakeups, make sure you have all the relevant
		5167	and latest kernel patches applied. No, I don't know which ones, but there
		5168	are multiple ones to apply, and afterwards, event ports actually work
		5169	great.
		5170
		5171	If you can't get it to work, you can try running the program by setting
		5172	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5173	C<select> backends.
		5174
		5175	=head2 AIX POLL BUG
		5176
		5177	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5178	this by trying to avoid the poll backend altogether (i.e. it's not even
		5179	compiled in), which normally isn't a big problem as C<select> works fine
		5180	with large bitsets on AIX, and AIX is dead anyway.
		5181
4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5182	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5183
		5184	=head3 General issues
4011		5185
4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5186	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4013	requires, and its I/O model is fundamentally incompatible with the POSIX	5187	requires, and its I/O model is fundamentally incompatible with the POSIX
4014	model. Libev still offers limited functionality on this platform in	5188	model. Libev still offers limited functionality on this platform in
4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5189	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4016	descriptors. This only applies when using Win32 natively, not when using	5190	descriptors. This only applies when using Win32 natively, not when using
4017	e.g. cygwin.	5191	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5192	as every compiler comes with a slightly differently broken/incompatible
		5193	environment.
4018		5194
4019	Lifting these limitations would basically require the full	5195	Lifting these limitations would basically require the full
4020	re-implementation of the I/O system. If you are into these kinds of	5196	re-implementation of the I/O system. If you are into this kind of thing,
4021	things, then note that glib does exactly that for you in a very portable	5197	then note that glib does exactly that for you in a very portable way (note
4022	way (note also that glib is the slowest event library known to man).	5198	also that glib is the slowest event library known to man).
4023		5199
4024	There is no supported compilation method available on windows except	5200	There is no supported compilation method available on windows except
4025	embedding it into other applications.	5201	embedding it into other applications.
4026		5202
4027	Sensible signal handling is officially unsupported by Microsoft - libev	5203	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4055	you do I<not> compile the F<ev.c> or any other embedded source files!):	5231	you do I<not> compile the F<ev.c> or any other embedded source files!):
4056		5232
4057	#include "evwrap.h"	5233	#include "evwrap.h"
4058	#include "ev.c"	5234	#include "ev.c"
4059		5235
4060	=over 4
4061
4062	=item The winsocket select function	5236	=head3 The winsocket C<select> function
4063		5237
4064	The winsocket C<select> function doesn't follow POSIX in that it	5238	The winsocket C<select> function doesn't follow POSIX in that it
4065	requires socket I<handles> and not socket I<file descriptors> (it is	5239	requires socket I<handles> and not socket I<file descriptors> (it is
4066	also extremely buggy). This makes select very inefficient, and also	5240	also extremely buggy). This makes select very inefficient, and also
4067	requires a mapping from file descriptors to socket handles (the Microsoft	5241	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4076	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5250	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4077		5251
4078	Note that winsockets handling of fd sets is O(n), so you can easily get a	5252	Note that winsockets handling of fd sets is O(n), so you can easily get a
4079	complexity in the O(n²) range when using win32.	5253	complexity in the O(n²) range when using win32.
4080		5254
4081	=item Limited number of file descriptors	5255	=head3 Limited number of file descriptors
4082		5256
4083	Windows has numerous arbitrary (and low) limits on things.	5257	Windows has numerous arbitrary (and low) limits on things.
4084		5258
4085	Early versions of winsocket's select only supported waiting for a maximum	5259	Early versions of winsocket's select only supported waiting for a maximum
4086	of C<64> handles (probably owning to the fact that all windows kernels	5260	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4101	runtime libraries. This might get you to about C<512> or C<2048> sockets	5275	runtime libraries. This might get you to about C<512> or C<2048> sockets
4102	(depending on windows version and/or the phase of the moon). To get more,	5276	(depending on windows version and/or the phase of the moon). To get more,
4103	you need to wrap all I/O functions and provide your own fd management, but	5277	you need to wrap all I/O functions and provide your own fd management, but
4104	the cost of calling select (O(n²)) will likely make this unworkable.	5278	the cost of calling select (O(n²)) will likely make this unworkable.
4105		5279
4106	=back
4107
4108	=head2 PORTABILITY REQUIREMENTS	5280	=head2 PORTABILITY REQUIREMENTS
4109		5281
4110	In addition to a working ISO-C implementation and of course the	5282	In addition to a working ISO-C implementation and of course the
4111	backend-specific APIs, libev relies on a few additional extensions:	5283	backend-specific APIs, libev relies on a few additional extensions:
4112		5284
…		…
4118	Libev assumes not only that all watcher pointers have the same internal	5290	Libev assumes not only that all watcher pointers have the same internal
4119	structure (guaranteed by POSIX but not by ISO C for example), but it also	5291	structure (guaranteed by POSIX but not by ISO C for example), but it also
4120	assumes that the same (machine) code can be used to call any watcher	5292	assumes that the same (machine) code can be used to call any watcher
4121	callback: The watcher callbacks have different type signatures, but libev	5293	callback: The watcher callbacks have different type signatures, but libev
4122	calls them using an C<ev_watcher *> internally.	5294	calls them using an C<ev_watcher *> internally.
		5295
		5296	=item pointer accesses must be thread-atomic
		5297
		5298	Accessing a pointer value must be atomic, it must both be readable and
		5299	writable in one piece - this is the case on all current architectures.
4123		5300
4124	=item C<sig_atomic_t volatile> must be thread-atomic as well	5301	=item C<sig_atomic_t volatile> must be thread-atomic as well
4125		5302
4126	The type C<sig_atomic_t volatile> (or whatever is defined as	5303	The type C<sig_atomic_t volatile> (or whatever is defined as
4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5304	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4150	watchers.	5327	watchers.
4151		5328
4152	=item C<double> must hold a time value in seconds with enough accuracy	5329	=item C<double> must hold a time value in seconds with enough accuracy
4153		5330
4154	The type C<double> is used to represent timestamps. It is required to	5331	The type C<double> is used to represent timestamps. It is required to
4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5332	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4156	enough for at least into the year 4000. This requirement is fulfilled by	5333	good enough for at least into the year 4000 with millisecond accuracy
		5334	(the design goal for libev). This requirement is overfulfilled by
4157	implementations implementing IEEE 754, which is basically all existing	5335	implementations using IEEE 754, which is basically all existing ones.
		5336
4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5337	With IEEE 754 doubles, you get microsecond accuracy until at least the
4159	2200.	5338	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5339	is either obsolete or somebody patched it to use C<long double> or
		5340	something like that, just kidding).
4160		5341
4161	=back	5342	=back
4162		5343
4163	If you know of other additional requirements drop me a note.	5344	If you know of other additional requirements drop me a note.
4164		5345
…		…
4226	=item Processing ev_async_send: O(number_of_async_watchers)	5407	=item Processing ev_async_send: O(number_of_async_watchers)
4227		5408
4228	=item Processing signals: O(max_signal_number)	5409	=item Processing signals: O(max_signal_number)
4229		5410
4230	Sending involves a system call I<iff> there were no other C<ev_async_send>	5411	Sending involves a system call I<iff> there were no other C<ev_async_send>
4231	calls in the current loop iteration. Checking for async and signal events	5412	calls in the current loop iteration and the loop is currently
		5413	blocked. Checking for async and signal events involves iterating over all
4232	involves iterating over all running async watchers or all signal numbers.	5414	running async watchers or all signal numbers.
4233		5415
4234	=back	5416	=back
4235		5417
4236		5418
		5419	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5420
		5421	The major version 4 introduced some incompatible changes to the API.
		5422
		5423	At the moment, the C<ev.h> header file provides compatibility definitions
		5424	for all changes, so most programs should still compile. The compatibility
		5425	layer might be removed in later versions of libev, so better update to the
		5426	new API early than late.
		5427
		5428	=over 4
		5429
		5430	=item C<EV_COMPAT3> backwards compatibility mechanism
		5431
		5432	The backward compatibility mechanism can be controlled by
		5433	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5434	section.
		5435
		5436	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5437
		5438	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5439
		5440	ev_loop_destroy (EV_DEFAULT_UC);
		5441	ev_loop_fork (EV_DEFAULT);
		5442
		5443	=item function/symbol renames
		5444
		5445	A number of functions and symbols have been renamed:
		5446
		5447	ev_loop => ev_run
		5448	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5449	EVLOOP_ONESHOT => EVRUN_ONCE
		5450
		5451	ev_unloop => ev_break
		5452	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5453	EVUNLOOP_ONE => EVBREAK_ONE
		5454	EVUNLOOP_ALL => EVBREAK_ALL
		5455
		5456	EV_TIMEOUT => EV_TIMER
		5457
		5458	ev_loop_count => ev_iteration
		5459	ev_loop_depth => ev_depth
		5460	ev_loop_verify => ev_verify
		5461
		5462	Most functions working on C<struct ev_loop> objects don't have an
		5463	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5464	associated constants have been renamed to not collide with the C<struct
		5465	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5466	as all other watcher types. Note that C<ev_loop_fork> is still called
		5467	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5468	typedef.
		5469
		5470	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5471
		5472	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5473	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5474	and work, but the library code will of course be larger.
		5475
		5476	=back
		5477
		5478
4237	=head1 GLOSSARY	5479	=head1 GLOSSARY
4238		5480
4239	=over 4	5481	=over 4
4240		5482
4241	=item active	5483	=item active
4242		5484
4243	A watcher is active as long as it has been started (has been attached to	5485	A watcher is active as long as it has been started and not yet stopped.
4244	an event loop) but not yet stopped (disassociated from the event loop).	5486	See L</WATCHER STATES> for details.
4245		5487
4246	=item application	5488	=item application
4247		5489
4248	In this document, an application is whatever is using libev.	5490	In this document, an application is whatever is using libev.
		5491
		5492	=item backend
		5493
		5494	The part of the code dealing with the operating system interfaces.
4249		5495
4250	=item callback	5496	=item callback
4251		5497
4252	The address of a function that is called when some event has been	5498	The address of a function that is called when some event has been
4253	detected. Callbacks are being passed the event loop, the watcher that	5499	detected. Callbacks are being passed the event loop, the watcher that
4254	received the event, and the actual event bitset.	5500	received the event, and the actual event bitset.
4255		5501
4256	=item callback invocation	5502	=item callback/watcher invocation
4257		5503
4258	The act of calling the callback associated with a watcher.	5504	The act of calling the callback associated with a watcher.
4259		5505
4260	=item event	5506	=item event
4261		5507
4262	A change of state of some external event, such as data now being available	5508	A change of state of some external event, such as data now being available
4263	for reading on a file descriptor, time having passed or simply not having	5509	for reading on a file descriptor, time having passed or simply not having
4264	any other events happening anymore.	5510	any other events happening anymore.
4265		5511
4266	In libev, events are represented as single bits (such as C<EV_READ> or	5512	In libev, events are represented as single bits (such as C<EV_READ> or
4267	C<EV_TIMEOUT>).	5513	C<EV_TIMER>).
4268		5514
4269	=item event library	5515	=item event library
4270		5516
4271	A software package implementing an event model and loop.	5517	A software package implementing an event model and loop.
4272		5518
…		…
4280	The model used to describe how an event loop handles and processes	5526	The model used to describe how an event loop handles and processes
4281	watchers and events.	5527	watchers and events.
4282		5528
4283	=item pending	5529	=item pending
4284		5530
4285	A watcher is pending as soon as the corresponding event has been detected,	5531	A watcher is pending as soon as the corresponding event has been
4286	and stops being pending as soon as the watcher will be invoked or its	5532	detected. See L</WATCHER STATES> for details.
4287	pending status is explicitly cleared by the application.
4288
4289	A watcher can be pending, but not active. Stopping a watcher also clears
4290	its pending status.
4291		5533
4292	=item real time	5534	=item real time
4293		5535
4294	The physical time that is observed. It is apparently strictly monotonic :)	5536	The physical time that is observed. It is apparently strictly monotonic :)
4295		5537
4296	=item wall-clock time	5538	=item wall-clock time
4297		5539
4298	The time and date as shown on clocks. Unlike real time, it can actually	5540	The time and date as shown on clocks. Unlike real time, it can actually
4299	be wrong and jump forwards and backwards, e.g. when the you adjust your	5541	be wrong and jump forwards and backwards, e.g. when you adjust your
4300	clock.	5542	clock.
4301		5543
4302	=item watcher	5544	=item watcher
4303		5545
4304	A data structure that describes interest in certain events. Watchers need	5546	A data structure that describes interest in certain events. Watchers need
4305	to be started (attached to an event loop) before they can receive events.	5547	to be started (attached to an event loop) before they can receive events.
4306		5548
4307	=item watcher invocation
4308
4309	The act of calling the callback associated with a watcher.
4310
4311	=back	5549	=back
4312		5550
4313	=head1 AUTHOR	5551	=head1 AUTHOR
4314		5552
4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5553	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5554	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4316		5555

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