ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.238 by root, Sat Apr 18 12:10:41 2009 UTC vs.
Revision 1.395 by root, Tue Jan 24 16:38:55 2012 UTC

…		…
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))
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))
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
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		597
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
495		600
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	604	might perform better.
504		605
505	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
509		620
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
512		623
513	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
514		625
515	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		629
519	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		639
521	=back	640	=back
522		641
523	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
526		645	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		646
555	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
556		648
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	650	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
560		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
561	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
562		659
563	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		667
571	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
574		671
575	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
579		680
580	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
581		682
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
588	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
589	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
590	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
591	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
593		693
594	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
597		700
598	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
602	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		715
611	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
612		717
613	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	719	otherwise.
615		720
616	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
617		722
618	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
621		726
622	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
625		745
626	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
627		747
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	749	use.
…		…
638		758
639	=item ev_now_update (loop)	759	=item ev_now_update (loop)
640		760
641	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
642	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
643	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
644		764
645	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
646	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
647	the current time is a good idea.	767	the current time is a good idea.
648		768
…		…
650		770
651	=item ev_suspend (loop)	771	=item ev_suspend (loop)
652		772
653	=item ev_resume (loop)	773	=item ev_resume (loop)
654		774
655	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
656	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
657		777
658	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
659	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
660	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
661	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
663	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
664		784
665	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
667	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
668	occured while suspended).	788	occurred while suspended).
669		789
670	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
672	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
673		793
674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
675	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
676		796
677	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
678		798
679	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
681	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
682		804
683	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
684	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
685		808
686	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
687	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
688	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
689	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
690	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
691	beauty.	814	beauty.
692		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
694	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
695	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
696	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
697		826
698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
699	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
700	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
701	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
702	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
703	iteration of the loop.	832	iteration of the loop.
704		833
705	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
706	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
708	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
709		838
710	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
711		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
712	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
713	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
714	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
715	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
716	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
717	as to not disturb the other process.	852	as to not disturb the other process.
718	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
719	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
720	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
721	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
722	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
723	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
724	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
725	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
727	- Queue all expired timers.	863	- Queue all expired timers.
728	- Queue all expired periodics.	864	- Queue all expired periodics.
729	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
730	- Queue all check watchers.	866	- Queue all check watchers.
731	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
732	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
733	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
735	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
736	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
737		877
738	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
739	anymore.	879	anymore.
740		880
741	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
742	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
743	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
744	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
745		885
746	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
747		887
748	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
749	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
752		892
753	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
754		894
755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
756		897
757	=item ev_ref (loop)	898	=item ev_ref (loop)
758		899
759	=item ev_unref (loop)	900	=item ev_unref (loop)
760		901
761	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
762	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
763	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
764		905
765	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
766	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
767	stopping it.	909	before stopping it.
768		910
769	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
770	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
771	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
772	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
773	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
774	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
775	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
776	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
777	in the callback).	919	in the callback).
778		920
779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
780	running when nothing else is active.	922	running when nothing else is active.
781		923
782	ev_signal exitsig;	924	ev_signal exitsig;
783	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
784	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
785	evf_unref (loop);	927	ev_unref (loop);
786		928
787	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
788		930
789	ev_ref (loop);	931	ev_ref (loop);
790	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
810	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
811		953
812	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
813	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
814	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
815	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
816	introduce an additional C<ev_sleep ()> call into most loop iterations.	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		959	sleep time ensures that libev will not poll for I/O events more often then
		960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
817		962
818	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
819	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
820	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
821	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
823		968
824	Many (busy) programs can usually benefit by setting the I/O collect	969	Many (busy) programs can usually benefit by setting the I/O collect
825	interval to a value near C<0.1> or so, which is often enough for	970	interval to a value near C<0.1> or so, which is often enough for
826	interactive servers (of course not for games), likewise for timeouts. It	971	interactive servers (of course not for games), likewise for timeouts. It
827	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
828	as this approaches the timing granularity of most systems.	973	as this approaches the timing granularity of most systems. Note that if
		974	you do transactions with the outside world and you can't increase the
		975	parallelity, then this setting will limit your transaction rate (if you
		976	need to poll once per transaction and the I/O collect interval is 0.01,
		977	then you can't do more than 100 transactions per second).
829		978
830	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
831	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
832	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
833	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	983	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
835	they fire on, say, one-second boundaries only.	984	they fire on, say, one-second boundaries only.
836		985
		986	Example: we only need 0.1s timeout granularity, and we wish not to poll
		987	more often than 100 times per second:
		988
		989	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		991
		992	=item ev_invoke_pending (loop)
		993
		994	This call will simply invoke all pending watchers while resetting their
		995	pending state. Normally, C<ev_run> does this automatically when required,
		996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1001
		1002	=item int ev_pending_count (loop)
		1003
		1004	Returns the number of pending watchers - zero indicates that no watchers
		1005	are pending.
		1006
		1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1008
		1009	This overrides the invoke pending functionality of the loop: Instead of
		1010	invoking all pending watchers when there are any, C<ev_run> will call
		1011	this callback instead. This is useful, for example, when you want to
		1012	invoke the actual watchers inside another context (another thread etc.).
		1013
		1014	If you want to reset the callback, use C<ev_invoke_pending> as new
		1015	callback.
		1016
		1017	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1018
		1019	Sometimes you want to share the same loop between multiple threads. This
		1020	can be done relatively simply by putting mutex_lock/unlock calls around
		1021	each call to a libev function.
		1022
		1023	However, C<ev_run> can run an indefinite time, so it is not feasible
		1024	to wait for it to return. One way around this is to wake up the event
		1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1026	I<release> and I<acquire> callbacks on the loop.
		1027
		1028	When set, then C<release> will be called just before the thread is
		1029	suspended waiting for new events, and C<acquire> is called just
		1030	afterwards.
		1031
		1032	Ideally, C<release> will just call your mutex_unlock function, and
		1033	C<acquire> will just call the mutex_lock function again.
		1034
		1035	While event loop modifications are allowed between invocations of
		1036	C<release> and C<acquire> (that's their only purpose after all), no
		1037	modifications done will affect the event loop, i.e. adding watchers will
		1038	have no effect on the set of file descriptors being watched, or the time
		1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1040	to take note of any changes you made.
		1041
		1042	In theory, threads executing C<ev_run> will be async-cancel safe between
		1043	invocations of C<release> and C<acquire>.
		1044
		1045	See also the locking example in the C<THREADS> section later in this
		1046	document.
		1047
		1048	=item ev_set_userdata (loop, void *data)
		1049
		1050	=item void *ev_userdata (loop)
		1051
		1052	Set and retrieve a single C<void *> associated with a loop. When
		1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1054	C<0>.
		1055
		1056	These two functions can be used to associate arbitrary data with a loop,
		1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1058	C<acquire> callbacks described above, but of course can be (ab-)used for
		1059	any other purpose as well.
		1060
837	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
838		1062
839	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
840	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
841	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
842	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
853		1077
854	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
856	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
857		1081
858	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
859	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
860	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
861		1086
862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
863	{	1088	{
864	ev_io_stop (w);	1089	ev_io_stop (w);
865	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
866	}	1091	}
867		1092
868	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
869		1094
870	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
871		1096
872	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
874	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
875		1100
876	ev_loop (loop, 0);	1101	ev_run (loop, 0);
877		1102
878	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
879	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
880	stack).	1105	stack).
881		1106
882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
884		1109
885	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
886	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
887	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
888	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
889	is readable and/or writable).	1114	and/or writable).
890		1115
891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
892	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
893	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
894	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
917	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
918		1143
919	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
920	writable.	1145	writable.
921		1146
922	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
923		1148
924	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
925		1150
926	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
927		1152
…		…
945		1170
946	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
947		1172
948	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
949		1174
950	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
951	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
952	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
953	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
954	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
955	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
956	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
957		1182
958	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
959		1184
960	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
961		1186
962	=item C<EV_FORK>	1187	=item C<EV_FORK>
963		1188
964	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
965	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
966		1195
967	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
968		1197
969	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
970		1199
…		…
1017		1246
1018	ev_io w;	1247	ev_io w;
1019	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1020	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1021		1250
1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1023		1252
1024	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
1025	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
1026	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
1027	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
1040		1269
1041	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
1042		1271
1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1044		1273
1045	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1046		1275
1047	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1048	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1049		1278
1050	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
1051	whole section.	1280	whole section.
1052		1281
1053	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1054		1283
1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1056		1285
1057	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
1058	the watcher was active or not).	1287	the watcher was active or not).
1059		1288
1060	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1085	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1086		1315
1087	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1088	(modulo threads).	1317	(modulo threads).
1089		1318
1090	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1091		1320
1092	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1093		1322
1094	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1127	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1128		1357
1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1130	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1131		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
1132	=back	1375	=back
1133		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1134		1379
1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1136		1381
1137	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1138	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1139	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1140	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1141	member, you can also "subclass" the watcher type and provide your own
1142	data:
1143		1386
1144	struct my_io	1387	=over 4
1145	{
1146	ev_io io;
1147	int otherfd;
1148	void *somedata;
1149	struct whatever *mostinteresting;
1150	};
1151		1388
1152	...	1389	=item initialiased
1153	struct my_io w;
1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
1155		1390
1156	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1157	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1158		1394
1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1160	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1161	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1162	...	1398	C<ev_TYPE_init> again.
1163	}
1164		1399
1165	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1166	instead have been omitted.
1167		1401
1168	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1169	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1170		1407
1171	struct my_biggy	1408	=item pending
1172	{
1173	int some_data;
1174	ev_timer t1;
1175	ev_timer t2;
1176	}
1177		1409
1178	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1179	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1180	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1181	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1182	programmers):	1414	callback.
1183		1415
1184	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1185		1422
1186	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1187	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1188	{	1425	active.
1189	struct my_biggy big = (struct my_biggy *
1190	(((char *)w) - offsetof (struct my_biggy, t1));
1191	}
1192		1426
1193	static void	1427	=item stopped
1194	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1195	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1196	struct my_biggy big = (struct my_biggy *	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1197	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1198	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1199		1441
1200	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1201		1443
1202	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1203	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1246		1488
1247	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1248	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1249	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1250	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1251	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1252	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1253	workable.	1495	workable.
1254		1496
1255	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1256	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1270	{	1512	{
1271	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1272	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1273	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1274		1516
1275	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1276	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1277	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1278	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1279	}	1521	}
1280		1522
1281	static void	1523	static void
1282	idle-cb (EV_P_ ev_idle *w, int revents)	1524	idle_cb (EV_P_ ev_idle *w, int revents)
1283	{	1525	{
1284	// actual processing	1526	// actual processing
1285	read (STDIN_FILENO, ...);	1527	read (STDIN_FILENO, ...);
1286		1528
1287	// have to start the I/O watcher again, as	1529	// have to start the I/O watcher again, as
…		…
1330	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1331	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1332	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1333	required if you know what you are doing).	1575	required if you know what you are doing).
1334		1576
1335	If you cannot use non-blocking mode, then force the use of a
1336	known-to-be-good backend (at the time of this writing, this includes only
1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1338
1339	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1340	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1341	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1342	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1343	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1344	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1345	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1346	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1347		1584
1348	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1349	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1350	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1351	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1352	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1353	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1354	indefinitely.	1591	indefinitely.
1355		1592
1356	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1357		1594
…		…
1385		1622
1386	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1387	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1388	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1389		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1390	=head3 The special problem of fork	1660	=head3 The special problem of fork
1391		1661
1392	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1393	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1394	it in the child.	1664	it in the child if you want to continue to use it in the child.
1395		1665
1396	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1397	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1398	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1399	C<EVBACKEND_POLL>.
1400		1669
1401	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1402		1671
1403	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1404	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1407		1676
1408	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1409	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1410	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1411		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1412		1719
1413	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1414		1721
1415	=over 4	1722	=over 4
1416		1723
…		…
1448	...	1755	...
1449	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1450	ev_io stdin_readable;	1757	ev_io stdin_readable;
1451	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1452	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1453	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1454		1761
1455		1762
1456	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1457		1764
1458	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1463	year, it will still time out after (roughly) one hour. "Roughly" because	1770	year, it will still time out after (roughly) one hour. "Roughly" because
1464	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1465	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1466		1773
1467	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
		1775	passed (not I<at>, so on systems with very low-resolution clocks this
		1776	might introduce a small delay, see "the special problem of being too
1468	passed. If multiple timers become ready during the same loop iteration	1777	early", below). If multiple timers become ready during the same loop
1469	then the ones with earlier time-out values are invoked before ones with	1778	iteration then the ones with earlier time-out values are invoked before
1470	later time-out values (but this is no longer true when a callback calls	1779	ones of the same priority with later time-out values (but this is no
1471	C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1472		1781
1473	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1474		1783
1475	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1476	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1520	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1829	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1521	member and C<ev_timer_again>.	1830	member and C<ev_timer_again>.
1522		1831
1523	At start:	1832	At start:
1524		1833
1525	ev_timer_init (timer, callback);	1834	ev_init (timer, callback);
1526	timer->repeat = 60.;	1835	timer->repeat = 60.;
1527	ev_timer_again (loop, timer);	1836	ev_timer_again (loop, timer);
1528		1837
1529	Each time there is some activity:	1838	Each time there is some activity:
1530		1839
…		…
1551		1860
1552	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1553	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1554	within the callback:	1863	within the callback:
1555		1864
		1865	ev_tstamp timeout = 60.;
1556	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1557		1868
1558	static void	1869	static void
1559	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1560	{	1871	{
1561	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1562	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1563		1874
1564	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1565	if (timeout < now)	1876	if (after < 0.)
1566	{	1877	{
1567	// timeout occured, take action	1878	// timeout occurred, take action
1568	}	1879	}
1569	else	1880	else
1570	{	1881	{
1571	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1572	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1573	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1574	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1575	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1576	}	1888	}
1577	}	1889	}
1578		1890
1579	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1580	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1581	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1582	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1583	re-schedule the timer to fire at that future time, to see if maybe we have
1584	a timeout then.
1585		1895
1586	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1587	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1588		1905
1589	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1590	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1591	libev to change the timeout.	1908	libev to change the timeout.
1592		1909
1593	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1594	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1595	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1596		1914
		1915	last_activity = ev_now (EV_A);
1597	ev_timer_init (timer, callback);	1916	ev_init (&timer, callback);
1598	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1599	callback (loop, timer, EV_TIMEOUT);
1600		1918
1601	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1602	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1603		1921
		1922	if (activity detected)
1604	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1605		1932
1606	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1607	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1608
1609	Changing the timeout is trivial as well (if it isn't hard-coded in the
1610	callback :) - just change the timeout and invoke the callback, which will
1611	fix things for you.
1612		1935
1613	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1614		1937
1615	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1616	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1643	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1644	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1645	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1646	overkill :)	1969	overkill :)
1647		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1648	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1649		2009
1650	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1651	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1652	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1653	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1654	lots of events in one iteration.	2014	lots of events in one iteration.
1655		2015
1656	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1657	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1663		2023
1664	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1665	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1666	()>.	2026	()>.
1667		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
		2060
		2061	=head3 The special problems of suspended animation
		2062
		2063	When you leave the server world it is quite customary to hit machines that
		2064	can suspend/hibernate - what happens to the clocks during such a suspend?
		2065
		2066	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2067	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2068	to run until the system is suspended, but they will not advance while the
		2069	system is suspended. That means, on resume, it will be as if the program
		2070	was frozen for a few seconds, but the suspend time will not be counted
		2071	towards C<ev_timer> when a monotonic clock source is used. The real time
		2072	clock advanced as expected, but if it is used as sole clocksource, then a
		2073	long suspend would be detected as a time jump by libev, and timers would
		2074	be adjusted accordingly.
		2075
		2076	I would not be surprised to see different behaviour in different between
		2077	operating systems, OS versions or even different hardware.
		2078
		2079	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2080	time jump in the monotonic clocks and the realtime clock. If the program
		2081	is suspended for a very long time, and monotonic clock sources are in use,
		2082	then you can expect C<ev_timer>s to expire as the full suspension time
		2083	will be counted towards the timers. When no monotonic clock source is in
		2084	use, then libev will again assume a timejump and adjust accordingly.
		2085
		2086	It might be beneficial for this latter case to call C<ev_suspend>
		2087	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2088	deterministic behaviour in this case (you can do nothing against
		2089	C<SIGSTOP>).
		2090
1668	=head3 Watcher-Specific Functions and Data Members	2091	=head3 Watcher-Specific Functions and Data Members
1669		2092
1670	=over 4	2093	=over 4
1671		2094
1672	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2095	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1685	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1686	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1687		2110
1688	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1689		2112
1690	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out, and restarts it again if it is
1691	repeating. The exact semantics are:	2114	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2115	timeout to the C<repeat> value and calling C<ev_timer_start>.
1692		2116
		2117	The exact semantics are as in the following rules, all of which will be
		2118	applied to the watcher:
		2119
		2120	=over 4
		2121
1693	If the timer is pending, its pending status is cleared.	2122	=item If the timer is pending, the pending status is always cleared.
1694		2123
1695	If the timer is started but non-repeating, stop it (as if it timed out).	2124	=item If the timer is started but non-repeating, stop it (as if it timed
		2125	out, without invoking it).
1696		2126
1697	If the timer is repeating, either start it if necessary (with the	2127	=item If the timer is repeating, make the C<repeat> value the new timeout
1698	C<repeat> value), or reset the running timer to the C<repeat> value.	2128	and start the timer, if necessary.
		2129
		2130	=back
1699		2131
1700	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2132	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1701	usage example.	2133	usage example.
		2134
		2135	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2136
		2137	Returns the remaining time until a timer fires. If the timer is active,
		2138	then this time is relative to the current event loop time, otherwise it's
		2139	the timeout value currently configured.
		2140
		2141	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2142	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2143	will return C<4>. When the timer expires and is restarted, it will return
		2144	roughly C<7> (likely slightly less as callback invocation takes some time,
		2145	too), and so on.
1702		2146
1703	=item ev_tstamp repeat [read-write]	2147	=item ev_tstamp repeat [read-write]
1704		2148
1705	The current C<repeat> value. Will be used each time the watcher times out	2149	The current C<repeat> value. Will be used each time the watcher times out
1706	or C<ev_timer_again> is called, and determines the next timeout (if any),	2150	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1732	}	2176	}
1733		2177
1734	ev_timer mytimer;	2178	ev_timer mytimer;
1735	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2179	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1736	ev_timer_again (&mytimer); /* start timer */	2180	ev_timer_again (&mytimer); /* start timer */
1737	ev_loop (loop, 0);	2181	ev_run (loop, 0);
1738		2182
1739	// and in some piece of code that gets executed on any "activity":	2183	// and in some piece of code that gets executed on any "activity":
1740	// reset the timeout to start ticking again at 10 seconds	2184	// reset the timeout to start ticking again at 10 seconds
1741	ev_timer_again (&mytimer);	2185	ev_timer_again (&mytimer);
1742		2186
…		…
1768		2212
1769	As with timers, the callback is guaranteed to be invoked only when the	2213	As with timers, the callback is guaranteed to be invoked only when the
1770	point in time where it is supposed to trigger has passed. If multiple	2214	point in time where it is supposed to trigger has passed. If multiple
1771	timers become ready during the same loop iteration then the ones with	2215	timers become ready during the same loop iteration then the ones with
1772	earlier time-out values are invoked before ones with later time-out values	2216	earlier time-out values are invoked before ones with later time-out values
1773	(but this is no longer true when a callback calls C<ev_loop> recursively).	2217	(but this is no longer true when a callback calls C<ev_run> recursively).
1774		2218
1775	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1776		2220
1777	=over 4	2221	=over 4
1778		2222
…		…
1813		2257
1814	Another way to think about it (for the mathematically inclined) is that	2258	Another way to think about it (for the mathematically inclined) is that
1815	C<ev_periodic> will try to run the callback in this mode at the next possible	2259	C<ev_periodic> will try to run the callback in this mode at the next possible
1816	time where C<time = offset (mod interval)>, regardless of any time jumps.	2260	time where C<time = offset (mod interval)>, regardless of any time jumps.
1817		2261
1818	For numerical stability it is preferable that the C<offset> value is near	2262	The C<interval> I<MUST> be positive, and for numerical stability, the
1819	C<ev_now ()> (the current time), but there is no range requirement for	2263	interval value should be higher than C<1/8192> (which is around 100
1820	this value, and in fact is often specified as zero.	2264	microseconds) and C<offset> should be higher than C<0> and should have
		2265	at most a similar magnitude as the current time (say, within a factor of
		2266	ten). Typical values for offset are, in fact, C<0> or something between
		2267	C<0> and C<interval>, which is also the recommended range.
1821		2268
1822	Note also that there is an upper limit to how often a timer can fire (CPU	2269	Note also that there is an upper limit to how often a timer can fire (CPU
1823	speed for example), so if C<interval> is very small then timing stability	2270	speed for example), so if C<interval> is very small then timing stability
1824	will of course deteriorate. Libev itself tries to be exact to be about one	2271	will of course deteriorate. Libev itself tries to be exact to be about one
1825	millisecond (if the OS supports it and the machine is fast enough).	2272	millisecond (if the OS supports it and the machine is fast enough).
…		…
1906	Example: Call a callback every hour, or, more precisely, whenever the	2353	Example: Call a callback every hour, or, more precisely, whenever the
1907	system time is divisible by 3600. The callback invocation times have	2354	system time is divisible by 3600. The callback invocation times have
1908	potentially a lot of jitter, but good long-term stability.	2355	potentially a lot of jitter, but good long-term stability.
1909		2356
1910	static void	2357	static void
1911	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2358	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1912	{	2359	{
1913	... its now a full hour (UTC, or TAI or whatever your clock follows)	2360	... its now a full hour (UTC, or TAI or whatever your clock follows)
1914	}	2361	}
1915		2362
1916	ev_periodic hourly_tick;	2363	ev_periodic hourly_tick;
…		…
1939		2386
1940	=head2 C<ev_signal> - signal me when a signal gets signalled!	2387	=head2 C<ev_signal> - signal me when a signal gets signalled!
1941		2388
1942	Signal watchers will trigger an event when the process receives a specific	2389	Signal watchers will trigger an event when the process receives a specific
1943	signal one or more times. Even though signals are very asynchronous, libev	2390	signal one or more times. Even though signals are very asynchronous, libev
1944	will try it's best to deliver signals synchronously, i.e. as part of the	2391	will try its best to deliver signals synchronously, i.e. as part of the
1945	normal event processing, like any other event.	2392	normal event processing, like any other event.
1946		2393
1947	If you want signals asynchronously, just use C<sigaction> as you would	2394	If you want signals to be delivered truly asynchronously, just use
1948	do without libev and forget about sharing the signal. You can even use	2395	C<sigaction> as you would do without libev and forget about sharing
1949	C<ev_async> from a signal handler to synchronously wake up an event loop.	2396	the signal. You can even use C<ev_async> from a signal handler to
		2397	synchronously wake up an event loop.
1950		2398
1951	You can configure as many watchers as you like per signal. Only when the	2399	You can configure as many watchers as you like for the same signal, but
		2400	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2401	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2402	C<SIGINT> in both the default loop and another loop at the same time. At
		2403	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2404
1952	first watcher gets started will libev actually register a signal handler	2405	When the first watcher gets started will libev actually register something
1953	with the kernel (thus it coexists with your own signal handlers as long as	2406	with the kernel (thus it coexists with your own signal handlers as long as
1954	you don't register any with libev for the same signal). Similarly, when	2407	you don't register any with libev for the same signal).
1955	the last signal watcher for a signal is stopped, libev will reset the
1956	signal handler to SIG_DFL (regardless of what it was set to before).
1957		2408
1958	If possible and supported, libev will install its handlers with	2409	If possible and supported, libev will install its handlers with
1959	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2410	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1960	interrupted. If you have a problem with system calls getting interrupted by	2411	not be unduly interrupted. If you have a problem with system calls getting
1961	signals you can block all signals in an C<ev_check> watcher and unblock	2412	interrupted by signals you can block all signals in an C<ev_check> watcher
1962	them in an C<ev_prepare> watcher.	2413	and unblock them in an C<ev_prepare> watcher.
		2414
		2415	=head3 The special problem of inheritance over fork/execve/pthread_create
		2416
		2417	Both the signal mask (C<sigprocmask>) and the signal disposition
		2418	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2419	stopping it again), that is, libev might or might not block the signal,
		2420	and might or might not set or restore the installed signal handler (but
		2421	see C<EVFLAG_NOSIGMASK>).
		2422
		2423	While this does not matter for the signal disposition (libev never
		2424	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2425	C<execve>), this matters for the signal mask: many programs do not expect
		2426	certain signals to be blocked.
		2427
		2428	This means that before calling C<exec> (from the child) you should reset
		2429	the signal mask to whatever "default" you expect (all clear is a good
		2430	choice usually).
		2431
		2432	The simplest way to ensure that the signal mask is reset in the child is
		2433	to install a fork handler with C<pthread_atfork> that resets it. That will
		2434	catch fork calls done by libraries (such as the libc) as well.
		2435
		2436	In current versions of libev, the signal will not be blocked indefinitely
		2437	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2438	the window of opportunity for problems, it will not go away, as libev
		2439	I<has> to modify the signal mask, at least temporarily.
		2440
		2441	So I can't stress this enough: I<If you do not reset your signal mask when
		2442	you expect it to be empty, you have a race condition in your code>. This
		2443	is not a libev-specific thing, this is true for most event libraries.
		2444
		2445	=head3 The special problem of threads signal handling
		2446
		2447	POSIX threads has problematic signal handling semantics, specifically,
		2448	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2449	threads in a process block signals, which is hard to achieve.
		2450
		2451	When you want to use sigwait (or mix libev signal handling with your own
		2452	for the same signals), you can tackle this problem by globally blocking
		2453	all signals before creating any threads (or creating them with a fully set
		2454	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2455	loops. Then designate one thread as "signal receiver thread" which handles
		2456	these signals. You can pass on any signals that libev might be interested
		2457	in by calling C<ev_feed_signal>.
1963		2458
1964	=head3 Watcher-Specific Functions and Data Members	2459	=head3 Watcher-Specific Functions and Data Members
1965		2460
1966	=over 4	2461	=over 4
1967		2462
…		…
1983	Example: Try to exit cleanly on SIGINT.	2478	Example: Try to exit cleanly on SIGINT.
1984		2479
1985	static void	2480	static void
1986	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2481	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1987	{	2482	{
1988	ev_unloop (loop, EVUNLOOP_ALL);	2483	ev_break (loop, EVBREAK_ALL);
1989	}	2484	}
1990		2485
1991	ev_signal signal_watcher;	2486	ev_signal signal_watcher;
1992	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2487	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1993	ev_signal_start (loop, &signal_watcher);	2488	ev_signal_start (loop, &signal_watcher);
…		…
1999	some child status changes (most typically when a child of yours dies or	2494	some child status changes (most typically when a child of yours dies or
2000	exits). It is permissible to install a child watcher I<after> the child	2495	exits). It is permissible to install a child watcher I<after> the child
2001	has been forked (which implies it might have already exited), as long	2496	has been forked (which implies it might have already exited), as long
2002	as the event loop isn't entered (or is continued from a watcher), i.e.,	2497	as the event loop isn't entered (or is continued from a watcher), i.e.,
2003	forking and then immediately registering a watcher for the child is fine,	2498	forking and then immediately registering a watcher for the child is fine,
2004	but forking and registering a watcher a few event loop iterations later is	2499	but forking and registering a watcher a few event loop iterations later or
2005	not.	2500	in the next callback invocation is not.
2006		2501
2007	Only the default event loop is capable of handling signals, and therefore	2502	Only the default event loop is capable of handling signals, and therefore
2008	you can only register child watchers in the default event loop.	2503	you can only register child watchers in the default event loop.
2009		2504
		2505	Due to some design glitches inside libev, child watchers will always be
		2506	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2507	libev)
		2508
2010	=head3 Process Interaction	2509	=head3 Process Interaction
2011		2510
2012	Libev grabs C<SIGCHLD> as soon as the default event loop is	2511	Libev grabs C<SIGCHLD> as soon as the default event loop is
2013	initialised. This is necessary to guarantee proper behaviour even if	2512	initialised. This is necessary to guarantee proper behaviour even if the
2014	the first child watcher is started after the child exits. The occurrence	2513	first child watcher is started after the child exits. The occurrence
2015	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2016	synchronously as part of the event loop processing. Libev always reaps all	2515	synchronously as part of the event loop processing. Libev always reaps all
2017	children, even ones not watched.	2516	children, even ones not watched.
2018		2517
2019	=head3 Overriding the Built-In Processing	2518	=head3 Overriding the Built-In Processing
…		…
2029	=head3 Stopping the Child Watcher	2528	=head3 Stopping the Child Watcher
2030		2529
2031	Currently, the child watcher never gets stopped, even when the	2530	Currently, the child watcher never gets stopped, even when the
2032	child terminates, so normally one needs to stop the watcher in the	2531	child terminates, so normally one needs to stop the watcher in the
2033	callback. Future versions of libev might stop the watcher automatically	2532	callback. Future versions of libev might stop the watcher automatically
2034	when a child exit is detected.	2533	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2534	problem).
2035		2535
2036	=head3 Watcher-Specific Functions and Data Members	2536	=head3 Watcher-Specific Functions and Data Members
2037		2537
2038	=over 4	2538	=over 4
2039		2539
…		…
2365	// no longer anything immediate to do.	2865	// no longer anything immediate to do.
2366	}	2866	}
2367		2867
2368	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2868	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2369	ev_idle_init (idle_watcher, idle_cb);	2869	ev_idle_init (idle_watcher, idle_cb);
2370	ev_idle_start (loop, idle_cb);	2870	ev_idle_start (loop, idle_watcher);
2371		2871
2372		2872
2373	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2873	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2374		2874
2375	Prepare and check watchers are usually (but not always) used in pairs:	2875	Prepare and check watchers are usually (but not always) used in pairs:
2376	prepare watchers get invoked before the process blocks and check watchers	2876	prepare watchers get invoked before the process blocks and check watchers
2377	afterwards.	2877	afterwards.
2378		2878
2379	You I<must not> call C<ev_loop> or similar functions that enter	2879	You I<must not> call C<ev_run> or similar functions that enter
2380	the current event loop from either C<ev_prepare> or C<ev_check>	2880	the current event loop from either C<ev_prepare> or C<ev_check>
2381	watchers. Other loops than the current one are fine, however. The	2881	watchers. Other loops than the current one are fine, however. The
2382	rationale behind this is that you do not need to check for recursion in	2882	rationale behind this is that you do not need to check for recursion in
2383	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2883	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2384	C<ev_check> so if you have one watcher of each kind they will always be	2884	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2468	struct pollfd fds [nfd];	2968	struct pollfd fds [nfd];
2469	// actual code will need to loop here and realloc etc.	2969	// actual code will need to loop here and realloc etc.
2470	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2970	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2471		2971
2472	/* the callback is illegal, but won't be called as we stop during check */	2972	/* the callback is illegal, but won't be called as we stop during check */
2473	ev_timer_init (&tw, 0, timeout * 1e-3);	2973	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2474	ev_timer_start (loop, &tw);	2974	ev_timer_start (loop, &tw);
2475		2975
2476	// create one ev_io per pollfd	2976	// create one ev_io per pollfd
2477	for (int i = 0; i < nfd; ++i)	2977	for (int i = 0; i < nfd; ++i)
2478	{	2978	{
…		…
2552		3052
2553	if (timeout >= 0)	3053	if (timeout >= 0)
2554	// create/start timer	3054	// create/start timer
2555		3055
2556	// poll	3056	// poll
2557	ev_loop (EV_A_ 0);	3057	ev_run (EV_A_ 0);
2558		3058
2559	// stop timer again	3059	// stop timer again
2560	if (timeout >= 0)	3060	if (timeout >= 0)
2561	ev_timer_stop (EV_A_ &to);	3061	ev_timer_stop (EV_A_ &to);
2562		3062
…		…
2640	if you do not want that, you need to temporarily stop the embed watcher).	3140	if you do not want that, you need to temporarily stop the embed watcher).
2641		3141
2642	=item ev_embed_sweep (loop, ev_embed *)	3142	=item ev_embed_sweep (loop, ev_embed *)
2643		3143
2644	Make a single, non-blocking sweep over the embedded loop. This works	3144	Make a single, non-blocking sweep over the embedded loop. This works
2645	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3145	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2646	appropriate way for embedded loops.	3146	appropriate way for embedded loops.
2647		3147
2648	=item struct ev_loop *other [read-only]	3148	=item struct ev_loop *other [read-only]
2649		3149
2650	The embedded event loop.	3150	The embedded event loop.
…		…
2710	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3210	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2711	handlers will be invoked, too, of course.	3211	handlers will be invoked, too, of course.
2712		3212
2713	=head3 The special problem of life after fork - how is it possible?	3213	=head3 The special problem of life after fork - how is it possible?
2714		3214
2715	Most uses of C<fork()> consist of forking, then some simple calls to ste	3215	Most uses of C<fork()> consist of forking, then some simple calls to set
2716	up/change the process environment, followed by a call to C<exec()>. This	3216	up/change the process environment, followed by a call to C<exec()>. This
2717	sequence should be handled by libev without any problems.	3217	sequence should be handled by libev without any problems.
2718		3218
2719	This changes when the application actually wants to do event handling	3219	This changes when the application actually wants to do event handling
2720	in the child, or both parent in child, in effect "continuing" after the	3220	in the child, or both parent in child, in effect "continuing" after the
…		…
2736	disadvantage of having to use multiple event loops (which do not support	3236	disadvantage of having to use multiple event loops (which do not support
2737	signal watchers).	3237	signal watchers).
2738		3238
2739	When this is not possible, or you want to use the default loop for	3239	When this is not possible, or you want to use the default loop for
2740	other reasons, then in the process that wants to start "fresh", call	3240	other reasons, then in the process that wants to start "fresh", call
2741	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3241	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2742	the default loop will "orphan" (not stop) all registered watchers, so you	3242	Destroying the default loop will "orphan" (not stop) all registered
2743	have to be careful not to execute code that modifies those watchers. Note	3243	watchers, so you have to be careful not to execute code that modifies
2744	also that in that case, you have to re-register any signal watchers.	3244	those watchers. Note also that in that case, you have to re-register any
		3245	signal watchers.
2745		3246
2746	=head3 Watcher-Specific Functions and Data Members	3247	=head3 Watcher-Specific Functions and Data Members
2747		3248
2748	=over 4	3249	=over 4
2749		3250
2750	=item ev_fork_init (ev_signal *, callback)	3251	=item ev_fork_init (ev_fork *, callback)
2751		3252
2752	Initialises and configures the fork watcher - it has no parameters of any	3253	Initialises and configures the fork watcher - it has no parameters of any
2753	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3254	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2754	believe me.	3255	really.
2755		3256
2756	=back	3257	=back
2757		3258
2758		3259
		3260	=head2 C<ev_cleanup> - even the best things end
		3261
		3262	Cleanup watchers are called just before the event loop is being destroyed
		3263	by a call to C<ev_loop_destroy>.
		3264
		3265	While there is no guarantee that the event loop gets destroyed, cleanup
		3266	watchers provide a convenient method to install cleanup hooks for your
		3267	program, worker threads and so on - you just to make sure to destroy the
		3268	loop when you want them to be invoked.
		3269
		3270	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3271	all other watchers, they do not keep a reference to the event loop (which
		3272	makes a lot of sense if you think about it). Like all other watchers, you
		3273	can call libev functions in the callback, except C<ev_cleanup_start>.
		3274
		3275	=head3 Watcher-Specific Functions and Data Members
		3276
		3277	=over 4
		3278
		3279	=item ev_cleanup_init (ev_cleanup *, callback)
		3280
		3281	Initialises and configures the cleanup watcher - it has no parameters of
		3282	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3283	pointless, I assure you.
		3284
		3285	=back
		3286
		3287	Example: Register an atexit handler to destroy the default loop, so any
		3288	cleanup functions are called.
		3289
		3290	static void
		3291	program_exits (void)
		3292	{
		3293	ev_loop_destroy (EV_DEFAULT_UC);
		3294	}
		3295
		3296	...
		3297	atexit (program_exits);
		3298
		3299
2759	=head2 C<ev_async> - how to wake up another event loop	3300	=head2 C<ev_async> - how to wake up an event loop
2760		3301
2761	In general, you cannot use an C<ev_loop> from multiple threads or other	3302	In general, you cannot use an C<ev_loop> from multiple threads or other
2762	asynchronous sources such as signal handlers (as opposed to multiple event	3303	asynchronous sources such as signal handlers (as opposed to multiple event
2763	loops - those are of course safe to use in different threads).	3304	loops - those are of course safe to use in different threads).
2764		3305
2765	Sometimes, however, you need to wake up another event loop you do not	3306	Sometimes, however, you need to wake up an event loop you do not control,
2766	control, for example because it belongs to another thread. This is what	3307	for example because it belongs to another thread. This is what C<ev_async>
2767	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3308	watchers do: as long as the C<ev_async> watcher is active, you can signal
2768	can signal it by calling C<ev_async_send>, which is thread- and signal	3309	it by calling C<ev_async_send>, which is thread- and signal safe.
2769	safe.
2770		3310
2771	This functionality is very similar to C<ev_signal> watchers, as signals,	3311	This functionality is very similar to C<ev_signal> watchers, as signals,
2772	too, are asynchronous in nature, and signals, too, will be compressed	3312	too, are asynchronous in nature, and signals, too, will be compressed
2773	(i.e. the number of callback invocations may be less than the number of	3313	(i.e. the number of callback invocations may be less than the number of
2774	C<ev_async_sent> calls).	3314	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2775		3315	of "global async watchers" by using a watcher on an otherwise unused
2776	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3316	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2777	just the default loop.	3317	even without knowing which loop owns the signal.
2778		3318
2779	=head3 Queueing	3319	=head3 Queueing
2780		3320
2781	C<ev_async> does not support queueing of data in any way. The reason	3321	C<ev_async> does not support queueing of data in any way. The reason
2782	is that the author does not know of a simple (or any) algorithm for a	3322	is that the author does not know of a simple (or any) algorithm for a
2783	multiple-writer-single-reader queue that works in all cases and doesn't	3323	multiple-writer-single-reader queue that works in all cases and doesn't
2784	need elaborate support such as pthreads.	3324	need elaborate support such as pthreads or unportable memory access
		3325	semantics.
2785		3326
2786	That means that if you want to queue data, you have to provide your own	3327	That means that if you want to queue data, you have to provide your own
2787	queue. But at least I can tell you how to implement locking around your	3328	queue. But at least I can tell you how to implement locking around your
2788	queue:	3329	queue:
2789		3330
…		…
2873	trust me.	3414	trust me.
2874		3415
2875	=item ev_async_send (loop, ev_async *)	3416	=item ev_async_send (loop, ev_async *)
2876		3417
2877	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3418	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2878	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3419	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3420	returns.
		3421
2879	C<ev_feed_event>, this call is safe to do from other threads, signal or	3422	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2880	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3423	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2881	section below on what exactly this means).	3424	embedding section below on what exactly this means).
2882		3425
2883	Note that, as with other watchers in libev, multiple events might get	3426	Note that, as with other watchers in libev, multiple events might get
2884	compressed into a single callback invocation (another way to look at this	3427	compressed into a single callback invocation (another way to look at
2885	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3428	this is that C<ev_async> watchers are level-triggered: they are set on
2886	reset when the event loop detects that).	3429	C<ev_async_send>, reset when the event loop detects that).
2887		3430
2888	This call incurs the overhead of a system call only once per event loop	3431	This call incurs the overhead of at most one extra system call per event
2889	iteration, so while the overhead might be noticeable, it doesn't apply to	3432	loop iteration, if the event loop is blocked, and no syscall at all if
2890	repeated calls to C<ev_async_send> for the same event loop.	3433	the event loop (or your program) is processing events. That means that
		3434	repeated calls are basically free (there is no need to avoid calls for
		3435	performance reasons) and that the overhead becomes smaller (typically
		3436	zero) under load.
2891		3437
2892	=item bool = ev_async_pending (ev_async *)	3438	=item bool = ev_async_pending (ev_async *)
2893		3439
2894	Returns a non-zero value when C<ev_async_send> has been called on the	3440	Returns a non-zero value when C<ev_async_send> has been called on the
2895	watcher but the event has not yet been processed (or even noted) by the	3441	watcher but the event has not yet been processed (or even noted) by the
…		…
2928		3474
2929	If C<timeout> is less than 0, then no timeout watcher will be	3475	If C<timeout> is less than 0, then no timeout watcher will be
2930	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3476	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2931	repeat = 0) will be started. C<0> is a valid timeout.	3477	repeat = 0) will be started. C<0> is a valid timeout.
2932		3478
2933	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3479	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2934	passed an C<revents> set like normal event callbacks (a combination of	3480	passed an C<revents> set like normal event callbacks (a combination of
2935	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3481	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2936	value passed to C<ev_once>. Note that it is possible to receive I<both>	3482	value passed to C<ev_once>. Note that it is possible to receive I<both>
2937	a timeout and an io event at the same time - you probably should give io	3483	a timeout and an io event at the same time - you probably should give io
2938	events precedence.	3484	events precedence.
2939		3485
2940	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3486	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2941		3487
2942	static void stdin_ready (int revents, void *arg)	3488	static void stdin_ready (int revents, void *arg)
2943	{	3489	{
2944	if (revents & EV_READ)	3490	if (revents & EV_READ)
2945	/* stdin might have data for us, joy! */;	3491	/* stdin might have data for us, joy! */;
2946	else if (revents & EV_TIMEOUT)	3492	else if (revents & EV_TIMER)
2947	/* doh, nothing entered */;	3493	/* doh, nothing entered */;
2948	}	3494	}
2949		3495
2950	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3496	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2951		3497
2952	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2953
2954	Feeds the given event set into the event loop, as if the specified event
2955	had happened for the specified watcher (which must be a pointer to an
2956	initialised but not necessarily started event watcher).
2957
2958	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3498	=item ev_feed_fd_event (loop, int fd, int revents)
2959		3499
2960	Feed an event on the given fd, as if a file descriptor backend detected	3500	Feed an event on the given fd, as if a file descriptor backend detected
2961	the given events it.	3501	the given events.
2962		3502
2963	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3503	=item ev_feed_signal_event (loop, int signum)
2964		3504
2965	Feed an event as if the given signal occurred (C<loop> must be the default	3505	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2966	loop!).	3506	which is async-safe.
2967		3507
2968	=back	3508	=back
		3509
		3510
		3511	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3512
		3513	This section explains some common idioms that are not immediately
		3514	obvious. Note that examples are sprinkled over the whole manual, and this
		3515	section only contains stuff that wouldn't fit anywhere else.
		3516
		3517	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3518
		3519	Each watcher has, by default, a C<void *data> member that you can read
		3520	or modify at any time: libev will completely ignore it. This can be used
		3521	to associate arbitrary data with your watcher. If you need more data and
		3522	don't want to allocate memory separately and store a pointer to it in that
		3523	data member, you can also "subclass" the watcher type and provide your own
		3524	data:
		3525
		3526	struct my_io
		3527	{
		3528	ev_io io;
		3529	int otherfd;
		3530	void *somedata;
		3531	struct whatever *mostinteresting;
		3532	};
		3533
		3534	...
		3535	struct my_io w;
		3536	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3537
		3538	And since your callback will be called with a pointer to the watcher, you
		3539	can cast it back to your own type:
		3540
		3541	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3542	{
		3543	struct my_io *w = (struct my_io *)w_;
		3544	...
		3545	}
		3546
		3547	More interesting and less C-conformant ways of casting your callback
		3548	function type instead have been omitted.
		3549
		3550	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3551
		3552	Another common scenario is to use some data structure with multiple
		3553	embedded watchers, in effect creating your own watcher that combines
		3554	multiple libev event sources into one "super-watcher":
		3555
		3556	struct my_biggy
		3557	{
		3558	int some_data;
		3559	ev_timer t1;
		3560	ev_timer t2;
		3561	}
		3562
		3563	In this case getting the pointer to C<my_biggy> is a bit more
		3564	complicated: Either you store the address of your C<my_biggy> struct in
		3565	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3566	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3567	real programmers):
		3568
		3569	#include <stddef.h>
		3570
		3571	static void
		3572	t1_cb (EV_P_ ev_timer *w, int revents)
		3573	{
		3574	struct my_biggy big = (struct my_biggy *)
		3575	(((char *)w) - offsetof (struct my_biggy, t1));
		3576	}
		3577
		3578	static void
		3579	t2_cb (EV_P_ ev_timer *w, int revents)
		3580	{
		3581	struct my_biggy big = (struct my_biggy *)
		3582	(((char *)w) - offsetof (struct my_biggy, t2));
		3583	}
		3584
		3585	=head2 AVOIDING FINISHING BEFORE RETURNING
		3586
		3587	Often you have structures like this in event-based programs:
		3588
		3589	callback ()
		3590	{
		3591	free (request);
		3592	}
		3593
		3594	request = start_new_request (..., callback);
		3595
		3596	The intent is to start some "lengthy" operation. The C<request> could be
		3597	used to cancel the operation, or do other things with it.
		3598
		3599	It's not uncommon to have code paths in C<start_new_request> that
		3600	immediately invoke the callback, for example, to report errors. Or you add
		3601	some caching layer that finds that it can skip the lengthy aspects of the
		3602	operation and simply invoke the callback with the result.
		3603
		3604	The problem here is that this will happen I<before> C<start_new_request>
		3605	has returned, so C<request> is not set.
		3606
		3607	Even if you pass the request by some safer means to the callback, you
		3608	might want to do something to the request after starting it, such as
		3609	canceling it, which probably isn't working so well when the callback has
		3610	already been invoked.
		3611
		3612	A common way around all these issues is to make sure that
		3613	C<start_new_request> I<always> returns before the callback is invoked. If
		3614	C<start_new_request> immediately knows the result, it can artificially
		3615	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3616	for example, or more sneakily, by reusing an existing (stopped) watcher
		3617	and pushing it into the pending queue:
		3618
		3619	ev_set_cb (watcher, callback);
		3620	ev_feed_event (EV_A_ watcher, 0);
		3621
		3622	This way, C<start_new_request> can safely return before the callback is
		3623	invoked, while not delaying callback invocation too much.
		3624
		3625	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3626
		3627	Often (especially in GUI toolkits) there are places where you have
		3628	I<modal> interaction, which is most easily implemented by recursively
		3629	invoking C<ev_run>.
		3630
		3631	This brings the problem of exiting - a callback might want to finish the
		3632	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3633	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3634	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3635	other combination: In these cases, C<ev_break> will not work alone.
		3636
		3637	The solution is to maintain "break this loop" variable for each C<ev_run>
		3638	invocation, and use a loop around C<ev_run> until the condition is
		3639	triggered, using C<EVRUN_ONCE>:
		3640
		3641	// main loop
		3642	int exit_main_loop = 0;
		3643
		3644	while (!exit_main_loop)
		3645	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3646
		3647	// in a modal watcher
		3648	int exit_nested_loop = 0;
		3649
		3650	while (!exit_nested_loop)
		3651	ev_run (EV_A_ EVRUN_ONCE);
		3652
		3653	To exit from any of these loops, just set the corresponding exit variable:
		3654
		3655	// exit modal loop
		3656	exit_nested_loop = 1;
		3657
		3658	// exit main program, after modal loop is finished
		3659	exit_main_loop = 1;
		3660
		3661	// exit both
		3662	exit_main_loop = exit_nested_loop = 1;
		3663
		3664	=head2 THREAD LOCKING EXAMPLE
		3665
		3666	Here is a fictitious example of how to run an event loop in a different
		3667	thread from where callbacks are being invoked and watchers are
		3668	created/added/removed.
		3669
		3670	For a real-world example, see the C<EV::Loop::Async> perl module,
		3671	which uses exactly this technique (which is suited for many high-level
		3672	languages).
		3673
		3674	The example uses a pthread mutex to protect the loop data, a condition
		3675	variable to wait for callback invocations, an async watcher to notify the
		3676	event loop thread and an unspecified mechanism to wake up the main thread.
		3677
		3678	First, you need to associate some data with the event loop:
		3679
		3680	typedef struct {
		3681	mutex_t lock; /* global loop lock */
		3682	ev_async async_w;
		3683	thread_t tid;
		3684	cond_t invoke_cv;
		3685	} userdata;
		3686
		3687	void prepare_loop (EV_P)
		3688	{
		3689	// for simplicity, we use a static userdata struct.
		3690	static userdata u;
		3691
		3692	ev_async_init (&u->async_w, async_cb);
		3693	ev_async_start (EV_A_ &u->async_w);
		3694
		3695	pthread_mutex_init (&u->lock, 0);
		3696	pthread_cond_init (&u->invoke_cv, 0);
		3697
		3698	// now associate this with the loop
		3699	ev_set_userdata (EV_A_ u);
		3700	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3701	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3702
		3703	// then create the thread running ev_run
		3704	pthread_create (&u->tid, 0, l_run, EV_A);
		3705	}
		3706
		3707	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3708	solely to wake up the event loop so it takes notice of any new watchers
		3709	that might have been added:
		3710
		3711	static void
		3712	async_cb (EV_P_ ev_async *w, int revents)
		3713	{
		3714	// just used for the side effects
		3715	}
		3716
		3717	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3718	protecting the loop data, respectively.
		3719
		3720	static void
		3721	l_release (EV_P)
		3722	{
		3723	userdata *u = ev_userdata (EV_A);
		3724	pthread_mutex_unlock (&u->lock);
		3725	}
		3726
		3727	static void
		3728	l_acquire (EV_P)
		3729	{
		3730	userdata *u = ev_userdata (EV_A);
		3731	pthread_mutex_lock (&u->lock);
		3732	}
		3733
		3734	The event loop thread first acquires the mutex, and then jumps straight
		3735	into C<ev_run>:
		3736
		3737	void *
		3738	l_run (void *thr_arg)
		3739	{
		3740	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3741
		3742	l_acquire (EV_A);
		3743	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3744	ev_run (EV_A_ 0);
		3745	l_release (EV_A);
		3746
		3747	return 0;
		3748	}
		3749
		3750	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3751	signal the main thread via some unspecified mechanism (signals? pipe
		3752	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3753	have been called (in a while loop because a) spurious wakeups are possible
		3754	and b) skipping inter-thread-communication when there are no pending
		3755	watchers is very beneficial):
		3756
		3757	static void
		3758	l_invoke (EV_P)
		3759	{
		3760	userdata *u = ev_userdata (EV_A);
		3761
		3762	while (ev_pending_count (EV_A))
		3763	{
		3764	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3765	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3766	}
		3767	}
		3768
		3769	Now, whenever the main thread gets told to invoke pending watchers, it
		3770	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3771	thread to continue:
		3772
		3773	static void
		3774	real_invoke_pending (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777
		3778	pthread_mutex_lock (&u->lock);
		3779	ev_invoke_pending (EV_A);
		3780	pthread_cond_signal (&u->invoke_cv);
		3781	pthread_mutex_unlock (&u->lock);
		3782	}
		3783
		3784	Whenever you want to start/stop a watcher or do other modifications to an
		3785	event loop, you will now have to lock:
		3786
		3787	ev_timer timeout_watcher;
		3788	userdata *u = ev_userdata (EV_A);
		3789
		3790	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3791
		3792	pthread_mutex_lock (&u->lock);
		3793	ev_timer_start (EV_A_ &timeout_watcher);
		3794	ev_async_send (EV_A_ &u->async_w);
		3795	pthread_mutex_unlock (&u->lock);
		3796
		3797	Note that sending the C<ev_async> watcher is required because otherwise
		3798	an event loop currently blocking in the kernel will have no knowledge
		3799	about the newly added timer. By waking up the loop it will pick up any new
		3800	watchers in the next event loop iteration.
		3801
		3802	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3803
		3804	While the overhead of a callback that e.g. schedules a thread is small, it
		3805	is still an overhead. If you embed libev, and your main usage is with some
		3806	kind of threads or coroutines, you might want to customise libev so that
		3807	doesn't need callbacks anymore.
		3808
		3809	Imagine you have coroutines that you can switch to using a function
		3810	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3811	and that due to some magic, the currently active coroutine is stored in a
		3812	global called C<current_coro>. Then you can build your own "wait for libev
		3813	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3814	the differing C<;> conventions):
		3815
		3816	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3817	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3818
		3819	That means instead of having a C callback function, you store the
		3820	coroutine to switch to in each watcher, and instead of having libev call
		3821	your callback, you instead have it switch to that coroutine.
		3822
		3823	A coroutine might now wait for an event with a function called
		3824	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3825	matter when, or whether the watcher is active or not when this function is
		3826	called):
		3827
		3828	void
		3829	wait_for_event (ev_watcher *w)
		3830	{
		3831	ev_cb_set (w) = current_coro;
		3832	switch_to (libev_coro);
		3833	}
		3834
		3835	That basically suspends the coroutine inside C<wait_for_event> and
		3836	continues the libev coroutine, which, when appropriate, switches back to
		3837	this or any other coroutine.
		3838
		3839	You can do similar tricks if you have, say, threads with an event queue -
		3840	instead of storing a coroutine, you store the queue object and instead of
		3841	switching to a coroutine, you push the watcher onto the queue and notify
		3842	any waiters.
		3843
		3844	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3845	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3846
		3847	// my_ev.h
		3848	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3849	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3850	#include "../libev/ev.h"
		3851
		3852	// my_ev.c
		3853	#define EV_H "my_ev.h"
		3854	#include "../libev/ev.c"
		3855
		3856	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3857	F<my_ev.c> into your project. When properly specifying include paths, you
		3858	can even use F<ev.h> as header file name directly.
2969		3859
2970		3860
2971	=head1 LIBEVENT EMULATION	3861	=head1 LIBEVENT EMULATION
2972		3862
2973	Libev offers a compatibility emulation layer for libevent. It cannot	3863	Libev offers a compatibility emulation layer for libevent. It cannot
2974	emulate the internals of libevent, so here are some usage hints:	3864	emulate the internals of libevent, so here are some usage hints:
2975		3865
2976	=over 4	3866	=over 4
		3867
		3868	=item * Only the libevent-1.4.1-beta API is being emulated.
		3869
		3870	This was the newest libevent version available when libev was implemented,
		3871	and is still mostly unchanged in 2010.
2977		3872
2978	=item * Use it by including <event.h>, as usual.	3873	=item * Use it by including <event.h>, as usual.
2979		3874
2980	=item * The following members are fully supported: ev_base, ev_callback,	3875	=item * The following members are fully supported: ev_base, ev_callback,
2981	ev_arg, ev_fd, ev_res, ev_events.	3876	ev_arg, ev_fd, ev_res, ev_events.
…		…
2987	=item * Priorities are not currently supported. Initialising priorities	3882	=item * Priorities are not currently supported. Initialising priorities
2988	will fail and all watchers will have the same priority, even though there	3883	will fail and all watchers will have the same priority, even though there
2989	is an ev_pri field.	3884	is an ev_pri field.
2990		3885
2991	=item * In libevent, the last base created gets the signals, in libev, the	3886	=item * In libevent, the last base created gets the signals, in libev, the
2992	first base created (== the default loop) gets the signals.	3887	base that registered the signal gets the signals.
2993		3888
2994	=item * Other members are not supported.	3889	=item * Other members are not supported.
2995		3890
2996	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3891	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2997	to use the libev header file and library.	3892	to use the libev header file and library.
…		…
3016	Care has been taken to keep the overhead low. The only data member the C++	3911	Care has been taken to keep the overhead low. The only data member the C++
3017	classes add (compared to plain C-style watchers) is the event loop pointer	3912	classes add (compared to plain C-style watchers) is the event loop pointer
3018	that the watcher is associated with (or no additional members at all if	3913	that the watcher is associated with (or no additional members at all if
3019	you disable C<EV_MULTIPLICITY> when embedding libev).	3914	you disable C<EV_MULTIPLICITY> when embedding libev).
3020		3915
3021	Currently, functions, and static and non-static member functions can be	3916	Currently, functions, static and non-static member functions and classes
3022	used as callbacks. Other types should be easy to add as long as they only	3917	with C<operator ()> can be used as callbacks. Other types should be easy
3023	need one additional pointer for context. If you need support for other	3918	to add as long as they only need one additional pointer for context. If
3024	types of functors please contact the author (preferably after implementing	3919	you need support for other types of functors please contact the author
3025	it).	3920	(preferably after implementing it).
3026		3921
3027	Here is a list of things available in the C<ev> namespace:	3922	Here is a list of things available in the C<ev> namespace:
3028		3923
3029	=over 4	3924	=over 4
3030		3925
…		…
3040	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3935	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3041		3936
3042	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3937	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3043	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3938	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3044	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3939	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3045	defines by many implementations.	3940	defined by many implementations.
3046		3941
3047	All of those classes have these methods:	3942	All of those classes have these methods:
3048		3943
3049	=over 4	3944	=over 4
3050		3945
3051	=item ev::TYPE::TYPE ()	3946	=item ev::TYPE::TYPE ()
3052		3947
3053	=item ev::TYPE::TYPE (struct ev_loop *)	3948	=item ev::TYPE::TYPE (loop)
3054		3949
3055	=item ev::TYPE::~TYPE	3950	=item ev::TYPE::~TYPE
3056		3951
3057	The constructor (optionally) takes an event loop to associate the watcher	3952	The constructor (optionally) takes an event loop to associate the watcher
3058	with. If it is omitted, it will use C<EV_DEFAULT>.	3953	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3091	myclass obj;	3986	myclass obj;
3092	ev::io iow;	3987	ev::io iow;
3093	iow.set <myclass, &myclass::io_cb> (&obj);	3988	iow.set <myclass, &myclass::io_cb> (&obj);
3094		3989
3095	=item w->set (object *)	3990	=item w->set (object *)
3096
3097	This is an B<experimental> feature that might go away in a future version.
3098		3991
3099	This is a variation of a method callback - leaving out the method to call	3992	This is a variation of a method callback - leaving out the method to call
3100	will default the method to C<operator ()>, which makes it possible to use	3993	will default the method to C<operator ()>, which makes it possible to use
3101	functor objects without having to manually specify the C<operator ()> all	3994	functor objects without having to manually specify the C<operator ()> all
3102	the time. Incidentally, you can then also leave out the template argument	3995	the time. Incidentally, you can then also leave out the template argument
…		…
3135	Example: Use a plain function as callback.	4028	Example: Use a plain function as callback.
3136		4029
3137	static void io_cb (ev::io &w, int revents) { }	4030	static void io_cb (ev::io &w, int revents) { }
3138	iow.set <io_cb> ();	4031	iow.set <io_cb> ();
3139		4032
3140	=item w->set (struct ev_loop *)	4033	=item w->set (loop)
3141		4034
3142	Associates a different C<struct ev_loop> with this watcher. You can only	4035	Associates a different C<struct ev_loop> with this watcher. You can only
3143	do this when the watcher is inactive (and not pending either).	4036	do this when the watcher is inactive (and not pending either).
3144		4037
3145	=item w->set ([arguments])	4038	=item w->set ([arguments])
3146		4039
3147	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4040	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3148	called at least once. Unlike the C counterpart, an active watcher gets	4041	method or a suitable start method must be called at least once. Unlike the
3149	automatically stopped and restarted when reconfiguring it with this	4042	C counterpart, an active watcher gets automatically stopped and restarted
3150	method.	4043	when reconfiguring it with this method.
3151		4044
3152	=item w->start ()	4045	=item w->start ()
3153		4046
3154	Starts the watcher. Note that there is no C<loop> argument, as the	4047	Starts the watcher. Note that there is no C<loop> argument, as the
3155	constructor already stores the event loop.	4048	constructor already stores the event loop.
3156		4049
		4050	=item w->start ([arguments])
		4051
		4052	Instead of calling C<set> and C<start> methods separately, it is often
		4053	convenient to wrap them in one call. Uses the same type of arguments as
		4054	the configure C<set> method of the watcher.
		4055
3157	=item w->stop ()	4056	=item w->stop ()
3158		4057
3159	Stops the watcher if it is active. Again, no C<loop> argument.	4058	Stops the watcher if it is active. Again, no C<loop> argument.
3160		4059
3161	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4060	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3173		4072
3174	=back	4073	=back
3175		4074
3176	=back	4075	=back
3177		4076
3178	Example: Define a class with an IO and idle watcher, start one of them in	4077	Example: Define a class with two I/O and idle watchers, start the I/O
3179	the constructor.	4078	watchers in the constructor.
3180		4079
3181	class myclass	4080	class myclass
3182	{	4081	{
3183	ev::io io ; void io_cb (ev::io &w, int revents);	4082	ev::io io ; void io_cb (ev::io &w, int revents);
		4083	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3184	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4084	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3185		4085
3186	myclass (int fd)	4086	myclass (int fd)
3187	{	4087	{
3188	io .set <myclass, &myclass::io_cb > (this);	4088	io .set <myclass, &myclass::io_cb > (this);
		4089	io2 .set <myclass, &myclass::io2_cb > (this);
3189	idle.set <myclass, &myclass::idle_cb> (this);	4090	idle.set <myclass, &myclass::idle_cb> (this);
3190		4091
3191	io.start (fd, ev::READ);	4092	io.set (fd, ev::WRITE); // configure the watcher
		4093	io.start (); // start it whenever convenient
		4094
		4095	io2.start (fd, ev::READ); // set + start in one call
3192	}	4096	}
3193	};	4097	};
3194		4098
3195		4099
3196	=head1 OTHER LANGUAGE BINDINGS	4100	=head1 OTHER LANGUAGE BINDINGS
…		…
3235	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4139	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3236		4140
3237	=item D	4141	=item D
3238		4142
3239	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4143	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3240	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4144	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3241		4145
3242	=item Ocaml	4146	=item Ocaml
3243		4147
3244	Erkki Seppala has written Ocaml bindings for libev, to be found at	4148	Erkki Seppala has written Ocaml bindings for libev, to be found at
3245	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4149	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4150
		4151	=item Lua
		4152
		4153	Brian Maher has written a partial interface to libev for lua (at the
		4154	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4155	L<http://github.com/brimworks/lua-ev>.
3246		4156
3247	=back	4157	=back
3248		4158
3249		4159
3250	=head1 MACRO MAGIC	4160	=head1 MACRO MAGIC
…		…
3264	loop argument"). The C<EV_A> form is used when this is the sole argument,	4174	loop argument"). The C<EV_A> form is used when this is the sole argument,
3265	C<EV_A_> is used when other arguments are following. Example:	4175	C<EV_A_> is used when other arguments are following. Example:
3266		4176
3267	ev_unref (EV_A);	4177	ev_unref (EV_A);
3268	ev_timer_add (EV_A_ watcher);	4178	ev_timer_add (EV_A_ watcher);
3269	ev_loop (EV_A_ 0);	4179	ev_run (EV_A_ 0);
3270		4180
3271	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4181	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3272	which is often provided by the following macro.	4182	which is often provided by the following macro.
3273		4183
3274	=item C<EV_P>, C<EV_P_>	4184	=item C<EV_P>, C<EV_P_>
…		…
3287	suitable for use with C<EV_A>.	4197	suitable for use with C<EV_A>.
3288		4198
3289	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4199	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3290		4200
3291	Similar to the other two macros, this gives you the value of the default	4201	Similar to the other two macros, this gives you the value of the default
3292	loop, if multiple loops are supported ("ev loop default").	4202	loop, if multiple loops are supported ("ev loop default"). The default loop
		4203	will be initialised if it isn't already initialised.
		4204
		4205	For non-multiplicity builds, these macros do nothing, so you always have
		4206	to initialise the loop somewhere.
3293		4207
3294	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4208	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3295		4209
3296	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4210	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3297	default loop has been initialised (C<UC> == unchecked). Their behaviour	4211	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3314	}	4228	}
3315		4229
3316	ev_check check;	4230	ev_check check;
3317	ev_check_init (&check, check_cb);	4231	ev_check_init (&check, check_cb);
3318	ev_check_start (EV_DEFAULT_ &check);	4232	ev_check_start (EV_DEFAULT_ &check);
3319	ev_loop (EV_DEFAULT_ 0);	4233	ev_run (EV_DEFAULT_ 0);
3320		4234
3321	=head1 EMBEDDING	4235	=head1 EMBEDDING
3322		4236
3323	Libev can (and often is) directly embedded into host	4237	Libev can (and often is) directly embedded into host
3324	applications. Examples of applications that embed it include the Deliantra	4238	applications. Examples of applications that embed it include the Deliantra
…		…
3404	libev.m4	4318	libev.m4
3405		4319
3406	=head2 PREPROCESSOR SYMBOLS/MACROS	4320	=head2 PREPROCESSOR SYMBOLS/MACROS
3407		4321
3408	Libev can be configured via a variety of preprocessor symbols you have to	4322	Libev can be configured via a variety of preprocessor symbols you have to
3409	define before including any of its files. The default in the absence of	4323	define before including (or compiling) any of its files. The default in
3410	autoconf is documented for every option.	4324	the absence of autoconf is documented for every option.
		4325
		4326	Symbols marked with "(h)" do not change the ABI, and can have different
		4327	values when compiling libev vs. including F<ev.h>, so it is permissible
		4328	to redefine them before including F<ev.h> without breaking compatibility
		4329	to a compiled library. All other symbols change the ABI, which means all
		4330	users of libev and the libev code itself must be compiled with compatible
		4331	settings.
3411		4332
3412	=over 4	4333	=over 4
3413		4334
		4335	=item EV_COMPAT3 (h)
		4336
		4337	Backwards compatibility is a major concern for libev. This is why this
		4338	release of libev comes with wrappers for the functions and symbols that
		4339	have been renamed between libev version 3 and 4.
		4340
		4341	You can disable these wrappers (to test compatibility with future
		4342	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4343	sources. This has the additional advantage that you can drop the C<struct>
		4344	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4345	typedef in that case.
		4346
		4347	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4348	and in some even more future version the compatibility code will be
		4349	removed completely.
		4350
3414	=item EV_STANDALONE	4351	=item EV_STANDALONE (h)
3415		4352
3416	Must always be C<1> if you do not use autoconf configuration, which	4353	Must always be C<1> if you do not use autoconf configuration, which
3417	keeps libev from including F<config.h>, and it also defines dummy	4354	keeps libev from including F<config.h>, and it also defines dummy
3418	implementations for some libevent functions (such as logging, which is not	4355	implementations for some libevent functions (such as logging, which is not
3419	supported). It will also not define any of the structs usually found in	4356	supported). It will also not define any of the structs usually found in
3420	F<event.h> that are not directly supported by the libev core alone.	4357	F<event.h> that are not directly supported by the libev core alone.
3421		4358
3422	In stanbdalone mode, libev will still try to automatically deduce the	4359	In standalone mode, libev will still try to automatically deduce the
3423	configuration, but has to be more conservative.	4360	configuration, but has to be more conservative.
		4361
		4362	=item EV_USE_FLOOR
		4363
		4364	If defined to be C<1>, libev will use the C<floor ()> function for its
		4365	periodic reschedule calculations, otherwise libev will fall back on a
		4366	portable (slower) implementation. If you enable this, you usually have to
		4367	link against libm or something equivalent. Enabling this when the C<floor>
		4368	function is not available will fail, so the safe default is to not enable
		4369	this.
3424		4370
3425	=item EV_USE_MONOTONIC	4371	=item EV_USE_MONOTONIC
3426		4372
3427	If defined to be C<1>, libev will try to detect the availability of the	4373	If defined to be C<1>, libev will try to detect the availability of the
3428	monotonic clock option at both compile time and runtime. Otherwise no	4374	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3492	be used is the winsock select). This means that it will call	4438	be used is the winsock select). This means that it will call
3493	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4439	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3494	it is assumed that all these functions actually work on fds, even	4440	it is assumed that all these functions actually work on fds, even
3495	on win32. Should not be defined on non-win32 platforms.	4441	on win32. Should not be defined on non-win32 platforms.
3496		4442
3497	=item EV_FD_TO_WIN32_HANDLE	4443	=item EV_FD_TO_WIN32_HANDLE(fd)
3498		4444
3499	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4445	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3500	file descriptors to socket handles. When not defining this symbol (the	4446	file descriptors to socket handles. When not defining this symbol (the
3501	default), then libev will call C<_get_osfhandle>, which is usually	4447	default), then libev will call C<_get_osfhandle>, which is usually
3502	correct. In some cases, programs use their own file descriptor management,	4448	correct. In some cases, programs use their own file descriptor management,
3503	in which case they can provide this function to map fds to socket handles.	4449	in which case they can provide this function to map fds to socket handles.
		4450
		4451	=item EV_WIN32_HANDLE_TO_FD(handle)
		4452
		4453	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4454	using the standard C<_open_osfhandle> function. For programs implementing
		4455	their own fd to handle mapping, overwriting this function makes it easier
		4456	to do so. This can be done by defining this macro to an appropriate value.
		4457
		4458	=item EV_WIN32_CLOSE_FD(fd)
		4459
		4460	If programs implement their own fd to handle mapping on win32, then this
		4461	macro can be used to override the C<close> function, useful to unregister
		4462	file descriptors again. Note that the replacement function has to close
		4463	the underlying OS handle.
3504		4464
3505	=item EV_USE_POLL	4465	=item EV_USE_POLL
3506		4466
3507	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4467	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3508	backend. Otherwise it will be enabled on non-win32 platforms. It	4468	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3547	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4507	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3548		4508
3549	=item EV_ATOMIC_T	4509	=item EV_ATOMIC_T
3550		4510
3551	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4511	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3552	access is atomic with respect to other threads or signal contexts. No such	4512	access is atomic and serialised with respect to other threads or signal
3553	type is easily found in the C language, so you can provide your own type	4513	contexts. No such type is easily found in the C language, so you can
3554	that you know is safe for your purposes. It is used both for signal handler "locking"	4514	provide your own type that you know is safe for your purposes. It is used
3555	as well as for signal and thread safety in C<ev_async> watchers.	4515	both for signal handler "locking" as well as for signal and thread safety
		4516	in C<ev_async> watchers.
3556		4517
3557	In the absence of this define, libev will use C<sig_atomic_t volatile>	4518	In the absence of this define, libev will use C<sig_atomic_t volatile>
3558	(from F<signal.h>), which is usually good enough on most platforms.	4519	(from F<signal.h>), which is usually good enough on most platforms,
		4520	although strictly speaking using a type that also implies a memory fence
		4521	is required.
3559		4522
3560	=item EV_H	4523	=item EV_H (h)
3561		4524
3562	The name of the F<ev.h> header file used to include it. The default if	4525	The name of the F<ev.h> header file used to include it. The default if
3563	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4526	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3564	used to virtually rename the F<ev.h> header file in case of conflicts.	4527	used to virtually rename the F<ev.h> header file in case of conflicts.
3565		4528
3566	=item EV_CONFIG_H	4529	=item EV_CONFIG_H (h)
3567		4530
3568	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4531	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3569	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4532	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3570	C<EV_H>, above.	4533	C<EV_H>, above.
3571		4534
3572	=item EV_EVENT_H	4535	=item EV_EVENT_H (h)
3573		4536
3574	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4537	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3575	of how the F<event.h> header can be found, the default is C<"event.h">.	4538	of how the F<event.h> header can be found, the default is C<"event.h">.
3576		4539
3577	=item EV_PROTOTYPES	4540	=item EV_PROTOTYPES (h)
3578		4541
3579	If defined to be C<0>, then F<ev.h> will not define any function	4542	If defined to be C<0>, then F<ev.h> will not define any function
3580	prototypes, but still define all the structs and other symbols. This is	4543	prototypes, but still define all the structs and other symbols. This is
3581	occasionally useful if you want to provide your own wrapper functions	4544	occasionally useful if you want to provide your own wrapper functions
3582	around libev functions.	4545	around libev functions.
…		…
3587	will have the C<struct ev_loop *> as first argument, and you can create	4550	will have the C<struct ev_loop *> as first argument, and you can create
3588	additional independent event loops. Otherwise there will be no support	4551	additional independent event loops. Otherwise there will be no support
3589	for multiple event loops and there is no first event loop pointer	4552	for multiple event loops and there is no first event loop pointer
3590	argument. Instead, all functions act on the single default loop.	4553	argument. Instead, all functions act on the single default loop.
3591		4554
		4555	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4556	default loop when multiplicity is switched off - you always have to
		4557	initialise the loop manually in this case.
		4558
3592	=item EV_MINPRI	4559	=item EV_MINPRI
3593		4560
3594	=item EV_MAXPRI	4561	=item EV_MAXPRI
3595		4562
3596	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4563	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3604	fine.	4571	fine.
3605		4572
3606	If your embedding application does not need any priorities, defining these	4573	If your embedding application does not need any priorities, defining these
3607	both to C<0> will save some memory and CPU.	4574	both to C<0> will save some memory and CPU.
3608		4575
3609	=item EV_PERIODIC_ENABLE	4576	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4577	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4578	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3610		4579
3611	If undefined or defined to be C<1>, then periodic timers are supported. If	4580	If undefined or defined to be C<1> (and the platform supports it), then
3612	defined to be C<0>, then they are not. Disabling them saves a few kB of	4581	the respective watcher type is supported. If defined to be C<0>, then it
3613	code.	4582	is not. Disabling watcher types mainly saves code size.
3614		4583
3615	=item EV_IDLE_ENABLE	4584	=item EV_FEATURES
3616
3617	If undefined or defined to be C<1>, then idle watchers are supported. If
3618	defined to be C<0>, then they are not. Disabling them saves a few kB of
3619	code.
3620
3621	=item EV_EMBED_ENABLE
3622
3623	If undefined or defined to be C<1>, then embed watchers are supported. If
3624	defined to be C<0>, then they are not. Embed watchers rely on most other
3625	watcher types, which therefore must not be disabled.
3626
3627	=item EV_STAT_ENABLE
3628
3629	If undefined or defined to be C<1>, then stat watchers are supported. If
3630	defined to be C<0>, then they are not.
3631
3632	=item EV_FORK_ENABLE
3633
3634	If undefined or defined to be C<1>, then fork watchers are supported. If
3635	defined to be C<0>, then they are not.
3636
3637	=item EV_ASYNC_ENABLE
3638
3639	If undefined or defined to be C<1>, then async watchers are supported. If
3640	defined to be C<0>, then they are not.
3641
3642	=item EV_MINIMAL
3643		4585
3644	If you need to shave off some kilobytes of code at the expense of some	4586	If you need to shave off some kilobytes of code at the expense of some
3645	speed, define this symbol to C<1>. Currently this is used to override some	4587	speed (but with the full API), you can define this symbol to request
3646	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4588	certain subsets of functionality. The default is to enable all features
3647	much smaller 2-heap for timer management over the default 4-heap.	4589	that can be enabled on the platform.
		4590
		4591	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4592	with some broad features you want) and then selectively re-enable
		4593	additional parts you want, for example if you want everything minimal,
		4594	but multiple event loop support, async and child watchers and the poll
		4595	backend, use this:
		4596
		4597	#define EV_FEATURES 0
		4598	#define EV_MULTIPLICITY 1
		4599	#define EV_USE_POLL 1
		4600	#define EV_CHILD_ENABLE 1
		4601	#define EV_ASYNC_ENABLE 1
		4602
		4603	The actual value is a bitset, it can be a combination of the following
		4604	values:
		4605
		4606	=over 4
		4607
		4608	=item C<1> - faster/larger code
		4609
		4610	Use larger code to speed up some operations.
		4611
		4612	Currently this is used to override some inlining decisions (enlarging the
		4613	code size by roughly 30% on amd64).
		4614
		4615	When optimising for size, use of compiler flags such as C<-Os> with
		4616	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4617	assertions.
		4618
		4619	=item C<2> - faster/larger data structures
		4620
		4621	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4622	hash table sizes and so on. This will usually further increase code size
		4623	and can additionally have an effect on the size of data structures at
		4624	runtime.
		4625
		4626	=item C<4> - full API configuration
		4627
		4628	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4629	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4630
		4631	=item C<8> - full API
		4632
		4633	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4634	details on which parts of the API are still available without this
		4635	feature, and do not complain if this subset changes over time.
		4636
		4637	=item C<16> - enable all optional watcher types
		4638
		4639	Enables all optional watcher types. If you want to selectively enable
		4640	only some watcher types other than I/O and timers (e.g. prepare,
		4641	embed, async, child...) you can enable them manually by defining
		4642	C<EV_watchertype_ENABLE> to C<1> instead.
		4643
		4644	=item C<32> - enable all backends
		4645
		4646	This enables all backends - without this feature, you need to enable at
		4647	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4648
		4649	=item C<64> - enable OS-specific "helper" APIs
		4650
		4651	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4652	default.
		4653
		4654	=back
		4655
		4656	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4657	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4658	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4659	watchers, timers and monotonic clock support.
		4660
		4661	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4662	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4663	your program might be left out as well - a binary starting a timer and an
		4664	I/O watcher then might come out at only 5Kb.
		4665
		4666	=item EV_API_STATIC
		4667
		4668	If this symbol is defined (by default it is not), then all identifiers
		4669	will have static linkage. This means that libev will not export any
		4670	identifiers, and you cannot link against libev anymore. This can be useful
		4671	when you embed libev, only want to use libev functions in a single file,
		4672	and do not want its identifiers to be visible.
		4673
		4674	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4675	wants to use libev.
		4676
		4677	This option only works when libev is compiled with a C compiler, as C++
		4678	doesn't support the required declaration syntax.
		4679
		4680	=item EV_AVOID_STDIO
		4681
		4682	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4683	functions (printf, scanf, perror etc.). This will increase the code size
		4684	somewhat, but if your program doesn't otherwise depend on stdio and your
		4685	libc allows it, this avoids linking in the stdio library which is quite
		4686	big.
		4687
		4688	Note that error messages might become less precise when this option is
		4689	enabled.
		4690
		4691	=item EV_NSIG
		4692
		4693	The highest supported signal number, +1 (or, the number of
		4694	signals): Normally, libev tries to deduce the maximum number of signals
		4695	automatically, but sometimes this fails, in which case it can be
		4696	specified. Also, using a lower number than detected (C<32> should be
		4697	good for about any system in existence) can save some memory, as libev
		4698	statically allocates some 12-24 bytes per signal number.
3648		4699
3649	=item EV_PID_HASHSIZE	4700	=item EV_PID_HASHSIZE
3650		4701
3651	C<ev_child> watchers use a small hash table to distribute workload by	4702	C<ev_child> watchers use a small hash table to distribute workload by
3652	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4703	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3653	than enough. If you need to manage thousands of children you might want to	4704	usually more than enough. If you need to manage thousands of children you
3654	increase this value (I<must> be a power of two).	4705	might want to increase this value (I<must> be a power of two).
3655		4706
3656	=item EV_INOTIFY_HASHSIZE	4707	=item EV_INOTIFY_HASHSIZE
3657		4708
3658	C<ev_stat> watchers use a small hash table to distribute workload by	4709	C<ev_stat> watchers use a small hash table to distribute workload by
3659	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4710	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3660	usually more than enough. If you need to manage thousands of C<ev_stat>	4711	disabled), usually more than enough. If you need to manage thousands of
3661	watchers you might want to increase this value (I<must> be a power of	4712	C<ev_stat> watchers you might want to increase this value (I<must> be a
3662	two).	4713	power of two).
3663		4714
3664	=item EV_USE_4HEAP	4715	=item EV_USE_4HEAP
3665		4716
3666	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4717	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3667	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4718	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3668	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4719	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3669	faster performance with many (thousands) of watchers.	4720	faster performance with many (thousands) of watchers.
3670		4721
3671	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4722	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3672	(disabled).	4723	will be C<0>.
3673		4724
3674	=item EV_HEAP_CACHE_AT	4725	=item EV_HEAP_CACHE_AT
3675		4726
3676	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4727	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3677	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4728	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3678	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4729	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3679	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4730	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3680	but avoids random read accesses on heap changes. This improves performance	4731	but avoids random read accesses on heap changes. This improves performance
3681	noticeably with many (hundreds) of watchers.	4732	noticeably with many (hundreds) of watchers.
3682		4733
3683	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4734	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3684	(disabled).	4735	will be C<0>.
3685		4736
3686	=item EV_VERIFY	4737	=item EV_VERIFY
3687		4738
3688	Controls how much internal verification (see C<ev_loop_verify ()>) will	4739	Controls how much internal verification (see C<ev_verify ()>) will
3689	be done: If set to C<0>, no internal verification code will be compiled	4740	be done: If set to C<0>, no internal verification code will be compiled
3690	in. If set to C<1>, then verification code will be compiled in, but not	4741	in. If set to C<1>, then verification code will be compiled in, but not
3691	called. If set to C<2>, then the internal verification code will be	4742	called. If set to C<2>, then the internal verification code will be
3692	called once per loop, which can slow down libev. If set to C<3>, then the	4743	called once per loop, which can slow down libev. If set to C<3>, then the
3693	verification code will be called very frequently, which will slow down	4744	verification code will be called very frequently, which will slow down
3694	libev considerably.	4745	libev considerably.
3695		4746
3696	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4747	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3697	C<0>.	4748	will be C<0>.
3698		4749
3699	=item EV_COMMON	4750	=item EV_COMMON
3700		4751
3701	By default, all watchers have a C<void *data> member. By redefining	4752	By default, all watchers have a C<void *data> member. By redefining
3702	this macro to a something else you can include more and other types of	4753	this macro to something else you can include more and other types of
3703	members. You have to define it each time you include one of the files,	4754	members. You have to define it each time you include one of the files,
3704	though, and it must be identical each time.	4755	though, and it must be identical each time.
3705		4756
3706	For example, the perl EV module uses something like this:	4757	For example, the perl EV module uses something like this:
3707		4758
…		…
3760	file.	4811	file.
3761		4812
3762	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4813	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3763	that everybody includes and which overrides some configure choices:	4814	that everybody includes and which overrides some configure choices:
3764		4815
3765	#define EV_MINIMAL 1	4816	#define EV_FEATURES 8
3766	#define EV_USE_POLL 0	4817	#define EV_USE_SELECT 1
3767	#define EV_MULTIPLICITY 0
3768	#define EV_PERIODIC_ENABLE 0	4818	#define EV_PREPARE_ENABLE 1
		4819	#define EV_IDLE_ENABLE 1
3769	#define EV_STAT_ENABLE 0	4820	#define EV_SIGNAL_ENABLE 1
3770	#define EV_FORK_ENABLE 0	4821	#define EV_CHILD_ENABLE 1
		4822	#define EV_USE_STDEXCEPT 0
3771	#define EV_CONFIG_H <config.h>	4823	#define EV_CONFIG_H <config.h>
3772	#define EV_MINPRI 0
3773	#define EV_MAXPRI 0
3774		4824
3775	#include "ev++.h"	4825	#include "ev++.h"
3776		4826
3777	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4827	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3778		4828
3779	#include "ev_cpp.h"	4829	#include "ev_cpp.h"
3780	#include "ev.c"	4830	#include "ev.c"
3781		4831
3782	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4832	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3783		4833
3784	=head2 THREADS AND COROUTINES	4834	=head2 THREADS AND COROUTINES
3785		4835
3786	=head3 THREADS	4836	=head3 THREADS
3787		4837
…		…
3838	default loop and triggering an C<ev_async> watcher from the default loop	4888	default loop and triggering an C<ev_async> watcher from the default loop
3839	watcher callback into the event loop interested in the signal.	4889	watcher callback into the event loop interested in the signal.
3840		4890
3841	=back	4891	=back
3842		4892
		4893	See also L<THREAD LOCKING EXAMPLE>.
		4894
3843	=head3 COROUTINES	4895	=head3 COROUTINES
3844		4896
3845	Libev is very accommodating to coroutines ("cooperative threads"):	4897	Libev is very accommodating to coroutines ("cooperative threads"):
3846	libev fully supports nesting calls to its functions from different	4898	libev fully supports nesting calls to its functions from different
3847	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4899	coroutines (e.g. you can call C<ev_run> on the same loop from two
3848	different coroutines, and switch freely between both coroutines running the	4900	different coroutines, and switch freely between both coroutines running
3849	loop, as long as you don't confuse yourself). The only exception is that	4901	the loop, as long as you don't confuse yourself). The only exception is
3850	you must not do this from C<ev_periodic> reschedule callbacks.	4902	that you must not do this from C<ev_periodic> reschedule callbacks.
3851		4903
3852	Care has been taken to ensure that libev does not keep local state inside	4904	Care has been taken to ensure that libev does not keep local state inside
3853	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4905	C<ev_run>, and other calls do not usually allow for coroutine switches as
3854	they do not call any callbacks.	4906	they do not call any callbacks.
3855		4907
3856	=head2 COMPILER WARNINGS	4908	=head2 COMPILER WARNINGS
3857		4909
3858	Depending on your compiler and compiler settings, you might get no or a	4910	Depending on your compiler and compiler settings, you might get no or a
…		…
3869	maintainable.	4921	maintainable.
3870		4922
3871	And of course, some compiler warnings are just plain stupid, or simply	4923	And of course, some compiler warnings are just plain stupid, or simply
3872	wrong (because they don't actually warn about the condition their message	4924	wrong (because they don't actually warn about the condition their message
3873	seems to warn about). For example, certain older gcc versions had some	4925	seems to warn about). For example, certain older gcc versions had some
3874	warnings that resulted an extreme number of false positives. These have	4926	warnings that resulted in an extreme number of false positives. These have
3875	been fixed, but some people still insist on making code warn-free with	4927	been fixed, but some people still insist on making code warn-free with
3876	such buggy versions.	4928	such buggy versions.
3877		4929
3878	While libev is written to generate as few warnings as possible,	4930	While libev is written to generate as few warnings as possible,
3879	"warn-free" code is not a goal, and it is recommended not to build libev	4931	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3915	I suggest using suppression lists.	4967	I suggest using suppression lists.
3916		4968
3917		4969
3918	=head1 PORTABILITY NOTES	4970	=head1 PORTABILITY NOTES
3919		4971
		4972	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4973
		4974	GNU/Linux is the only common platform that supports 64 bit file/large file
		4975	interfaces but I<disables> them by default.
		4976
		4977	That means that libev compiled in the default environment doesn't support
		4978	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4979
		4980	Unfortunately, many programs try to work around this GNU/Linux issue
		4981	by enabling the large file API, which makes them incompatible with the
		4982	standard libev compiled for their system.
		4983
		4984	Likewise, libev cannot enable the large file API itself as this would
		4985	suddenly make it incompatible to the default compile time environment,
		4986	i.e. all programs not using special compile switches.
		4987
		4988	=head2 OS/X AND DARWIN BUGS
		4989
		4990	The whole thing is a bug if you ask me - basically any system interface
		4991	you touch is broken, whether it is locales, poll, kqueue or even the
		4992	OpenGL drivers.
		4993
		4994	=head3 C<kqueue> is buggy
		4995
		4996	The kqueue syscall is broken in all known versions - most versions support
		4997	only sockets, many support pipes.
		4998
		4999	Libev tries to work around this by not using C<kqueue> by default on this
		5000	rotten platform, but of course you can still ask for it when creating a
		5001	loop - embedding a socket-only kqueue loop into a select-based one is
		5002	probably going to work well.
		5003
		5004	=head3 C<poll> is buggy
		5005
		5006	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5007	implementation by something calling C<kqueue> internally around the 10.5.6
		5008	release, so now C<kqueue> I<and> C<poll> are broken.
		5009
		5010	Libev tries to work around this by not using C<poll> by default on
		5011	this rotten platform, but of course you can still ask for it when creating
		5012	a loop.
		5013
		5014	=head3 C<select> is buggy
		5015
		5016	All that's left is C<select>, and of course Apple found a way to fuck this
		5017	one up as well: On OS/X, C<select> actively limits the number of file
		5018	descriptors you can pass in to 1024 - your program suddenly crashes when
		5019	you use more.
		5020
		5021	There is an undocumented "workaround" for this - defining
		5022	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5023	work on OS/X.
		5024
		5025	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5026
		5027	=head3 C<errno> reentrancy
		5028
		5029	The default compile environment on Solaris is unfortunately so
		5030	thread-unsafe that you can't even use components/libraries compiled
		5031	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5032	defined by default. A valid, if stupid, implementation choice.
		5033
		5034	If you want to use libev in threaded environments you have to make sure
		5035	it's compiled with C<_REENTRANT> defined.
		5036
		5037	=head3 Event port backend
		5038
		5039	The scalable event interface for Solaris is called "event
		5040	ports". Unfortunately, this mechanism is very buggy in all major
		5041	releases. If you run into high CPU usage, your program freezes or you get
		5042	a large number of spurious wakeups, make sure you have all the relevant
		5043	and latest kernel patches applied. No, I don't know which ones, but there
		5044	are multiple ones to apply, and afterwards, event ports actually work
		5045	great.
		5046
		5047	If you can't get it to work, you can try running the program by setting
		5048	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5049	C<select> backends.
		5050
		5051	=head2 AIX POLL BUG
		5052
		5053	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5054	this by trying to avoid the poll backend altogether (i.e. it's not even
		5055	compiled in), which normally isn't a big problem as C<select> works fine
		5056	with large bitsets on AIX, and AIX is dead anyway.
		5057
3920	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5058	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5059
		5060	=head3 General issues
3921		5061
3922	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5062	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3923	requires, and its I/O model is fundamentally incompatible with the POSIX	5063	requires, and its I/O model is fundamentally incompatible with the POSIX
3924	model. Libev still offers limited functionality on this platform in	5064	model. Libev still offers limited functionality on this platform in
3925	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5065	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3926	descriptors. This only applies when using Win32 natively, not when using	5066	descriptors. This only applies when using Win32 natively, not when using
3927	e.g. cygwin.	5067	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5068	as every compiler comes with a slightly differently broken/incompatible
		5069	environment.
3928		5070
3929	Lifting these limitations would basically require the full	5071	Lifting these limitations would basically require the full
3930	re-implementation of the I/O system. If you are into these kinds of	5072	re-implementation of the I/O system. If you are into this kind of thing,
3931	things, then note that glib does exactly that for you in a very portable	5073	then note that glib does exactly that for you in a very portable way (note
3932	way (note also that glib is the slowest event library known to man).	5074	also that glib is the slowest event library known to man).
3933		5075
3934	There is no supported compilation method available on windows except	5076	There is no supported compilation method available on windows except
3935	embedding it into other applications.	5077	embedding it into other applications.
		5078
		5079	Sensible signal handling is officially unsupported by Microsoft - libev
		5080	tries its best, but under most conditions, signals will simply not work.
3936		5081
3937	Not a libev limitation but worth mentioning: windows apparently doesn't	5082	Not a libev limitation but worth mentioning: windows apparently doesn't
3938	accept large writes: instead of resulting in a partial write, windows will	5083	accept large writes: instead of resulting in a partial write, windows will
3939	either accept everything or return C<ENOBUFS> if the buffer is too large,	5084	either accept everything or return C<ENOBUFS> if the buffer is too large,
3940	so make sure you only write small amounts into your sockets (less than a	5085	so make sure you only write small amounts into your sockets (less than a
…		…
3945	the abysmal performance of winsockets, using a large number of sockets	5090	the abysmal performance of winsockets, using a large number of sockets
3946	is not recommended (and not reasonable). If your program needs to use	5091	is not recommended (and not reasonable). If your program needs to use
3947	more than a hundred or so sockets, then likely it needs to use a totally	5092	more than a hundred or so sockets, then likely it needs to use a totally
3948	different implementation for windows, as libev offers the POSIX readiness	5093	different implementation for windows, as libev offers the POSIX readiness
3949	notification model, which cannot be implemented efficiently on windows	5094	notification model, which cannot be implemented efficiently on windows
3950	(Microsoft monopoly games).	5095	(due to Microsoft monopoly games).
3951		5096
3952	A typical way to use libev under windows is to embed it (see the embedding	5097	A typical way to use libev under windows is to embed it (see the embedding
3953	section for details) and use the following F<evwrap.h> header file instead	5098	section for details) and use the following F<evwrap.h> header file instead
3954	of F<ev.h>:	5099	of F<ev.h>:
3955		5100
…		…
3962	you do I<not> compile the F<ev.c> or any other embedded source files!):	5107	you do I<not> compile the F<ev.c> or any other embedded source files!):
3963		5108
3964	#include "evwrap.h"	5109	#include "evwrap.h"
3965	#include "ev.c"	5110	#include "ev.c"
3966		5111
3967	=over 4
3968
3969	=item The winsocket select function	5112	=head3 The winsocket C<select> function
3970		5113
3971	The winsocket C<select> function doesn't follow POSIX in that it	5114	The winsocket C<select> function doesn't follow POSIX in that it
3972	requires socket I<handles> and not socket I<file descriptors> (it is	5115	requires socket I<handles> and not socket I<file descriptors> (it is
3973	also extremely buggy). This makes select very inefficient, and also	5116	also extremely buggy). This makes select very inefficient, and also
3974	requires a mapping from file descriptors to socket handles (the Microsoft	5117	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3983	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5126	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3984		5127
3985	Note that winsockets handling of fd sets is O(n), so you can easily get a	5128	Note that winsockets handling of fd sets is O(n), so you can easily get a
3986	complexity in the O(n²) range when using win32.	5129	complexity in the O(n²) range when using win32.
3987		5130
3988	=item Limited number of file descriptors	5131	=head3 Limited number of file descriptors
3989		5132
3990	Windows has numerous arbitrary (and low) limits on things.	5133	Windows has numerous arbitrary (and low) limits on things.
3991		5134
3992	Early versions of winsocket's select only supported waiting for a maximum	5135	Early versions of winsocket's select only supported waiting for a maximum
3993	of C<64> handles (probably owning to the fact that all windows kernels	5136	of C<64> handles (probably owning to the fact that all windows kernels
3994	can only wait for C<64> things at the same time internally; Microsoft	5137	can only wait for C<64> things at the same time internally; Microsoft
3995	recommends spawning a chain of threads and wait for 63 handles and the	5138	recommends spawning a chain of threads and wait for 63 handles and the
3996	previous thread in each. Great).	5139	previous thread in each. Sounds great!).
3997		5140
3998	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5141	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3999	to some high number (e.g. C<2048>) before compiling the winsocket select	5142	to some high number (e.g. C<2048>) before compiling the winsocket select
4000	call (which might be in libev or elsewhere, for example, perl does its own	5143	call (which might be in libev or elsewhere, for example, perl and many
4001	select emulation on windows).	5144	other interpreters do their own select emulation on windows).
4002		5145
4003	Another limit is the number of file descriptors in the Microsoft runtime	5146	Another limit is the number of file descriptors in the Microsoft runtime
4004	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5147	libraries, which by default is C<64> (there must be a hidden I<64>
4005	or something like this inside Microsoft). You can increase this by calling	5148	fetish or something like this inside Microsoft). You can increase this
4006	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5149	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
4007	arbitrary limit), but is broken in many versions of the Microsoft runtime	5150	(another arbitrary limit), but is broken in many versions of the Microsoft
4008	libraries.
4009
4010	This might get you to about C<512> or C<2048> sockets (depending on	5151	runtime libraries. This might get you to about C<512> or C<2048> sockets
4011	windows version and/or the phase of the moon). To get more, you need to	5152	(depending on windows version and/or the phase of the moon). To get more,
4012	wrap all I/O functions and provide your own fd management, but the cost of	5153	you need to wrap all I/O functions and provide your own fd management, but
4013	calling select (O(n²)) will likely make this unworkable.	5154	the cost of calling select (O(n²)) will likely make this unworkable.
4014
4015	=back
4016		5155
4017	=head2 PORTABILITY REQUIREMENTS	5156	=head2 PORTABILITY REQUIREMENTS
4018		5157
4019	In addition to a working ISO-C implementation and of course the	5158	In addition to a working ISO-C implementation and of course the
4020	backend-specific APIs, libev relies on a few additional extensions:	5159	backend-specific APIs, libev relies on a few additional extensions:
…		…
4027	Libev assumes not only that all watcher pointers have the same internal	5166	Libev assumes not only that all watcher pointers have the same internal
4028	structure (guaranteed by POSIX but not by ISO C for example), but it also	5167	structure (guaranteed by POSIX but not by ISO C for example), but it also
4029	assumes that the same (machine) code can be used to call any watcher	5168	assumes that the same (machine) code can be used to call any watcher
4030	callback: The watcher callbacks have different type signatures, but libev	5169	callback: The watcher callbacks have different type signatures, but libev
4031	calls them using an C<ev_watcher *> internally.	5170	calls them using an C<ev_watcher *> internally.
		5171
		5172	=item pointer accesses must be thread-atomic
		5173
		5174	Accessing a pointer value must be atomic, it must both be readable and
		5175	writable in one piece - this is the case on all current architectures.
4032		5176
4033	=item C<sig_atomic_t volatile> must be thread-atomic as well	5177	=item C<sig_atomic_t volatile> must be thread-atomic as well
4034		5178
4035	The type C<sig_atomic_t volatile> (or whatever is defined as	5179	The type C<sig_atomic_t volatile> (or whatever is defined as
4036	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5180	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4059	watchers.	5203	watchers.
4060		5204
4061	=item C<double> must hold a time value in seconds with enough accuracy	5205	=item C<double> must hold a time value in seconds with enough accuracy
4062		5206
4063	The type C<double> is used to represent timestamps. It is required to	5207	The type C<double> is used to represent timestamps. It is required to
4064	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5208	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4065	enough for at least into the year 4000. This requirement is fulfilled by	5209	good enough for at least into the year 4000 with millisecond accuracy
		5210	(the design goal for libev). This requirement is overfulfilled by
4066	implementations implementing IEEE 754 (basically all existing ones).	5211	implementations using IEEE 754, which is basically all existing ones.
		5212
		5213	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5214	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5215	is either obsolete or somebody patched it to use C<long double> or
		5216	something like that, just kidding).
4067		5217
4068	=back	5218	=back
4069		5219
4070	If you know of other additional requirements drop me a note.	5220	If you know of other additional requirements drop me a note.
4071		5221
…		…
4133	=item Processing ev_async_send: O(number_of_async_watchers)	5283	=item Processing ev_async_send: O(number_of_async_watchers)
4134		5284
4135	=item Processing signals: O(max_signal_number)	5285	=item Processing signals: O(max_signal_number)
4136		5286
4137	Sending involves a system call I<iff> there were no other C<ev_async_send>	5287	Sending involves a system call I<iff> there were no other C<ev_async_send>
4138	calls in the current loop iteration. Checking for async and signal events	5288	calls in the current loop iteration and the loop is currently
		5289	blocked. Checking for async and signal events involves iterating over all
4139	involves iterating over all running async watchers or all signal numbers.	5290	running async watchers or all signal numbers.
4140		5291
4141	=back	5292	=back
4142		5293
4143		5294
		5295	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5296
		5297	The major version 4 introduced some incompatible changes to the API.
		5298
		5299	At the moment, the C<ev.h> header file provides compatibility definitions
		5300	for all changes, so most programs should still compile. The compatibility
		5301	layer might be removed in later versions of libev, so better update to the
		5302	new API early than late.
		5303
		5304	=over 4
		5305
		5306	=item C<EV_COMPAT3> backwards compatibility mechanism
		5307
		5308	The backward compatibility mechanism can be controlled by
		5309	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5310	section.
		5311
		5312	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5313
		5314	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5315
		5316	ev_loop_destroy (EV_DEFAULT_UC);
		5317	ev_loop_fork (EV_DEFAULT);
		5318
		5319	=item function/symbol renames
		5320
		5321	A number of functions and symbols have been renamed:
		5322
		5323	ev_loop => ev_run
		5324	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5325	EVLOOP_ONESHOT => EVRUN_ONCE
		5326
		5327	ev_unloop => ev_break
		5328	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5329	EVUNLOOP_ONE => EVBREAK_ONE
		5330	EVUNLOOP_ALL => EVBREAK_ALL
		5331
		5332	EV_TIMEOUT => EV_TIMER
		5333
		5334	ev_loop_count => ev_iteration
		5335	ev_loop_depth => ev_depth
		5336	ev_loop_verify => ev_verify
		5337
		5338	Most functions working on C<struct ev_loop> objects don't have an
		5339	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5340	associated constants have been renamed to not collide with the C<struct
		5341	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5342	as all other watcher types. Note that C<ev_loop_fork> is still called
		5343	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5344	typedef.
		5345
		5346	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5347
		5348	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5349	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5350	and work, but the library code will of course be larger.
		5351
		5352	=back
		5353
		5354
4144	=head1 GLOSSARY	5355	=head1 GLOSSARY
4145		5356
4146	=over 4	5357	=over 4
4147		5358
4148	=item active	5359	=item active
4149		5360
4150	A watcher is active as long as it has been started (has been attached to	5361	A watcher is active as long as it has been started and not yet stopped.
4151	an event loop) but not yet stopped (disassociated from the event loop).	5362	See L<WATCHER STATES> for details.
4152		5363
4153	=item application	5364	=item application
4154		5365
4155	In this document, an application is whatever is using libev.	5366	In this document, an application is whatever is using libev.
		5367
		5368	=item backend
		5369
		5370	The part of the code dealing with the operating system interfaces.
4156		5371
4157	=item callback	5372	=item callback
4158		5373
4159	The address of a function that is called when some event has been	5374	The address of a function that is called when some event has been
4160	detected. Callbacks are being passed the event loop, the watcher that	5375	detected. Callbacks are being passed the event loop, the watcher that
4161	received the event, and the actual event bitset.	5376	received the event, and the actual event bitset.
4162		5377
4163	=item callback invocation	5378	=item callback/watcher invocation
4164		5379
4165	The act of calling the callback associated with a watcher.	5380	The act of calling the callback associated with a watcher.
4166		5381
4167	=item event	5382	=item event
4168		5383
4169	A change of state of some external event, such as data now being available	5384	A change of state of some external event, such as data now being available
4170	for reading on a file descriptor, time having passed or simply not having	5385	for reading on a file descriptor, time having passed or simply not having
4171	any other events happening anymore.	5386	any other events happening anymore.
4172		5387
4173	In libev, events are represented as single bits (such as C<EV_READ> or	5388	In libev, events are represented as single bits (such as C<EV_READ> or
4174	C<EV_TIMEOUT>).	5389	C<EV_TIMER>).
4175		5390
4176	=item event library	5391	=item event library
4177		5392
4178	A software package implementing an event model and loop.	5393	A software package implementing an event model and loop.
4179		5394
…		…
4187	The model used to describe how an event loop handles and processes	5402	The model used to describe how an event loop handles and processes
4188	watchers and events.	5403	watchers and events.
4189		5404
4190	=item pending	5405	=item pending
4191		5406
4192	A watcher is pending as soon as the corresponding event has been detected,	5407	A watcher is pending as soon as the corresponding event has been
4193	and stops being pending as soon as the watcher will be invoked or its	5408	detected. See L<WATCHER STATES> for details.
4194	pending status is explicitly cleared by the application.
4195
4196	A watcher can be pending, but not active. Stopping a watcher also clears
4197	its pending status.
4198		5409
4199	=item real time	5410	=item real time
4200		5411
4201	The physical time that is observed. It is apparently strictly monotonic :)	5412	The physical time that is observed. It is apparently strictly monotonic :)
4202		5413
4203	=item wall-clock time	5414	=item wall-clock time
4204		5415
4205	The time and date as shown on clocks. Unlike real time, it can actually	5416	The time and date as shown on clocks. Unlike real time, it can actually
4206	be wrong and jump forwards and backwards, e.g. when the you adjust your	5417	be wrong and jump forwards and backwards, e.g. when you adjust your
4207	clock.	5418	clock.
4208		5419
4209	=item watcher	5420	=item watcher
4210		5421
4211	A data structure that describes interest in certain events. Watchers need	5422	A data structure that describes interest in certain events. Watchers need
4212	to be started (attached to an event loop) before they can receive events.	5423	to be started (attached to an event loop) before they can receive events.
4213		5424
4214	=item watcher invocation
4215
4216	The act of calling the callback associated with a watcher.
4217
4218	=back	5425	=back
4219		5426
4220	=head1 AUTHOR	5427	=head1 AUTHOR
4221		5428
4222	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5429	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5430	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4223		5431

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines